O-97 Oxygen Nonstoichiometry, Conductivity, and Seebeck Coefficient of La0.3Sr0.7Fe1-xGaxO2.65+delta Perovskites [] / M. V. Patrakeev, E. B. Mitberg, A. A. Lakhtin, I. A. Leonidov, V. L. Kozhevnikov, V. V. Kharton, M. Avdeev, M. B. Marques // Journal of Solid State Chemistry. - 2002. - V. 167, N 1. - С. 203-213 . - ISSN 0022-4596 Рубрики: ХИМИЧЕСКИЕ НАУКИ Кл.слова (ненормированные): ПЕРОВСКИТЫ -- ОКСИДНАЯ НЕСТЕХИОМЕТРИЯ -- НЕСТЕХИОМЕТРИЯ ОКСИДНАЯ -- ОКСИДНАЯ ТЕРМОДИНАМИКА -- ТЕРМОДИНАМИКА ОКСИДНАЯ -- ЭЛЕКТРОННО-ДЫРОЧНАЯ ПРОВОДИМОСТЬ -- Ga -- ГАЛЛИЙ -- ЛЕГИРОВННЫЕ ФЕРРИТЫ -- ФЕРРИТЫ ЛЕГИРОВАННЫЕ -- ЭНТАЛЬПИЯ -- ЭНТРОПИЯ Аннотация: The total electrical conductivity and the Seebeck coefficient of perovskite phases La0.3Sr0.7Fe1-xGaxO2.65+delta (x = 0-0.4) were determined as functions of oxygen nonstoichiometry in the temperature range 650-950°C at oxygen partial pressures varying from 10-4 to 0.5 atm. Doping with gallium was found to decrease oxygen content, p-type electronic conduction and mobility of electron holes. The results on the oxygen nonstoichiometry and electrical properties clearly show that the role of gallium cations in the lattice is not passive, as it could be expected from the constant oxidation state of Ga3+. The nonstoichiometry dependencies of the partial molar enthalpy and entropy of oxygen in La0.3Sr0.7(Fe,Ga)O2.65+delta are indicative of local inhomogeneities, such as local lattice distortions or defect clusters, induced by gallium incorporation. Due to B-site cation disorder, this effect may be responsible for suppressing long-range ordering of oxygen vacancies and for enhanced st ability of the perovskite phases at low oxygen pressures, confirmed by high-temperature X-ray diffraction and Seebeck coefficient data. The values of the electron-hole mobility in La0.3Sr0.7(Fe,Ga)O2.65+delta, which increases with temperature, suggest a small-polaron conduction mechanism |
H 99 Influence of Oxygen Nonstoichiometry on the Special Properties of Solid Solutions LaNb2-2xTa2xVO9-delta (x = 0-0.4) and LaTa2-2xNb2xVO9-delta (x = 0-0.1) [] / M. G. Zuev, E. V. Arkhipova, L. A. Perelyaeva, L. V. Zolotukhina, O. B. Lapina, R. N. Pletnev // Journal of Solid State Chemistry. - 2002. - V.167, N 1. - С. 73-79 . - ISSN 0022-4596 Рубрики: ХИМИЧЕСКИЕ НАУКИ Кл.слова (ненормированные): ТВЕРДЫЕ РАСТВОРЫ -- ОКСИДНАЯ НЕСТЕХИОМЕТРИЯ -- НЕСТЕХИОМЕТРИЯ ОКСИДНАЯ -- ЭПР -- ЭЛЕКТРОННЫЙ ПАРАМАГНИТНЫЙ РЕЗОНАНС -- ЯМР -- ЯДЕРНЫЙ МАГНИТНЫЙ РЕЗОНАНС -- ИК-СПЕКТРОСКОПИЯ -- ИНФРАКРАСНАЯ СПЕКТРОСКОПИЯ -- СПЕКТРОСКОПИЯ ИНФРАКРАСНАЯ -- СПЕКТРАЛЬНЫЕ СВОЙСТВА -- СВОЙСТВА СПЕКТРАЛЬНЫЕ -- La -- Nb -- Ta -- V -- ЛАНТАН -- НИОБИЙ -- ТАНТАЛ -- ВАНАДИЙ -- СПЕКТРОСКОПИЯ КОМБИНАЦИОННОГО РАССЕЯНИЯ Аннотация: Phase equilibria in the LaVO4-Nb2O5-Ta2O5 system were analyzed. New solid solutions LaTa2-2xNb2xVO9-delta (x = 0-0.1) and LaNb2-2xTa2xVO9-delta (x = 0-0.4) were detected in this system. The structures of the vanadate-niobate LaNb2VO9 and vanadate-tantalate LaTa2VO9 are not known. The structures of the vanadate-tantalate LaTa2VO9 and LaTa2VO9-based solid solutions are similar to the structure of LaTa7O19, which refers to the hexagonal crystal system. The influence of the oxygen nonstoichiometry delta (x) on crystallochemical characteristics and spectral properties of these solid solutions were examined by the X-ray phase analysis, IR and radio spectroscopic methods. A correlation between the nonstoichiometry delta (x) and the volume of a unit cell V(x) of solid solutions LaTa2-2xNb2xVO9-delta was found. The IR spectrum of LaTa2VO9-delta transformed in going from delta = 0 to delta # 0. Two types of VO4 tetrahedra were formed in solid solutions LaNb2-2xTa2xVO9-delta depending on delta (x) |