High oxygen permeation in Ba_0.95La_0.05FeO _3-δ membranes with surface modification

Selective oxygen separation from air was carried out using ceramic membranes composed of Ba_0.95La_0.05FeO_3-δ. We demonstrated that surface abrasion of Ba_0.95La _0.05FeO_3-δ membranes led to a significant increase in oxygen permeation fluxes at 700-930 °C because of an increase in surface reaction sites. Abrasion of the oxygen desorption side of the membrane resulted in a higher oxygen permeability than with abrasion on the oxygen sorption side. Moreover, an increase in the area of the oxygen desorption side also increased the oxygen permeability. The results suggest that oxygen permeation through Ba_0.95La_0.05FeO_3-δ membranes is limited by the desorption of oxygen (surface reaction) and bulk diffusion. Attachment of a porous layer made of Ba_0.95La_0.05FeO _3-δ to the membrane surface was also effective in increasing oxygen permeability. For example, a high permeation flux of 3.2 cm³ min^-1 cm^-2 was achieved at 930 °C under a He/air gradient for a membrane (0.5 mm thickness) coated with a porous layer (14.4 μm).