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

摘要

The series of (Ba_(0.5)Sr_(0.5))(Co_(0.8)Fe _(0.2))_(1-z)Zr_zO_(3-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 (Ba_(0.5)Sr_(0.5))(Co 0.8Fe0.2)0.97Zr0.03O 3-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 Ba _(0.5±x)Sr_(0.5±x)CoO_3 and a rhombohedral Ba_(1-x)Sr_xCo_(2-y)Fe_yO _(5-δ).