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Revealing whether dislocations accelerate oxygen ion transport is important for providing abilities in tuning the ionic conductivity of ceramic materials. In this study, we report how dislocations affect oxygen ion diffusion in Sr-doped LaMnO3 (LSM), a model perovskite oxide that serves in energy conversion technologies. LSM epitaxial thin films with thicknesses ranging from 10 nm to more than 100 nm were prepared by pulsed laser deposition on single-crystal LaAlO3 and SrTiO3 substrates. The lattice mismatch between the film and substrates induces compressive or tensile in-plane strain in the LSM layers. This lattice strain is partially reduced by dislocations, especially in the LSM films on LaAlO3. Oxygen isotope exchange measured by secondary ion mass spectrometry revealed the existence of at least two very different diffusion coefficients in the LSM films on LaAlO3. The diffusion profiles can be quantitatively explained by the existence of fast oxygen ion diffusion along threading dislocations that is faster by up to 3 orders of magnitude compared to that in LSM bulk.

Isotope exchange depth profiling and electrochemical impedance spectroscopy are usually regarded as complementary tools for measuring the surface oxygen exchange activity of mixed conducting oxides, for example used in solid oxide fuel cell (SOFC) electrodes. Only very few studies compared electrical (k(q)) and tracer (k*) exchange coefficients of solid-gas interfaces measured under identical conditions. The 1:1 correlation between k(q) and k* often made is thus more an assumption than experimentally verified. In this study it is shown that the measured rates of electrical and tracer exchange of oxygen may strongly differ. Simultaneous acquisition of k(q) and k* on La0.6Sr0.4FeO3-δ and SrTi0.3Fe0.7O3-δ thin film electrodes revealed that k*100 k(q) in humid oxidizing ((16)O2 + H2(18)O) and humid reducing (H2 + H2(18)O) atmospheres. These results are explained by fast water adsorption and dissociation on surface oxygen vacancies, forming two surface hydroxyl groups. Hence, interpreting experimentally determined k* values in terms of electrochemically relevant oxygen exchange is not straightforward.

International audience; We employed operando anomalous surface X-ray diffraction to investigate the buried interface between the cathode and the electrolyte of a model solid oxide fuel cell with atomic resolution. The cell was studied under different oxygen pressures at elevated temperatures and polarizations by external potential control. Making use of anomalous X-ray diffraction effects at the Y and Zr K-edges allowed us to resolve the interfacial structure and chemical composition of a (100)-oriented, 9.5 mol % yttria-stabilized zirconia (YSZ) single crystal electrolyte below a La0.6Sr0.4CoO3-delta (LSC) electrode. We observe yttrium segregation toward the YSZ/LSC electrolyte/electrode interface under reducing conditions. Under oxidizing conditions, the interface becomes Y depleted. The yttrium segregation is corroborated by an enhanced outward relaxation of the YSZ interfacial metal ion as layer. At the same time, an increase in point defect concentration in the electrolyte at the interface was observed, as evidenced by reduced YSZ crystallographic site occupancies for the cations as well as the oxygen ions. Such changes in composition are expected to strongly influence the oxygen ion transport through this interface which plays an important role for the performance of solid oxide fuel cells. The structure of the interface is compared to the bare YSZ(100) surface structure near the microelectrode under identical conditions and to the structure of the YSZ(100) surface prepared under ultrahigh vacuum conditions

Many efforts are being made to tune perovskite thin film cathodes toward improving their oxygen reduction kinetics and thereby improving overall solid oxide fuel cell performance. One approach is to enhance oxygen diffusion via introduction of larger concentrations of grain boundaries during thin film growth. While such grain boundary engineering has been shown to enhance ionic transport and surface reaction kinetics in some cases, little attention has been paid on its corresponding influence on electronic conductivity. To provide insights into the role of grain boundaries and their contribution to the cathode performance, we have investigated separately the electronic and ionic conductivity of La0.8Sr0.2MnO3(LSM) thin films by Van-der-Pauw and18O tracer exchange measurements respectively, as well as their combined contributions by electrochemical impedance spectroscopy. All three types of experiments were performed on the same kind of samples with varying LSM microstructure to illustrate the effects of grain boundaries on both electron and ion conduction. Correlations between active electrode area and microstructure-dependent partial conductivities are presented. The findings can also be used for optimizing current collector spacing in thin film solid oxide fuel cells. Keywords: grain boundary engineering; LSM; thin film, United States. Department of Energy (Grant DE-SC0002633)

Protection of Public Interest in Civil Procedure Protection of public interest is the procedure which safeguards the most significant public value. Even though there might be an impression that this doctrine has been widely discussed and as a result it may lack scientific sensitivity, the author does not agree with that. The significance and characteristics of public interest are challenges themselves and as a consequence, they determine the importance of continuous investigation in the field of public interest. Legal regulation changes, inconsistency of judicial practice and lack of systematic analysis of specific doctrines are of great importance for this investigation and reveal a wide range of research problems. However, the most important aspect of this research is that the author does not limit himself only to the field of the usual public interest research (for example, the doctrine of public interest or the concept of public interest). On the contrary, the author chooses new directions meanwhile paying attention to the important issues that previously have not been analysed. As a result, the problem of justifying the efficiency, the prosecutor's supervisory role and the legal basis of the state and municipalities are the areas that demonstrate the uniqueness of this very research. On the other hand, the researcher is not only a passive observer. After analysing scientific positions, the author looks for new arguments in order to deny or support the theories and discuss and justify his own position. Finally, the researcher comes to the conclusions that allow one to decide on: 1) the prevailing concept of the shared values in Lithuania and the possible duality of the concepts; 2) the criterion on the justification of the public interest; 3) the approval of prosecutor´s supervisory role; 4) the duties of the state and municipalities; 5) the groundlessness of the court, as an entity, protecting the public interest; and other aspects important for the protection of public interest in civil proceedings.

The different properties of acceptor-doped (hard) and donor-doped (soft) lead zirconate titanate (PZT) ceramics are often attributed to different amounts of oxygen vacancies introduced by the dopant. Acceptor doping is believed to cause high oxygen vacancy concentrations, while donors are expected to strongly suppress their amount. In this study, La3+ donor-doped, Fe3+ acceptor-doped and La3+/Fe3+-co-doped PZT samples were investigated by oxygen tracer exchange and electrochemical impedance spectroscopy in order to analyse the effect of doping on oxygen vacancy concentrations. Relative changes in the tracer diffusion coefficients for different doping and quantitative relations between defect concentrations allowed estimates of oxygen vacancy concentrations. Donor doping does not completely suppress the formation of oxygen vacancies; rather, it concentrates them in the grain boundary region. Acceptor doping enhances the amount of oxygen vacancies but estimates suggest that bulk concentrations are still in the ppm range, even for 1% acceptor doping. Trapped holes might thus considerably contribute to the charge balancing of the acceptor dopants. This could also be of relevance in understanding the properties of hard and soft PZT.

In this study, the contribution of grain boundaries to the oxygen reduction and diffusion kinetics of La[subscript 0.8]Sr[subscript 0.2]MnO[subscript 3] (LSM) thin films is investigated. Polycrystalline LSM thin films with columnar grains of different grain sizes as well as epitaxial thin films were prepared by pulsed laser deposition. 18O tracer exchange experiments were performed at temperatures from 570 °C to 810 °C and subsequently analyzed by secondary ion mass spectrometry (SIMS). The isotope concentration depth profiles of polycrystalline films clearly indicate contributions from diffusion and surface exchange in grains as well as in grain boundaries. Measured depth profiles were analyzed by finite element modeling and revealed the diffusion coefficients D and oxygen exchange coefficients k of both the grain bulk and grain boundaries. Values obtained for grain boundaries (D[subscript gb] and k[subscript gb]) are almost three orders of magnitude higher than those of the grains (D[subscript g] and k[subscript g]). Hence, grain boundaries may not only facilitate fast oxygen diffusion but also fast oxygen exchange kinetics. Variation of the A-site stoichiometry ((La[subscript 0.8]Sr[subscript 0.2])0.95MnO[subscript 3]) did not lead to large changes of the kinetic parameters. Properties found for epitaxial layers without grain boundaries (Db and kb) are close to those of the grains in polycrystalline layers., Austrian Science Fund (FWF project F4509-N16), Austrian Science Fund (FWF project P21960-N17), Austrian Science Fund (FWF project W1243-N16), United States. Dept. of Energy. Office of Basic Energy Sciences (Grant No. DE-SC000263)

Zahlreiche Forschungsaktivit��ten auf dem Gebiet der Festk��rperionik (solid state ionics) befassten sich mit der ionischen Leitf��higkeit in Nanomaterialien, einschlie��lich D��nnschichten. Starke Abweichungen von makroskopischen Eigenschaften im Volumen der Materialen wurden gefunden sind aber oft nur teilweise verstanden. Viele Studien wurden an Yttrium stabilisiertem Zirconiumdioxid (YSZ) durchgef��hrt, aber nur in Volumenproben von YSZ k��nnen Korn- und Korngrenzleitf��higkeiten leicht separiert werden. Auch f��r ein besseres Verst��ndnis der Leitf��higkeitsmechanismen in d��nnen Filmen wird die Trennung von Korn- und Korngrenzleitf��higkeiten ben��tigt, die jedoch bisher durch die Streukapazit��t des Substrats verhindert wurde. In dieser Arbeit wird ein Verfahren vorgeschlagen, welches die Korn- und Korngrenzleitf��higkeit in nanokristallinen YSZ D��nnschichten durch eine optimierte Elektrodengeometrie trennt. Als weitere Eigenschaft wird in dieser Arbeit die Anisotropie der Leitf��higkeit von YSZ D��nnschichten diskutiert. Dabei wird die Leitf��higkeit von d��nnen Schichten senkrecht und entlang der D��nnschichtebene (in-plane) gemessen. Beide Arten von Messungen sind wichtig, zeigen m��gliche Anisotropien der Leitf��higkeit und k��nnen gew��hnlich nur separat gemessen werden. F��r die senkrechten Messungen werden Substrate mit einem geringen spezifischen Widerstand als YSZ ben��tigt, w��hrend f��r die in-plane Messungen Substrate mit h��herem Widerstand verwendet werden. Dar��ber hinaus k��nnen senkrechte Messungen schwierig auf sehr d��nnen Schichten durchgef��hrt werden, da dies oft zu Kurzschl��ssen aufgrund kleiner L��cher in der Schicht f��hrt. Hier wird ein neues Verfahren vorgestellt, um diese Probleme durch Leitf��higkeitsmessungen von d��nnen YSZ Schichten auf Silizium zu ��berwinden. Siliziumsubstrate haben in der Regel eine native Siliziumdioxidschicht, die f��r Leitf��higkeitsmessungen ausgenutzt werden kann. F��r senkrechte Leitf��higkeitsmessungen wurden Impedanz-Spektren mit kreisf��rmigen Mikroelektroden auf der YSZ-Schicht und einer Gegenelektrode an der Unterseite einer Probe bestimmt. Die Siliziumoxidschicht wirkt dabei als Sperrkapazit��t f��r niedrige Frequenzen und vermeidet Kurzschl��sse, w��hrend sie f��r die hohen Frequenzen stromdurchl��ssig bleibt. Es wird belegt, dass unterschiedliche Elektrodendurchmesser und Schichtdicken die YSZ Impedanzspektren beeinflussen. Leitf��higkeiten und Kapazit��ten von Siliziumoxid und YSZ D��nnschichten (bis 20 nm Schichtdicke) konnten im Temperaturbereich von 200 ��C - 400 ��C erfolgreich untersucht werden. Die Schichtdicke zeigt einen geringen Einflu�� auf die senkrechte Leitf��higkeit der YSZ Schichten, welche nur geringf��gig niedriger ist als die Leitf��higkeit einer polykristallinen YSZ-Probe. Experimentelle Ergebnisse von senkrechten Leitf��higkeitsmessungen werden durch Finite-Elemente-Simulationen (COMSOL) unterst��tzt. Die in-plane Messungen wurden mit parallelen Streifenelektroden auf YSZ durchgef��hrt. Der hohe Gleichstromwiderstand der Siliziumoxid-Zwischenschicht bewirkt stark frequenzabh��ngige Stromverteilungen und erlaubt deswegen die Bestimmung der in-plane und senkrechten YSZ Leitf��higkeiten aus einen einzigen Impedanzspektrum. Der hochfrequente Teil eines Impedanzspektrum entspricht Experimenten mit senkrechtem Stromfluss, w��hrend der niederfrequente Teil die Leitf��higkeitsergebnisse einer in-plane Probengeometrie zeigt. Die G��ltigkeit dieser Analyse wurde durch Variieren der Elektrodengeometrie bez��glich Breite und Abstand der Elektroden bewiesen. Es wird auch gezeigt, dass die gemessene Leitf��higkeit in der Ebene (in-plane Geometrie) etwa eine Gr����enordnung niedriger ist als die senkrecht gemessene Leitf��higkeit. Diese Anisotropie wird auf die Sperrwirkung der Korngrenzen in den s��ulenf��rmig strukturierten d��nnen YSZ Schichten zur��ckgef��hrt. Die experimentellen Ergebnisse werden durch zus��tzliche Finite-Elemente-Simulationen (COMSOL) unterst��tzt. Schlie��lich wurde das isolierende Oxid auf Si variiert (ZrO2, Al2O3 und Y2O3 statt SiO2) und der Einfluss auf die Leitf��higkeiten (senkrecht un in-plane) analysiert., Numerous recent research activities in solid state ionics dealt with the ionic conductivity in nanomaterials, including thin films. Strong deviations from bulk properties are often found but only partly understood. Many studies were performed on yttria stabilized zirconia (YSZ), but only on YSZ bulk materials grain and grain boundary conductivity can easily be separated. For a better understanding of the conductivity mechanisms in thin films, separation of grain and grain boundary conductivities is needed, which becomes highly sophisticated and limited by the stray capacitance of the substrate. In this thesis a method is introduced which allows grain and grain boundary conductivity separation in nanocrystalline YSZ thin films by an optimized electrode geometry. The other important property discussed in the thesis is the anisotropy of the conductivity of YSZ thin films. The conductivity of thin layers can be measured perpendicular and lateral to the thin film plane. Both types of measurements are important and reveal any potential anisotropy of the conductivity. Usually YSZ in- and across-plane conductivities are measured separately, because for in-plane measurements substrates with a higher resistivity than YSZ are needed while for across-plane measurements it is vice versa. Moreover, across-plane measurements are very difficult to be done on very thin layers, since this usually leads to short-circuits due to pin holes in the layer. Here a novel method is presented to overcome these problems by deposition of YSZ thin films on silicon. Silicon substrates usually have a native silica layer, which can be made use of in conductivity measurements. For across-plane conductivity measurements impedance spectra were obtained with circular microelectrodes on top of the YSZ layer and a counter electrode at the bottom side of the sample. The silica layer acts as a blocking capacitance for low frequencies, which helps to avoid short circuit, while for the high frequencies it is transmittable. The contribution of YSZ is identified by varying diameter of the electrodes and layer thickness. Silica and YSZ conductivities and capacitances can be successfully separated in the temperature range from 200 ��C - 400 ��C for YSZ films as thin as 20 nm. The across-plane conductivity of the YSZ films does not significantly depend on the layer thickness and is only slightly lower than the bulk conductivity of a YSZ polycrystalline sample. Experimental results of across-plane conductivity measurements are supported by finite element simulations (COMSOL). The in-plane measurements on silicon substrates are done with parallel stripe electrodes on YSZ. The high dc resistance of the silica interlayer causes strongly frequency dependent current lines and allows determination of the in- and across-plane conductivity of the YSZ film from a single impedance spectrum. The high frequency part of the impedance spectrum corresponds to an across-plane measurement geometry while the low frequency part is governed by in-plane current flow. Validity of this analysis is proven by varying electrode width and distance between the electrodes. It is shown that the measured in-plane conductivity is about one order of magnitude lower than the across-plane bulk conductivity. This anisotropy is attributed to the blocking effect of grain boundaries in the columnar structured YSZ films. Again the experimental results are well supported by finite element simulations (COMSOL). This insulating oxide on silicon was varied (ZrO2, Al2O3 and Y2O3 instead of SiO2) and its effect on in- and across-plane conductivity was analysed.

Chemistry of materials 28(11), 3727 - 3733(2016). doi:10.1021/acs.chemmater.6b00351, We employed operando anomalous surface X-ray diffraction to investigate the buried interface between the cathode and the electrolyte of a model solid oxide fuel cell with atomic resolution. The cell was studied under different oxygen pressures at elevated temperatures and polarizations by external potential control. Making use of anomalous X-ray diffraction effects at the Y and Zr K-edges allowed us to resolve the interfacial structure and chemical composition of a (100)-oriented, 9.5 mol % yttria-stabilized zirconia (YSZ) single crystal electrolyte below a La$_{0.6}$Sr$_{0.4}$CoO$_{3−δ}$ (LSC) electrode. We observe yttrium segregation toward the YSZ/LSC electrolyte/electrode interface under reducing conditions. Under oxidizing conditions, the interface becomes Y depleted. The yttrium segregation is corroborated by an enhanced outward relaxation of the YSZ interfacial metal ion layer. At the same time, an increase in point defect concentration in the electrolyte at the interface was observed, as evidenced by reduced YSZ crystallographic site occupancies for the cations as well as the oxygen ions. Such changes in composition are expected to strongly influence the oxygen ion transport through this interface which plays an important role for the performance of solid oxide fuel cells. The structure of the interface is compared to the bare YSZ(100) surface structure near the microelectrode under identical conditions and to the structure of the YSZ(100) surface prepared under ultrahigh vacuum conditions., Published by American Chemical Society, Washington, DC