Characterization of oxygen-dependent stability of selected mixed-conducting perovskite oxides

Abstract For high-temperature energy applications, e.g., as solid oxide fuel cell cathodes or as dense ceramic oxygen-transport membranes, mixed ionic-electronic conducting (MIEC) perovskites, namely of the composition (A x Sr 1 −  x )(Co y Fe 1 −  y )O 3− δ (A = La, Pr, Ba), are promising candidates given their excellent oxygen-ionic and electronic transport properties. A high level of oxygen non-stoichiometry is an important prerequisite for a high performance; however, the structural stability of the oxide is also affected by oxygen deficiency. By coulometric titration experiments performed on selected state-of-the-art MIEC powder samples in a tubular zirconia “oxygen pump” setup, facilitating precise control of the oxygen partial pressure in the entire range between p O 2  = 10 − 18 …1 bar at temperatures between 700…1000 °C, the low- p O 2 stability limits can be determined. By monitoring the electrical current necessary for pumping oxygen through the solid electrolyte into or out of the measurement chamber, the amount of oxygen transported and, thus, changes in oxygen stoichiometry can be determined. The low- p O 2 stability limits for all investigated high-performance MIEC oxides were similar (below 10 − 10  bar at 900 °C).