CO₂-tolerant mixed conducting oxide for catalytic membrane reactor

A new kind of La_0.85Ce_0.1Ga_0.3Fe_0.65Al_0.05O_3-δ (LCGFA) mixed conducting oxide was prepared by solid-state reaction method. The crystal structure, chemical stability, thermal expansion behavior, mechanical strength and oxygen permeability of this oxide were investigated. LCGFA powder was multiphase and mainly composed of perovskite phase and CeO₂ phase. After annealing in 20 vol.% CO₂ + He for 100 h or in 5 vol.% H₂ + He for 25 h at 900 °C, LCGFA powders still maintained full perovskite structure. LCGFA oxide showed very low chemical expansion and the average thermal expansion coefficients were 10.29(8), 10.68(8) and 10.73(6) × 10^-6 °C^-1 in the temperature ranges of 200-1000 °C in air, nitrogen and carbon dioxide atmospheres, respectively. The three-point bending strength of the LCGFA sample reached 110 ± 5 MPa. At 950 °C, the oxygen flux of the supported LCGFA membrane with 200 μm membrane layer was 6.54(5) × 10^-7 mol cm^-2 s^-1. The degradation of the membrane performances on either temperature cycling or during prolonged isothermal tests was found almost negligible.