Development of REBa2Cu3Ox Coated Conductor on Textured Metal Substrate

REBa2Cu3Ox (RE: Y and rare-earth elements) coated conductors are a prospective material for use in various applications.(1) Examples of applications are power transmission cables, superconducting magnetic energy storage systems (SMESs) and electrical transformers. The authors are researching the application of RE123 conductors to AC cables. In general, RE123 conductors are in the form of a multi-layer tape comprising a metal substrate, buffer layers, a superconducting layer, a stabilization layer, and a protective layer. It is important that the superconducting layer of a RE123 conductor is biaxially oriented and has a high crystallinity. There has been two methods for obtaining a biaxially oriented texture. One method is to prepare an oriented buffer layer on an amorphous layer, and the other method is to prepare a textured metal substrate.(2) The authors use the latter method for obtaining textured metal substrates. Textured metal substrates can be made from face centered cubic(FCC) metals, such as Cu, Ni, Ag and their alloys.(2) The authors used textured Ni alloys as substrates.(3)-(5) However, Ni-alloy substrates are unsuitable for use in AC applications. This is because textured Ni alloys have high magnetization loss and low mechanical strength. High magnetization loss can cause high AC loss and low mechanical strength makes handling of RE123 conductors difficult. To solve these problems, several reports have been made on the development of textured Ni-alloys that exhibit low magnetization loss at 77.3K. The authors developed a new type of textured metal substrate and called it “clad-type” substrate. The clad-type substrate has low magnetization loss and high mechanical strength. However, the critical current (Ic) of a RE123 conductor grown on the clad-type substrate had been lower than that of a RE123 conductor grown on the Ni-alloy substrate. In this paper, the authors report on the development of a high-Ic RE123 conductor grown on the clad-type substrate.