Growth of biaxially textured RE2O3buffer layers on rolled-Ni substrates using reactive evaporation for HTS-coated conductors

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Abstract
In an effort to develop alternative single buffer layer architectures for YBCO (YBa2Cu3O7-y) coated conductors, we have studied RE2O3 (RE = Y, and rare earths) as candidate materials. High-quality Y2O3, Gd2O3 and Yb2O3 buffer layers were grown epitaxially on biaxially textured Ni (100) substrates using reactive electron beam evaporation. Using thermodynamic considerations for the formation of metal oxides, we employed both reducing atmospheres and water vapour to oxidize the film in situ to form stoichiometric RE2O3. We have also prevented NiO formation at the substrate-film interface during this process. Detailed x-ray studies have shown that the Y2O3, Gd2O3 and Yb2O3 films were grown with a single epitaxial orientation. The lattice mismatch between YBCO and Gd2O3 was small as compared with that of YBCO with other rare earth oxides. SEM micrographs indicated that ~0.5 µm thick Y2O3 films on rolled-Ni substrates were dense, continuous and crack free. A high Jc of 1.8 × 106 A cm-2 at 77 K and self-field was obtained on YBCO films grown on alternative buffer layers with a layer sequence of YBCO/Yb2O3 (sputtered)/Y2O3 (e-beam)/Ni.

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