Oxygen permeability and phase stability of Ba0.5Sr0.5Co0.8Fe0.2O3-δ dense membrane

A dense membrane of perovskite Ba0.5Sr0.5Co0.8Fe0.2O3-δ has been successfully prepared by polymerized complex method. Precursor of Ba0.5Sr0.5Co0.8Fe0.2O3-δ was analyzed by thermal gravimetric analysis and XRD to investigate optimum calcination temperature. The optimum sintering temperature of precursor is between 1000 and 1100 ℃ at which single perovskite powder is obtained without impurities. The oxygen flux of of Ba0.5Sr0.5Co0.8Fe0.2O3-δ membrane increased with increasing temperature and decreasing thickness, and the oxygen permeation flux through 1.0 mm membrane with modified surface exposed to flowing air (Ph =0.21 atm) and helium (Pl =10⁻⁵ atm) was ca. 1.4 ml/cm²·min at 950 ℃. At high temperature over 850 ℃ surface reaction is more important than bulk diffusion. Membranes after permeation test were stable in view of crystal structure irrespective of surface modification but swollen part was formed in feed-side surface of non-modified membrane. Low oxygen permeation flux of non-modified membrane might be originated from low surface adsorption and barium surface diffusion in feed side.