Growth of biaxially textured RE_2O_3 buffer layers on rolled-Ni substrates using reactive evaporation for HTS-coated conductors

摘要

In an effort to develop alternative single buffer layerarchitectures for YBCO(YBa_2Cu_3O_7-?) coated conductors,we have studied RE_2O_3(RE=Y, and rare earths) as candidatematerials. High-quality Y_2O_3, Gd_2O_3 and Yb_2O_3 bufferlayers were grown epitaxially on biaxially textured Ni(100)substrates using reactive electron beam evaporation. Usingthermodynamic considerations for the formation of metal oxides,we employed both reducing atmospheres and water vapour tooxidize the film in situ to form stoichiometric RE_2O_3. We havealso prevented NiO formation at the substrate-film interfaceduring this process. Detailed x-ray studies have shown that theY_2O_3, Gd_2O_3 and Yb_2O_3 films were grown with a singleepitaxial orientation. The lattice mismatch between YBCO andGd_2O_3 was small as compared with that of YBCO with otherrate earth oxides. SEM micrographs indicated that ~0.5#mu#mthick Y_2O_3 films on rolled –Ni substrates were dense,continuous and crack free. A high J_c of 1.8x 10~6 A cm~-2 at77K and self-field was obtained on YBCO films grown onalternative buffer layers with a layer sequence ofYBCO/Yb_2O_3(sputtered)/Y_2O_3(e-beam)/Ni.