To achieve a high oxygen permeation rate at medium and high temperature, an asymmetrically structured membrane, in which a thin dense layer (30 mu m) made of La0.6Ca0.4CoO3-delta (LCC) and BaFe0.975Zr0.025O3-delta (BFZ) was formed on a porous LCC support, was fabricated and tested for its oxygen permeability. The oxygen permeation flux significantly increased by mixing BFZ with LCC and reached a fairly high value of 1.60 cm(3) min(-1) cm(-2) even at 780 degrees C.