High-J_c YBCO coatings on reel-to-reel dip-coated Gd₂O₃ seed buffer layers epitaxially fabricated on biaxially textured Ni and Ni-(3at%W-1.7at%Fe) alloy tapes

A low-cost, non-vacuum reel-to reel dip-coating system has been used to continuously fabricate epitaxial Gd₂O₃ buffer layers on mechanically strengthened, biaxially textured Ni-(3at.%W-1.7at%Fe), defined as Ni-alloy, metal tapes. X-ray diffraction analysis of the seed Gd₂O₃ layers indicated that well textured films can be obtained at processing temperatures (T_p) between 1100 and 1175°C. Processing speed did not significantly affect the crystalline quality of the Gd₂O₃. Scanning electron microscopy revealed a continuous, dense and crack-free surface morphology for these dip-coated buffers. The Gd₂O₃ layer thickness led to remarkable differences in the growth characteristics of the subsequent YSZ and CeO₂ layers deposited by rf-magnetron sputtering. Epitaxial YBCO films grown by pulsed laser deposition on the short prototype CeO₂/YSZ/Gd₂O₃/Ni-(3at%W-1.7at%Fe) conductors yielded self-field critical current densities (J_c) as high as 1.2×10⁶ A/cm² at 77 K. Pure Ni tapes were used to asses the viability of dip-coated buffers for long length coated conductor fabrication. The YBCO films, grown on 80 cm long and 1 cm wide CeO₂/YSZ/Gd₂O₃ buffered Ni tapes by the industrially scalable ex-situ BaF₂ precursor process, exhibited end-to-end self-field J_c of 6.25×10⁵ A/cm² at 77 K.