Development of Cu substrate for low cost coated conductors

A textured Cu {100} (001) 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 Δφ and Δ 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-δ 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).