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 H₂. We reported on a MIEC oxide, Sr _0.7Ba_0.3Fe_0.9Mo_0.1O _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 % H₂/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 Fe³⁺/Fe²⁺ couples. SBFM also exhibited good tolerance to a CO₂ atmosphere at high temperature (≥900 °C) but reacted with CO₂ 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.