Abstract: The present invention is a method for manufacturing ultrathin inorganic membranes comprising yttria-stabilized zirconia (YSZ) in a thickness of .ltoreq.0.5 .mu.m which has been deposited onto a lanthanum-doped alumina surface layer of a porous alumina substrate having an average pore diameter of less than about 50 nm. The inorganic membranes formed by the method provide oxygen flux rates superior to those known in the art and are suitable for numerous uses including processes for separating oxygen from oxygen-containing gaseous mixtures and in processes for partially oxidizing hydrocarbons to their corresponding oxidized products.