Chemical diffusion and oxygen exchange of LaNi0.4Fe0.6O3−δ ceramics

Abstract

Oxygen surface exchange and oxygen chemical diffusion coefficients of LaNi0.4Fe0.6O3−δ ceramics are determined via conductivity relaxation method after stepwise change of temperature in the range of 700–950 °C in air and Ar/O2 gas flow at oxygen partial pressures (po2) of 4 Pa, 18 Pa, 37 Pa, 47 Pa and 59 Pa. The highest conductivity (about 160 S·cm−1) is found at 950 °C in air. No oxygen exchange (δ = 0) below 700 °C is observed in the investigated (po2 range. The oxygen exchange coefficients determined in reduction mode are higher than those determined in oxidation mode. This is explained by clusterization of oxygen vacancies on the surface of the sample investigated in oxidation mode. The opposite tendency is found for chemical diffusion coefficients. Unlike surface, the oxygen vacancies of the volume region are probably not clustered and have predetermined the higher oxygen diffusion mobility of the sample treated in oxidation mode.