Electrodeposited Cu-Stabilization Layer for High-Temperature Superconducting Coated Conductors

We have developed a nonaqueous-based process for electrodepositing a Cu-stabilization layer on a YBCO superconductor tape. Conventional approaches to electroplating Cu layers use a cyanide-based solution to prevent uncontrolled hydrogen evolution from the aqueous-based solution; these are very reactive with the superconductor layer, and thus destroy its critical-current capability when plated directly onto high-temperature superconductor (HTS) tape. It has been found that a capping layer at least 1 micron thick is needed between the superconductor and stabilizer layers to avoid such a reaction and the subsequent reduction in the critical-current capability of the superconductor layer. In contrast, the nonaqueous electroplating solution is nonreactive to the HTS layer, allowing the Ag capping layer to be thinner. We demonstrated that direct Cu plating on YBCO tapes using a nonaqueous solvent does not destroy the superconducting YBCO layer. The superconducting current capabilities of these tapes were measured by noncontact magnetic measurements. Contact current–voltage (I–V) measurements required a 0.1-micron-thick Ag capping layer on YBCO tapes, which is sufficient for subsequent Cu plating from the non-aqueous solvent.