Synthesis and thermal/oxygen permeation characteristics of La0.1Sr0.9Co0.9Fe0.1O3-δ compounds with La-doped ceria as ideal dual-phase composites

La0.1Sr0.9Co0.9Fe0.1O3-s (LSCF) is a typical mixed conductive oxide exhibiting high oxygen permeability. This compound has applications in air-oxygen separation membranes for pure oxygen generator or H2 production based on partial oxidation reforming. However, the large thermal expansion of LSCF remains an impediment to practical usage. Oxygen-permeable composite ceramics composed of fluorite-type ceria-based oxide ion conductors combined with LSCF could be one approach to mitigating this problem. However, reactions between the two phases remain an issue. This study examined composites having essentially the same La concentrations in both phases as a means of inhibiting reactivity. The oxide ion conductor La0.07Ce0.93O2-s (LDC0.07) was combined with LSCF, with both phases having almost identical La concentrations. This LSCF-LDC0.07 dual-phase composite showed minimal inter-phase reactions along with reduced thermal expansion, which is the specific finding of this study. In particular, an 80 vol%LSCF-20 vol%LDC0.07 specimen demonstrated both high oxygen permeability and low thermal expansion, suggesting that this composite could be a viable component of oxygen separation membranes.