Oxygen Permeation Properties of Co-Free Perovskite-Type Oxide Membranes Based on BaFe[sub 1−y]Zr[sub y]O[sub 3−δ]

Partially Zr-substituted membranes were developed as a Co-free oxygen permeable membrane. In order to stabilize the cubic perovskite structure, Fe sites in were partially substituted with . In the substitution range of , the cubic perovskite structure was stabilized even at room temperature. Among the membranes prepared, a material showed the highest oxygen permeation flux of (standard temperature pressure) at under an air/He gradient. The oxygen permeation flux was higher than that of partially Ce-substituted membranes reported previously. From the results obtained by chemical and scanning electron microscope analyses, it appears that the oxygen permeability for membranes was well correlated with the amount of oxygen defects in the lattice as well as the grain size. In addition, the oxygen permeation flux of the membrane was significantly increased after decreasing the thickness of the membrane from . For thin membranes , the thickness dependence of the oxygen permeability deviated from the Wagner equation, suggesting that the oxygen permeation of is controlled by not only bulk diffusion of oxide ions but also their surface reactions.