Oxygen permeability, electrical property and stability of La_0.8Sr_0.2Co_0.2Fe_0.8O_3-δ membrane

A typical dense membrane of perovskite La_0.8Sr_0.2Co_0.2Fe_0.8O_3-δ have been successfully prepared by citrate method using nitrate salts as cation source and citrate as an organic agent. Precursor of La_0.8Sr_0.2Co_0.2Fe_0.8O_3-δ was analyzed by thermal gravimetric analysis and XRD to investigate optimum calcination temperature. Organic compound and nitrate burned out below 400°C. Weight loss observed over 700°C is due to decomposition of SrCO₃. The recommended temperature for calcination of precursor is over 900°C at which single perovskite powder is obtained without impurities. The electrical property, oxygen permeation and stability of membrane were investigated in the range of 700 to 950°C. The electrical conductivity increased with increasing temperature but then decreased over 850°C (20% O₂) and 750°C (1% O₂) due to oxygen loss from the crystal lattice. The oxygen flux of La_0.8Sr_0.2Co_0.2Fe_0.8O_3-δ membrane increased with the increasing temperature. Themaximum oxygen permeation was measured to be 0.19 mL/min cm² at 950°C. The activation energy for oxygen permeation was calculated to be 78 kJ/mol. Perovskite structure and phase did not change even after permeation test of 40 h.