High performance oxygen permeation membrane: Sr and Ti co-doped BaFeO3-δ ceramics

•Sr-doping stabilizes the cubic perovskite structure of BaFeO3-based materials.•Ba0.8Sr0.2FeO3-δ delivers high oxygen permeability of 1.25 mL cm−2 min−1 at 900 °C.•More Sr-doping for Ba is favorable to the structural stability.•A slight amount of Ti at Fe-site enhances remarkably the structural stability.•Ba0.6Sr0.4Fe0.92Ti0.08O3-δ shows excellent overall performance. Novel cobalt-free perovskite-type oxides of Ba1-xSrxFeO3-δ (x = 0–0.4) and Ba0.6Sr0.4Fe1-yTiyO3-δ (y = 0–0.12) were successfully prepared by traditional solid-state method and systematically characterized as oxygen permeation membranes. When doping strontium ranges from × = 0.2 to 0.4, cubic perovskite-type structure can be stabilized down to ambient temperature for Ba1-xSrxFeO3-δ. The oxygen permeation flux decreases but the structural stability increases slightly with increasing Sr doping level. The Ba0.8Sr0.2FeO3-δ membrane shows the highest oxygen permeation flux of 1.25 mL cm−2 min−1 at 900 °C under air/He gradient oxygen partial pressure condition for a 1 mm thick membrane. The Ti substitution for partial Fe enhances significantly the chemical and structural stability of Ba0.6Sr0.4Fe1-yTiyO3-δ against H2 and CO2 containing atmospheres but at a slight expense of oxygen permeability. The Ba0.6Sr0.4Fe0.92Ti0.08O3-δ membrane, with excellent structural stability and high oxygen permeation flux of 0.93 mL cm−2 min−1 at 900 °C, shows great potential in oxygen separation and related membrane reactor applications.