Electrode supported solid oxide fuel cells: Electrolyte films prepared by DC magnetron sputtering

An electrode supported fuel cell concept with DC magnetron sputtered electrolyte films on the fuel electrode has been demonstrated. NiO/yttria-zirconia substrates with porosity up to 32% were used for depositing thin films (5-16 mu m) of yttria stabilised zirconia (YSZ) electrolyte. By controlling film deposition parameters and surface porosity of the substrate, and by careful annealing of deposited films, highly dense and impervious films of YSZ have been produced. The annealed electrolyte films as well as cross-sections of half cells before and after reduction of NiO in hydrogen atmosphere have been carefully characterised by scanning electron microscopy. X-ray diffraction studies indicate the presence of a single cubic phase in the annealed film. The conductivity has been measured by impedance spectroscopy. Complete fuel cells have been prepared and evaluated in the temperature range of 700-800 degrees C. Their current-voltage characteristics have been determined with a current interruption technique. Early results on small cells have shown power densities in the vicinity of 600 mW cm(-2) for air/H-2 (2-3% H2O) at 800 degrees C, 440 mW cm(-2) at 750 degrees C and 210 mW cm(-2) at 700 degrees C. The preparation of dense and impervious electrolyte films on 50 mm x 50 mm anode supports has been successfully demonstrated.