Oxygen vacancy concentration variation, diffusivity and thermo-chemical stability of La_0.2Ba_0.8Co_0.2Fe_0.8O_3-δ membranes

Perovskite type La_0.2Ba_0.8Co_0.2Fe_0.8O_3-δ (LBCF) powders were synthesized by modified citrate pyrolysis and LBCF membranes were prepared by isostatic pressing. The oxygen vacancy concentration variation of the LBCF powders becomes substantial above 973 K due to order-disorder transition. The unsteady-steady oxygen permeation flux of the LBCF membrane decreases with time and it takes about 40 min to get the steady state. In the temperature range of 1073-1223 K, the oxygen vacancy diffusivity of the LBCF membrane increases almost a magnitude and the increasing of oxygen permeation flux is mainly attributed to the increasing of oxygen vacancy diffusivity. An in-situ high-temperature X-ray diffraction was used to study the stability of the LBCF membrane, indicating that it has good thermochemical stability at elevated temperatures and low oxygen partial pressures.