Oxygen permeability and stability of Al₂O₃-doped SrCo_0.8Fe_0.2O_3-δ mixed conducting oxides

A new series of Al₂O₃-doped SrCo_0.8Fe_0.2O_3-δ (SCFA) mixed conducting oxides were synthesized by the conventional solid-state reaction method. Effects of doping Al₂O₃ (1, 3, 5 and 10 wt.%, respectively) on the crystal structure, order-disorder phase transition, microstructure, oxygen permeability and structure stability of SrCo_0.8Fe_0.2O_3-δ (SCF) were investigated by XRD, TG-DSC, SEM, oxygen permeation measurement and the partial oxidation of methane (POM) to syngas reaction. Although the oxygen permeability of the SCF was weakened in the oxygen permeation measurement at the air/He gradient due to the doping of Al₂O₃, perovskite structure of SCFA was found stable in the low oxygen partial pressure (about 1.01325 × 10² Pa (10^-3 atm)). In the POM reaction, the rate of the oxygen permeation of SCFA3 (the addition amount of Al₂O₃ was 3 wt.%) membrane was about 10 times higher than that in the oxygen permeation measurement at 1223 K, and the SCFA3 membrane was successfully operated in the POM reaction for more than 500 h without fracture.