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 × 10−6 mol cm−2 s−1 at 900 °C under an air/helium gradient. Long-term permeation study at 850 °C indicates that Sr0.95Y0.05Co0.95Y0.05O3−δ can operate stably as oxygen semi-permeable membrane.