Synthesis and hydrogen permeation properties of membranes based on dense SrCe0.95Yb0.05O3−α thin films

Dense SrZr0.95Y0.05O3−α and SrCe0.95Yb0.05O3−α thin films with perovskite structure were prepared on porous SrZr0.95Y0.05O3−α substrates by spin coating colloidal suspensions of powders prepared by combustion methods. Porous substrates were prepared by treating carbon/SrZr0.95Y0.05O3−α composites in air at 1273–1573 K in order to combust the carbon and partially sinter the resulting porous oxide. This procedure led to strong porous solids with a high gas permeability. Matching the shrinkage of the porous substrate and of the thin film by this pre-sintering of the porous substrate led to thin films free of fissures and other defects. Thin films prepared by these methods did not transport He at ambient temperature or N2 at 900–1000 K. H2 permeation rates through SrCe0.95Yb0.05O3−α thin films at 950 K were as high as 500 times larger than on 1-mm disks and reached values of 6×10−4 mol H2/cm2 min for 2 μm films. H2 permeation rates were proportional to the inverse of the membrane thickness, indicating that permeation in SrCe0.95Yb0.05O3−α thin films is controlled by bulk diffusion and not by H2 dissociative chemisorption or by boundary layer transport, even for 2 μm films.