Reduction-Tolerant Oxygen-Permeable Perovskite-Type Oxide Sr0.7Ba0.3Fe0.9Mo0.1O3-δ

The mixed ionic-electronic conducting (MIEC) materials that have been developed for catalytic membrane reactors are vulnerable to a reducing atmosphere, especially H-2. We reported on a MIEC oxide, Sr0.7Ba0.3Fe0.9Mo0.1O3-delta (SBFM), with a cubic perovskite structure (a = 3.91 angstrom at room temperature). SBFM can maintain full perovskite structure in a 5 vol % H-2/He atmosphere at 900 degrees C even for 50 h. The high reduce-tolerant property was mainly attributed to the synergistic effect between Mo(VI)/Mo(V) and Fe3+/Fe2+ couples. SBEM also exhibited good tolerance to a CO2 atmosphere at high temperature (>= 900 degrees C) but reacted with CO2 at relatively low temperature (<800 degrees C). The introduction of Mo ion into the Fe site greatly improved the thermal stabilization of the SBFM oxide. The average thermal expansion coefficients in nitrogen atmosphere were 12.8 x 10(-6) and 20.8 x 10(-6)degrees C-1 in the temperature ranges of 200-600 and 600-900 degrees C, respectively. At 900 degrees C, the oxygen permeation flux of SBEM membrane (1 mm in thickness) was 4.39 x 10-7 mol cm(-2) s(-1). The oxygen permeation activation energy (E-a) was 42 kJ mol(-1), which was significantly lower than that of commonly used MIEC membranes.