O-97 Oxygen Nonstoichiometry and Ionic Conductivity of Sr3Fe2-xScxO7-delta / A. A. Markov, M. V. Patrakeev, V. V. Kharton, Y. V. Pivak, I. A. Leonidov, V. L. Kozhevnikov // Chemistry of Materials. - 2007. - v.19, № 16. - С. 3980-3987. - Bibliogr. : 30 ref. Рубрики: ХИМИЧЕСКИЕ НАУКИ Кл.слова (ненормированные): НЕСТЕХИОМЕТРИЯ КИСЛОРОДНАЯ -- ПРОВОДИМОСТЬ ИОННАЯ -- СКАНДИЙ -- ЖЕЛЕЗО -- СТРОНЦИЙ Аннотация: The substitution of scandium for iron in the Ruddlesden-Popper Sr3Fe2-xScxO7-delta (x=0-0.3) system increases tetragonal unit-cell volume and oxygen nonstoichiometry and decreases partial p- and n-type electronic conductivities studied in the oxygen partial pressure range from 1 x 10(-20) to 0.7 atm at 973-1223 K. The solubility of Sc(3+) corresponds to approximately x ~ 0.35. The relatively low, temperatureactivated hole mobility indicates a small-polaron mechanism of the electronic transport, as for undoped Sr3Fe2O7-delta. The atomistic computer simulations showed that major contribution to the ionic conductivity is provided by the oxygen sites surrounded by iron cations in the perovskite-type layers of Sr3(Fe,Sc)2O7-delta structure, whereas stable ScO6 octahedra are essentially excluded from the oxygen diffusion processes.??Minimum migration energy, 0.9-1.4 eV, was found for nonlinear pathways formed by the apical O1??sites linking iron-oxygen polyhedra along the c-axis and equatorial O3 positions in the perovskite-type??planes. The direct O3 f O3 jumps are characterized with higher energetic barrier, 1.5-2.2 eV. Because??of the increasing concentration of vacant O3 sites induced by scandium doping, the apparent activation energy for oxygen-ionic transport decreases from about 2 eV, as observed for undoped strontium ferrite at 1123-1223 K, down to 0.95-1.15 eV for Sr3Fe2-xScxO7-delta (x = 0.2-0.3). As a result, the partial ionic conductivity of Sr3Fe1.7Sc0.3O7-delta at temperatures below 1000 K becomes higher than that in Sr3Fe2O7-delta |