Mixed-conducting LSC/CGO composites for passive oxygen separation membranes

Dense mixed-conducting composite materials of LSC (La0.9Sr0.1CoO3 − δ or La0.6Sr0.4CoO3 − δ) and CGO (Ce0.9Gd0.1O2 − δ) prepared by conventional powder mixing and sintering have been studied for possible application as oxygen separation membranes. The composites showed high relative density (above 95%), low background gas leakage and also good electrical conduction. The percolation threshold of the electronic-conducting component was determined to be approximately 20 vol.% for both LSC compositions. Isotopic exchange and depth profiling by secondary ion mass spectrometry was used to investigated the oxygen tracer diffusion (D*) and surface exchange coefficient (k*) of the composites. Composites exceeding the electronic percolation threshold, showed high oxygen diffusivities and surface exchange properties and intermediate thermal expansion thus combining the benefits of their constituent materials.