Mixed-conducting oxides are used in many applciations, including fuel cells, gas separation membranes, sensors, and electrocatalysis. This paper describes mixed-conducting ceramic membranes that are being developed to selectively remove oxygen and hydrogen from gas streams in a nongalvanic mode ofoperation. Because of its high ocmbined elelctronic/ionic ocnductivity and significant oxygen permeability, the mixed-conducting Sr-Fe-Co oxide ahs bee ndeveloped for high-purity oxygen separation and/or partial oxidation of methone to synthesis gas, i.e., syngas, a mixture of carbon mooxide and hydrogne. The electronic and ionic ocnductivities of SFC were found to be comparable in magunitude and are presented as a function of temperature. The oxygen flux through dense SFC tuges durign separation of oxygen from air is compared with the oxygen flux during methane conversion. Unlike SFC, in which the ionic and electronic conductivities are nearly equlvalent, BaCE_0.08Y_0.2O_3 exhibits protonic ocnductivity that is significantly higher than its electronic conductivity. To enhance the electronic conductivity and increase hydrogne permeation, metal powdr was combined with the BCY to form a cermet membrane. Nongalvnaic permeation of hydrogen thorugh the cermet membrane was demonstrated and characterized as a function of membrane thickness. A sintering aid was developed to avoid interconnected porosity in and improve the mechanical propeties of the cermet membrane.
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