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

Cubic BaCo 0.7 Fe 0.3− x Y x O 3−δ (BCFY, x = 0.08−0.2) 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 from 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 the oxygen ion diffusion passages. BaCo 0.7 Fe 0.22 Y 0.08 O 3−δ membrane exhibits a high oxygen permeability of 1.73 mL min −1 cm −2 at 900 °C, thus being a promising candidate material for oxygen separation or POM applications.