Oxygen absorption and desorption behavior of Ba0.5La0.5FeO3-δ and its effect on crystal structure and electrical conduction properties

Abstract

As a new mixed conductor with high property, the preparation of Ba0.5La0.5FeO3-δ with cubic perovskite structure was examined under different values of oxygen partial pressure, P(O2). An almost-single-phase Ba0.5La0.5FeO3-δ with cubic perovskite structure was successfully prepared by sintering at 1200 °C under P(O2) values ranging between 1 and 10−9 atm. The existence of two types of cubic Ba0.5La0.5FeO3-δ phases, one with a smaller δ and paramagnetic Fe with valence between 3+ and 4+ and the other with larger δ and antiferromagnetic Fe with valence of almost 3+, was clarified. Moreover, the above two phases could be interchanged with each other by annealing at 1200 °C under controlled P(O2). It was revealed that the oxygen-deficient cubic phase rapidly absorbed oxygen above 300 °C in air and that δ increased with temperature above 400 °C in air. Rapid oxygen absorption or desorption by switching the gas flow between O2 and N2, as well as its cyclic behavior with high reproducibility, was also observed. Under P(O2) values ranging between 1.0 and 1.02 × 10−2 atm, the temperature dependence of electrical conductivity was small regardless of P(O2), and the difference in electrical conductivity by P(O2) was scarcely observed. Log σ reached approximately 1.5 at 400 °C. With P(O2) decreasing to 1.01 × 10−3 or less, a slight increase in electrical conductivity was observed with an almost constant log σ on temperature.