Fabrication and properties of epitaxial buffer layers on nonmagnetic textured ni based alloy substrates

摘要

Biaxially aligned YBCO thick films on oxide buffered metallic substrates is a promising route toward the fabrication of superconducting tapes operating tapes operating at liquid nitrogen temperature. The role of buffer layer is to reduce the lattice mismatch between the substrate and the YBCO film, to adapt the thermal expansion coefficient, to hamper the diffusion of Ni in YBCO film and to prevent the oxidation of the metallic substrate surface. This paper presents a study regarding CeO_2 buffer layer deposition on a new nonmagnetic (001)[100] textured Ni-V~§ alloy substrates. The deposition of CeO_2 was performed by both pulsed laser ablation and e-beam evaporation techniques. The #theta#-2#theta# X-ray diffraction pattern mainly exhibits the (00l) peaks of CeO_2, indicating that the films are epitaxially grown with the c axis perpendicular to the substrate. Rocking curves through the CeO_2 (002) peak have a FWHM of about 6 deg. The SEM studies have shown that the surface is smooth, continuos and free of cracks. Texture analysis reveals a good in-plane orientation for the ablated CeO_2 film, whereas the electron beam evaporated CeO_2 shows two textures in the growth plane. Further efforts are focused on the deposition of YBCO thick films on the as buffered nonmagnetic metallic substrate.