Bulk solution techniques to fabricate high J_c YBCO coated conductors

Low-cost, non-vacuum bulk solution technique has been developed to deposit epitaxial Gd₂O₃ and La₂Zr₂O₇ (LZO) buffer layers directly onto both textured Ni and mechanically strengthened biaxially textured Ni-W(3 at.%)-Fe(1.7 at.%) (hereafter referred to as Ni-W) substrates. A reel-to-reel continuous dip-coating unit was used to produce meter lengths of highly textured, crack-free Gd₂O₃ and LZO buffers on Ni and Ni-W tapes. Auger electron spectroscopy analysis of the textured Ni-W substrates indicated the presence of sulfur segregation to the surface, which possibly facilitated the growth of solution seed layers directly on Ni-W substrates. On dip-coated seed layers, a reel-to-reel sputtering unit was used to deposit epitaxially 200 nm thick YSZ layers followed by 10 nm thick CeO₂ to complete the RABiTS architecture. Pulsed laser deposition was used to grow YBa₂Cu₃O_7-δ (YBCO) films on these tapes in short lengths. YBCO films with J_c values of 1.2 × 10⁶ and 1.9 × 10⁶ A/cm² at 77 K were obtained on Gd₂O₃ and LZO buffered Ni-W substrates, respectively. YBCO films grown by ex situ BaF₂ precursor process on 80 cm long, 1 cm wide CeO₂/YSZ/Gd₂O₃/Ni tapes exhibited end-to-end J_c of 6.25 × 10⁵ A/cm² at 77 K and self-field. This demonstrates that the solution layers provide a very good crystallographic template for the growth of high current density YBCO films, with performance approaching that of vacuum-deposited seed layers.