Development of Cu Substrate for Low Cost Coated Conductors

A textured Cu {100} lang001rang substrate for practical use in low cost coated conductor applications has been successfully fabricated. A textured Cu substrate is a promising substrate for a coated conductor template. This is the result of a low material cost base, no magnetization loss and good electro conductivity. One of the issues for a Cu substrate is surface oxidation. During REBCO deposition, the Cu substrate is exposed to an oxygen atmosphere, and de-lamination of the buffer layer can occur. To prevent this issue a thin Ni layer was formed on the textured Cu substrate by electroplating. After a further annealing process the Ni electroplated Cu substrates exhibit a good sharp texture and a smoother surface. The Deltaphi and Deltaomega of the substrate were about 4.6 and 4.5 degrees, respectively. The surface roughness was estimated at 6.8 nm Ra by AFM. Using this substrate and clad type Cu/SUS316 substrates, we deposited a CeO₂/YSZ/CeO₂ layer by pulsed laser deposition (PLD) and an YBa₂Cu₃O_7-delta layer by PLD and metal-organic chemical vapor deposition (MOCVD). The results show no occurrence of de-lamination. Typical critical temperature of the coated conductors was 90.5 K and critical current density was a maximum of 4.5 MA/cm² (at 77 K in a self-field).