Investigation of Zr-doped BSCF perovskite membrane for oxygen separation in the intermediate temperature range

The series of (Ba0.5Sr0.5)(Co0.8Fe0.2)1−zZrzO3−δ (z=0, 0.01, 0.03, 0.05, 0.07, and 0.09) was synthesized by a sol–gel method. The materials with a zirconium content up to 3 mol% were found to be single phase. Further increase results in formation of a mixed (Ba,Sr)ZrO3 by-phase, which was found along the grain boundaries and in the grains. With increasing zirconium content the oxygen permeation flux decreases considerably. The effect of the zirconium substitution on the long-term phase stability was investigated by long-term oxygen permeation experiments and X-ray diffraction. A slight stabilization of the oxygen flux of (Ba0.5Sr0.5)(Co0.8Fe0.2)0.97Zr0.03O3−δ was found after 180 h at 1023 K. However, all compositions show a decrease in permeation flux with time, but the pure BSCF membrane exhibited the strongest drop after 180 h of operation. The decomposition products of the cubic perovskite phase were found to be a hexagonal Ba0.5±xSr0.5±xCoO3 and a rhombohedral Ba1−xSrxCo2−yFeyO5−δ. - Graphical abstract: Backscattered-electron channeling contrast image of BSCF membrane cross-section after long-term oxygen permeation at 1023 K showing different phases in different colors. Highlights: ► Ba0.5Sr0.5Co0.8Fe0.2O3−δ systematically doped with increasing amount of zirconium. ► Cubic single-phase materials up to 3 wt% zirconium. ► Mixed (Ba,Sr)ZrO3 by-phase formed mainly in the grain boundaries. ► Jänecke prism was proposed by XRD and EDXS data. ► (Ba0.5Sr0.5)(Co0.8Fe0.2)0.97Zr0.03O3−δ showed a slight stabilization of oxygen flux as compared to pure Ba0.5Sr0.5Co0.8Fe0.2O3−δ