Oxygen permeability and stability of Sr0.95Co0.8Fe0.2O3-δ in a CO2- and H2O-containing atmosphere

The oxygen permeability and stability of a perovskite oxide membrane of nominal composition Sr0.95Co0.81Fe0.2O3-sigma were investigated in an atmosphere containing CO2 and H2O. It was observed that, at a temperature of 810 degrees C, the oxygen permeation flux through the membrane decreased significantly with time when an air stream containing both CO2 and H2O impurities was used as the feed gas and the membrane partially decomposed, whereas in air containing either CO2 or H2O species alone, the oxygen flux decreased slightly and the membrane retained its phase composition and microstructure. It was also found that, at a higher temperature of 900 degrees C, the oxygen flux was almost unaffected by the presence of these species and the membrane remained intact. The effects of CO2 and H2O were explained in terms of formation of bicarbonate on the membrane surface, and optimal operation conditions for the membrane were proposed.