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Academic literature on the topic 'Non-stoichiometric oxide'

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Published: 4 June 2021
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Journal articles on the topic "Non-stoichiometric oxide"

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Mani, A. "?Non-stoichiometric? tin oxide deposits." Journal of Materials Science Letters 10, no. 16 (1991): 953–56. http://dx.doi.org/10.1007/bf00722144.

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Ramanavicius, Simonas, and Arunas Ramanavicius. "Insights in the Application of Stoichiometric and Non-Stoichiometric Titanium Oxides for the Design of Sensors for the Determination of Gases and VOCs (TiO2−x and TinO2n−1 vs. TiO2)." Sensors 20, no. 23 (November 29, 2020): 6833. http://dx.doi.org/10.3390/s20236833.

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In this review article, attention is paid towards the formation of various nanostructured stoichiometric titanium dioxide (TiO2), non-stoichiometric titanium oxide (TiO2−x) and Magnéli phase (TinO2n−1)-based layers, which are suitable for the application in gas and volatile organic compound (VOC) sensors. Some aspects related to variation of sensitivity and selectivity of titanium oxide-based sensors are critically overviewed and discussed. The most promising titanium oxide-based hetero- and nano-structures are outlined. Recent research and many recently available reviews on TiO2-based sensors and some TiO2 synthesis methods are discussed. Some promising directions for the development of TiO2-based sensors, especially those that are capable to operate at relatively low temperatures, are outlined. The applicability of non-stoichiometric titanium oxides in the development of gas and VOC sensors is foreseen and transitions between various titanium oxide states are discussed. The presence of non-stoichiometric titanium oxide and Magnéli phase (TinO2n−1)-based layers in ‘self-heating’ sensors is predicted, and the advantages and limitations of ‘self-heating’ gas and VOC sensors, based on TiO2 and TiO2−x/TiO2 heterostructures, are discussed.
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Swallow, Jessica G., Mostafa Youssef, and Krystyn J. Van Vliet. "Defect-Mediated Mechanics in Non-Stoichiometric Oxide Films." MRS Advances 3, no. 10 (2018): 537–45. http://dx.doi.org/10.1557/adv.2018.9.

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ABSTRACTChemomechanical coupling is a hallmark of the functional oxides that are used widely for energy conversion and storage applications including solid oxide fuel cells (SOFCs). These oxides rely on the presence of oxygen vacancies to enable important properties including ionic conductivity and gas exchange reactivity. However, such defects can also facilitate chemical expansion, or coupling between material volume and defect content. Such chemomechanical coupling is particularly relevant with the recent interest in thin film SOFCs which have the potential to decrease operating temperatures and enable portable applications. Thin films present a particular challenge for modelling, as experimental results indicate that film defect chemistry can differ significantly from bulk counterparts under the same experimental conditions. In this study, we explore the influence of point defects, including oxygen vacancies and cation dopants, on the elastic properties of a model material, PrxCe1-xO2-δ (PCO), using density functional theory (DFT + U) simulations. Previously, we showed that PCO films exhibit a decrease in Young’s elastic modulus E due to chemical expansion, but that this decrease can be larger than predicted based on bulk defect models. Here, we apply DFT + U to show that the biaxial elastic modulus of PCO decreases with increased oxygen vacancy content in both bulk and membrane forms. We consider the relative influences of oxygen vacancies and cation dopants on this trend, and highlight local structural changes in the presence of such defects. By relating our computational and experimental results, we evaluate the relative importance of increased oxygen vacancy content and finite thickness on the mechanical properties of oxides that are subject to chemical expansion under operando conditions. This work informs the design of μ-SOFCs, emphasizing the need to characterize thin films separately from bulk counterparts and demonstrating how functional defect content can influence development of stress and strain in devices by changing both material volume and elastic properties.
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Zhang, Sushu, Li Zhang, Shun Fang, Jie Zhou, Jiajie Fan, and Kangle Lv. "Plasmonic semiconductor photocatalyst: Non-stoichiometric tungsten oxide." Environmental Research 199 (August 2021): 111259. http://dx.doi.org/10.1016/j.envres.2021.111259.

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Grzesik, Z., M. Migdalska, and S. Mrowec. "Chemical diffusion in non-stoichiometric cuprous oxide." Journal of Physics and Chemistry of Solids 69, no. 4 (April 2008): 928–33. http://dx.doi.org/10.1016/j.jpcs.2007.10.014.

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Raja, Shilpa N., Jessica G. Swallow, Sean R. Bishop, Yen-Ting Chi, Ting Chen, Nicola H. Perry, Harry L. Tuller, and Krystyn J. Van Vliet. "Analysis of Electrochemomechanical Coupling in Non-Stoichiometric Oxide Thin Films." ECS Meeting Abstracts MA2018-01, no. 32 (April 13, 2018): 1933. http://dx.doi.org/10.1149/ma2018-01/32/1933.

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Non-stoichiometric oxides are used in a wide variety of applications including solid oxide fuel cells (SOFCs), lithium ion batteries (LIBs), gas sensors, and catalysis. Through the capacity of such materials to support large point defect concentrations, these functional oxides can readily store, transport, and exchange ions. An important consequence of this non-stoichiometry is a tendency toward chemomechanical coupling, particularly in the form of chemical expansion, or the coupling between material volume and defect concentration. Thin films of non-stoichiometric oxides are of particular interest in such device designs, given the potential for strain engineering. For example, it has been shown for several materials that tensile strain can increase the ionic conductivity or gas exchange reactivity for oxygen by up to an order of magnitude, potentially enabling enhanced device efficiency or decreased operating temperatures1. In electrochemical devices, chemical expansion can generate stress or strain that can lead to mechanical failure, and/or changes in mechanical properties including elastic moduli. Given the extreme environments and range of non-stoichiometric oxides in which chemical expansion can be expected, robust device design requires accurate, flexible, and rapid characterization of environmental conditions and materials that maximize (or minimize) chemical expansion in situ. However, methods used at present for characterizing chemomechanical expansion, such as dilatometry, synchrotron techniques, reflectometry, and others, are not amenable to thin films or are difficult to implement in standard laboratory settings. Recently, Swallow et al. described an approach for characterizing thin film non-stoichiometric oxide chemical expansion at high temperatures by way of electrochemically induced actuation that addresses the above needs2. That work characterized volume change within a fluorite film of PrxCe1-xO2-δ (PCO) and structural deflection of the PCO/YSZ (yttria-stablized zirconia) bilayer during electrochemical pumping of oxygen ions into the PCO film. It also demonstrated a positive attribute of such chemical expansion in the form of high temperature oxide actuators, which harness electrochemically generated chemical strain to produce measurable, nanoscale device deflections. The actuation produced ranged between 5-15 nm of displacement amplitude depending on the experimental conditions2. Here, we provide an extended and graphically rich analysis of electrical and mechanical response data from such experiments. We model the current and mechanical response of PCO to an electrochemical driving force using previously established defect equilibria and kinetic relationships for that oxide, demonstrating the contributions that material properties and sample geometries make to device deflection and electrochemical pumping. We also extend the measurement approach to an additional material system, the perovskite-structured oxide SrTi0.65Fe0,35O3-δ (STF) used as part of magnetic memory devices, gas transport membranes, and fuel cells. This case study demonstrates the broad applicability of this measurement method, as well as means to leverage chemical expansion effects at elevated temperatures for diverse actuating and functional devices. Yildiz, B. ‘Stretching’ the energy landscape of oxides—Effects on electrocatalysis and diffusion. MRS Bull. 39, 147–156 (2014). Swallow, J. G. et al. Dynamic chemical expansion of thin-film non-stoichiometric oxides at extreme temperatures. Nat Mater (2017). doi:10.1038/nmat4898
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Ji, Chunlin, Chuanmeng Cui, Sulan Liu, Kuihan Wang, Zhanguo Fan, and Guofan Zhang. "DETERMINATION OF OXYGEN NON-STOLCHIOMETRIC FRACTION, δ, IN SINGLE-PHASE SUPERCONDUCTING YBa2Cu3Om+δ." International Journal of Modern Physics B 01, no. 02 (June 1987): 285–88. http://dx.doi.org/10.1142/s0217979287000347.

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The hydrogen/carbon mono-oxide reduction method, based on the difference in thermodynamic stability of yttrium oxide, barium oxide and copper oxide, has been used to determine the oxygen non-stoichiometric fraction, the δ value, in single-phase superconducting YBa2Cu3O6.5+δ . The δ value was found to +0.27 for samples produced by directed reaction process under the given conditions. The present authors regard YBa2Cu3O6.77 as a copper-deficient non-stoichiometric compound.
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MORIWAKE, Hiroki, Takuoki HATA, Masaaki KATSUMATA, Masayuki TAKAHASHI, and Isao SHIMONO. "Electric Conductivity of Non-Stoichiometric Oxide MgCr2-xO4." Journal of the Ceramic Society of Japan 107, no. 1243 (1999): 258–62. http://dx.doi.org/10.2109/jcersj.107.258.

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Schweika, W. "The defect structure of non-stoichiometric ferrous oxide." Acta Crystallographica Section A Foundations of Crystallography 52, a1 (August 8, 1996): C408. http://dx.doi.org/10.1107/s010876739608316x.

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Brett, M. J., and R. R. Parsons. "Structural properties of non-stoichiometric zinc oxide films." Journal of Materials Science 22, no. 10 (October 1987): 3611–14. http://dx.doi.org/10.1007/bf01161468.

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Dissertations / Theses on the topic "Non-stoichiometric oxide"

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Swallow, Jessica G. "Chemomechanics of non-stoichiometric oxide films for energy conversion." Thesis, Massachusetts Institute of Technology, 2018. http://hdl.handle.net/1721.1/115606.

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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Materials Science and Engineering, 2018.
This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references.
Electrochemical energy conversion and storage devices including solid oxide fuel cells (SOFCs) and lithium ion batteries (LIBs) are enabled by materials known as "non-stoichiometric oxides" that contain large concentrations of point defects such as oxygen or lithium vacancies. While this non-stoichiometry provides the essential functional properties of ionic conductivity or reactivity that make these materials useful, it also tends to couple to material volume through the effect of chemical expansion. Chemical expansion, or volume coupled to defect concentration, is in turn tied to mechanical variables including stress, strain, and elastic constants. This electrochemomechanical coupling, or interaction between functional properties, defect chemistry, and mechanical variables, can have important consequences for devices operated in extreme environments, where unexpected stress may lead to fracture, or well-engineered strain may enhance device efficiency. Such effects are particularly important in thin film devices, where strain engineering is within reach, undesired fracture can devastate performance, and defect chemistry and related properties can differ from bulk systems. In this thesis, we present a concerted investigation of chemomechanical coupling, including interactions between material chemistry, environmental conditions, stress, strain, and mechanical properties, for films of the model material PrxCe1-xO2-[delta] (PCO) that is a fluorite-structured oxide relevant to SOFC applications. PCO is an excellent model system because of its well-established defect chemistry model and known thermal and chemical expansion coefficients. The thesis begins by first characterizing key chemomechanical effects in PCO, including electrochemically induced high temperature actuation and nonstoichiometry- dependent mechanical properties that are modulated by environmental conditions including temperature and oxygen partial pressure. We then explore the mechanisms and microstructural contributions to these effects via computational modeling and high temperature transmission electron microscopy, identifying ways in which chemomechanical effects in thin film non-stoichiometric oxides differ from those in bulk. Finally, we extend the experimental and computational methods developed in the thesis to characterizing similar effects in Li-storage materials, demonstrating the broad applicability of results across the classes of non-stoichiometric oxides. We first describe an experimental study in which we developed a novel method of detecting chemical expansion on short time scales in the model system PCO and characterized material deformation for a range of conditions of temperature and effective oxygen partial pressure (pO2). In this method, electrically-stimulated chemical expansion caused mechanical deflection of a substrate, an effect that for PCO was enhanced for elevated temperatures or reducing conditions ...
by Jessica G. Swallow.
Ph. D.
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Curelea, Sergiu. "Non stoichiometric effects in cobalt rich complex oxides." Caen, 2012. http://www.theses.fr/2012CAEN2031.

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This memory is devoted to the research and characterization of new complex cobalt-rich oxides, by transmission electron microscopy (TEM) techniques. A part of the work presents the study of a “114”-type compound, non-stoichiometric at the level of the oxygen content, YBaCo4O7+δ, for the case when δ has a value of approximately 1. 5. When an extra oxygen content is applied to the original, stoichiometric material, it has been found during the TEM studies that these extra oxygen atoms cause the formation of a complex superstructure that has been characterized in terms of the lattice parameters. This is accompanied by a reduction of the original trigonal symmetry to an orthorhombic one. Layered, cobalt-rich materials in the Ba–Co–O system, formed by the intergrowth of the hexagonal perovskite, more exactly the Ba2Co9O14 and Ba3Co10O17 compounds, are presented in the second part of the memory. These materials are part of a larger structural family, which corresponds to the [BaCoO3]n[BaCo8O11] chemical formula, where n denotes the thickness (number) of hexagonal perovskite blocs [BaCoO3] in their structure. The second part of the formula represents the chemical composition of another block, common to all these materials. Which is a CdI2-type one, responsible for the magnetic properties at low temperature, that these compounds exhibit. Concerning the n = 2 term, it is impossible to synthesize the pure phase, systematically obtaining secondary phases (like BaCoO3 or Co3O4). Chemical doping, by replacing a part of the cobalt species with iron, and using the sol-gel technique, leads to obtaining a nearly pure phase Ba3(Fe,Co)10O17, which has been analyzed by X-ray diffraction, neutron diffraction and transmission electron microscopy.
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Schmidt, Marek Wojciech, and Marek Schmidt@rl ac uk. "Phase formation and structural transformation of strontium ferrite SrFeOx." The Australian National University. Research School of Physical Sciences and Engineering, 2001. http://thesis.anu.edu.au./public/adt-ANU20020708.190055.

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Non-stoichiometric strontium iron oxide is described by an abbreviated formula SrFeOx (2.5 ≤ x ≤ 3.0) exhibits a variety of interesting physical and chemical properties over a broad range of temperatures and in different gaseous environments. The oxide contains a mixture of iron in the trivalent and the rare tetravalent state. The material at elevated temperature is a mixed oxygen conductor and it, or its derivatives,can have practical applications in oxygen conducting devices such as pressure driven oxygen generators, partial oxidation reactors in electrodes for solid oxide fuel cells (SOFC). ¶ This thesis examines the behaviour of the material at ambient and elevated temperatures using a broad spectrum of solid state experimental techniques such as: x-ray and neutron powder diffraction,thermogravimetric and calorimetric methods,scanning electron microscopy and Mossbauer spectroscopy. Changes in the oxide were induced using conventional thermal treatment in various atmospheres as well as mechanical energy (ball milling). The first experimental chapter examines the formation of the ferrite from a mixture of reactants.It describes the chemical reactions and phase transitions that lead to the formation of the oxide. Ball milling of the reactants prior to annealing was found to eliminate transient phases from the reaction route and to increase the kinetics of the reaction at lower temperatures. Examination of the thermodynamics of iron oxide (hematite) used for the reactions led to a new route of synthesis of the ferrite frommagnetite and strontium carbonate.This chapter also explores the possibility of synthesis of the material at room temperature using ball milling. ¶ The ferrite strongly interacts with the gas phase so its behaviour was studied under different pressures of oxygen and in carbon dioxide.The changes in ferrite composition have an equilibrium character and depend on temperature and oxygen concentration in the atmosphere. Variations of the oxygen content x were described as a function of temperature and oxygen partial pressure, the results were used to plot an equilibrium composition diagram. The heat of oxidation was also measured as a function of temperature and oxygen partial pressure. ¶ Interaction of the ferrite with carbon dioxide below a critical temperature causes decomposition of the material to strontium carbonate and SrFe12O19 . The critical temperature depends on the partial pressure of CO2 and above the critical temperature the carbonate and SrFe12O19 are converted back into the ferrite.The resulting SrFe12O19 is very resistant towards carbonation and the thermal carbonation reaction does not lead to a complete decomposition of SrFeOx to hematite and strontium carbonate. ¶ The thermally induced oxidation and carbonation reactions cease at room temperature due to sluggish kinetics however,they can be carried out at ambient temperature using ball milling.The reaction routes for these processes are different from the thermal routes.The mechanical oxidation induces two or more concurrent reactions which lead to samples containing two or more phases. The mechanical carbonation on the other hand produces an unknown metastable iron carbonate and leads a complete decomposition of the ferrite to strontiumcarbonate and hematite. ¶ Thermally and mechanically oxidized samples were studied using Mossbauer spectroscopy. The author proposes a new interpretation of the Sr4Fe4O11 (x=2.75) and Sr8Fe8O23 (x=2.875)spectra.The interpretation is based on the chemistry of the compounds and provides a simpler explanation of the observed absorption lines.The Mossbauer results froma range of compositions revealed the roomtemperature phase behaviour of the ferrite also examined using x-ray diffraction. ¶ The high-temperature crystal structure of the ferrite was examined using neutron powder diffraction.The measurements were done at temperatures up to 1273K in argon and air atmospheres.The former atmosphere protects Sr2Fe2O5 (x=2.5) against oxidation and the measurements in air allowed variation of the composition of the oxide in the range 2.56 ≤ x ≤ 2.81. Sr2Fe2O5 is an antiferromagnet and undergoes phase transitions to the paramagnetic state at 692K and from the orthorhombic to the cubic structure around 1140K.The oxidized formof the ferrite also undergoes a transition to the high-temperature cubic form.The author proposes a new structural model for the cubic phase based on a unit cell with the Fm3c symmetry. The new model allows a description of the high-temperature cubic form of the ferrite as a solid solution of the composition end members.The results were used to draw a phase diagramfor the SrFeOx system. ¶ The last chapter summarizes the findings and suggests directions for further research.
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Maity, Avishek. "Etude des mécanismes de diffusion de l’oxygène dans SrFeO3-x et Pr2NiO4+d, réalisée par diffraction du rayonnement synchrotron in situ sur monocristal." Thesis, Montpellier, 2016. http://www.theses.fr/2016MONTT188/document.

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La compréhension des aspects fondamentaux de la diffusion de l'oxygène dans les oxydes solides à des températures modérées, jusqu'à température ambiante, est un enjeu majeur pour le développement d'une variété de dispositifs technologiques dans un avenir proche. Cela concerne, par exemple, le développement de la prochaine génération des électrolytes et membranes solides d'oxygène pour les piles à combustible de type SOFC. Autrement, les réactions d'intercalation de l'oxygène réalisées à basse température présentent un outil puissant pour contrôler le dopage en oxygène ainsi que des propriétés physiques. Dans ce contexte, les oxydes ayant une structure type brownmillérite (A2BB'O5) ou type K2NiF4, ont attiré beaucoup d'attention, car ils montrent une mobilité de l'oxygène déjà à température ambiante.Dans cette thèse, nous avons étudié les mécanismes d'intercalation d'oxygène dans SrFeO2.5+x, ainsi que Pr2NiO4+x par des méthodes de diffraction in situ, réalisées sur des monocristaux dans une cellule électrochimique spécifiquement conçue, explorant principalement le rayonnement synchrotron. Ceci a permis d’explorer en 3D tout le réseau réciproque, et d'obtenir des informations précieuses sur la diffusion diffuse, sur les faibles intensités des raies de surstructure, ainsi que des informations sur la fraction volumique des différents domaines de maclage au cours de la réaction, impossibles à accéder par diffraction de poudre.Les deux systèmes montrent des changements structuraux complexes, accompagnés par une mise en ordre de l'oxygène à longue portée. Au cours de l'intercalation d'oxygène nous avons mis en évidence deux phases intermédiaires, SrFeO2.75 et SrFeO2.875, possédant des lacunes en oxygène ordonnées à longue échelle. En raison du maclage, avec jusqu'à douze possibles individus, nous avons suivi directement la formation et l'évolution des domaines de maclage ainsi que leur micro-structure apparentée. Nous avons ainsi observé un mécanisme de réaction topotactique pour SrFeO2.5 vers SrFeO2.75, tandis que l'oxydation de SrFeO2.75 conduit à des importants réarrangements de l’oxygène, associés à un changement de nombre de domaines de maclage. La réduction électrochimique de la phase orthorhombique Pr2NiO4.25 donne Pr2NiO4.0 comme produit final, ayant la même symétrie, tandis que la phase tétragonale Pr2NiO~4.12 apparaît comme phase intermédiaire. Utilisant un monocristal avec un diamètre de 50 microns, la réaction se déroule dans des conditions d'équilibre dans moins que 24 heures, ce qui implique un coefficient de diffusion de l’oxygène anormalement élevé, supérieur à 10-^11cm2*s-1 à température ambiante. Nous avons également étudié le diagramme de phase de Pr2NiO4.25 sur monocristal jusqu’à 1100°C en chauffant sous air. Une série complexe de transition de phases a été mise en évidence, la vraie symétrie de Pr2NiO4.25 s’avérée en fait monoclinique.Outre l'exploration des diagrammes de phases complexes de SrFeO2.5+x et Pr2NiO4+d, nous avons pu étudier les changements détaillés concernant la micro-structure à l'aide de diffraction sur monocristaux in situ, impossible à accéder par des méthodes de diffraction de poudre classique. Les changements de la micro-structure des domaines va bien au-delà des composés étudiés ici et porte une grande importance pour extrapoler sur la performance, la stabilité et la durée de vie par exemple des matériaux utilisés pour le stockage de l’énergie
Understanding fundamental aspects of oxygen diffusion in solid oxides at moderate temperatures, down to ambient, is an important issue for the development of a variety of technological devices in the near future. This concerns e.g. the progress and invention of next generation solid oxygen ion electrolytes and oxygen electrodes for solid oxide fuel cells (SOFC) as well as membrane based air separators, oxygen sensors and catalytic converters to transform e.g. NOx or CO from exhaust emissions into N2 and CO2. On the other hand oxygen intercalation reactions carried out at low temperatures present a powerful tool to control hole doping, i.e. the oxygen stoichiometry, in electronically correlated transition metal oxides. In this aspect oxides with Brownmillerite (A2BB’O5) and K2NiF4-type frameworks, have attracted much attention, as they surprisingly show oxygen mobility down to ambient temperature. In this thesis we investigated oxygen intercalation mechanisms in SrFeO2.5+x as well as Pr2NiO4+x by in situ diffraction methods, carried out on single crystals in especially designed electrochemical cell, mainly exploring synchrotron radiation. Following up oxygen intercalation reactions on single crystals is challenging, as it allows to scan the whole reciprocal lattice, enabling to obtain valuable information as diffuse scattering, weak superstructure reflections, as well as information of the volume fraction of different domains during the reaction, to highlight a few examples, difficult or impossible to access by powder diffraction. Both title systems are able to take up an important amount of oxygen on regular and interstitial lattice sites, inducing structural changes accompanied by long range oxygen ordering. For SrFeO2.5+x the uptake of oxygen carried out by electrochemical oxidation yields SrFeO3 as the final reaction product. The as grown SrFeO2.5 single crystals we found to show a complex defect structure, related to the stacking disorder of the octahedral and tetrahedral layers. During the oxygen intercalation we evidenced the formation of two reaction intermediates, SrFeO2.75 and SrFeO2.875, showing complex and instantly formed long range oxygen vacancies. Due to the specific twinning with up to totally twelve possible twin individuals, we directly follow up the formation and changes of the specific domain and related micro-structure. We thus observed a topotactic reaction mechanism from SrFeO2.5 to SrFeO2.75, while further oxidation lead to important rearrangements in the dimensionality of the oxygen defects in SrFeO2.75, implying the formation of an additional twin domain in course of the reaction. The electrochemical reduction of orthorhombic Pr2NiO4.25 yields stoichiometric Pr2NiO4.0 as the final reaction product with the same symmetry, while tetragonal Pr2NiO~4.12 appears as a non-stoichiometric intermediate phase. Using a single crystal with 50µm diameter, the reaction proceeded under equilibrium conditions in slightly less than 24h, implying an unusually high oxygen ion diffusion coefficient of > 10^-11cm2*s-1 at already ambient temperature. From the changes of the associated twin domain structure during the reduction reaction, the formation of macro twin domains was evidenced. Heating up Pr2NiO4.25 single crystals in air revealed a complex series of phase transition, evidencing the true symmetry of the starting phase to be in fact monoclinic. Beside exploring the complex phase diagrams of SrFeO2.5+x and Pr2NiO4+d we were able to investigate detailed changes in the micro-structure using in situ single crystal diffraction techniques, impossible to access by classical powder diffraction methods. The importance of changes in the domain structure goes far beyond the investigated title compounds and has utmost importance of the performance, stability and lifetime of e.g. battery materials
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Dutta, Rajesh. "Etude in situ, par diffraction des rayons X et diffusion neutronique sur monocristaux, de la complexité structurale de l'oxyde fortement corrélé Pr2-xSrxNiO4+δ." Thesis, Bordeaux, 2017. http://www.theses.fr/2017BORD0754/document.

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Les oxydes non-stoechiométriques de type Ruddlesden-Popper, tel que Pr2NiO4+δ, peuvent être dopés en trous par substitution du strontium au praséodyme ou par insertion d’oxygène. Ces modes de dopage s’accompagnent de mises en ordre complexes impliquant la distribution des ions oxygène excédentaires, des ordres de charge et/ou de spin. Le diagramme de phase de Pr2-xSrxNiO4+δ a été exploré par diffraction des rayons X (en laboratoire et par rayonnement synchrotron) ainsi que neutronique. Pour la phase Pr2NiO4.25, nous avons mis en évidence une sur-structure incommensurable avec des réflexions satellites au 6ème ordre, produisant un spectre de diffraction très complexe avec 4 individus et 8 domaines incommensurables. Par diffractions synchrotron et neutronique, un ordre de charge de type échiquier a été identifié dès la température ambiante, suivi en dessous de 170 K par un ordre de type rubans ; un ordre de spin incommensurable s’établit au-dessous de 99 K. Ce travail a permis de révéler un ensemble complexe de phases ordonnées structuralement et électroniquement, gouvernées par des variations subtiles de stoechiométrie en strontium et oxygène
Non-stoichiometric oxides from the Ruddlesden-Popper series, such as Pr2NiO4+δ, can be hole-doped by substituting strontium to praseodymium or by oxygen insertion. This leads to complex structural ordering involving oxygen-, charge- and spin ordering. The complex phase diagram of Pr2-xSrxNiO4+δ was explored using X-ray (laboratory and synchrotron) as well as neutron diffractions. For the doped phase of highest oxygen content (Pr2NiO4.25), we could evidence an incommensurate structure with satellite reflections of 6th order, yielding a very complex diffraction pattern of up to four twin-individuals and eight incommensurate domains. Checkerboard-type charge ordering was identified already at ambient temperature, while stripe charge ordering was observed below 170 K by synchrotron and neutron diffraction; incommensurate spin ordering appears below 99 K. This thesis reveals the existence of many complex oxygen and electronically ordered phases going along with small variations of the oxygen/strontium stoichiometry
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Fiori, Costantino. "Oxydation du silicium et modification de l'ordre à courte distance dans les oxydes de silicium induits par un rayonnement laser ultra violet." Grenoble 1, 1986. http://www.theses.fr/1986GRE10131.

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Etude par spectrometrie auger de la structure de la surface de si(111) faiblement recouverte d'oxygene sec. L'irradiation par un faible flux de photons uv induit d'importants rearrangements atomiques dans la phase adsorbees avec formation d'une monocouche tres desordonnee de sio::(2) se transformant en sio::(2) amorphe stable apres un recuit thermique a 949 k. L'irradiation de ces couches par un rayonnement laser uv les rend instables. Formation d'une forte densite de defauts structuraux. Etablissement d'une correlation entre les phenomenes physiques evoques
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Caignaert, Vincent. "Non-stoechiometrie par creation de lacunes anioniques : oxydes mixtes de manganese et de fer, de structure apparentee a la perovskite." Caen, 1986. http://www.theses.fr/1986CAEN2007.

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Etude des possibilites d'ecarts a la stoechiometrie sur le sous reseau anionique des perovskites amn::(1-x) fe::(x)o::(3-y) (a=ca, sr, ba) par diffraction x et neutron, microscopie electronique haute resolution, spectre moessbauer et mesures magnetiques. Caracterisation de plusieurs types d'ordre des lacunes oxygene en fonction du cation a et du taux de mn
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Chaillout-Bougerol, Catherine. "Contribution à l'étude du système BaPb(1-x)Bi(x)O(3) : relations entre les propriétés structurales, chimiques et physiques." Grenoble 1, 1986. http://www.theses.fr/1986GRE10017.

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Etude de la solution solide du titre du fait de l'interet suscite par ses proprietes physiques : phrase supraconductrice pour 0,05 x 0,30 avec tc# 13k, transition metal-semiconducteur pour x # 0,30. La structure de ces composes est de type perovskite. Selon la concentration en pb et bi, la structure de base cubique se deforme differemment. Etude de la valence de bi et de la stoechiometrie en oxygene, dans babi0::(3) en particulier. Proposition de modeles qui permettent de concilier divers resultats publies anterieurement concernant les proprietes structurales et physiques
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Faulmann, Christophe. "Conducteurs derives de metaux de transition : complexes moleculaires, polymeres, oxydes de cuivre." Toulouse 3, 1988. http://www.theses.fr/1988TOU30160.

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Schmidt, Marek Wojciech. "Phase formation and structural transformation of strontium ferrite SrFeOx." Phd thesis, 2001. http://hdl.handle.net/1885/48187.

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Non-stoichiometric strontium iron oxide is described by an abbreviated formula SrFeOx (2.5 ≤ x ≤ 3.0) exhibits a variety of interesting physical and chemical properties over a broad range of temperatures and in different gaseous environments. The oxide contains a mixture of iron in the trivalent and the rare tetravalent state. The material at elevated temperature is a mixed oxygen conductor and it, or its derivatives,can have practical applications in oxygen conducting devices such as pressure driven oxygen generators, partial oxidation reactors in electrodes for solid oxide fuel cells (SOFC). ¶ This thesis examines the behaviour of the material at ambient and elevated temperatures using a broad spectrum of solid state experimental techniques such as: x-ray and neutron powder diffraction,thermogravimetric and calorimetric methods,scanning electron microscopy and Mossbauer spectroscopy. Changes in the oxide were induced using conventional thermal treatment in various atmospheres as well as mechanical energy (ball milling). ¶ ...
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Books on the topic "Non-stoichiometric oxide"

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Kerkar, Moussa. A structural investigation of evaporated non-stoichiometric silicon oxide films. [s.l.]: typescript, 1986.

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Stoklosa, Andrzej. Non-Stoichiometric Oxides Of 3d-Metals. Trans Tech Publications, Limited, 2015.

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Andrzej Stokłosa. Non-Stoichiometric Oxides Of 3d-Metals. Trans Tech Publications, Limited, 2015.

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Book chapters on the topic "Non-stoichiometric oxide"

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Alcock, C. B. "The Control of Stoichiometry in Oxide Systems." In Non-Stoichiometric Compounds, 3–10. Dordrecht: Springer Netherlands, 1989. http://dx.doi.org/10.1007/978-94-009-0943-4_1.

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Su, Ming-Yih, and George Simkovich. "Point Defect Structure of Chromium (III) Oxide." In Non-Stoichiometric Compounds, 93–113. Dordrecht: Springer Netherlands, 1989. http://dx.doi.org/10.1007/978-94-009-0943-4_7.

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Boukamp, B. A., K. J. Vries, and A. J. Burggraaf. "Surface Oxygen Exchange in Bismuth Oxide Based Materials." In Non-Stoichiometric Compounds, 299–309. Dordrecht: Springer Netherlands, 1989. http://dx.doi.org/10.1007/978-94-009-0943-4_20.

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Stubican, V. S., and C. M. Lin. "Influence of Point Defects on the Near-Surface Diffusion in some Oxide Systems." In Non-Stoichiometric Compounds, 423–31. Dordrecht: Springer Netherlands, 1989. http://dx.doi.org/10.1007/978-94-009-0943-4_29.

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Hirschwald, W. "Characterization of Defects on Oxide Surfaces and Their Impact on Surface Reactivity and Catalysis." In Non-Stoichiometric Compounds, 203–19. Dordrecht: Springer Netherlands, 1989. http://dx.doi.org/10.1007/978-94-009-0943-4_15.

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Boudriss, A., and L. C. Dufour. "Defects and Reactivity at Oxide Surfaces: Experimental Aspects of the Interaction of Hydrogen, Co And Co2 with the Nio{001} Surface." In Non-Stoichiometric Compounds, 311–20. Dordrecht: Springer Netherlands, 1989. http://dx.doi.org/10.1007/978-94-009-0943-4_21.

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Swaminathan, Narasimhan, and Jianmin Qu. "Determination of Chemical Expansion Coefficient and Elastic Properties of Non-Stoichiometric GDC Using Molecular Dynamic Simulations." In Advances in Solid Oxide Fuel Cells III, 401–11. Hoboken, NJ, USA: John Wiley & Sons, Inc., 2009. http://dx.doi.org/10.1002/9780470339534.ch36.

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Boureau, G., M. Benzakour, and R. Tetot. "Statistical Thermodynamics of Non-Stoichiometric Oxides." In Non-Stoichiometric Compounds, 155–61. Dordrecht: Springer Netherlands, 1989. http://dx.doi.org/10.1007/978-94-009-0943-4_11.

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Saito, Y., and T. Maruyama. "Phase Relations of Metal Oxides by Coulometric Titration." In Non-Stoichiometric Compounds, 11–26. Dordrecht: Springer Netherlands, 1989. http://dx.doi.org/10.1007/978-94-009-0943-4_2.

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Cormack, A. N. "Defect Interactions, Extended Defects and Non-Stoichiometry in Ceramic Oxides." In Non-Stoichiometric Compounds, 45–52. Dordrecht: Springer Netherlands, 1989. http://dx.doi.org/10.1007/978-94-009-0943-4_4.

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Conference papers on the topic "Non-stoichiometric oxide"

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Dube, Paras, Suraj Parwani, and Netram Kaurav. "Study of dielectric properties of non-stoichiometric nickel oxide." In NATIONAL CONFERENCE ON PHYSICS AND CHEMISTRY OF MATERIALS: NCPCM2020. AIP Publishing, 2021. http://dx.doi.org/10.1063/5.0060883.

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Dubey, Paras, K. K. Choudhary, Kiran Singh, and Netram Kaurav. "Effect of sintering temperature on the dielectric properties of non-stoichiometric nickel oxide." In PROF. DINESH VARSHNEY MEMORIAL NATIONAL CONFERENCE ON PHYSICS AND CHEMISTRY OF MATERIALS: NCPCM 2018. Author(s), 2019. http://dx.doi.org/10.1063/1.5098725.

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Kodama, Tatsuya, Nobuki Imaizumi, Nobuyuki Gokon, Tsuyoshi Hatamachi, Daiki Aoyagi, and Ken Kondo. "Comparison Studies of Reactivity on Nickel-Ferrite and Cerium-Oxide Redox Materials for Two-Step Thermochemical Water Splitting Below 1400°C." In ASME 2011 5th International Conference on Energy Sustainability. ASMEDC, 2011. http://dx.doi.org/10.1115/es2011-54277.

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A two-step thermochemical water splitting cycle using a redox system of non-volatile metal oxide is one of the promising processes for converting concentrated solar high-temperature heat into clean hydrogen in sun-belt regions. In the 1st step of the cycle or the thermal reduction step, metal oxide is thermally reduced to release oxygen molecules in an inert gas atmosphere at a higher temperature above 1400°C. In the second step or the water-decomposition step at a lower temperature, the thermally-reduced metal oxide reacts with steam to produce hydrogen. As the reactive redox metal oxide materials to be capable of working below 1400°C, nickel-doped iron oxides or Ni-ferrites supported on zirconia, and non-stoichiometric cerium oxides are the promising working materials. In the present work, a series of the nickel-ferrite redox materials of monoclinic-zirconia-supported, cubic-YSZ(yttrium-stabilized zirconia)-supported, and non-supported Ni-ferries and non-stoichiometric cerium oxide were compared on reactivity for two-step thermochemical water splitting cycle. The monoclinic-zirconia-supported Ni-ferrite produced the most quantity of hydrogen in the repeated cycles when the thermal reduction step was performed for 30 min at 1400°C and the water decomposition step for 60 min at 1000°C.
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Lapp, Justin, Jane Davidson, and Wojciech Lipiński. "Heat Transfer Analysis of a Solid-Solid Heat Recuperation System for Solar-Driven Non-Stoichiometric Redox Cycles." In ASME 2012 6th International Conference on Energy Sustainability collocated with the ASME 2012 10th International Conference on Fuel Cell Science, Engineering and Technology. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/es2012-91078.

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Heat transfer is analyzed numerically for a solid-solid heat recuperation system employed in a novel directly-irradiated solar thermochemical reactor realizing a metal oxide based non-stoichiometric redox cycle for production of synthesis gas from water and carbon dioxide. The system is designed for continuous operation with heat recuperation from a rotating hollow cylinder of a porous reactive material to a counter rotating inert solid cylinder via radiative transfer. A transient heat transfer model coupling conduction, convection, and radiation heat transfer modes is developed to predict temperatures of both components, rates of heat transfer, and the effectiveness of heat recuperation. Heat recovery effectiveness of over 50% is attained within a parametric study of geometric and material parameters corresponding to the design of a two-step solar thermochemical reactor.
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Durocher, Antoine, Jiayi Wang, Gilles Bourque, and Jeffrey M. Bergthorson. "Impact of Boundary Condition and Kinetic Parameter Uncertainties on NOx Predictions in Methane-Air Stagnation Flame Experiments." In ASME Turbo Expo 2021: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2021. http://dx.doi.org/10.1115/gt2021-59404.

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Abstract A comprehensive understanding of uncertainty sources in experimental measurements is required to develop robust thermochemical models for use in industrial applications. Due to the complexity of the combustion process in gas turbine engines, simpler flames are generally used to study fundamental combustion properties and measure concentrations of important species to validate and improve modelling. Stable, laminar flames have increasingly been used to study nitrogen oxide (NOx) formation in lean-to-rich compositions in low-to-high pressures to assess model predictions and improve accuracy to help develop future low-emissions systems. They allow for non-intrusive diagnostics to measure sub-ppm concentrations of pollutant molecules, as well as important precursors, and provide well-defined boundary conditions to directly compare experiments with simulations. The uncertainties of experimentally-measured boundary conditions and the inherent kinetic uncertainties in the nitrogen chemistry are propagated through one-dimensional stagnation flame simulations to quantify the relative importance of the two sources and estimate their impact on predictions. Measurements in lean, stoichiometric, and rich methane-air flames are used to investigate the production pathways active in those conditions. Various spectral expansions are used to develop surrogate models with different levels of accuracy to perform the uncertainty analysis for 15 important reactions in the nitrogen chemistry and the 6 boundary conditions (ϕ, Tin, uin, du/dzin, Tsurf, P) simultaneously. After estimating the individual parametric contributions, the uncertainty of the boundary conditions are shown to have a relatively small impact on the prediction of NOx compared to kinetic uncertainties in these laboratory experiments. These results show that properly calibrated laminar flame experiments can, not only provide validation targets for modelling, but also accurate indirect measurements that can later be used to infer individual kinetic rates to improve thermochemical models.
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Albrecht, Kevin J., and Robert J. Braun. "Thermodynamic Analysis of Non-Stoichiometric Perovskites as a Heat Transfer Fluid for Thermochemical Energy Storage in Concentrated Solar Power." In ASME 2015 9th International Conference on Energy Sustainability collocated with the ASME 2015 Power Conference, the ASME 2015 13th International Conference on Fuel Cell Science, Engineering and Technology, and the ASME 2015 Nuclear Forum. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/es2015-49409.

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The implementation of efficient and cost effective thermal energy storage in concentrated solar power (CSP) applications is crucial to the wide spread adoption of the technology. The current push to high-temperature receivers enabling the use of advanced power cycles has identified solid particle receivers as a desired technology. A potential way of increasing the specific energy storage of solid particles while simultaneously reducing plant component size is to implement thermochemical energy storage (TCES) through the use of non-stoichiometric perovskite oxides. Materials such as strontium-doped lanthanum cobalt ferrites (LSCF) have been shown to have significant reducibility when cycling temperature and oxygen partial pressure of the environment [1]. The combined reducibility and heat of the oxidation and reduction reactions with the sensible change in temperature of the material leads to specific energy storage values approaching 700 kJ kg−1. A potential thermochemical energy storage system configuration and modeling strategy is reported on, leading to a parametric study of critical operating parameters on the TCES subsystem performance. For the LSCF material operating between 500 and 900°C with oxygen partial pressure swings from ambient to 0.0001 bar, system efficiencies of 68.6% based on the net thermal energy delivered to the power cycle relative to the incident solar flux on the receiver and auxiliary power requirements, with specific energy storage of 686 kJ kg−1 are predicted. Alternatively, only cycling the temperature between 500 and 900°C without oxygen partial pressure swings results in TCES subsystem efficiencies up to 76.3% with specific energy storage of 533 kJ kg−1.
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Reports on the topic "Non-stoichiometric oxide"

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Migilori, A., Z. Fisk, Ming Lei, D. Mandrus, J. Sarrao, J. Thompson, S. Trugman, P. Canfield, and W. Clark. Structural phase transitions on non-stoichiometric oxides and other materials. Office of Scientific and Technical Information (OSTI), April 1996. http://dx.doi.org/10.2172/212687.

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