Phase Structure and Oxygen Permeability of Partially B-site-substituted BaCoxFe1−xO3−δ Ceramic Membranes

Effect of Co dopant on phase structure and oxygen permeability of BaFeO3−δ hexagonal composite was explored via comparative studies. It demonstrated that the introduction of Co can induce hexagonal BaFeO3−δ to transform into a cubic perovskite structure. Especially, the partial substitution of Fe with Co by 10–50% can lead to the stabilization of pure cubic perovskite structure even at room temperature. We demonstrated that the improvement in cobalt doping content can increase the lattice volume and oxygen permeability of BaCoxFe1−xO3−δ (x = 0.1–0.5) due to appropriate structural optimization. Amongst BaCoxFe1−xO3−δ (x = 0.1–0.5) samples, BaCo0.4Fe0.6O3−δ displays an excellent oxygen permeability and structural stability owing to optimal Gold Schmidt tolerance factor. Although BaCo0.5Fe0.5O3−δ display the highest oxygen permeation flux at elevated temperature, its moderate-low temperature oxygen permeability below 750 °C is poor due to structural phase transition. This study clarifies an optimal doping range of Co cations in BaCoxFe1−xO3−δ to stabilize their cubic perovskite structure.