Oxygen permeation and phase structure properties of partially A-site substituted BaCo0.7Fe0.225Ta0.075O3-δ perovskites

Ba0.9R0.1Co0.7Fe0.225Ta0.075O3-δ (BRCFT, R = Ca, La or Sr) membranes were synthesized by a solid-state reaction. Metal cation Ca2+, La3+ or Sr2+ doping on A-site partially substituted Ba2+ in BaCo0.7Fe0.225Ta0.075O3-δ oxides, and its subsequent effects on phase structure stability, oxygen permeability and oxygen desorption were systematically investigated by XRD, TG-DSC, H2-TPR, O2-TPD techniques and oxygen permeation experiments. The partial substitution with Ca2+, La3+ or Sr2+, whose ionic radii are smaller than that of Ba2+, succeeded in stabilizing the cubic perovskite structure without formation of impurity phases, as revealed by XRD analysis. Oxygen-involving experiments showed that BRCFT with A-site fully occupied by Ba2+ exhibited good oxygen permeation flux under He flow, reaching about 2.3 mL·min−1 ·cm−2 at 900 °C with 1 mm thickness. Of all the membranes, BLCFT membrane showed better chemical stability in CO2, owing to the reduction in alkalinity of the mixed conductor oxide by La doping. In addition, we also found the stability of the perovskite structure under reducing atmospheres was strengthened by increasing the size of A-site cation (Ba2+>La3+>Sr2+>Ca2+).

Graphical AbstractThe A-site fully occupied by Ba2+ makes the membranes display very high oxygen permeability, 2.3 mL·min−1 ·cm−2 at 900 °C with 1.0 mm thickness.Figure optionsDownload as PowerPoint slide