YBCO thick films on alumina substrates with sprayed YSZ buffer layers

YBCO thick films of 10-30 mu m thickness were fabricated on polycrystalline alumina substrates using a simple screen-printing method. All films on bare alumina substrate showed very poor or non-superconducting properties above 77 K due to aluminium diffusion from the substrate into the film. We have therefore fabricated yttria-stabilized-zirconia (YSZ) buffer layers on alumina substrates by the screen-printing method or by spraying a suspension consisting of ultrafine YSZ powders. The sprayed buffer layers showed a dense and less cracked structure compared with the screen-printed layers, and were found to act as a successful buffer to aluminium diffusion. The J(c) values of YBCO films on sprayed layers, fired by the solid-phase sintering method and the liquid-phase processing method, were about 400 and 1300 A cm(-2) respectively at 77 K, 0 T. These values are about two-thirds of those for films on single-crystal YSZ substrates.