Investigation of structure and oxygen permeability of Ba–Ce–Co–Fe–O system

Mixed ionic–electronic conducting perovskite oxides, BaCe0.1CoxFe0.9−xO3−δ, were synthesized with a combined citric acid and EDTA complexing method. The structure and oxygen permeability of BaCe0.1CoxFe0.9−xO3−δ series was investigated by X-ray diffraction (XRD), scanning electron microscope (SEM) and oxygen permeation operation. XRD characterization showed that pure cubic perovskite structure can be obtained only if the content of cobalt and cerium in B-site of Ba–Ce–Co–Fe–O series is no more than 40% and 15%, respectively. Lattice parameters of BaCe0.1CoxFe0.9−xO3−δ gradually increase with cobalt and cerium content, iodine titration experiment revealed that the doping of cerium ions with big radius can keep B-site cobalt and iron ions in low valence state. Oxygen permeation operation showed that oxygen permeation flux of all BaCe0.1CoxFe0.9−xO3−δ membranes gradually increases with testing time in the initial stage, and the time to reach steady state becomes longer with the increase of cobalt content. After reaching permeation steady state, BaCe0.1Co0.4Fe0.5O3−δ exhibits highest oxygen flux amongst BaCe0.1CoxFe0.9−xO3−δ series.