Functional oxides – synthesis, structure, properties and applications

Resume : Zinc oxide nanorods have been investigated as an alternative to mesoporous TiO2 for use in dye-sensitised solar cells (DSSCs) due to improved charge transport properties and a direct current pathway to the transparent electrode. However, due to the significantly lower surface area and subsequent reduction in dye loading, low current densities generally limit efficiency around or below 1 %. Here we present a method for the growth of lamellae on the surface of ZnO nanorods to produce brush-like structures which allows higher dye adsorption, leading to increased efficiency. By coating ~ 6 um long nanorods using an optimised precursor concentration for lamellae growth, a power conversion efficiency of ~2 % is achieved for cells using N719 dye and iodide-based electrolyte, which is one of the highest efficiencies reported for ZnO nanorod-based DSSCs. A number of methods are used to maximise the device efficiency. For example, it is shown that by increasing the nanorod growth time, greater length and therefore surface area is achieved. In addition, the use of a hydrogel-derived seed layer is shown to lead to a higher density of thinner nanorods, further contributing to the high surface area and therefore efficiency. Correct choice of annealing conditions is also shown to be important to improve the crystallinity of the ZnO lamellae while retaining the high surface area of the structure. Overall this study shows that a number of methods can be used to increase the surface area of ZnO nanorod arrays, including correct choice of seed layer, extended growth time, and the addition of appropriate surface structures. Combining these techniques has produced high efficiency ZnO nanorod-based devices, and higher efficiencies may be possible using these methods, for example by further increasing the nanorod length or using dyes optimised for ZnO-based devices.

Resume : Greenhouse effect is nowadays a major concern to our society. Recently, many countries have demonstrated their awareness by signing the important agreement reached in the ?2015 United Nations Climate Change Conference? in Paris in order to mitigate the global warming. In this compromise, CO2 is denoted as one of the Greenhouse gases whose emission must be immediately limited. These emissions are mainly produced in thermal power stations to generate energy and different activities involving combustion processes. Unfortunately, many of these activities are intense CO2 emitters whereas feasible alternative technologies do not exist. Consequently, one of the main strategies to mitigate the emissions is related to CO2 sequestration technologies. One of these techniques is based on lithium orthosilicate, a material which has demonstrated a high CO2 adsorption capacity. In this work we present a preliminary approach to the CO2 adsorption process by lithium orthosilicate nanofibers. A novel method based on Laser Spinning process to obtain pure silica nanofibers followed by a chemical process to transform them into lithium orthosilicate is reported. These nanofibers show an extremely high surface to volume ratio, they do not agglomerate as nanoparticles do and their high flexibility allow them to adapt to any recipient. The production method was evaluated by X-Ray Diffraction analysis of the obtained material. Following, the adsorption capacity of these fibers was investigated. A Thermogravimetric analysis (TGA) was performed in order to study the CO2 adsorption process as well as the chemical reaction to transform silica into lithium orthosilicate. So far, 14 % of adsorption capacity was achieved, and more efforts are being done in order to improve their performance.

Resume : The investigation of lattice strain effects as a way to modulate defect and transport properties in ionic conductors is growing in importance in recent years, driven by the interest in the fabrication of thin film devices. In this context, the computational prediction of materials properties is particularly relevant in a field, such as the deposition of epitaxially strained thin films, where experiments are demanding. Olivine-type phosphates LiFePO4 and NaFePO4 are among the most widely studied cathode materials for rechargeable batteries. To improve their rate behaviour for future applications, enhancement of the alkali ion conductivity is crucial. In this study, atomistic simulation methods are used to investigate the effect of lattice strain on ion transport and defect formation energies in olivine-type cathode materials, as these properties are directly related to their intercalation behaviour. The results suggest that lattice strain can have a remarkable effect on the rate performance of cathode materials. Such understanding is important for the future optimization of high-rate cathodes for rechargeable batteries, and is relevant to the growing interest in developing thin film solid-state batteries. C. Tealdi, J. Heath, M.S. Islam, J. Mater. Chem. A, 2016, 4, 6998-7004.

Resume : Multiferroics are uniquely capable of hosting more than one spontaneous order parameter simultaneously. The cross-control between the magnetic and electric phases was most unambiguously studied in multiferroic orthorhombic TbMnO3 [Nature 426, 55 (2003)]. TbMnO3 shows a transition to a paraelectric incommensurate antiferromagnetic phase at 41 K and successively locks into a ferroelectric bc-cycloidal phase below 28 K [Phys. Rev. Lett. 95, 087206 (2005)]. The polar ordering along the c-axis due to antisymmetric exchange striction makes it an ideal candidate to study the effects of strain on the multiferroic properties. We grew epitaxial TbMnO3 thin films on YAlO3 substrates with control over the strain based on the lattice mismatch. X-ray diffraction studies confirmed the growth of an epitaxial highly strained film. Interestingly, neutron diffraction experiments indicate drastic changes in the magnetic order as compared to bulk. The magnetic order was observed to lock into a commensurate E-type phase below 33 K with and the ferroelectric order was enhanced and switched towards the a-axis. We attribute these strain induced changes of the multiferroic properties to a switch between the dominant magnetoelectric coupling mechanisms. In the oral presentation I will elaborate on these results with an attempt to establish the intrinsic strain as a tool to tailor the multiferroic ground state in rare-earth manganites.

Resume : Our group has developed new high-temperature neutron and high-resolution synchrotron X-ray diffraction techniques to study the precise crystal structures, nuclear and electron density in inorganic materials up to 1900 K. Bond valence method is useful to examine the ion diffusion paths. These techniques enabled precise structure analysis leading to diffusion path and structural disorder in ionic conductors. Here we present the diffusion path of oxide ions in Bi2O3, Bi1.4Yb0.6O3, (La0.8Sr0.2)(Ga0.8Mg0.15Co0.05)O3-?, CeO2, Ce0.93Y0.07O1.96, PrBaCo2O5+? [1], (Pr0.9La0.1)2(Ni0.74Cu0.21Ga0.05)O4+? [2,3], Pr2(Ni0.75Cu0.25)0.95Ga0.05)O4+? [4], and La0.64(Ti0.92Nb0.08)O3 at high temperatures. A novel material NdBaInO4 has been synthesized by solid-state reactions and its crystal structure has been determined by synchrotron X-ray and neutron powder diffraction and ab initio electronic calculations [5]. The bond valence sums (BVS) map of NdBaInO4 at 1000 °C strongly suggests two-dimensional network of oxide-ion diffusional pathways in the Nd2O3 unit. We have discovered the novel material NdBaInO4 belonging to a new perovskite-related structure family, and its crystal structure has been determined. NdBaInO4 exhibits oxide-ion conduction. It was found that the Sr substitution at the Nd site improves the oxide-ion conductivity of NdBaInO4 [6]. The present finding might open a new window in chemistry, physics and materials science. [1] Y.-C. Chen, M. Yashima, J. Peña-Martínez and J. A. Kilner, Chem. Mater. 25, 2638 (2013). [2] M. Yashima, M. Enoki, T. Wakita, R. Ali, Y. Matsushita, F. Izumi, T. Ishihara, J. Am. Chem. Soc. 130, 2762 (2008). [3] M. Yashima, N. Sirikanda, T. Ishihara, J. Am. Chem. Soc. 132, 2385 (2010). [4] M. Yashima, H. Yamada, S. Nuansaeng, T. Ishihara, Chem. Mater. 24, 4100 (2012). [5] K. Fujii, Y. Esaki, K. Omoto, M. Yashima, A. Hoshikawa, T. Ishigaki and H. R. Hester, Chem. Mater. 26, 2488 (2014). [6] K. Fujii, M. Shiraiwa, Y. Esaki, M. Yashima, S. J. Kim and S. Lee, J. Mater. Chem. A 3, 11985 (2015).

Resume : Figure of merit (ZT) of oxide-based TE materials can be improved by introducing planar faults into the microstructure. It is expected that in-grown planar faults will reduce thermal conductivity which would consequently increase the ZT value. In our work, microstructure and thermoelectric properties of two different materials were studied: polycrystalline Sr(Ti0.8Nb0.2)O3 (STN) with the addition of either Sr3Ti2O7 platelet crystals or SrO or CaO and polycrystalline ZnO with the addition of In2O3. The microstructure analysis of the STN samples revealed that the addition of either Sr3Ti2O7 or SrO or CaO into STN resulted in formation of Ruddlesden-Popper-type (RP) planar faults with the rock salt-type structure that formed either random 3D networks along {001} STN crystallographic planes and/or more or less ordered polytypoidic sequences with general formula (Sr,Ca)O*n(Sr(Ti,Nb)O3). The thermoelectric measurements showed that thermal conductivities of doped STN samples were app. twice lower as compared to undoped STN. Consequently, the figure of merit (ZT) for e.g. CaO-doped STN was improved by a factor of two. In In2O3-doped ZnO ceramics pure indium monolayers were readily observed by the HAADF. These basal inversion domain boundaries (IDB’s) run parallel to the {0001} ZnO lattice planes and separate domains with different orientation. Thermoelectric measurements confirmed that the thermal conductivity of the ZnO decreased with the increasing addition of In2O3 which resulted in increased ZT value. Our investigation showed that in-growth planar faults reduced thermal conductivity in both investigated materials systems and that by such nanostructured tailoring of the material it is possible to improve the ZT value in oxide-based thermoelectric materials.

Resume : Heterogeneous photocatalysis utilises semiconductor (SC) materials to harvest electromagnetic radiation yielding a potential difference which is used to drive redox reactions at the surface of the SC material. Environmental applications include the degradation of organic pollutants and inactivation of microorganisms in water and wastewater, degradation of organic pollutants in air (and oxidation of NOx), and self-cleaning surfaces for the built environment (e.g. self-cleaning glass), and self-disinfecting coatings for healthcare. Solar energy harvesting applications include water splitting to yield hydrogen and the reduction of carbon dioxide to fuels and platform chemicals. Photocatalytic materials are typically metal oxides, many of which are wide band gap semiconductors (>3.0 eV e.g. TiO2, WO¬3, ZnO). The most studied photocatalyst material is TiO2 because it is photoactive, photostable, insoluble in water and inexpensive. The disadvantage with TiO2 is that it requires UV excitation which limits the solar efficiency to a maximum of 4%. Attempts to improve the solar efficiency of TiO2 photocatalysis have focused on shifting the band gap energy into the visible domain by metal and non-metal doping. There is significant debate in the community about how successful this approach might be with the visible activity usually being only a fraction of the UV activity. A wide range of other materials have been studied, with the metal oxides being the most stable in aqueous environments. This paper will present the basic mechanism of photocatalysis and discuss the required properties of materials for water treatment, water splitting and CO2 reduction.

Resume : Nanotechnology is still holding the promise to increase industries efficiency bringing profoundly new applications, but to achieve this goal specific, synergic and coordinated research involving scientists form different disciplines are necessary to boost nanotechnology. Material science is at the base of nanotechnology. Concerning functional materials, easy and cheap growth techniques for the production of nanostructures in a variety of morphologies are constantly proposed by the research community. Metal oxides represent an assorted and appealing class of materials which properties cover the entire range from metals to semiconductors and insulators and almost all aspects of material science and physics in areas including superconductivity and magnetism. In particular metal oxides in forms of nanowires are interesting materials for their peculiar morphology that assures a high surface to volume ratio necessary to maximize surface related properties like the ones governing chemical sensing transduction principles. When developing 1D nanocrystals the most important requirements are dimensions and morphology control, uniformity and crystalline properties. The thermal evaporation and oxidation methods have been used to prepare a variety of oxides such as tin, zinc, copper, nickel, tungsten and will be extensively described since they are among the most explored in the recent papers and the cheapest for single crystal production. Furthermore the integration of these metal oxide nanostructures into sensing devices will be presented together with their application as chemical sensors. Acknowledgements The research leading to these results has received funding from the European Community?s FP7-ICT-2013-10, MSP? Multi-Sensor-Platform for Smart Building Management under the project n° 611887.

Resume : Among oxide perovskites, RNiO3 compounds display an interesting phase diagram. Except LaNiO3, they undergo, as the temperature decreases, a metal to insulator phase transition (MIT), linked to the appearance of a charge ordering/charge disproportionation and a symmetry lowering from Pbnm to P21/n. Despite a consensus on the important role of the oxygen breathing mode in this MIT, the exact way it opens the gap is still debated. In the present work, we explore that further from DFT U calculations, focusing on YNiO3 as a prototypical example. First, a careful study of the structural, magnetic and electronic properties as a function of the U parameter allows us to identify a value of U with which DFT U correctly describes YNiO3. Based on this approach, we then report a simple Heisenberg model that properly reproduces the magnetic properties. Finally, we discuss the interplay between lattice and electronic properties. We quantify the couplings between oxygen breathing, rotation and tilt distortions and highlight their respective role on the MIT.

Resume : Bulk BaBiO3 is a fascinating material, presenting a very rich phase diagram with a charge density wave insulating phase that is suppressed upon doping, giving place to high-TC superconductivity. Recently, it has been theoretically suggested that the (001) BaBiO3 surface should become metallic if a Bi-termination is achieved (V. Vildosola et al., Phys. Rev. Lett. 110, 206805 (2013)). This metallic state presents a 2D character and has a very promising potential in the field of oxide electronics. The experimental confirmation of this prediction, which is extremely challenging, remains lacking due to the absence of low-mismatch substrates. Here we follow a different approach by growing and characterizing (100) highly textured (but not epitaxial) BaBiO3 thin films on silicon. We show that it is possible to control the out-of-plane texture of the films by controlling the growth conditions, being possible to switch from highly (100)-textured to polycrystalline-like films. XPS spectra display an anomalous Bi doublet which is maximized for (100)-texture. The origin of this doublet is linked to our ab-initio calculations results, which suggest that electron doping stabilizes Bi3+ species and shortens Bi-O bonds at the (100)-surface. This also implies a reduction of the band gap and an increase of the surface conductivity, consistently with our transport measurements. We conclude that as the texture of the films can be easily controlled by the growth conditions, it is possible to tune the electronic properties at the surface of these films.

Resume : Electrochemical energy storage devices featuring both high energy and high power density are of critical importance for the upcoming applications such as the storage of solar energy peaks and the fast transmission of the energy to the grid. This development can greatly benefit from nanostructuring concepts due to the short diffusion pathways in nanoscale materials, greatly decreased sintering temperatures, and flexibility in optimizing the material and device morphology. Using a novel solvothermal tert butanol synthesis route we have developed new pathways for the fabrication of different metal oxide nanoparticles for the application in lithium-ion batteries as well as the ways to their controlled assembly into continuous crystalline networks with extremely high surface areas. We were able to obtain fully crystalline interconnected porous frameworks composed of ultrasmall titania (TiO2) and lithium titanate spinel nanocrystals, which was shown to be the fastest ever-reported titanate morphology as anode material for lithium ion insertion.[1, 2] Here we show the extension of our successful synthesis strategy to the development of nanostructured lithium cobalt oxide LiCoO2 (LCO) as a cathode for Li-ion batteries. In a solvothermal reaction in tert-butanol, crystalline lithium rich CoO nanoparticles are obtained. The easily dispersible nanoparticles can be assembled to porous nanostructured electrodes using amphiphilic polymers as soft templates, and transformed to the nanostructured LCO cathodes via calcination at temperatures far below the conventional solid state synthesis. References [1] J. M. Szeifert et al, J. Amer. Chem. Soc. 132, 12605-12611 (2010). [2] J. M. Feckl et al, Angew. Chem. Int. Ed. 51, 7459-7463 (2012).

Resume : Resistive random access memories (RRAM) are very promising candidates in search for a ?universal memory? whose traits include non-volatility, rapid-low power reading and writing, and scalability [1]. Traditionally, resistive memory refers to a metal-insulator-metal structure, with the ON and OFF states characterized by formation and rupture respectively of a conducting filament through the insulator connecting the metal electrodes [1]. Here, via field control of interfacial chemistry we obtain memristive behavior in Al-LaNiO3 (LNO), a metal-metal interface, and demonstrate reproducible multiple resistance states with ON-OFF resistance ratios between the extreme states ~100. We show that Al grabs oxygen from LNO forming an active AlxOy layer at the interface. Using aberration corrected electron microscopy, spectroscopy and transport measurements, we show that the resistive switching occurs due to the electric field driven O2- (or Vo??) cycling between LNO (reservoir) and the interlayer, redox reaction at the electrodes and Al nanocluster dynamics. We discuss the significant morphological differences in the self-formed interlayers, and show that it is possible to stabilize intermediate resistance states by engineering a desired morphology through electric field. Our findings not only offer new insights into designing novel memristors based on controlling the interface chemistry, but also on tuning interfacial oxygen chemistry to obtain desired functions on oxide interfaces. References: [1] D.J. Wouters, R. Waser, M. Wuttig., Phase-Change and Redox-Based Resistive Switching Memories, Proceedings of the IEEE, Vol.103, 1274, 2015

Resume : An important phenomenon sometimes observed with exposure of oxides to radiation damage, is an order-to-disorder (O-D) transition. O-D transitions can occur on either anion or cation sublattices (or both) and they can occur due to the gradual accumulation of radiation-induced lattice point defects, or they can occur directly within ballistic displacement cascades. The disordering tendencies of various oxides is highly dependent on many physical properties, including crystal structure and chemistry, structural distortions from ideality, intrinsic atomic disorder, bonding (ionic vs. covalent), and defect formation energies (e.g., Frenkel and antisite defects). Sometimes O-D transitions are quite simple, such as inversion in spinel compounds, while in other cases, the observed O-D transitions involve complex rearrangements of atoms into new configurations. In this presentation, a geometric layered atom stacking model will be used both to describe the initial atomic structures of complex (multicomponent) oxides, as well as to assess structural changes associated with radiation-induced O-D transitions in certain oxides. The model presented here is based on a layer stacking model for magnetic oxides developed by Shuichi Iida in 1957 [1]. We will develop idealized geometrical models for selected compounds and compare these to real (relaxed) crystal structures. We will also develop layer descriptions for the disordered states of these compounds. Finally, we will consider how these crystal structure concepts relate to the radiation tolerance (observed or predicted) of various complex oxides. [1] S. Iida, "Layer Structures of Magnetic Oxides," Journal of the Physical Society of Japan 12 (1957) 222-233.

Resume : As characterization techniques continue to advance, the materials community is reminded again and again that our samples are not as perfect as we generally describe them to be. This presentation will describe two case studies that focus on the impacts and control of heterogeneous cation distributions in single-phase perovskite dielectrics. In one case, through-thickness B-site gradients were identified in solution-derived Pb(Zr,Ti)O3 thin films; eventually two independent sources of these gradients were identified, and via targeted process modifications, eliminated, resulting in bulk-like properties from solution-derived thin films. In the other case, subtle mesoscale cation gradients have been identified as a key factor in the phenomenal temperature- and field-stable permittivity of Bi(Zn0.5Ti0.5)O3?BaTiO3-based dielectrics. Ongoing investigations using both solution-derived films and powder-derived ceramics are providing important clues about the source(s) of these gradients and suggest exciting opportunities for using clever processing to take advantage of mesoscale heterogeneity. These two case studies highlight the large effects that can result from seemingly subtle differences in processing and the need for multiple complementary characterization and measurement techniques for effective description of complex functional materials.

Resume : Sr2FeMoO6 (SFMO) is a half-metallic double perovskite which is of fundamental and potentially technological interest for next-generation spintronics devices especially for magnetic tunnel junctions [1]. This results from the spin polarization and its low-magnetoresistance response at room temperature. Furthermore, the exceptionally high Curie temperature Tc of more than 400 K has opened the door to intensive research activity. However, the application has been hindered by the inability to synthesize ?perfect? SFMO films due to the presence of defects and the epitaxial strain induced by the lattice mismatch with the substrates [2]. In this theoretical investigation within the density functional theory (DFT) framework, we have carried out a systematic study of structural properties of perfect SFMO and a comparative study of defects in it, both under the influence of biaxial strain. We study the impact of biaxial strain on the formation probability of certain point defects by means of formation energy calculations. Our results show that the formation of anti-site defects is unfavoured at all strains while the stability of an oxygen vacancy is enhanced by tensile strain. The stability of other cation vacancies under strain such as VSr, VFe and VMo and compositional disorder such as FeMo and MoFe are also discussed in relation to possible applications. All the calculations were performed using DFT with the projector augmented wave method as implemented in the Vienna ab initio simulation package [3]. [1] Kobayashi, K. I. Nature 395, 677-680 (1998). [2] Jalili, H, Heinig, N. F. and Leung, K. T. Phys. Rev. B 79, 174427 (2009). [3] Kresse, G. and Hafner, J. Phys. Rev. B 47, 558 (1993).

Resume : The discovery of a two-dimensional electron gas (2DEG) at the interface between LaAlO3 and SrTiO3 has disclosed new perspectives in the research field for novel materials engineering. Apart from LaAlO3, the 2DEG has also been detected in many other perovskite materials and in amorphous samples, suggesting a rather universal mechanism for the conductivity onset. Among trivalent perovskites, BiFeO3 is a promising candidate material for epitaxial ABO3/SrTiO3 heterojunctions. The 2DEG, combined with the room-temperature multiferroic behaviour of BiFeO3, could enable the production of new nanotechnology devices, in which the electrical properties could be tailored magnetically. Sputtering deposition is one of the most common techniques used for device fabrication, due to the fast and cheap growth of films with a large practicable area. Sputtering is usually considered a rough and inhomogeneous deposition technique; however, with a good control of growth conditions, sputtering can actually produce high-quality epitaxial films. In this work we demonstrate the reliability of RF sputtering in the growth of epitaxial BiFeO3 ultrathin films, where X-ray photoelectron diffraction (XPD) has been used as a tool to probe the transition from amorphous to epitaxial thin films, while retaining chemical selectivity both on substrate and BiFeO3 layer. The similitudes between BiFeO3/SrTiO3 and LaAlO3/SrTiO3 junctions are further proved by an XPS analysis of valence band electronic states.

Resume : The endeavour for new material never stops which has again been highlighted with the recent report on “entropy stabilised oxides” where it has been shown that up to five cations in equiatomic amounts can be incorporated into a single cubic lattice (Mg0.2Co0.2Ni0.2Cu0.2Zn0.2O). The idea originated from its metallic counterpart “high entropy alloys” wherein the high configurational entropy plays a pivotal role in formation of single phase. In this study, equiatomic nanocrystalline rare earth oxides (REOs) comprising of 3–7 rare earth cations are synthesized by nebulized spray pyrolysis with the primary intention of studying the type and stability of the phases formed in order to understand this new class of materials. This is followed by the study of their functional properties. Rietveld analysis of X-ray diffraction patterns revealed that the REOs crystallize as a single phase with a high symmetry crystal structure. Energy dispersive spectroscopy confirmed the equiatomic composition the nanopowders.

Resume : Recent studies on molybdate compounds showed that this class of materials has great potential for being used as antibacterial agents [1,2]. In the same time, Ag and Cu compounds are known as bactericidal, whereas CaOH is used in endodontic treatment against infections. Based on these premises, different molybdate powders (Ag2MoO4, CuMoO4, Cu3Mo2O9 and CaMoO4) were produced by green chemical synthesis and their morphological and structural properties have been studied. Different powder concentrations were tested for antibacterial activity against E. coli BL21DE3 both under daylight and in the dark. The aims were to find new antibacterial materials and to clarify which is the responsible mechanism for their antibacterial feature. All powders showed antibacterial properties with the exception of CaMoO4, and their ability to inactivate the E. coli was independent of illumination. This fact excluded that a possible photocatalytic mechanism under visible light is the responsible factor for the proven activity. Therefore, investigations of metal ions leakage have been performed by ICP-OES both in H2O and Lysogeny Broth. Large differences between ions release in these media were found. This study clarifies the antibacterial mechanism though which these compounds acted: metal ions leaching, and points to the importance of performing such tests. [1] C. C. Mardare, A. W. Hassel, ACS Comb. Sci. 2014, 6, 631 [2] C. C. Mardare et al., Phys. Status Solidi A 2016, DOI 10.1002/pssa.201532786

Resume : Hybrids comprised of plasmonic metal nanoparticles and semiconducting materials are attractive for the study of photocatalytic and plasmonically-driven transformations. In this project, we aimed at investigating the effect of the presence of TiO2 over the formation of holes in Au NPs mediated by their surface-plasmon resonance (SPR) excitation and its subsequent photocatalytic activities. To this end, we employed TiO2 colloidal spheres decorated with Au NPs (TiO2-Au) displaying uniform sizes and dispersion over the TiO2 surface as model materials and the photocatalytic degradation of methylene blue (MB) under visible light exposure as a target transformation. We found that the photocatalytic activity towards MB degradation due to the formation of holes in the Au NPs was significantly higher for the TiO2-Au hybrid relative to its individual Au NPs or TiO2 counterparts under visible light. These results could be explained based on the transfer of hot electrons generated upon the SPR excitation from Au NPs to the TiO2 conduction band in the TiO2-Au material, which leave holes in Au NPs that lead to the formation of hydroxyl radicals that contribute and improve the photocatalytic degradation of MB. This mechanism was supported by the fact that the presence of TiO2 leads to a decrease in the p-aminothiophenol (PATP) to p,p'-dimercaptoazobenzene (DMAB) SPR-mediated oxidation in the TiO2-Au NPs. We believe the results reported herein suggest that TiO2-Au materials may represent attractive systems for designing photocatalysts with improved performances using solar/visible light as the energy input.

Resume : Titanium Dioxide thin films were deposited onto fluorine doped tin oxide coated glass substrates from the electric field assisted aerosol chemical vapour deposition reaction of titanium isopropoxide in toluene at 450 °C. The electric fields were generated by applying a potential difference between the electrodes of the glass substrates during the deposition. The deposited films were characterised using scanning electron microscope, X-ray diffraction, Raman spectroscopy and UV-VIS spectroscopy. The photoactivity and hydrophilicity of deposited films were also analysed using reazurin dye degredation tests and water-contact angles measurements. The results show that the incorporation of electric fields into the deposition reaction influenced the film microstructure, preferential orientation and photocatalytic properties of the deposited titanium dioxide thin films. Specifically field strength correlated to crystallographic texturing and the ability to grow films orientated along a specific crystallographic axis such as the (200), (004) or (211). Reazurin dye photocatalytic testing indicated that the films with a strong (004) orientation had the highest photocatalytic activity, significantly higher than that of titanium dioxide thin films grown without the application of an electric field.

Resume : In a context of significant interest for energy and environment, nanostructured-based ceramic materials are considered ideal candidates for the development of cost and energy efficient innovative systems. Such an attention is essentially due to the unique properties originating from the confinement of either one or more dimensions into the nanoscale level. Among others the large surface-to-volume ratio is a feature that greatly increases the reactivity of the nanomaterials towards gaseous species when compared with the non-nano dimensional materials. With this regards, catalysis is one of those applications that unquestionable benefits from this novel feature. In addition, when nanofibers (1D nanostructure) are used as catalysts, the further advantage of a self-supported wide open and well-interconnected porous structure is achieved. Herein we demonstrate nanofibers as catalysts for the removal of the NOx in exhausts via the NH3 Selective Catalytic Reduction (SCR) method. By combining electrospinning and sol-gel chemistry, materials are processed as nanofibers with the catalytic components (e. g. V2O5-WO3) incorporated as dopants into the supporting anatase phase (e. g. TiO2). Remarkable high NOx conversion efficiencies are obtained and associated with the unique features deriving from the synergism among the doping approach, the nanoscale confinement, and the nano-fibrous texture. A novel concept of self-supported, lightweight and ultra-compact design SCR reactor is defined.

Resume : Cerium oxide is important in catalysis for its ability to store, release and transport oxygen. We studied ceria epitaxial ultrathin films on Pt(111) as model systems to gain more insight into ceria based materials. Reducing thermal treatments in UHV lead to chemical, structural and morphological modifications in the films. However, while the stoichiometry and the atomic structure can be brought back to the original ones by thermal treatments in O2, the morphology is irreversibly modified (1). Low energy electron microscopy (LEEM) and microprobe low energy electron diffraction (u-LEED) are powerful instruments for an in-depth dynamic investigation (2). We followed in real-time the growth, reduction and oxidation of ceria on Pt(111) to better understand the above points, studying the effects of different deposition temperatures on morphology and structure and using dynamic intensity-voltage LEEM as a tool to identify different growth regimes (3). Reduction involves an evolution of the LEED pattern with the appearance of a superposition of different structures. Real-space LEEM imaging during reduction allows to identify a new phase that extends on the uncovered substrate surface. By oxidation this phase is replaced by irregularly-shaped oxidized ceria islands, suggesting that the formation of a Ce-Pt alloy could take place during reduction highlighting the strong interaction between Pt and ceria. (1) P Luches, F Pagliuca, S Valeri, Phys Chem Chem Phys 16, 18848 (2014) (2) B Kaemena, SD Senanayake, A Meyer, JT Sadowski, J Falta, JI Flege, J Phys Chem C 117, 221 (2013) (3) M Sauerbrey, G Gasperi, P Luches, J Falta, S Valeri, JI Flege, Top Catal (2016), in press

Resume : Two dimensional (2D) materials show unique electronic and optical properties, due to the quantum confinement and high surface volume ratio, which make them promising for various electronic applications. We report a facile, controllable and sustainable top down, wet chemical thinning method, to obtain 2D MoO3 (Molybdenum Trioxide) crystals of desired thickness. Here, a chemical etchant has been used to thin down the mechanically exfoliated MoO3 crystals, deposited on SiO2/Si substrates. An optimum ratio of the etchant has been determined for the thinning process throughout the experiment. The etch rate has been determined from the change in thickness of the crystals, pre and post etching, with respect to etch duration. The thickness of the crystals has been measured using AFM (atomic force microscope). Raman spectroscope and TEM (transmission electron microscope) has been used to study and compare the compositional and structural integrity of the pristine and etched MoO3 crystals. The Raman spectra and selected area electron diffraction patterns show that the composition and crystalline structure of the etched crystals are identical to that of pristine MoO3. The findings of this report show that the chemical thinning is a propitious top down method to obtain quasi-2D crystals from mechanically exfoliated MoO3. The etched crystals in quasi-2D structure facilitate the fabrication of electronic devices through photolithography, to study the electronic properties of the material.

Resume : Transition metal oxides with the perovskite structure attract a growing interest due to their exceptionally broad range of functionalities arising from the complex interplay between charge, orbital, spin and lattice degrees of freedom and controllable by external stimuli [1]. Their integration in monolith forms opens the way for all-oxide electronic devices. Among them, SrVO3 (SVO) is particularly interesting because it is a model material for the study of strongly correlated systems due to its relatively simple cubic structure with only one electron per vanadium and its electronic properties. It is in the heart of fundamental research for studying the metal insulator transition [2] and is a promising candidate as solid oxide fuel cell anode [3], electrode in all oxide epitaxial heterostructure [4] and transparent conductor [5]. We investigate the growth by Pulsed Laser Deposition of SrVO3 thin films on SrTiO3 substrates and their stability in oxidizing atmosphere. Film grown in vacuum exhibit a very smooth surface while films grown at higher oxygen pressure becomes rough and presents crystallites at the surface. These crystallites are auto-organized and identified as Sr3V2O8. Additionally, we show the way to prevent formation of this phase and improve the transport properties by subsequent thermal treatments in a precise range of temperature and oxygen pressure. We demonstrate thus the proper conditions to obtain high quality smooth SVO films with improved electrically conducting SrVO3. SVO can take a complementary place with respect to SrRuO3 or LaNiO3 as electrode brick in ?all oxide heterostructures? for transparent conductor?s application because of its stability region under low oxygen pressure. [1] P. Zubko, S. Gariglio, M. Gabay, P. Ghosez, J.-M. Triscone, Annu. Rev. Condens. Matter Phys. 2011, 2, 141. [2] K. Yoshimatsu, T. Okabe, H. Kumigashira, S. Okamoto, S. Aizaki, A. Fujimori, M. Oshima, Phys. Rev. Lett. 2010, 104, 147601. [3] A. A. Yaremchenko, B. Brinkmann, R. Janssen, J. R. Frade, Solid State Ion. 2013, 247?248, 86. [4] J. A. Moyer, C. Eaton, R. Engel-Herbert, Adv. Mater. 2013, 25, 3578. [5] L. Zhang, Y. Zhou, L. Guo, W. Zhao, A. Barnes, H.-T. Zhang, C. Eaton, Y. Zheng, M. Brahlek, H. F. Haneef, N. J. Podraza, M. H. W. Chan, V. Gopalan, K. M. Rabe, R. Engel-Herbert, Nat. Mater. 2015, 15, 204.

Resume : We have found that orientation selective epitaxial (OSE) growth of CeO2(100) and (110) layers on Si(100) is capable by controlling surface potential distribution. during the growth process. With the aim of application to hybrid orientation technology for higher speed CMOS devices, we are studying the hybrid orientation structure of the CeO2(100) and (110) regions on Si(100) substrates using electron beam-induced OSE growth by reactive magnetron sputtering. Two separate areas of growth are seen, with CeO2(100) layers found to grow in areas irradiated by electrons during the growth process, and the CeO2(110) layers growing in the areas without irradiation. The lateral orientation mapping by X-ray diffraction measurements reveal the existence of transition regions between these two orientation areas. The width of the transition region is found to?be considerably large and  decrease proportionally as the logarithm of the underlying Si substrate resistivity. To make a breakthrough in the limitation in reduction of the transition region width, we propose a new method of OSE growth on silicon on insulator (SOI) substrates with lithographically formed trenches. The trenches prevent spread of the potential distribution to the neighboring Si islands. We report the experimental results showing perfect isolation between OSE grown regions having different crystallographic orientations, optimizing the Si layer thickness of SOI and the cross-sectional geometry of the trenches.

Resume : In recent years, photocatalysis technology has received universal attention due to its applications in the abatement of pollutants in water. The development of magnetic photocatalysts and magnetically induced acceleration of photocatalytic reactions are current trends in the photocatalysis. A magnetic field effect on the photocatalytic activity of multiferroic photocatalyst Ce-modified BiFeO3 was observed for the first time under visible region. A hydrothermal method has been adapted to synthesize single phase [Bi1-xCexFeO3 (BCFO: x=0.0, 0.05, 0.10 and 0.15)] nanoparticles. Synthesized nanoparticles were characterized for investigating the phase, structural, chemical bonds, magnetic, optical properties, photocatalytic activity in the presence and absence of magnetic field effect using XRD, FTIR, VSM, UV-DRS, and UV-Vis spectroscopy respectively. The photocatalytic activities in absence and presence of 0.5 T magnetic field were evaluated by the degradation of phenol red under visible-light irradiation and the concentration of phenol red was determined by measuring the absorbance at 435nm using a UV-Vis spectrophotometer. The enhanced photocatalytic activity of BCFO nanoparticles observed in the presence of magnetic field. In addition, the kinetics of the photodecomposition for both the systems was investigated using the Langmuir-Hinshelwood (L-H) model.

Resume : We report surface chemical cation composition analysis of high quality superconducting LiTi2O4 thin films, grown epitaxially on MgAl2O4 (111) substrates, by pulsed laser deposition. The superconducting transition temperature of the films was ~13.8 K. Surface chemical composition is crucial for the formation of a good LiTi2O4/insulator interface in the perspective of integrating LiTi2O4 in full-oxide spin-filtering devices. In consideration of this, we report a detailed Angle Resolved X-ray photoelectron spectroscopy analysis. Results show Li segregation at the surface of LiTi2O4 films. We attribute this process due to an out diffusion of Li toward the outermost LiTi2O4 layers.

Resume : The electrical characteristics of Metal?high-k (HfO2?Al2O3)?Si (MOS) structures were investigated in order to assess their applicability in non?volatile charge trapping memory devices. The stacked HfO2?Al2O3 layers have been fabricated on Si by Atomic Layer Deposition. Charge trapping layers with different Al2O3 thickness were prepared. The effect of post deposition annealing (O2, 600°C) on the charge storage properties were studied based on capacitance?voltage (C?V) and current?voltage (I?V) measurements. The effective dielectric constant of the as?grown layers is 17.7 for stacks with thinner Al2O3 sublayers, and 15.5 in the case of thicker ones. The initial oxide charge present in the stacks is positive with density also depending on the Al2O3 thickness. The stacks with lower Al2O3 content exhibit higher oxide charge density of ~3x10^12 cm^2 compared to the ones with thicker Al2O3 (~6x10^11 cm2). The annealing decreases the layer?s thickness and increases their effective dielectric constant; the density of the initial oxide charge also increases. Memory windows of up to ~10 V depending on the magnitude of the charge pulse are obtained. The memory effect results from a trapping/detrapping of electric charge in the dielectric stack upon applying positive and negative voltage pulses, respectively. The Al2O3 content of the stacks and annealing affect the charge storage ability of the layers. Acknowlegdements. The work was supported by the EU 7th FP REGPOT project INERA (GA3 16309).

Resume : Ceramic zirconium oxides (ZrO2) are an important material with an increasing range of applications. Zirconia ceramic components have excellent fracture toughness, very good wear resistance, high corrosion stability, low thermal conductivity and coefficient of thermal expansion in range of steel. Their functional properties characterize zirconia as a leading structure material for a dental medicine [1] and solid-oxide fuel-cell design [2] and catalytic technologies [3]. This material are drawn attention towards the remarkable structural properties: with increasing temperature structure of pure zirconia with monoclinic symmetry (P21/c) [4] transforms to tetragonal symmetry (P42 /nmc), by approximately 1180 °C [5] and then to fluorite structure with a cubic symmetry (Fm-3m) starting about 2370 °C with melting by 2716 °C. The alloying of pure ZrO2 with CeO2, or with lower valence oxides such as CaO, MgO, La2O3, Y2O3 or certain other metal oxides, it is possible to stabilize the tetragonal phase at room temperature. These metastable phases are analogous to those in pure zirconia but have dopant ions which substituted Zr4 ions and a corresponding concentration of oxygen vacancies to retain charge neutrality. The main aim of the work is the determination of influence of Y and Ce ions on the features of crystal structure and microstructural parameters of zirconia ceramic. The substitution of the Zr with Y or Ce in zirconium oxides leads to a transition from the monoclinic to tetragonal structure (Fig.1). Ceramic samples doped with Y ions are inhomogeneous. The volume of unit cell increases as the concentration of Y ions is increased. In Ce doped zirconium oxides we observed a difference of the phase composition between the surface layer of the sample and the phase composition of the bulk samples. We attributed this difference to the various oxygen concentration in the surface layer and in the bulk sample. 1. Panadero, R.A.; Roman-Rodriguez, J. L.; Ferreiroa, A.; Sola-Ruiz, M. F.; Fons-Font, Journal of Clinical and Experimental Dentistry 2014,6, 66-73. 2. Badwal, S.P.S.; Giddey, S.; Munnings, C.; Kulkarni, A.; Journal of the Australian Ceramics Society 2014, 50, 23-37. 3. Mercer, P.D.L.; Van Ommen, J.G.; Doesburg, E.B.M.; Burgraff, A.J.; Ross, J.R.H. Applied catalysis 1991, 71, 363-391. 4. J. D. McCullough and K. N. Trueblood, Acta Crystallogr. 1959, 12, 507. 5. G. Teufer, Acta Crystallogr. 1962, 15, 1187.

Resume : We report here results of our investigation of oxide nanometric films integrated with silicon substrates for new multifunctional applications. Ultraviolet photons of KrF-laser (248 nm) was used for the synthesis of nanometeric films based on iron and chromium oxides (Fe2O3-X(0?x?1) and Cr3-XO3-Y(0?x?2; 0?y?2)) with variable thickness, stoichiometry and electrical properties. Films deposition was carried out on the silicon substrate Si < 100> at the substrate?s temperature ?S = 293°K. Atomic force microscopy methods as well as X-ray diffraction and X-ray reflectometry analysis were used for nanometric films characterization. Fe2O3-X(0?x?1) nanometric films demonstrates the negative magnetoresistance in magnetic fields up 0.7 ?. At the same time, for hybrid systems of the alternate layers Fe2O3-X(0?x?1)/Cr3-XO3-Y(0?x?2; 0?y?2) the positive magnetoresistance as well as the magnetic hysteresis and magnetoresistivity switching effect in the low magnetic fields were observed. SPV spectra of multi-component composite structure with several types of surface carriers transporting materials were studied. It was found a significant rise in value and expansion of the spectral range of the surface photo-voltage.

Resume : Metal oxide nanostructures like CuO have been widely investigated for their applications ranging from energy storage, catalysis, sensing and magnetic.1,2 Recently, CuO hollow nanostructures have been shown to have 10 times higher catalytic activity than solid nanostructures of nearly similar dimensions.3 Present work deals with synthesis of CuO nanoflakes like structures having catalytic activity even higher than the hollow nanostructures. The growth mechanism of the particle/structure leads to a high effective surface area that synergically contributes in the properties that are dependent on the surface states. CuO nanoflakes, synthesized using simple precipitation method, shows an increased catalytic conversion of p-nitrophenol to p-aminophenol in presence of NaBH4 with a reaction rate constant of 4.87 x 10-2 s-1.Degradation process follows pseudo- first order phenomenon with good repeatability yield, tested for four subsequent cycles.The observed catalytic rate constant for CuO nanoflakes is much higher than those reported for solid or even hollow nanostructures.

Resume : Molybdenum based oxide is one of the promising electrode material for next generation energy storage. The majority of the literature for Molybdenum oxides has been focused on using crystalline materials that suffers from problems such as irreversible phase transformations and large volume expansions. It appears that nanostructuring methods can mitigate these shortcomings but this puts a restrain due to the complexity of the synthesis process. One promising alternative is the use of amorphous structured materials. While some recent reports have shown the potential the amorphous molybdenum oxide structures can provide,1,2 there still lack detail understanding in the workings of the material. This is especially so for the underlying mechanisms in ions insertion and extraction where conflicting models about intercalation and conversation are proposed. Thin film studies are ideal model setup to shed light on such mechanism. Therefore, in this work, we provided detail studies to investigate the lithium insertion mechanism deposited molybdenum oxide thin films. We study the effects of varying stoichiometry, via electrochemical and surface characterisation to propose a more unified model for lithium insertion in amorphous systems. 1. Ku, J. H. et al., Adv. Funct. Mater. 22, 3658?3664 (2012). 2. Chen, W. et al, Electrochim. Acta 144, 369?375 (2014).

Resume : Zinc oxide (ZnO) pure or doped are one of the most promising metal oxide semiconductors for gas sensing applications due the well-known high surface-to-volume area and surface conductivity. It was show that ZnO is an excellent gas-sensing material for different gases such as CO, O2, NO2 and ethanol. In this context, pure and doped ZnO exhibiting different morphologies and a high surface/volume ratio can be a good option regarding the limitations of the current commercial sensors. Different studies showed that the sensitivity of metal-doped ZnO (e.g. Co, Fe, Mn,) enhanced its gas sensing properties. Motivated by these considerations, the aim of this study consisted on the investigation of the role of Co ions on structural, morphological and the gas sensing properties of nanostructured ZnO samples. ZnO and Zn1-xCoxO (0 < x < 5 wt%) thin films were obtained via the polymeric precursor method. The sensitivity, selectivity, response time and long-term stability gas sensing properties were investigate when the sample was exposed to different concentration range of ozone (O3) at different working temperatures. The gas sensing property was probed by electrical resistance measurements. The long and short-range order structure around Zn and Co atoms were investigate by X-ray diffraction and X-ray absorption spectroscopy. X-ray photoelectron spectroscopy measurement were performed in order to identify the elements present on the film surface as well as to determine the sample composition. Microstructural characteristics of the films were analyzed by a field-emission scanning electron microscope (FE-SEM). Zn1-xCoxO XRD patterns were indexed to the wurtzite ZnO structure and any second phase was observed even at a higher cobalt content. Co-K edge XANES spectra revealed the predominance of Co2 ions. XPS characterization revealed that Co-doped ZnO samples possessed a higher percentage of oxygen vacancies than the ZnO samples, which also contributed to their excellent gas sensing performance. Gas sensor measurements pointed out that ZnO and Co-doped ZnO samples exhibit a good gas sensing performance concerning the reproducibility and a fast response time (around 10 s). Furthermore, the Co addition contributed to reduce the working temperature for ozone detection and improve the selective sensing properties.

Resume : ZnO epitaxial layers deposited by Atomic Layer Deposition were implanted with Yb ions to a fluence of 1x1016 at./cm2 at energy of 150 keV. Different types of annealing (in oxygen or ambient atmosphere) of ZnO:Yb samples have been performed: millisecond range flash lamp annealing (FLA), rapid thermal annealing (RTA) up to 30 min. and tube furnace annealing (TFA) up to 1 h at 800oC. It was found that the optical properties of ZnO:Yb films are strongly affected by the annealing time. According to Rutherford Backscattering and channeling (RBS/c) the annealing of implanted films leads to a partial recovery of the crystal lattice. The photoluminescence (PL) spectra in combination with RBS/c reveal that the worse reconstruction of lattice and reduction of the fraction of substitutional Yb ions results in more intense emission around 0.98 µm in case of RTA and TFA annealing. Surprisingly, the FLA annealing has shown very good result in terms of PL intensity at RT as a thermal quenching effect is much weaker in this case. The RBS/c and PL results lead to a conclusion that RTA and FTA annealing promotes cluster formation and outdiffusion of Yb while FLA suppresses it. Acknowledgements. The work was supported by the NCBiR (Poland) through the project PBS2/A5/34/2013 and by the EU 7th FP project REGPOT-CT-2013-316014 (EAgLE). It was also co-financed by Helmholtz Zentrum Dresden-Rossendorf (HZDR) in the frame of the program Access to Infrastructure (15100222-ST).

Resume : The properties of ZnO thin films depend greatly on the crystallographic texture, and the control of the crystallization and growth direction is therefore essential. For example, the use of ZnO in light emitting diodes and sensor arrays require a (002) orientation [1]. As other specific orientations may exhibit different interesting properties, the precise control of the final films texture is a key parameter for their wider development. With significantly lower investment costs and a highly-controlled ZnO thin films elaboration, the sol-gel process has emerged as being very attractive compared to other deposition methods. Zinc acetate dihydrate, ethanol and monoethanolamine were used as starting materials, solvent and stabilizer, respectively. The multi thin layers are prepared by spin-coating onto glass substrates, and are transformed into ZnO upon annealing at 500°C. The structural, morphological, and optical properties of the thin films as a function of precursor concentration and layer number have been investigated using XRD (Rietveld, texture analysis), SEM, AFM and m-lines spectroscopy. The results obtained from the different characterization techniques will be presented and discussed. On all samples, the different analyses show two main fiber texture components < 00.2> and < 05.2>. From the Orientation Distribution Function, volume fractions of these two components were calculated. [1] C.S. Lao, Q. Kuang, Z.L. Wang, M.C. Park, Y. Deng, Appl. Phys. Lett. 90 (2007) 262107.

Resume : Cerium dioxide is one of the most attractive oxides used in catalytic applications today. Its high reducibility (ability of forming, filling and transporting oxygen vacancies) makes this material appealing for applications like fuel cells and biomedicine. Understanding the structural modifications occurring during CeO2 reduction has a key role for the optimization of material reducibility. This system shows interesting novel properties induced by spatial confinement and by the interaction with the supporting substrate. We investigated cerium dioxide ultrathin epitaxial film growth on Pt(111) and reduced by thermal treatments in vacuum. The structural and electronic modifications were studied using x-ray absorption spectroscopy (XAS) at the Ce L3 edge in the near and extended energy range. Analysis of the spectra in near edge range shows that thermal treatment drastically modifies Ce oxidation state in the thinner sample (thickness less than 1nm), while the analysis of the extended energy range shows a contraction of the Ce-O bond by 2-3% compared to initial CeO2 cubic fluorite lattice. Differently, the same thermal treatments do not remarkably modify neither the structure nor the electronic state of thicker films (approximately 3nm~10 ML). This fact is consistent with the hypothesis that reduction involves only the topmost surface layers and does not influence the bulk structure of the film. It also suggests that the metal substrate has a key role in the process.

Resume : The whitlockite unit cell is formed by substitution of Mg, Fe and OH in a basic Ca3(PO4)2 compound. Whitlockite is a mineral of the formula Ca9(MgFe)(PO4)6PO3OH (rhombohedral symmetry, R3c space group). This structure type is known also for compounds with phosphorus replaced by vanadium. The multicomponent whitlockite-related vanadates can have the specific formulae created by particular doping of the Ca3(VO4)2 compound, e.g. Ca3-xM2x/3(VO4)2 or Ca9M(VO4)7, where M = a trivalent cation. A number of solid solutions with formula Ca3-xRE2x/3(VO4)2 are known as high temperature ionic conductors. Moreover, these compounds are attractive as laser materials, and materials for non-linear optics due to efficient second harmonic generation (SHG). Ca9Dy(VO4)7 and doped Ca9Gd(VO4)7 have been found to be suitable for white light emission LEDs, whereas Ca9Eu1?xLnx(VO4)7 is considered as a red phosphor material. In the present work, characterization of Ca9R(VO4) single crystals by determination of their structure is presented. The structure of polycrystalline samples prepared from perfect single crystals grown by Czochralski growth method is studied. Phase analysis has shown that the crystals are pure whitlockite-type. The results of refinements show a consistency with scarce literature data. Similarities and differences between the present data and the literature data obtained for polycrystalline sample synthesised by solid state reaction will be discussed.

Resume : Yb:YAG is a perspective material for diode-pumped solid-state lasers [1,2]. Comparing to traditional for YAG active ions Nd3+, Yb3+ has several advantages, such as unlimited solubility, high quantum efficiency (up to 75% [3]), and low heat generation [4]. The present work is devoted to the study of microstructure formation features of Yb:YAG ceramics during the solid-state sintering and to spectroscopic and laser characterization of Yb:YAG transparent ceramics. Yb:YAG ceramic samples were prepared from nanopowders of initial oxides, mixed together in stoichiometric composition to form the garnet structure. Samples were sintered in a vacuum furnace with tungsten heating elements at T=1700 - 1800?C during 0.5 - 20 hours, and then annealed in air at 1300?C to recover oxygen vacancies and convert ytterbium ions into Yb3+ state. The optimal sintering temperature to produce near pore-free Yb:YAG ceramics was determined to be 1800?C. According to microstructure observations, higher temperature will cause abnormal grain growth. In-line optical transmittances, absorption and luminescence spectra of ceramics with 5 up to 15 at.% Yb ions have been studied. All spectral lines corresponded to Yb3+ ions. Spectral lines that could be attributed to Yb2+ ions were not detected, indicating complete oxidation of ytterbium ions. The laser output performances of Yb:YAG ceramics were evaluated using the pump at 970 nm with a fiber-coupled diode laser and linear plane-plane (l=8 mm) resonator. Several out-coupling mirror (OCM) with T between 3% and 20% in the range of 1020 nm-1080 nm were used. Output energy of 5.2 mJ at 1030 nm for 11.1 mJ of absorbed pump energy was achieved in quasi-continuous operation with 15 at.% Yb:YAG ceramics; the slope efficiency was 47%. [1] C. Stewen et al., IEEE J. Sel. Top. Quantum Electron. 6 (2000) 650. [2] M. Tsunekane and T. Taira, Appl. Phys. Lett. 90 (2007) 121101. [3] T.Taira et. al. // Appl. Opt. 36(9), 1997, 1867-1874. [4] T. Y. Fan // IEEE J. Quant. Electron. 29(6), 1993, 1457-1459.

Resume : Tungsten oxide (WOx) is an oxide with a wide range of applications. WOx is often studied for its sensorial properties. Here we present the study of thin layers of tungsten oxide deposited by a reactive magnetron sputtering. The layers were examined for their hydrogen gas sensorial response assembled as a conductometric sensor. Sputtering conditions can be tuned to produce a required crystallographic phase. An optimization of the deposition (e.g., by changing the substrate tilt, varying the thickness, optimizing the substrate temperature) can result in sensorial properties almost comparable with nanostructured tungsten oxide (nanorods, nanowires etc.), yet the sputtering deposition is more simple, tunable and stable process than commonly used processes for a manufacturing of the nanostructure-based devices. Moreover reactive magnetron sputtering enabled us the tuning of the stoichiometry which strongly affects the sensorial rersponse. For sensorial measurements hydrogen was chosen as a reactive gas, therefore, nobel metal catalysts (Pd, Cu) were used to support the response. The metal was deposited as sub-10-nm clusters by unique deposition system using magnetron sputtering with aggregation chamber for forming adjustable metal clusters. The prepared layers were characterized by means of X-Ray diffraction, scanning electron microscopy and atomic force microscopy. The stoichiometry was determined by energy dispersive spectroscopy. The layers were tested for a response in ranging hydrogen concentration in the synthetic air at various temperatures. Response sensitivity and response time are evaluated.

Resume : A number of semiconductors such as TiO2, ZnO and alpha-Fe2O3 (hematite) have been investigated for Photoelectrochemical (PEC) water splitting [1]. This work reports on the fabrication of doped and undoped hematite thin films for photo-electrochemical hydrogen production prepared by electrodeposition. The latter consists of spreading few drops of FeCl3 (0.8 M) aqueous solution on the top of the substrate, using the electrodeposition consisted of an aqueous solution of 5 mM FeCl3 5 mM KF 1 M H2O2 0.1 M KCl .The thin films were deposited on glass substrate coated with fluorine-doped tin oxide (SnO2:F, FTO) (FTO). In order to obtain the ?-Fe2O3 phase, the substrates were annealed in a furnace in air at 600°C for 2h. The structure of the crystalized films was investigated by X-ray diffraction (XRD) and Raman spectroscopy. UV-Visible spectrum was employed to analyze the optical properties of the films (band-gap energy and transmittance). Finally the photoelectrochemical properties of the hematite thin films were measured using a three-electrode photoelectrochemical cell in 1 M NaOH electrolyte by applying a potential bias to the cell. The photocurrent densities versus the potential (J-V) were measured and electrochemical impedance spectroscopy (EIS) performed.

Resume : TiO2 materials are the most commonly used photocatalysts for environmental remediation due to its physiochemical properties. Herein, meso- and macroporous anatase TiO2 beads with different sizes, porosity and high specific surface area were prepared via the environmental sustainable ionotropic gelation method. Scanning Electron Microscopy (SEM), X-ray diffraction (XRD), Mercury porosimetry, BET surface area and ultraviolet-visible (UV-vis) absorption spectroscopy were employed to investigate the material morphology and properties. The photocatalytic performance of the samples was evaluated by photodegradation of a positively charged dye (methylene blue) under UV light irradiation. It was found that porous TiO2 beads can be regenerated and reused for several cycles with no loss in material stability, weight and performance compared to TiO2-P25 reference catalyst. These materials can be further functionalized with specific nanoparticles to enhance the photocatalytic activity in organic pollutant degradation under UV and visible light irradiation.

Resume : We present a joint experimental and state-of-the-art ab initio simulations study of the compression of arsenolite . Experiments on this molecular solid at high pressures with different pressure-transmitting media have been interpreted thanks to the ab initio calculations. Our studies confirm arsenolite is one of the most compressible minerals and provide evidence that He is not so noble under pressure. Our results show evidence for ordered helium trapping above 3 GPa between adamantane-type As4O6 cages. At relatively small pressures, helium forms charge-shift bonds with arsenic resulting in a new compound with stoichiometry As4O6·2He. The structural inclusion of helium modifies all the properties of parent arsenolite. In particular, pressure-induced amorphization, which occurs in arsenolite above 15 GPa, is impeded in As4O6·2He, thus resulting in a mechanical stability of As4O6·2He beyond 30 GPa. The evidence of the He-bonds under pressure can become relevant in high pressure experiments using gas as pressure transmission media, and to explore the formation of alternative compounds by pressure-induced trapping and reaction of gases, and small atoms.

Resume : The use of titanium oxides nanotubes is now one of the most attractive techniques applied for surface modification of biomaterials. Presence of the nanotubes on the top of surface increases osteoblast adhesion, proliferation, bioactivity and possibility of their use as a drug delivery system. One of the techniques, applied for obtaining highly ordered single-walled nanotubes can be an anodic oxidation. Dependently on the type and concentration of the electrolyte three generation of TiO2 nanotubes can be produced. The aim of presented studies was to form three generation of TiO2 nanotubes on surface of the Ti13Nb13Zr biomedical alloy by anodization. The morphology and structure of the anodized surface of the Ti13Nb13Zr alloy was characterized using grazing incidence X-ray diffraction (GIXD), X-ray photoelectron spectroscopy (XPS) and field emission scanning electron microscopy (FE-SEM). It was found that the anodic oxidation of the Ti13Nb13Zr alloy allowed for obtaining layer, which was formed from the single-walled nanotubes. The XPS results revealed the presence of TiO2, Nb2O5 and ZrO2 oxides on the samples after anodization.

Resume : The mineral mixture in the hand or foot warmers used to improve the comfort of man working in a cold environment is composed of iron powder,carbon, water, sodium chloride, vermiculite and diatomite. The main source of the thermal effect is iron oxidation but each component plays a role in the process of heat emission and the effectiveness of mixtures. The aim of this study was to evaluate the impact of changing external conditions, the humidity and temperature on the thermal effect of the mineral compounds.Simulated climatic conditions were proposed on the basis of surveys conducted in cold environments. Conditions were selected on the basis of temperature and humidity recorded inside the gloves of employees working in the cold store.The measurements of humidity and temperature on the surface of packaged mineral mixtures in varying climatic conditions were done. Temperature was measured at 5-second intervals via data loggers (iButton Temperature/Humidity Logger, Maxim Integrated Company). The microstructure and chemical composition of the active compound before and after heat release process was analyzed. Studies have assessed the impact of changing environmental conditions (temperature and humidity) on the heat release process by the mineral compounds mixture and could be applied to develop more effective protective cloths used in cold working environment. The paper is based on the results of COLDPRO project:The use of active ecological mineral compounds in the production of cold-protective gloves and footwear? funded in the years 2015-2018by National Centre for Research and Development.

Resume : For multicomponent oxides of garnet structure type (Ia-3d space group), materials characterized by properties such as low thermal conductivity, high resistance for plastic flow even at high temperatures, and by high Mohs hardness value (up to 8.5) have been reported. The physical properties make that specific garnet-type materials are considered for specific applications. Garnet materials have been considered for use as optical pressure sensors [1, 2], as components of solid-state lasers [3] and substrates for deposition of superconducting films [4]. A four-component garnet chemical formula for is X3M2Z3O12, with divalent X, trivalent M, and tetravalent Z cations or with all trivalent cations. In four-component garnets (X3M2Z3O12), the X atoms are bonded to eight oxygens (distorted cube), M atoms ? to six oxygens (octahedral), and Z atoms ? to four oxygens (tetrahedral). The crystals studied in this work were prepared by The powder diffraction experiments were carried out at a modern laboratory Bragg-Brentano diffractometer (X'Pert Pro Alpha1 MPD, Panalytical. Crystallographic characterisation and structure refinement was done with help of Fullprof.2k (v. 2.70) program. The results of phase analysis and structure refinement for Ca3M2Ge3O12 (M= Cr, Mn, Fe and Ga) garnets will be shown and discussed on the basis of literature data. [1] J. Liu, Y.K. Vohra, Appl. Phys. Lett. 64, 3386 (1994). [2] S. Kobyakov et al., Appl. Phys. Lett. 88, 234102 (2006). [3] J. Lu et al. J. Alloys Compds. 341, 220 (2002). [4] P. Mukhopadhyay, Supercond. Sci. Technol. 7, 298 (1993).

Resume : The intrinsic anisotropic elastic properties of lithium-manganese spinel was exhibited by the anisotropy of the observed elastic microstrain. Tensor surfaces representing microstructural properties of the lithium-manganese oxide as a function of the direction of the diffraction vector at two temperatures and under varied pressure was determined in DAC using synchrotron radiation at the MSPD-BL04 beamline of the ALBA synchrotron. The microscopic picture was completed by analyzing the isosurface of the anisotropic microstrain which is connected with the strong shear strain of neighboring coordination polyhedra in the spinel structure. Microstrain of the sample at HP/HT and at HP condition was compared.

Resume : Conformal growth of very thin films on Porous Anodic Alumina (PAA) substrates is of great interest for obtaining multifunctional hierarchical structures with a wide range of applications. Depending on the parameters of a PAA substrate (variable pore dimension, one or double side opened) and deposited layer characteristics (dielectric, semiconductor, metal) variable structure functionality could be tailored. In this work, the growth of ZnO:Al layers on PAA substrates employing Atomic Layer Deposition has been investigated. Three layer thicknesses were chosen (7 nm, 15 nm and 200 nm) in order to obtain partially or full filling of the pores. Scanning electron microscopy images revealed conformal pore filling by the ZnO:Al layers. The investigations were complemented by photoluminescence, XRD, TEM, AFM and Complex Impedance Spectroscopy. Acknowledgements. The work was supported by the EU 7th FP REGPOT project INERA (GA3 16309).

Resume : The recharge kinetics Cr3+ to Cr4+ and exchange kinetics of Cr4+ ions between octahedral and tetrahedral lattice sites were investigated in Cr:YAG ceramics under the air annealing. The garnet ceramics of Cr,Ca:YAG (Ca 0.5 at.%, Cr 0.1 at.%) were produced by solid state reaction sintering in vacuum. The Cr3+ ions in after sintering ceramics have been recharged to Cr4+ by air annealing. The time dependence of Cr4+ ion concentration was carried out at four evaluated temperature to determine activation energy of both the recharge and exchange processes. The evolution of distribution of Cr and Ca in the grains and on the grain boundaries was investigated by HRTEM and EDS. Time dependence of Cr4+ concentration was described with Jander model. Kinetic of recharge Cr4+ ion in octahedral and tetrahedral crystallographic position are limited by the same stages. The value of activation energy of Cr3+ recharging was calculated as 2,67 eV, which coincides with energy of activation of oxygen diffusion into YAG ceramics. That allows to conclude that recharge of Cr3+ to Cr4+ in ceramics Cr,Ca:YAG Cr4+ ions controlled by diffusion of oxygen through ceramics. The concentration ratio between tetrahedral and octahedral Cr4+ ions no time and temperature depended under air annealing at 1000 to 1300 oC and equal of 0.55. That means the transfer of Cr4+ between octahedral and tetrahedral crystallographic position occurs without energy barrier and enthalpy of exchange reaction is close to zero.

Resume : Ytterbium doped Calcium Gadolinum Aluminate (CaGdAlO4 CALGO) crystal is a new material considered for perspective application in the technology of ultra-fast lasers with femtosecond pulse duration. The technology of growth of these crystals by Czochralski method is presently developed at Institute of Electronic Materials Technology. There are only few papers concerning CALGO crystals [1-3], especially dealing with the structural perfection of the crystals. In the present papers the series of samples cut out perpendicularly to the < 100> growth axis from the initial and end parts of CALGO crystals undoped and doped with different concentration of Yb have been studied. Investigations were performed by means of X-ray diffraction topography exploring both synchrotron and conventional X-ray sources. The synchrotron topographic investigations were performed at ESRF in transmission geometry using the radiation of significantly short wavelength, while the conventional topographs were obtained in the back-reflection geometry by means of double crystal method. Some additional investigations were performed with EDAX equipped SEM, and polarization microscopy. Apart from slightly pronounced segregation fringes and core region the diffraction topographs revealed numerous volume defects, which most probably can be interpreted as the solute trails. The characteristic feature of the presently observed volume defects were the details of the contrasts on their boundaries. These details suggested the presence of strong stress and the generation of the dislocations. The increase of the defect concentration with the ytterbium concentration was observed. [1] J. Di, X. Xu, C. Xia, Q. Sai, D. Zhou, Z. Lv, J. Xu, J. Lumin. 155 (2014) 101–107; [2] S. Gao, Z. You, J. Xu, Y. Sun, C. Tu, Mater. Lett. 141 (2015) 59–62; [3] J. Roudeile, F. Druon, M. Hanna, P. Georges, Y. Zaouter, E. Cormier, J. Petit, P. Goldner, B. Viana, Optics Lett. 32 (2007) 1962

Resume : In this work we present the optical and structural characteristics of ZnO/MgO short period superlattices grown on c-plane ZnO. The structures were composed on 80 pairs of ZnO/MgO thin layers. Rutherford backscattering allowed to estimate the real thickness of the structures and compare them with the intended one. The thicknesses differed from growth to growth and they were on the order of 1 nm ZnO to 1-1.5 nm MgO. The thickness of MgO layers was crucial for the growth mode and resulting quality of the structures. Channeling measurement revealed that in the case of the thinnest MgO layers the growth of superlattices was coherent, as χmin of the backscattering yield for the superlattice is the same as for ZnO substrate. This very good crystalline quality was also reflected in photoluminescence (PL) measurements, which revealed PL typical of superlattice. However, the PL of some structures showed that ZnMgO alloy was formed instead of the superlattice. PL excitation spectra allowed to determine the band gap values of the ZnO/MgO structures by observation of the PL from the ZnO substrate. Reasons for it are discussed. Transmission Electron Microscope imaging allows to compare both types of structures. Acknowledgements. The work was supported by the NCN project DEC-2014/15/B/ST3/04105 and by the EU 7th FP project REGPOT-CT-2013-316014 (EAgLE).

Resume : Tungstate compounds are successfully used and designed for various purposes. There are scintillator crystals, luminescent nanoparticles, laser crystal, etc. Design of luminescent spectra of tungstates and understanding of physical processes responsible for their changes are important tasks for future applications of these compounds. The RE doping as well as thermal treatment in oxygen-containing atmospheres decrease content of lead and oxygen vacancies, those are the most probable defects in the PWO crystals grown by Czochralski method. That is why, adding of RE impurities changes significantly the defect composition of the crystal lattice and can effect on centres responsible for matrix emission. We have carried out comparable investigation of spectral properties of thermally untreated and annealed at various temperatures for the PWO crystals doped with luminescent RE ions and undoped ones. In our study we use complex approach that includes spectral investigations and mathematical analysis of the matrix emission spectra. We have found correlations in behaviour of matrix emission and impurity emission and revealed competition in excitation of the red band of matrix emission and the RE3+ emission. Thus, the RE doping could be used for suppression of the red matrix emission, if it is undesired. We have also studied mechanisms of enhancement of the blue emission band in the RE-doped crystals that could improve spectral characteristics of the PWO scintillators.

Resume : The memristor phenomenon in BaTiO3 (BTO) based ferroelectric tunnel junctions has been studied extensively in recent years. However, the multistate switching in much thicker films remains unexplored, where the bulk can play dominant role in resistive switching behaviour. In this work, we present the memristive effect in pulsed laser deposited Au/BTO/Nb:SrTiO3 junctions with BTO thickness ranging from 100 nm to 400 nm. While the polarization loops attest the ferroelectricity, the read resistance (R) - write voltage (Vw) hysteresis loop displays continuous and stable resistance modulation after poling the devices by negative/positive voltage. The tunability (ROFF/RON resistance ratio) of these devices shows increasing trend with thickness and Vw. These devices have clear memory window with ratio of 102, excellent reproducibility and endurance. This behaviour can be explained by the modulation of extra barrier due to accumulation and depletion of charge carriers in Nb:STO near the interface.

Resume : A new double perovskite Ca2FeMnO6 with a layered arrangement of Mn4 and unusually high valence Fe4 was obtained by oxidizing the brownmillerite Ca2FeMnO5 with ozone at 200 °C. The low-temperature topotactic reaction kept the layered cation arrangement of the brownmillerite but oxidized Mn3 to Mn4 and Fe3 to Fe4 . Even with the two-dimensional layered arrangement, the instability of the unusually high valence Fe4 in Ca2FeMnO6, like that of the Fe4 in the perovskites CaFeO3 and CaCu3Fe4O12 with three-dimensional arrangements of Fe4 , was relieved by charge?disproportionation below 200 K, and the charge disproportionated Fe3 and Fe5 are ordered in a checkerboard manner in the two-dimensional Fe layers. The compound showed a magnetic transition at 95 K followed by the charge disproportionation transition, and the magnetic structure of Mn4 (S = 3/2), Fe3 (S = 5/2), and Fe5 (S = 3/2) is commensurate but non-collinear. The antiferromagnetic coupling of Fe3 and Fe5 spins in the FeO6 octahedral layer produces the ferrimagnetism of Ca2FeMnO6. The unique magnetic structure is described as a result of two-dimensional localization of the ligand holes with effective spins.

Resume : Recently, spinFET has received much attention. We have taken notice of alpha(a)-(In,Fe)2O3 (alpha means rhombohedral) as a potential magneto-semiconductor material for spin injection source. a-(In,Fe)2O3 is an alloy of a-In2O3 and a-Fe2O3, which are a semiconductor and a magnetic material, respectively. Additionally, room-temperature ferromagnetism of a-(In,Fe)2O3 films was reported in our previous research. However, their resistivity was as high as 104 Ohm cm, which was not suitable for spin injection source due to the possibility of impedance mismatches with channel layers. To decrease the resistance, we chose Sn4+ as electron donors and fabricated Sn-doped a-(In,Fe)2O3 films with various Sn doping concentrations (y) using mist CVD method. Resistivities of 0.27~4.7 Ohm cm were obtained with Sn-doped a-(In1-xFex)2O3 films with x was 0.7 to 1.0. As for the magnetic property, hysteresis curves of magnetization were acquired with Sn-doped films when magnetic field was applied at 300 K. The saturation magnetization of a-(In0.16Fe0.84)2O3 with y of 1.6% was 0.17 uB/Fe, which was much lower than the effective moment of Fe3+ (5.9 uB/Fe). It predicted that it showed typical magnetic mechanism caused by Dzyaloshinsky-Moriya interaction. At the point of spin injection, reducing spin scattering at the interface is necessary, highly-crystalline and lattice-matched interface between magnetic material layers and channel layers is demanded. We focused on a-(In,Ga)2O3 as a channel layer which can be lattice-matched with a-(In,Fe)2O3 perfectly. We will discuss the properties of fabricated a-(In,Ga)2O3 alloy films in the presentation.

Resume : Creating novel functionality utilizing abundant element is a major challenge in material research. 12CaO?7Al2O3(C12A7) with a crystal structure composed of 3D-connected sub-nanometer-sized cages entrapping oxygen ions as the counter anion is an insulator with a band gap of ~7eV. We have attempted to realize novel functionalities by replacing these oxygen ions with unconventional anions such as O-, H- and electron. C12A7:O- and C12A7:H- exhibit high oxidation power enough to oxidize Pt and light-induced insulator-electronic conductor conversion, respectively. The striking results were obtained for C12A7:e-, a first RT electride ; the conductivity at RT is changed from ~E-10 to E+3 Scm-1 and metal-superconductor transition occurs at low temperatures. The most unique property is its low work function of 2.4eV, comparable to metal potassium, but chemically stable. This property led to the finding of high performance catalyst for ammonia synthesis at ambient pressure when Ru nanoparticles are loaded on the surface of C12A7:e-. A series of finding on electro-active functionality in C12A7 demonstrated the power of nanostructure composed of abundant elements and may be regarded as a pioneering research of ?Element Strategy Initiative?, a Japan-original science and technology project. We expect the recent discovery of 2D-electride Ca2N and Y2C along with material design concept would open a new frontier. Recently, we have created amorphous C12A7:e thin films by sputtering. The resulting thin films are optically transparent but retain a low work function (~3.0eV). Such a unique properties meet the requirement for electron injection layers of inverted-type OLEDs. In this talk I show the recent advances in science and application of C12A7:e along with the background.

Resume : Within the last years several concepts were developed for creating environmentally friendly energy sources, such as photovoltaics, fuel cells, and photo-electrochemical cells, which are based on novel nanostructured morphologies and material combinations. For these energy conversion systems semiconducting oxide nanostructures are of great interest since they can be used as e.g. electrode materials or photocatalysts. The occurring interfaces and defects within the nanostructures are the key parameters which determine the functionality and limit charge carrier separation and charge transport. To improve the performance, the inorganic nanostructures can be modified by e.g. doping and/or by creating core-shell structures. Annealing treatments can be performed to minimize defects and to induce phase transformation leading to crystal modifications with a more suitable band gap. Two examples will be presented in this talk, Nb3O7(OH) [1] and TiO2 [2,3] nanowire arrays which can be applied as electrode material in dye sensitized hybrid solar cells and in light induced water-splitting devices. The nanostructures were synthesized hydrothermally. Different advanced transmission electron microscopy (TEM) techniques were applied to study the crystal structure, atomic arrangement, chemical composition, bonding behavior and band gap of the individual nanowires and networks on the atomic scale The results were correlated to the synthesis conditions and used to construct growth models. In addition, the functional properties of the Nb3O7(OH) and TiO2 nanostructures were measured in photo-electrochemical and dye sensitized hybrid solar cells. The properties like charge carrier mobility and lifetime were evaluated and further improved by using modified systems developed with the insights obtained by TEM [3]. [1] S. B. Betzler, A. Wisnet, B. Breitbach, C. Mitterbauer, J. Weickert, L. Schmidt-Mende, and C. Scheu, J. Mater. Chem. A, 2014, 2, 12005 [2] A. Wisnet, S. B. Betzler, R. V. Zucker, J. A. Dorman, P. Wagatha, S. Matich, E.Okunishi, L. Schmidt-Mende, and C. Scheu, Cryst. Growth & Design, 2014, 14(9), 4658. [3] A. Wisnet, K. Bader, S. B. Betzler, M. Handloser, J. Weickert, A. Hartschuh, L. Schmidt-Mende, C. Scheu, J. A. Dorman., Adv. Funct. Mater., 2015, 25, 2601. [4] The author would like to thank the colleagues and co-workers who contributed to this work and the German Research Foundation (DFG) for financial support.

Resume : Perovskite oxides have received significant attention in recent years, in part due to their ability to generate very high density two-dimensional electron gases (2DEGs) at interfaces between polar and nonpolar materials [1]. Most of these complex oxides have degenerate conduction bands composed of transition-metal d states, leading to large effective masses and low mobilities, a detriment for electronic applications. BaSnO3 has emerged as an alternative: it crystallizes in the perovskite structure but its conduction band is nondegenerate and composed of Sn s states, resulting in high mobility, favorable for a transparent conductor. I will show how cutting-edge first-principles calculations shed light on the multiple aspects of this problem: band alignment and confinement of the 2DEG [1,2], mobility [3], and for applications requiring transparency, fundamental limits on absorption [4]. Work performed in collaboration with B. Himmetoglu, A. Janotti, E. Kioupakis, K. Krishnaswamy, and H. Peelaers, and supported by ONR, DOE, LEAST, and NSF. [1] L. Bjaalie, B. Himmetoglu, L. Weston, A. Janotti and C. G. Van de Walle, New J. Phys. 16, 025005 (2014). [2] K. Krishnaswamy, L. Bjaalie, B. Himmetoglu, A. Janotti, L. Gordon, and C. G. Van de Walle, Appl. Phys. Lett. 108, 083501 (2016). [3] B. Himmetoglu, A. Janotti, H. Peelaers, A. Alkauskas, and C. G. Van de Walle, Phys. Rev. B 90, 241204(R) (2014). [4] H. Peelaers, E. Kioupakis, and C.G. Van de Walle, Phys. Rev. B 92, 235201 (2015).

Resume : The stoichiometry of metal cations in complex oxides has a major impact on properties and on their application as functional materials. Synthetic methods must therefore aim at controlling composition. Atomic layer deposition (ALD) is a technique for depositing nanoscale thin films with unparalleled control of thickness, uniformity and conformality. However the control of stoichiometry is not so straightforward. In this talk we show how the cyclic nature of ALD can be exploited to formulate a 'rule of mixtures' for the stoichiometry of ternary oxides in thin film form. We then show how experimental deviations from this rule can be related to chemical reactivity of particular ALD precursors, computed at first principles level (1). This reveals what reactions are taking place at interfaces at the nanoscale. A second major factor affecting oxide properties is morphology, but so far there is little understanding of why certain ALD processes give amorphous films while others give a certain crystal phase. We investigate this question through first principles simulations of the likely surface structures that result from ALD reactions. The system that we study is the deposition of alumina from trimethylaluminium with water or oxygen plasma as co-reagent, where recent data from synchrotron experiments suggest that a nanocrystalline phase is present in the 'amorphous' as-deposited film, which directs the morphology towards the theta-alumina phase on annealing. Our results show that theta-like structural motifs are associated with the incorporation of protons into the film during growth.

Resume : It is well known that Pulsed Laser Deposition (PLD) is a very flexible and versatile technique allowing fast optimization of new and complex material thin films. Among these are Pb(Zr,Ti)O3, PMN-PT, BaTiO3, LiNbO3 and other materials of interest for applications in piezo-MEMS. Furthermore, the unique features of PLD allow for the integration of ?Beyond Moore? materials in CMOS and new devices. Using Solmates PLD platform, such devices become now readily available for commercialization. The robust and reliable hardware allows uniform thin film deposition up to 200 mm diameter with high process reproducibility. The process can therefore be easily scaled towards as (pilot) production. In this contribution, the focus will be on wafer scale integration of Solmates new generation high performance PZT thin films. By interface engineering, we demonstrate the possible production of epitaxial piezo thin films on silicon wafers by means of TiN electrodes, buffer layers and nanosheets. Comparison to state of the art textured thin films will be shown. Excellent stability of the electrical and piezoelectric properties of those new films is shown and compared to the properties of state of the art textured PZT thin films grown on standard platinum.

Resume : Lead-free oxides with perovskite structure are being intensively studied in order to replace widely used PZT-based materials. Bismuth-containing solid solutions on the base of BiFeO3 and (Na0.5Bi0.5)TiO3 close to the Morphotropic Phase Boundaries reveal high TC values, and may be used as basic oxides for the development of new piezoelectric materials. We studied ceramic solid solutions in the systems (1-y)[(1-x)BiFeO3 - xBaTiO3] - yBi(Mg0.5Ti0.5)O3 with x=0.2, y=0 - 0.2 (I), (1-y)[(1-x)(Na0.5Bi0.5)TiO3-x(K0.5Bi0.5)TiO3]-yBiFeO3 with x=0.15, y=0 - 0.6 (II), and (1-y)[(1-x)(Na0.5Bi0.5)TiO3-xBaTiO3]- yBi(Mg0.5Ti0.5)O3 with x=0.2, y=0 - 0.2 (III). To improve sintering and compensate Bi oxide losses during sintering, over stoichiometric additives KCl, LiF and Bi2O3 were used. The samples were prepared by the two-step solid-state reaction method at temperatures 900 ? 1350 K. Crystal structure parameters, microstructure, phase transitions, dielectric and ferroelectric properties were characterized by the X-ray Diffraction, Scanning Electron Microscopy, Second Harmonic Generation, and Dielectric Spectroscopy methods. The formation of pure perovskite solid solutions with varying content of rhombohedral, tetragonal and pseudocubic phases depending on composition and preparation conditions was observed in the systems I - III. The influence of phase content and microstructure on ferroelectric properties, Curie temperature TC value and effects of dielectric relaxation was revealed, prospects for new piezoelectric materials development confirmed. Acknowledgment. The work was supported by the Russian Fund for Basic Research (Project 15-03-03269).

Resume : The most studied electrodes for rechargeable Li-ion batteries are LiCoO2 and LiMn2O4 which consist of transition metals that have unpaired electrons in d-shell. Depending on the splitting energy between eg and t2g, spin state of these transition metals can be changed leading to structural modifications such as Jahn-Teller distortion. Magnetic properties can be tailored via substitution, pressure, temperature, applied magnetic field or crystal field. Especially, during charge and discharge process, due to changes in the crystal structure, crystal field may change causing changes in spin state of the transition metal. We report the effects of Boron substitution on magnetic, structural and electrochemical properties of LiCoO2 and LiMn2O4 and investigate the correlations between these properties. We found that in both cases, small amount of B substitution improves the structural stability and enhances the cycling performance of these cathode materials. Keywords: Li-ion batteries, magnetic properties, spin transition Acknowledgement: This study was supported by TÜB?TAK (The Scientific and Technical Research Council of Turkey) under grant no TUBITAK 112M487

Resume : Although defects might be seen as detrimental, in complex oxides they may present an opportunity to enhance particular properties, or even engineer new ones. An archetypal example is the high-Tc superconductor YBa2Cu3O7?? (YBCO), where defects are indispensable to pin quantized vortices in the presence of magnetic fields. Therefore, determining the atomic structure of defects is critical to unravel and control their effect on the physical properties. In this talk, we will do precisely that with an unforeseen complex point defect that leads to an unexpected formation of ferromagnetic clusters embedded within a superconductor. The commonest YBCO defect comprises the doubling of Cu-O chains between Ba-O planes, a ubiquitous intergrowth regardless of the deposition technique. Here, we will unclothe the true nature of this defect using a combination of experiments and theory to provide a complete picture of the structure and chemistry of these intergrowths at the atomic-scale and their effect on the electronic and magnetic properties of YBCO. First, we will show, by means of scanning transmission electron microscopy (STEM), how the system solves the local off-stoichiometry induced by the extra Cu-O chain, removing half of the Cu atoms in selected chains. Secondly, we will show using density functional theory (DFT) how the complex structure of these intergrowths affects the electronic properties, and yields a magnetization density that extends into the neighboring Cu-O planes. Finally, we will present X-ray magnetic circular dichroism (XMCD) spectroscopy results, which provide evidence of the theoretically predicted Cu magnetic moments and the presence of a dilute network of magnetic defects within the high-Tc superconducting state.

Resume : Hydrogen, the smallest and the lightest one among atomic elements, is reversibly incorporated into the interstitial site of vanadium dioxide (VO2), a 3d1 correlated metal oxide undergoing metal-insulator transition at ~ 68 °C, and then induces dramatic electronic phase modulation. It is widely reported that hydrogen stabilizes the metallic phase in low doping regime, but the understanding of hydrogen in high doping regime is very limited so far due to the difficulty of heavy hydrogenation. Here, we present that hydrogenation can be achieved up to two hydrogen atoms per VO2 unit cell, and hydrogen is reversibly absorbed into and released out of VO2 without destroying the lattice framework due to the low temperature annealing process. More importantly, this massive hydrogenation process allows to elucidate phase modulation of vanadium oxyhydride (HxVO2), remarkably demonstrating two-step insulator (VO2) – metal (HxVO2) – insulator (HVO2) phase transition using in-situ electrical measurement. Our finding opens up the potential application for novel hydrogen storage and the possibility of reversible and dynamic control of topotactic phase transition in VO2. The author is grateful to Hyojin Yoon, Hyunah Kwon, Prof. Jong-Kyu Kim (POSTECH), Prof. Minseok Choi (Inha University), Dr. Si-Young Choi (KIMS), Dr. Kyuwook Ihm (PAL) for helpful discussions and collaboration.

Resume : Lithium-Ion batteries are important devices for present and future energy storage, offering high energy density and durability. Positive electrode (cathode) materials are predominantly transition metal oxides containing lithium, such as layered oxides or oxides with spinel structure. The electronic (and ionic) structure of these materials is a key for their properties, such as electrode potential, degradation and reactivity. This contribution gives an overview of surface science investigations on battery materials, addressing both electronic structure of layered-oxide cathode materials and cathode-electrolyte interface formation. In a surface science approach, well-defined surfaces/interfaces are prepared and analyzed with surface sensitive analytical methods such as photoelectron spectroscopy (XPS, UPS). Surface science offers the possibility to analyze the electronic and chemical structure of surfaces and interfaces, allowing conclusions on the electronic structure of the bulk, on reactivity with other phases, and on electrochemical interface formation. After a brief introduction to the methodology as well as fundamental phenomena [1], the contribution focuses on the role of electronic structure and electric double layer for electrode degradation and surface layer formation [2]. Charge transfer (electrons and ions) and defect formation will be discussed on basis of energy level diagrams extracted from experimental data. The results indicate that presently available concepts should be improved. 1. Hausbrand, R., D. Becker, and W. Jaegermann, Progress in Solid State Chemistry, 2014. 42(4): p. 175-183. 2. Hausbrand, R., et al., Materials Science and Engineering B, 2015. 192: p. 3-25.

Resume : Dye-sensitized solar cells (DSSC) and perovskite solar cells (PSC) are one of the most promising systems belonging to the so called emerging photovoltaics, with the best laboratory efficiencies exceeding 14% for DSSC and 21% for PSC. An important role in the architecture of these solar cells is played by different metal oxide semiconductors, which are used as charge selective and charge transporting materials. The most frequently applied oxides are TiO2, ZnO, SnO, NiO, used for charge transport, as well as ZrO2 and Al2O3 used as thin blocking layers. The past achievements, present studies and future prospects of the above oxide in DSSC and PSC will be presented. Special attention will be paid on the dynamics of charge separation processes taking place at the interfaces between light absorbers and metal-oxide materials. A few examples of time-resolved studies from our laboratory will be shown, illustrating the complex electron transfer pathways in solar cells, taking place on the time scales from femtoseconds to seconds. Different metal oxide materials and the different morphology of their nanostructures (planar layers, nanoparticles, nanowires) will be compared to discuss their impact on the global performance of DSSC and PSC.

Resume : The delafossites are a series of layered compounds with triangular lattices similar to that of NaCoO2 but with a different stacking sequence along the c axis. They are host to intriguing magnetic insulators and semimetals, as well as metals such as PdCoO2, PtCoO2, PdCrO2 and PdRhO2. The properties of these metals are remarkable. Although they are strongly two-dimensional, their room temperature conductivity is higher per carrier than that of any element, and PdCoO2 crystals can have a low temperature resistivity of only a few n?cm, corresponding to mean free paths of tens of microns. Our group is attempting on the one had to accept this huge conductivity and profit from it, and on the other hand to investigate it, concentrating on spectroscopic properties and electronic structure calculations.

Resume : Over the past three decades we have used a multifaceted approach that includes synthesis, thermodynamics, inelastic and quasielastic neutron scattering (INS and QENS) and modeling methods to study the physicochemical properties of thin molecular films adsorbed on bare and metal decorated metal oxide (MO) surfaces, such as MgO, ZnO, SBA-15 silica, and alumina. Our main objective is to use these investigations to understand how the microscopic behavior of these adsorbed films are changed when they are confined at pure or nm sized metal decorated MO interfaces. Furthermore, we strive to aid in the development of robust intermolecular potentials that can be employed to accurately model the potential energy surfaces that can improve our knowledge of surface mediated chemical reactions and to develop novel energy materials to store, separate and transform atomic and molecular species. We will select examples from recent studies of normal alkanes on MgO surfaces, hydrogen adsorption and spillover on Pd decorated ZnO and the hydrogenation of cinnamaldehyde to cinnamyl alcohol to illustrate the power of this combined microscopic and macroscopic approach.

Resume : Zinc oxide is a II-VI semiconducting material nowadays widely tested as a good candidate for numerous electronic and optoelectronic applications, including the transparent electrodes for solar cells, non-volatile cross-bar memories, gas sensors, radiation (ultraviolet) detectors etc. These devices are based on good quality, stable in time rectifying junctions. However, in order to increase their rectification ratio to the possibly highest level, the knowledge related to defects in ZnO as well as the transport phenomena is indispensable. Therefore, during the lecture three types of the ZnO?based structures will be presented, i.e. the n-ZnO/p-GaN heterojunction, Ag/HfO2/ZnO/ITO Schottky diodes and ZnO:N/Al2O3/ZnO homojunctions. Noteworthy, for the ZnO growth the low temperature Atomic Layer Deposition (ALD) process was used. In the case of p-n heterostucture, the investigations concerning the analysis of trap levels in the device will be discussed, while in the latter two cases the role of thin dielectric interlayer in the rectifiers-transport properties will be analyzed in frames of the differential approach. This, in turn, will allow to define the main carriers injection/recombination regimes in such structures, showing the applicability of ALD-ZnO-based devices in the demanding field of modern electronics. The research was supported by the grant of the National Science Center of Poland (decision number: DEC?2013/09/D/ST5/03879).

Resume : Most of the existing photovoltaic (PV) solar cells are already optimized in terms of their absorption and conversion efficiency, however any strategy that can help to raise their efficiency is welcome, especially if it is cheap and does not require any modification of the solar cell fabrication technology. One possibility to increase solar cell’s efficiency is the use of a material that could convert the high energy photons from the sun spectrum, namely UV and blue light, which are otherwise inefficiently absorbed by the amorphous Si, CdTe, CIGS and organic PV cells, and re-emit them as lower energy photons, for which the conversion efficiency of these cells is optimal. This so-called “down-shifting”. We study down-shifting materials based on ZnO nanoparticles. It naturally absorbs the blue and UV light thanks to a wide band gap of about 3.37 eV and it can also emit visible light, from yellow to red, depending on the nature of the crystalline and surface defects involved in the emission process. We present a quick and convenient chemical solution approach to get unique mesospheric self-assembly hybrid ZnO system with intense photoluminescent quantum yield of 40-75 % and stable visible emissions. Furthermore, the possibility of application of other ZnO nanostructures, namely zinc oxide nanowires, in gas sensors, is presented. Their excitonic and visible emission is studied in the presence of gas vapors and the results demonstrate the change of the visible photoluminescence of ZnO nanowire array and that the material is able to adsorb gases.

Resume : The preparation of good-quality nanocrystals of highly refractory compounds requires original methods to achieve high crystallinity while preserving the nanometric size. Glycothermal synthesis, consisting in synthesizing inorganic compounds in glycols under mild thermal conditions (~300°C) and under autogenous pressure, has been explored with success. Ce3+-doped Y3Al5O12 (YAG) nanoparticles were synthesized with an average size around 50 nm and a high colloidal stability. These particles present a broad emission band centered at 537 nm under a 457-nm excitation, which makes them appropriate nanophosphors for LED-based white-light generation. However, the polycrystalline character of the particles is responsible for their poor photostability due to a Ce3+ to Ce4+ oxidation. We present here our study on the formation mechanism of YAG nanoparticles based on photoluminescence measurements and transmission electron microscopy images. This allows obtaining single-crystal Ce-doped YAG nanoparticles. We extend our work to other garnet materials and succeed in preparing luminescent Ce3+-doped Gd3Sc2Al3O12 (GSAG) nanoparticles, with an emission band centered at 550 nm. Thanks to its large unit cell parameter, GSAG matrix is able to incorporate 5 times more Ce3+ ions (15 mol.%) than YAG matrix (3 mol.%), significantly increasing light absorption.

Resume : Many functional materials are traditionally synthesized by slow reaction processes that are energy and time consuming. In the present world there is strong demand on development of modern materials and materials processing methods that could offer rapid reaction rates, energy efficiency and be environmentally safe. Perovskite oxide ceramics have found wide applications in energy storage capacitors, electromechanical transducers and piezoelectric, and ferroelectric devices. The conventional methods to prepare Perovskite oxide ceramics are time and energy consuming. The objective of the present study is to investigate the application of an Electric Discharge Assisted Mechanical Milling (EDAMM)[1] technique to synthesize various Perovskite oxide ceramics, in particular formation of nano-phases and characterize the structural, physical, and optical properties. By using EDAMM, high purity single phase multi-element oxides can be formed in as little as 0.1% of the processing time required in conventional solid-state techniques. An even more important feature of EDAMM is that the crystallite size of the synthesized compound is able to be reduced to nanometer size, by careful selection of process parameters. We use EDAMM for (i) synthesis of oxides from elemental powders by oxidation in oxygen plasma and for (ii) synthesis of single phase multi element oxides from pre-mixed oxides as starting materials. This presentation provides an overview of recent development of EDAMM method and it’s application in rapid synthesis of Perovskite ABO3 type oxide ceramics such as BaHfO3, BaTiO3, PbZrO3 and others. [1] Nature, 419,(2002)147-151

Resume : Layers and nanostructures of titanium dioxide (TiO2) have found several practical applications for paints, sunscreens, protecting layers, photocatalysis, water splitting or photovoltaics. The applicability of this material depends on its crystalline phase. Among the three possible crystal structures of TiO2, anatase is commonly used for photocatalysis. TiO2 with anatase structure, however, can undergo transition to the rutile phase, which is accelerated by the heat treatment at temperatures between 450 and 1200 °C. In our work, we obtained undoped and nitrogen-doped titanium dioxide (TiO2:N) films, grown by atomic layer deposition, with a stable anatase structure. The as-grown amorphous films were deposited at 120 °C on single crystalline Si substrates. After deposition samples were annealed by flash lamp annealing for 20 ms in nitrogen ambient. Annealed films show anatase structure which is stable up to anneal temperatures close to the melting point of Si (< 1400 °C). This was confirmed by ?-Raman and x-ray diffraction studies. We analyze the anatase crystal structure of the annealed TiO2:N films as a function of the annealing energy density and the N concentration. The investigations are complemented by temperature-dependent photoluminescence measurements. The work was partially supported by the EU 7th Framework Programme project REGPOT-CT-2013-316014 (EAgLE).

Resume : Bilayer films of nanostructured vanadium dioxide and titanium dioxide have been deposited on glass substrates from electric field aerosol assisted chemical vapour deposition (AACVD) and sol-gel spin coating. Their thermochromic and self-cleaning properties have been investigated. VO2 layers were deposited under the influence of various strength electric fields at 430 °C. Thin films of TiO2 were deposited on the VO2 by sol-gel and spin coating and subsequent annealed at 600 °C. The plain VO2 films were yellow/brown in colour; while TiO2 layers introduced a light pink colour. VO2/TiO2 bilayer films exhibited a stronger adherence to the substrate, compared to plain VO2 films as determined by the adhesive-tape peel test and could not be scratched by a scalpel. The deposited films were analysed and characterised using scanning electron microscopy, X-ray diffraction, variable temperature UV/Vis/NIR spectroscopy and FTIR. Introduction of additional layers resulted in a dramatic increase in the visible light transmission by up to 30 % compared to a plain VO2 sample. VO2/TiO2 bilayer films showed a higher transmittance modulation in the near infrared of up to 20% compared to bare VO2 films upon the thermochromic transition. These films had multifunctional properties combining thermochromic properties and self-cleaning behaviour when exposed to UV light. After 30 min irradiation, 50 % of the stearic acid destroyed, while upon 120 min UV irradiation, the complete destruction of stearic acid was observed. Keywords: Thin films, Vanadium dioxide, aerosol assisted chemical vapour deposition, titanium dioxide, self-cleaning.

Resume : Due to the development of nanotechnology in the field of energy correlated with eco-responsible label, the research for new high-performance ecologic materials takes place as a real societal challenge. In particular, lead-based piezo-/ferroelectric thin films integrated in many electronic devices have to be replaced. In this context, the discovery of new lead-free materials with functional properties has become essential. In this context, our study was focused on the growth of new lead-free oxides such as A2O3-WO3 (A = Bi2 +, La3 +, Ln3 +). In this work, Ln2WO6 (Ln = La and Nd) thin films have been grown on (001)-oriented SrTiO3 substrates by pulsed laser deposition. The structural properties were systematically investigated by High Resolution X-ray Diffraction and Transmission Electron Microscopy (TEM). The stabilization of the high temperature allotropic variety of the material was demonstrated, and a growth of high-quality epitaxial c-axis is successfully obtained for the films. Then, piezo- and ferro-electricity was evidenced into the Ln2WO6 layers on the nanoscale by Piezo-Force Microscopy analysis.[1, 2] As-grown ferroelectric domain patterns were recorded, while poling experiments and remnant piezoloops measurements have demonstrated local switching behavior and electromechanical activity. Besides, piezo-/ferroelectric signals were locally detected by an original in situ combination of TEM and Scanning Tunneling Microscopy techniques. In addition, leakage currents were characterized at the surface of the films by means of the conductive mode of the Atomic Force Microscopy. These findings pave the way to new eco-responsible multifunctional oxide thin-films dedicated to advanced electronic devices. [1] T. Carlier et al., ACS Applied Materials & Interfaces 7, 24409−24418 (2015). [2] T. Carlier et al., Thin Solid Films, in press. doi:10.1016/j.tsf.2016.02.054.

Resume : In surface science and model catalysis, cerium oxide (ceria) is often grown as an ultra-thin film on a metal substrate to understand fundamental mechanisms involved in surface chemistry processes. However, ultra-thin films do not have the contribution of bulk ceria underneath that is often needed for the functionality of a reducible oxide based device. I discuss the surface morphology of CeO2(111) single crystals and silicon supported ceria thick ?lms, both having substantial oxygen storage capacity. Surface morphology and surface atomic structure are investigated by non-contact atomic force microscopy (NC-AFM) and Kelvin probe force microscopy (KPFM) for various annealing conditions. The surface stoichiomentry is determined by X-ray photoelectron spectroscopy (XPS). Annealing bulk samples at 1100 K results in small terraces with rounded ledges and steps with predominantly one O?Ce?O triple layer height while annealing at 1200 K produces well-ordered straight step edges in a hexagonal motif and step bunching. By epitaxial film growth, a metastable ceria surface with a morphology dominated by terraced pyramids with an oriented triangular base is produced. Upon heating the film, the morphology and topographic details of ?lms are similar to the ones of the surface of a bulk crystal, however, ?lms are destroyed upon heating them above 1100 K. By atomic resolution imaging, we identify different states of surface reduction related to the thermal treatment of the surface. Exposure to oxygen allows a re-oxidation of an initially reduced surface and yields an atomically flat, fully stoichiometric CeO2 surface.

Resume : The surfaces of transition metal oxides are quite often not just bulk-like terminated but chemically and geometrically reconstructed. There can be vacancies within either the oxygen or cation lattice as well as site switches towards interstitial positions. Even a completely different crystal structure and/or stoichiometry can develop in the near-surface region. These structural variations are not necessarily restricted to the very surface but can also occur - even exclusively - in the subsurface region and by that remain largely hidden to imaging methods like scanning tunneling microscopy. For ultra-thin oxide films grown on reactive substrates the situation further complicates by the competition of binding forces within the film and towards the substrate. This may lead to Moire-type films with a laterally modulated structure. Even more, the modification of the substrate interaction, e.g. by introducing an only atomically thick buffer layer of chemically different material, can alter the growth orientation for thicker films. Finally, in the sub-monolayer regime unforeseen hybrid structures between oxide and substrate can form in a self-organized way exhibiting unique structural, chemical, and magnetical properties. The talk will demonstrate the capabilities an limitations of today?s surface low-energy electron structure determinations. Using numerous examples it will be shown that not only the principal structural model can be revealed, but also its parameters can be determined with picometer accuracy. This, however, requires great preparational and methodical efforts, which in some cases might be hard or even impossible to achieve and thus will be the major challenge for future analyses.

Resume : We present microstructure evolution in depleted uranium dioxide nuclear fuel pellet, fabricated from powder, where the sample was sintered at 1400?C for 12 hours to achieve a theoretical density > 95%. Microstructure of a cylindrical section of the UO2 pellet with dimensions ~0.3*0.3*1.5 mm3 was machined and characterized using high-energy X-ray diffraction microscopy (HEDM) and computed micro-tomography (?-CT) techniques. The initial microstructure was measured in the as-sintered state, and the sample was then annealed ex-situ at 2200? C in an induction furnace for 2.6 hours in an ultra-high-purity argon gas environment. The non-destructive nature of HEDM and ?-CT measurements enabled a second measurement of the microstructure following the annealing. IceNine and Midas software were used for reconstructing microstructure information from diffraction data and Recon was used for tomographic density map reconstruction, of both initial and final states of the specimen. The initial measured microstructure was then used as an input to the Monte Carlo grain growth simulation based on the Potts model. Model parameters were calibrated using the measured microstructure obtained after heat-treatment. Microstructure evolution, grain size distribution, and texture change were quantified and observation was compared with Monte Carlo simulation for grain growth where possible.

Resume : Chemical characterization of surface and interface are important in materials science in order to understand the underlying physical properties. This is particularly true for strongly correlated electron systems like perovskite based materials where electronic correlations, structure, strain, intermixing, oxygen deficiency, surface reconstructions, are the means to control the properties of oxide thin films and heterostructures . X-Ray photoelectron spectroscopy (XPS) is a powerful tool to investigate the chemical composition and the chemical environment of the atoms situated at surfaces and is a direct measurement of band offsets. Nevertheless, the analysed depth is between 1 to 10 nm and surface contaminants (water, adsorbed molecules) at the surface could provide a non-negligible contribution which modifies the analysis. In order to obtain clean surface, thin films are commonly analysed just after deposition or ion bombardment is used to clean and profile the surfaces. However, the traditional ion etching with mono-atomic argon ions tends to modify the materials, challenging the analysis. We will present a method for surface cleaning and profiling with cluster ion gun where the energy per atom is much less important based on model system like SrTiO3. By comparison with monoatomic etching, this cluster ion etching appears to be gentler for any surfaces, limiting the creation of oxygen vacancies, the lowering of oxidation states of titanium and preserving the cationic stoichiometry. Due to its unique characteristics, first results on the LaAlO3/SrTiO3 interface will also be presented and we will show that the cluster ion sputtering technique offers new insights in the depth-resolved chemical analysis of buried oxide interface

Resume : Transition metal oxides are the key materials for future energy-efficient electronics in particular for logic and memory devices based on the resistive switching effect. Since the switching effect is related to a local reaction of the oxide to an external gradient of the electrical and chemical potential, we investigate the influence of electrochemical stress on the prototype perovskite SrTiO3. We demonstrate that upon application of a DC voltage under UHV conditions, the surface region of alkaline earth titanates transforms into lower binary oxides with nanoporous structure. By means of IRT, XPS, EDX, HR-TEM, and LC-AFM we present that this transformation takes place at relatively low temperatures and is related to a fundamental macroscopic decomposition of the oxide changing the physical properties of the surface region up to depths of several tens of micrometers. Our results demonstrate that in ternary oxides phase transformations can be induced by gradients of the electrochemical potential using a technologically simple method, which not only opens up a new way for tailoring micro layers of functional transition metal oxides with bespoke properties for optical, electronic and chemical applications but also demonstrates the mutability of metal oxides under electrical stress being relevant for the understanding of the electroforming and switching process in novel memristive devices.

Resume : Glass-ceramics materials composed of the glass matrix and embedded micro/nanocrystals possesse the host property like glass and keeps the optical (luminescence) properties of the micro/nanocrystal phosphors. Developing of the transparent inorganic glass?ceramics phosphor converters (PC) is an alternative way to conventional polymer-based PC and they are able to replace them, especially if speak about high-power WLEDs. The low temperature (melting temperature of un-doped glass is 1277 ?) glass-ceramics based on lithium- germanium oxides Li2O-x(GeO2) (LGO) as optical materials practically had not been studied before. Recently the authors have made and measured characteristics of the LGO single crystals, doped with some ions that inspired us in our intention to take luminescence from similar micro/nanocrystals embedded into LGO glass matrix. The technologies of lithium germanate glass and nanostructured glass ceramics producing have been developed by us. The structure of the LGO crystals is of framework type that is formed by (rigid) germanium-oxygen tetrahedra and octahedra. Such structural elements are suitable for doping with ions of transition groups (Fe and La groups), that state Li2O-x(GeO2) compounds as attractive for new optical materials elaboration. So, we have shown after that multifunctional LGO glass-ceramics (e.g. capable to transit in ferroelectric state) is a promising optical material and particularly it can help to solve tasks of light transformation The doped with the Cr and Eu ions LGO glass-ceramics layers were made and studied. In order to decrease the melting temperature to influence directly the absorption and luminescence spectral characteristics the addition of bismuth oxide, Bi2O3, to starting pre-cursor oxide composition was applied.