Reduction-Tolerant Oxygen-Permeable Perovskite-Type Oxide Sr_0.7Ba_0.3Fe_0.9Mo_0.1O_3−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, Sr 0.7 Ba 0.3 Fe 0.9 Mo 0.1 O 3−δ (SBFM), with a cubic perovskite structure ( a = 3.91 Å at room temperature). SBFM can maintain full perovskite structure in a 5 vol % H 2 /He atmosphere at 900 °C even for 50 h. The high reduce-tolerant property was mainly attributed to the synergistic effect between Mo(VI)/Mo(V) and Fe 3+ /Fe 2+ couples. SBFM also exhibited good tolerance to a CO 2 atmosphere at high temperature (≥900 °C) but reacted with CO 2 at relatively low temperature (<800 °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 × 10 −6 and 20.8 × 10 −6 °C −1 in the temperature ranges of 200−600 and 600−900 °C, respectively. At 900 °C, the oxygen permeation flux of SBFM membrane (1 mm in thickness) was 4.39 × 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.