Continuous deposition of thermally co-evaporated YBCO/CeO2/Ni coated conductors

By using a simple single-pass reel-to-reel system, we demonstrate a simple and robust in-situ route for the continuous deposition of 1-2 m long Coated Conductors (CC) consisting of 1 μm thick superconducting YBa₂Cu₃O₇ (YBCO) films deposited by thermal co-evaporation onto 100 nm thick CeO₂ buffered cube textured Ni tapes. The buffer layer was deposited by either e-beam or thermal evaporation using respectively ceria or metallic cerium. The structural and morphological properties of the samples were investigated by X-ray ϑ-2ϑ Bragg-Brentano, and pole figure diffraction, Nomarsky optical microscopy and Scanning Electron Microscopy (SEM) analysis. The 123 composition was controlled during deposition by means of an atomic absorption system. The optimized buffer layer and YBCO layer are grown at 690°C in respectively forming gas and oxygen partial pressures of 5×10^-5 mbar. These conditions ensure the growth of dense and crack-free layers with good biaxial texture, as indicated by FWHM´s values in the 5-7° range for both in- and out-of-plane orientations. Zero-resistance critical temperatures T_c=86-87 K with transition widths ΔT_c<3 K are reproducibly obtained. End-to-end critical current densities J_c at 77 K and self-field typically are in the 1.5-2.5 MA/cm² range, as measured by transport measurements. It is found that tape motion does not significantly affect these properties.