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

Dense SrZr0.95Y0.05O3-chi and SrCe0.95Yb0.05O3-chi thin films with perovskite structure were prepared on porous SrZr0.95Y0.05O3-chi substrates by spin coating colloidal suspensions of powders prepared by combustion methods. Porous substrates were prepared by treating carbon/SrZr0.95Y0.05O3-chi 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 N-2 at 900- 1000 K. H-2 permeation rates through SrCe0.95Yb0.05O3-chi thin films at 950 K were as high as 500 times larger than on 1-mm disks and reached values of 6 X 10(-4) mol H-2/cm(2) min for 2 mum films. H-2 permeation rates were proportional to the inverse of the membrane thickness, indicating that permeation in SrCe9.95Yb0.05O3-chi thin films is controlled by bulk diffusion and not by H-2 dissociative chemisorption or by boundary layer transport, even for 2 mum films. (C) 2002 Elsevier Science B.V. All rights reserved.