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

Abstract

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, Sr0.7Ba0.3Fe0.9Mo0.1O3−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 (Ea) was 42 kJ mol−1, which was significantly lower than that of commonly used MIEC membranes.