[Truncated abstract] New, double-doped, Bi2O3-based materials in the Bi2O3 Ln2O3 PbO (Ln = La, Nd, Er and Yb) and Bi2O3 WO3 PbO systems were prepared using solid-state reactions. For the Bi2O3 Er2O3 PbO and Bi2O3 Yb2O3 PbO systems, the air-quenchable compositional domain of the fcc fluorite-type phase was partially established. Temperature dependent conductivity measurements were performed on these quenched-in fluorite-type materials using AC impedance spectroscopy. Conductivity at 750[degrees Celsius] generally increased with increasing Pb2+/Ln3+ and decreasing (Ln3++Pb2+)/Bi3+ ratios. The material (BiO1.5)0.70(ErO1.5)0.15(PbO)0.15 had a conductivity of 0.66 [plus-minus] 0.05 S cm-1 at 750[degrees Celsius], placing it among the most highly conductive Bi2O3-based materials, and was the best new fluorite-type material from a combined conductivity and structural stability viewpoint. Some of the new materials in the Bi2O3 La2O3 PbO and Bi2O3 Nd2O3 PbO systems appeared to have the quenched-in fluorite type structure based on powder X-ray diffraction data. These materials had very high conductivities at 750[degrees Celsius] of `~ 1 S cm-1, but underwent rapid symmetry lowering transformations during heating, thus making them unsuitable for use as solid electrolytes. The fluorite-type structure was not air-quenchable in the Bi2O3 WO3 PbO system, for the compositions synthesised. Room temperature neutron powder diffraction data were collected for quenched-in fluorite-type materials in the (BiO1.5)0.80(LnO1.5)0.20-x(PbO)x, Ln = Er and Yb, x = 0, 0.03, 0.06 and 0.09, and (BiO1.5)0.97-y(ErO1.5)y(PbO)0.03, y = 0.27, 0.17 and 0.12, series. ... This suggests that Pb2+ dopant cations occupy face-centre positions in the fcc unit cell, and the Pb2+ lone pair electrons are likely to be orientated towards an oxide ion vacancy in an adjacent tetrahedral site. Pb2+/oxide ion vacancy interactions affect the migration of oxide ions/oxide ion vacancies through the structure, and are responsible for the significantly larger activation energy for oxide ion migration in the Pb2+-doped materials relative to the Pb2+-free materials. For example, the activation energies of (BiO1.5)0.80(ErO1.5)0.20-x(PbO)x, x = 0.03 and 0.06, were 1.50 [plus-minus] 0.02 and 1.54 [plus-minus] 0.02 eV, respectively, while the activation energy for (BiO1.5)0.80(ErO1.5)0.20 was 1.25 [plus-minus] 0.04 eV. Long-term annealing of the quenched in fluorite-type materials in the Bi2O3 Er2O3 PbO and Bi2O3 Yb2O3 PbO systems at 500 and 600[degrees Celsius] resulted in conductivity lowering structural transformations, making these materials unsuitable for practical use as solid electrolytes at these temperatures. For example, the materials (BiO1.5)0.80(ErO1.5)0.20-x(PbO)x, x = 0.03, 0.06 and 0.09, underwent a fluorite-type to tetragonal transformation during annealing at 500[degrees Celsius] due to <100> oxide ion vacancy ordering, and the rate of conductivity decay at 500[degrees Celsius] increased with increasing Pb2+/Er3+ ratio. Long-term annealing experiments at 500[degrees Celsius] performed on air quenched (Bi2O3)0.705(Er2O3)0.245(WO3)0.050 showed that the disordered fluorite-type structure of this material was not fully stabilised, as evidenced by the presence of superlattice reflections in selected area electron diffraction patterns for the material annealed for 2000 hours, and a gradual conductivity decay after ~ 150 hours annealing.

Accomplir les spécifications des nouvelles réglementations concernant les gaz d'échappement de post-traitement des technologies automobiles, par exemple, TWC, implique la disponibilité et l'utilisation de matériaux catalytiquement actifs et notamment des composés tampons d'oxygène, ce qui peut réversible stocker et libérer de grandes quantités de l'oxygène. Oxyde de cérium dopé présente encore aujourd'hui le seul composé de référence pour un support approprié, en raison de sa grande capacité de stockage de l'oxygène et possibilité de créer facilement des lacunes en ions d'oxygène. Cependant, pour des raisons économiques et de l'abondance naturelle très limitée à quelques pays, la substitution de l'oxyde de cérium semble être obligatoire; Dans ce contexte, nous notons que l'oxyde de cérium est partie de la liste des 13 matières premières économiquement importants qui ont été identifiés par la Commission européenne comme soumis à un risque élevé d'interruption de l'alimentation. Dans ce contexte, les oxydes de type brownmillérite sont d'un intérêt potentiel, car ils révèlent oxygène mobilité ionique jusqu'à la température ambiante. En outre, ils permettent de régler la présence de défauts étendus par exemple frontières anti-phase au cours de conditions de synthèse, et qui se sont avérés diminuer de manière significative l'énergie d'activation pour la diffusion d'oxygène. Nous avons ainsi pu montrer que vice-riche nano-Ca2Fe2O5, traditionnellement connue comme une ligne phase stoechiométrique, peut être oxydé dans des conditions douces à CaFeO3, tandis que l'oxydation de Ca2Fe2O5 ordinaire nécessite généralement des conditions de réaction extrême, soit 1100 ° C et plusieurs GPa pression partielle d'oxygène. Ainsi, l'introduction d'une forte concentration de défauts semble être un concept prometteur pour transformer ligne phases stoechiométriques même traditionnellement connus pour devenir une sorte d'éponge de l'oxygène et de se comporter en tant que composé de stockage / tampon d'oxygène à des températures très modérées. Ce comportement est donc comparable à la capacité de stockage d'oxygène d'oxyde de cérium dopé, et dispose d'un potentiel réel pour l'application dans la catalyse. Par conséquent, le brownmillérite Ca2Fe2O5 semble être un candidat prometteur pour étudier en raison de ses oxygène connue propriétés de conductivité ionique.Objectif principal de ce travail est d'établir la relation fondamentale entre structure / microstructure, propriétés de mobilité de l'oxygène et de l'activité catalytique, simultanément entrepris pour deux systèmes: Ca2Fe2O5 avec la structure brownmillérite-type et CeO2 avec une structure de type fluorite. Nous essentiellement exploré les critères sous-jacents qui régissent leur composition chimique / activité catalytique, utilisant de l'oxygène comportement d'échange des isotopes par TG expériences couples de MS. D'autres études utilisant la spectroscopie Raman essentiellement permis de conclure à partir d'une dynamique de réseau modifiées pour différents isotopes de l'oxygène à la différence entre masse et la participation à l'oxygène de la surface au mécanisme d'oxydation du CO en CO2. Pour une meilleure compréhension mécaniste de l'oxydation de CO, nous avons développé un nouveau test catalytique, par rapport à une variation dynamique de la pression partielle d'oxygène dans le récipient de réaction, ce qui permet de conclure à la fois sur l'activité catalytique du catalyseur et sa libération de l'oxygène / comportement absorption , non accessible par le test d'activité catalytique classique interprétée sous un flux de gaz constant. De cette façon, nous avons eu un nouvel aperçu de différencier la participation de la surface et de l'activité vrac d'oxygène pour les catalyseurs à base d'oxyde de cérium et Ca2Fe2O5 différente. / Accomplishing specifications of new regulations regarding automotive exhaust after-treatment technologies, e.g. TWC, imply the availability and usage of catalytically active materials and especially oxygen buffer compounds, which can reversibly store and release high quantities of the oxygen. Doped cerium oxide presents still today the only reference compound for a suitable support, due to its high oxygen storage capacity and ability to easily create oxygen ion vacancies. However, for economic reasons and very limited natural abundance to a few countries, the substitution of ceria appears to be mandatory; in this context we note that ceria is part of the list of 13 economically important raw materials which were identified by the European Commission as subject to a high risk of supply interruption.In this context, Brownmillerite-type oxides are of potential interest, since they reveal oxygen ion mobility down to ambient temperature. Furthermore, they allow to adjust the presence of extended defects e.g. anti-phase boundaries, during synthesis conditions, and which have been shown to significantly decrease the activation energy for oxygen diffusion. We were thus able to show that defect-rich nano-Ca2Fe2O5, traditionally known as a stoichiometric line-phase, can be oxidized under mild conditions to CaFeO3, while the oxidation of ordinary Ca2Fe2O5 usually requires extreme reaction conditions, i.e. 1100°C and several GPa oxygen partial pressure. Thus, introducing a high concentration of defects seems to be a promising concept to transform even traditionally known stoichiometric line-phases to become a kind of oxygen sponge and behave as oxygen storage/buffer compound at very moderate temperatures. This behavior is thus comparable to the oxygen storage capacity of doped cerium oxide, and offers a true potential for application in the catalysis. Consequently, the Brownmillerite Ca2Fe2O5 appears to be a promising candidate to study due to its known oxygen ion conductivity properties.Primary aim of this work is to establish fundamental relation between structure/microstructure, oxygen mobility properties and catalytic activity, simultaneously undertaken for two systems: Ca2Fe2O5 with Brownmillerite-type structure and CeO2 with Fluorite-type structure. We essentially explored the underlying criteria governing their chemical/catalytic activity, using oxygen isotope exchange behavior by TG couples MS experiments. Further studies using essentially Raman spectroscopy allowed concluding from a modified lattice dynamics for different oxygen isotopes to differentiate between bulk and surface oxygen participation to the oxidation mechanism of CO to CO2. For a deeper mechanistic understanding of the CO oxidation, we developed a new catalytic test, based on a dynamic variation of the oxygen partial pressure in the reaction vessel, allowing to conclude simultaneously on the catalytic activity of the catalyst and its oxygen release/uptake behavior, not accessible by the classical catalytic activity test performed under constant gas flow. In this way we got a new insight to differentiate the participation of surface and bulk oxygen activity for different Ca2Fe2O5 and ceria based catalysts.

This work is devoted to studying of electric properties, chemical stability and features of disordering in a crystal structure of the phases La28-xW4+xO54+1,5x[VО]2-1,5x (x=0,85; 1,01; 1,17; 1,33) and Pr28-xW4+xO54+1,5x[VО]2-1,5x (x = 0,92; 1,12; 1,33; 1,55) with cubic structure of defective double fluorite with an incomplete oxygen sublattice. Phases are received by solid-state ceramic technology. Using X-ray difractiion method phase composition is established, structural parameters and presumable phase composition taking into account shift of parameters are determined. Measurements of temperature dependence of conductivity are taken by method of impedance spectroscopy at a variation of temperature, partial pressure of oxygen pO2 and water vapors pH2O. Activation energy calculated of mixed hole, oxygen-ion conductivity and proton conductivity is calculated. Dependences of total ionic transport numbers t (ion) on pO2 for La28-хW4+хO54+1,5х[VO]2-1,5х are calculated from experimental isotherms of conductivity. Ion transport number t (ion) for Pr28-xW4+xO54+1,5x[VО]2-1,5x are measured by the EMF method, the type of the dominating charge carriers is defined. Chemical stability of ceramics La28-хW4+хO54+1,5х[VO]2-1,5х to hydrolytic decomposition and its interactions with acid gases were estimated increasing of grain boundary resistance after the cycle "hydration/dehydration", and also by results of X-ray phase analysis, thermogravimetric analysis and research of surfaces of the samples by of the optical and scanning electronic microscopy methods. Water uptake XH2O and extent of filling of structural vacancies of the phases La28-хW4+хO54+1,5х[VO]2-1,5х are defined by the thermogravimetric analysis the 2-1,5kh and, hydration enthalpies ΔНгидр are calculated. An influence of pO2 and pH2O on loss of weight of Pr28-xW4+xO54+1,5x[VО]2-1,5x samples testifies to susceptibility of the phases to oxidation. / Данная работа посвящена изучению электрических свойств, химической устойчивости и особенностей разупорядочения в кристаллической решетке фаз La28-xW4+xO54+1,5x[VО]2-1,5x (х=0,85; 1,01; 1,17; 1,33) и Pr28-xW4+xO54+1,5x[VО]2-1,5x (х = 0,92; 1,12; 1,33; 1,55), обладающих кубической структурой дефектного двойного флюорита с некомплектной кислородной подрешеткой. Фазы получены твердофазным синтезом по керамической технологии, методом РФА установлен фазовый состав, определены параметры кристаллической решетки и предположительный фазовый состав с учетом сдвига параметров. Проведены измерения температурной зависимости проводимости методом импедансной спектроскопии при вариации температуры, парциального давления кислорода Ро2 и паров воды Рн2о. Рассчитаны энергии активации смешанной дырочно-кислородной проводимости и протонной проводимости. Из экспериментальных изотерм проводимости La28-хW4+хO54+1,5х[VO]2-1,5х рассчитаны зависимости суммарных ионных чисел переноса t(ион) от Ро2. Для Pr28-xW4+xO54+1,5x[VО]2-1,5x t(ион) измерены методом ЭДС, определен тип доминирующих переносчиков заряда. Проведена оценка устойчивости керамики La28-хW4+хO54+1,5х[VO]2-1,5х к гидролизному разложению и взаимодействию с кислотными газами по приросту зернограничного сопротивления после цикла «гидратация/дегидратация», а также по результатам рентгенофазового анализа, термогравиметрического анализа и исследованием поверхностей образцов методами оптической и сканирующей электронной микроскопии. С помощью термогравиметрического анализа определена степень гидратации Хн2о фаз La28-хW4+хO54+1,5х[VO]2-1,5х и степень заполнения структурных вакансий, рассчитаны энтальпии гидратации ΔНгидр. Влияние Ро2 и Рн2о на потерю массы образцами Pr28-xW4+xO54+1,5x[VО]2-1,5x свидетельствует о подверженности фаз окислению.