Oxygen permeable membrane and process for its preparation

The invention relates to a composite membrane for the selective gas separation, comprising, arranged a layer system with a continuously porous, mechanically strong, backing layer which has an average pore size in the micrometer range with at least one on the support layer, through intermediate porous layer has an average pore size in the range has between 2 and 200 nm, and arranged with a on the intermediate layer, gas-tight functional layer of a mixed conducting material having a maximum thickness of 1 micron. The support layer consists of a structural ceramic, a metal or a cermet, and has a layer thickness of at most 1 mm. The intermediate layer is present in a total layer thickness of a maximum of 100 microns and has an average pore size in the range between 10 and 100 nm. The functional layer comprises a perovskite, a fluorite or a material having a K The layer thickness of the functional layer is at most 50 nm, in particular between 25 and 400 nm. For the preparation of this composite membrane is applied to a continuously porous, mechanically stable carrier layer having an average pore size in the micron range, at least one porous intermediate layer, wherein the intermediate layer has an average pore size in the range between 2 and 200 nm. In this intermediate layer ...