Oxygen Permeation Properties of Partially A-Site Substituted BaFeO[sub 3−δ] Perovskites

To explore oxygen permeable materials, oxygen permeation properties of partially A-site substituted perovskites were investigated. Ba sites in were substituted with cations such as Na, Rb, Ca, Y, and La by 5%. The partial substitution with Ca, Y, and La, whose ionic radii are smaller than that of Ba, succeeded in stabilizing a cubic perovskite structure that is a highly oxygen permeable phase, as revealed by X-ray diffraction analysis. This can be explained in terms of a decrease in the tolerance factor . Among the (M = Na, Rb, Ca, Y, and La) membranes tested, showed the highest oxygen permeability at 600–930°C, owing to the stabilization of the cubic phase without the formation of impurity phases. From chemical analysis, the oxygen permeability of membranes was correlated with the amount of oxygen defects (δ) in the lattice. The oxygen permeation flux of membrane was significantly increased by reducing its thickness. Furthermore, a membrane exhibited good phase stability under He flow at elevated temperatures. The obtained results indicate the promising properties of membranes as a cobalt-free material that has a high oxygen permeability, good phase stability, and low cost.