The processing and properties of high Tc thick films

The influence of processing conditions on the microstructure and properties of YBa₂Cu₃O_x thick films on yttria-stabilized zirconia substrates is reported. Films processed below the peritectic temperature are fine grained, exhibit little preferred orientation, and generally have low critical currents. Above the peritectic temperature, the morphology changes dramatically and large, highly textured, spherulitic crystals are observed, with an associated increase in critical current and an improved T_c. Properties in these materials are generally much better than those of bulk YBa₂Cu₃O_x . The relationship between microstructure and properties is shown to be complex. The influence of silver additions to the films is examined, and examples are given of thick-film devices which are being evaluated. Thick-film devices under evaluation include flux transformers, TE₀₁₁ cavities, coaxial and helical resonators, microstrip resonators, current limiters, and shields