The results of chemical and self-diffusion coefficient of O vacancies, O ionic conductivity and ionic transport numbers measured as a function of O partial pressure PO2 and temperature in the ranges −4 ≤ log(PO2, atm) ≤ 0 and 900 ≤ T, C ≤ 1050, respectively, were presented for the perovskite-type undoped LaCoO3−δ and doped with chromium LaCo0.7Cr0.3O3−δ cobaltites. The dependencies of these properties on O partial pressures were shown to have monotonic character. This could therefore indicate that defect clusters or associates containing O vacancies did not form in the oxides over complete PO2 range investigated. The predominant charge carriers in both undoped and Cr-doped lanthanum cobaltite were electron defects, since O vacancies transport numbers did not exceed 2 x 10−3%. The substitution of Cr for Co was found to lead to decrease of both ionic conductivity and O chemical diffusion coefficient. Activation energy of ionic conductivity of the oxides studied decreased with the O nonstoichiometry increase. Self-diffusion coefficient of O vacancies and their mobility were shown to be independent of O partial pressure and nonstoichiometry most likely due to lack of the defects interaction in the oxide studied.

Oxide Ion Transport in Undoped and Cr-Doped LaCoO3−δ. D.S.Tsvetkov, A.Y.Zuev, A.I.Vylkov, A.N.Petrov: Solid State Ionics, 2007, 178[25-26], 1458-62