Perovskite-type B-site Bi-doped ceramic membranes for oxygen separation

Novel mixed conducting oxides, B-site Bi-doped perovskites were exploited and synthesized. Cubic perovskite structures were formed for BaBi0.2CoyFe0.8-yO3-δ (y S0.4) and BaBixCo0.2Fe0.8-xO3-δ(x=0.1-0.5). The materials exhibited considerable high oxygen permeability at high temperature. The oxygen permeation flux of BaBi0.2Co0.35Fe0.45O3-δ membrane reached about 0.77×10-6 mol/cm2 · s under an air/helium oxygen partial pressure gradient at 900°C, which was much higher than that of other bismuth-contained mixed conducting membranes. The permeation fluxes of the materials increased with the increase of cobalt content, but no apparent simple relationship was found with the bismuth content. The materials also demonstrated excellent reversibility of oxygen adsorption and desorption. Stable time-related oxygen permeation fluxes were found for BaBi0.22O0.35Co0.35Fe0.45O33-δ and BaBi0.3Co0.2Fe0.5O3-δ membranes at 875°C.