Solid state synthesis of SrFeCo_0.5O_x asymmetric membranes for oxygen separation

SrFeCo_0.5O_x asymmetric membranes for oxygen permeation consisting of a thin dense layer and a porous support layer were prepared using a simple method. A given amount of SrFeCo_0.5O_x powder was placed in a die, and then a mixture of SrFeCo_0.5O_x powder and ethyl cellulose powder was added on top of the SrFeCo_0.5O_x powder. The layered powders were pressed into a 13-mm-diameter disk, and calcined at 1423 K. This produced a membrane with a thin dense layer and, through the elimination of the ethyl cellulose, a porous support layer. Oxygen flux through membranes thus produced increased with decreasing dense-layer thickness. The maximum oxygen flux through an asymmetric membrane at 1173 K observed was 0.23 cm³ (STP) cm^-2 min^-1, which was 2.8 times larger than that through a 0.95-mm-thick symmetric membrane. Oxygen permeation was primarily limited by bulk diffusion in the thin dense layer, although the porous support layer acted to resist oxygen permeation.