I-76 Ion-electron transport in strontium ferrites: relationships with structural features and stability [Text] / M. V. Patrakeev, I. A. Leonidov, V. L. Kozhevnikov, V. V. Kharton // Solid State Sciences. - 2004. - Vol. 6, № 9. - P907-913. - Bibliogr. : p. 913 (27 ref.) Рубрики: ХИМИЧЕСКИЕ НАУКИ Кл.слова (ненормированные): ФЕРРИТ СТРОНЦИЯ -- НЕСТЕХИОМЕТРИЯ КИСЛОРОДНАЯ -- ПРОВОДИМОСТЬ ИОННАЯ -- ИОННЫЙ ПЕРЕНОС -- ЭЛЕКТРОННЫЙ ТРАНСПОРТ Аннотация: The total electrical conductivity of strontium ferrites, including intergrowth Sr4Fe6O13+delta, Sr3Fe2O6+delta with a Ruddlesden-Popper??structure, and SrFeO2.5+delta where the cubic perovskite lattice transforms into vacancy-ordered brownmillerite at p(O2) < 10 Pa and??T < 850 .C, was measured at 650.1000 .C in the oxygen partial pressure range 10.15 Pa to 50 kPa. The data were used in order to determine partial ion, p- and n-type electron contributions in the vicinity of electron.hole equilibrium point. The ferrites with brownmillerite and Ruddlesden-Popper structures exhibit substantial ion transport due to thermally-activated disordering of oxygen vacancies and??oxygen ions in the perovskite structural slabs, whereas the ion conductivity of Sr4Fe6O13+delta remains below 0.01 S cm.1 in the studied??conditions. The bonding energy of oxygen ions, evaluated from the formation enthalpy of n-type charge carriers, increases in the sequence??Sr4Fe6O13+delta < SrFeO3+delta < Sr3Fe2O6delta. These values correlate with thermodynamic stability of strontium ferrites at low p(O2). The??transition of SrFeO2.5+delta brownmillerite into disordered cubic phase above 850 .C leads to higher stability in reducing atmospheres. The??level of p-type conductivity is mainly governed by the concentration of electron holes, which was calculated from the oxygen content??determined by coulometric titration technique. The hole mobility, which is quite similar for all strontium ferrites and has a temperatureactivated??character, varies in the range 0.005.0.05 cm2 V.1 s.1 indicative of small-polaron conduction mechanism \\\\Expert2\\nbo\\Solid State Sciences\\2004, v.6, N 9, p.907.pdf |