Oxygen Permeability and Stability of Sr_0.95Co_0.8Fe_0.2O_3-δ in a CO₂- and H₂O-Containing Atmosphere

The oxygen permeability and stability of a perovskite oxide membrane of nominal composition Sr 0.95 Co 0.8 Fe 0.2 O 3 - δ were investigated in an atmosphere containing CO 2 and H 2 O. It was observed that, at a temperature of 810 °C, the oxygen permeation flux through the membrane decreased significantly with time when an air stream containing both CO 2 and H 2 O impurities was used as the feed gas and the membrane partially decomposed, whereas in air containing either CO 2 or H 2 O 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 °C, the oxygen flux was almost unaffected by the presence of these species and the membrane remained intact. The effects of CO 2 and H 2 O were explained in terms of formation of bicarbonate on the membrane surface, and optimal operation conditions for the membrane were proposed.