Double-site yttria-doped Sr1-xYxCo1-yYyO3-δ perovskite oxides as oxygen semi-permeable membranes

New mixed conducting oxides with the composition of Sr1-xYxCo1-yYyO3-δ (x = 0.0-0.8, y = 0.0-0.1) were exploited and synthesized. The resulted materials were investigated by X-ray diffraction, four-probe dc conductivity, temperature-programmed desorption characterization, and oxygen permeability measurement. As compared with the oxides with only one-site (A or B) being Y3+-doped, i.e., Sr1-xYxCoO3-δ and SrCo1-yYyO3-δ, the double-site Y3+-doped ones show improved phase stability, higher electrical conductivity under reduced atmosphere, and higher oxygen permeability and stability. Particularly, Sr0.95Y0.05Co0.95Y0.05O3-δ oxide demonstrates stable cubic perovskite phase in air, oxygen and nitrogen, high electrical conductivity of ∼110 S cm-1 in air and ∼50 S cm-1 in nitrogen, and a maximum permeation flux of 1.35 x 10-6 mol cm-2 s-1 at 900 deg. C under an air/helium gradient. Long-term permeation study at 850 deg. C indicates that Sr0.95Y0.05Co0.95Y0.05O3-δ can operate stably as oxygen semi-permeable membrane