Investigation of Mixed Conductor BaCo0.7Fe0.3-xYxO3-δ with High Oxygen Permeability

Cubic BaCo0.7Fe0.3-xYxO3-delta (BCFY, x = 0.08-0.02) was prepared by the conventional solid state reaction route as oxygen permeation membranes. The effects of Y-doping on the crystal structure, electrical conductivity, and oxygen permeability are investigated, and the factors influencing the activation energy of oxygen migration are discussed front the viewpoints of metal oxygen bonding energy and geometric lattice structure. Y-substitution decreases the electrical conductivity but increases the oxygen vacancy concentration of BCFY samples. Nevertheless, the oxygen permeability decreases with increasing Y-doping level. Both the strong Y-O bonding energy and the decreased critical radius (r(C)) with Y-doping should be responsible for the increased activation energy. First principle calculation reveals that Y-doping results in the nonequivalent positions of the mobile oxygen ions and thus limits die oxygen ion diffusion passages. BaCo0.7Fe0.3-xYxO3-delta membrane exhibits a high oxygen permeability of 1.73 mL.min(-1) cm(-2) at 900 degrees C, thus being a promising candidate material for oxygen separation or POM applications.