Bismuth doping effects on the structure, electrical conductivity and oxygen permeability of Ba0.6Sr0.4Co0.7Fe0.3O3−δ ceramic membranes

A series of Ba0.6Sr0.4Co0.7Fe0.3−xBixO3−δ (BSCFB, x = 0–0.2) ceramic membranes were prepared by solid state reaction method. The doping effects on the phase structure, structural stability, electrical conductivity and oxygen permeability were investigated. Little amount of Bi (x = 0–0.08) can maintain the cubic perovskite structure of BSCFB materials while more Bi (x > 0.08) will result in the generation of other impurities. Even in the Bi solid solution range, Bi doping is unfavorable for the enhancement of structural stability of BSCFB membranes. The electrical conductivity decreases with Bi doping level, while the oxygen permeability of BSCF membrane can be increased remarkably with little amount of Bi doping (x = 0.05). More Bi leads to the structure deterioration of membrane surface under oxygen permeation condition, resulting in a severe decrease in oxygen permeability. Considering the overall performance, a low Bi doping amount such as x = 0.05 is favored for the membrane applications.