On the structural stability and oxygen permeation behavior of inorganic SrCo0.8Fe0.2O3−δ membranes

The high oxygen permeability combined with reasonable structural stability of perovskite-type ABO3−δ compounds is vital for their potential applications in gas separation, solid oxide fuel cells, sensors, etc. Hence, an attempt is made to develop SrCo0.8Fe0.2O3−δ-based dense membranes with sol-gel-derived oxalates and study their phase stability and oxygen permeation. While X-ray diffraction confirms the presence of a perovskite-type cubic phase above 800 °C, X-ray photoelectron spectroscopy reveals the presence of cobalt and iron in 3+ and 4+ oxidation states with O2 2−, O2 − and O− species. The electrical conductivity increases up to a characteristic temperature and decreases slowly thereafter via pronounced carrier scattering. A 1.5-mm-thick membrane displays reasonable oxygen permeability of 1.05 × 10−6 mol cm−2 s−1 at 900 °C but has inadequate stability. Partial substitution of iron with zirconium is shown to improve permeability and stability significantly. Thus, SrCo0.8Fe0.15Zr0.05O3−δ membrane shows promise for oxygen permeation purposes.