Influence of Microstructure and Surface Activation of Dual-Phase Membrane Ce0.8Gd0.2O2--FeCo2O4 on Oxygen Permeation

Dual-phase oxygen transport membranes are fast-growing research interest for application in oxyfuel combustion process. One such potential candidate is CGO-FCO (60wt% Ce0.8Gd0.2O2--40wt% FeCo2O4) identified to provide good oxygen permeation flux with substantial stability in harsh atmosphere. Dense CGO-FCO membranes of 1mm thickness were fabricated by sintering dry pellets pressed from powders synthesized by one-pot method (modified Pechini process) at 1200 degrees C for 10h. Microstructure analysis indicates presence of a third orthorhombic perovskite phase in the sintered composite. It was also identified that the spinel phase tends to form an oxygen deficient phase at the grain boundary of spinel and CGO phases. Surface exchange limitation of the membranes was overcome by La0.6Sr0.4Co0.2Fe0.8O3- (LSCF) porous layer coating over the composite. The oxygen permeation flux of the CGO-FCO screen printed with a porous layer of 10mthick LSCF is 0.11mL/cm(2) per minute at 850 degrees C with argon as sweep and air as feed gas at the rates of 50 and 250mL/min.