Stabilities of La0.6Sr0.4Co0.2Fe0.8O3−δ oxygen separation membranes-Effects of kinetic demixing/decomposition and impurity segregation

Effects of kinetic demixing/decomposition and impurity segregation on stabilities of the La0.6Sr0.4Co0.2Fe0.8O3−δ (LSCF) membranes in hollow fibre geometry were studied under oxygen separation conditions. The membranes were operated under 0.21/0.008 oxygen partial pressure (bar) difference at 950 °C for 1128 h. Cobalt oxide grains were found to be separated on the air side of the membrane surface after the long-term operation, and strontium and iron were also enriched with the 50 nm depth from the surface layer of air side. Glassy sodium-rich second phase was identified and was found to be segregated at the grain boundary in the LSCF bulk, and had grown during high temperature operations. The oxygen permeation performance is, however, stable after being operated for 1128 h, indicating that the kinetic demixing/decomposition and impurity segregation cause the negligible effects on the permeability of the LSCF membranes at the operating conditions applied.