YBCO thick films on alumina substrates with BaSO 4/BaF 2 barrier layers

Abstract

Thick films of YBa 2Cu 3O 7−δ(YBCO) have been fabricated on technologically attractive alumina substrates by utilising barrier layers of BaSO 4 with 10 wt.% BaF 2 additions. BaSO 4 is relatively inert in reacting with YBCO at the high temperatures involved in thick film processing (≁1050°C). The screen printed barrier layers have been given a series of varying heat treatments, in order to determine the optimum processing conditions. The quality of the barrier layers has been found to depend on the firing temperature. A reduced processing temperature of 950°C has increased the density of the barrier layer and reduced the diffusion of aluminium into the thick films. Resistivity measurements have shown that T zero's as high as 82 K can be obtained for the thick films processed on the barrier layers, which is a significant improvement on thick films processed directly on alumina substrates.