Y-Ba-Cu-O superconducting films grown on (100) magnesia and sapphire substrates by a melt growth method without crucible

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Abstract
Superconducting Y-Ba-Cu-O films were successfully prepared by a melt growth method without crucible on (100) MgO and sapphire substrates using a Ba2Cu7O10 flux. It was found that without a Y2BaCuO5 (211) buffer layer, film formation is not feasible due to a wetting problem. The 211 layer reacts with the melt and is partly converted to the YBa2Cu3Ox (123) film. The 123 film thickness is 1/2 to 2/3 that of the former 211 layer, whose quality in turn dominates the surface structure of the 123 film. The degree of preferred (00L) orientation is greater than 99% for the films on the 211 buffered (100) MgO, and 80% for those on the (100) sapphire. 2 to 3 mu m superconducting films with Tc-onset>80 K and Tc-zero>60 K were reproducibly obtainable on (100) MgO.