Rare-earth mixed oxide thin films as 100% lattice match buffer layers for YBa2Cu3O7−x coated conductors

Buffer layers with 100% lattice match with YBa2Cu3O7 − δ (YBCO) were prepared from mixed rare-earth-oxides applying a simple sol–gel process and dip-coating method. Structural analysis of the sol–gel derived powder by X-ray diffraction revealed that the mixing parameter, which eliminates the lattice mismatch with YBCO, is x = 0.2382, 0.1852, 0.1252, 0.0906, 0.0793 and 0.0395 in (Eu1 − xHox)2O3, (Eu1 − xErx)2O3, (Eu1 − xYbx)2O3, (Gd1 − xHox)2O3, (Gd1 − xYx)2O3 and (Gd1 − xYbx)2O3, respectively. Microstructural investigations were carried out for Gd1.819Ho0.181O3 films epitaxially grown on cube-textured Ni (100) substrates by sol–gel dip-coating process. X-ray diffraction of the buffer showed strong out-of-plane orientation on Ni tape. The (Gd1 − xHox)2O3 (222) pole figure indicated a single cube-on-cube textured structure. The omega and phi scans revealed good out-of-plane and in-plane alignments. The full-width at half-maximum values of omega and phi scan of (Gd1 − xHox)2O3 films was observed at 4.21° and 6.81°, respectively. Micrographs of the film obtained by using environmental scanning electron microscope and atomic force microscope revealed pinhole-free, crack-free, smooth and dense microstructures.