Recent progress in high-T_C superconducting wires and their applications for electric power apparatus

Abstract

The development of superconducting wires is one of the key issues in realizing superconducting equipment. Superconducting wires made of alloys such as NbTi have already been commercialized and applied to MRI and NMR, and superconducting wires made of metal compounds such as Nb₃Sn have been manufactured for use in high-field applications such as accelerators and nuclear fusion. Since a high-T_C superconductor (over 77K) was discovered approximately 25 years ago, it has been expected that they will be used in electric power apparatus such as cables and electricity storage devices. Among the various high-T_C superconductors, Bi₂Sr₂Ca₂Cu₃O₁₀ (Bi2223) and REBa₂Cu₃O_y (RE123) (RE: rare earth elements) have mainly been investigated with aim of producing superconducting wires. Among the other superconductors, MgB₂ superconductors, which are expected to lead to a lower manufacturing cost, and the recently discovered iron-based superconductors are being studied at present. This article is focused on the development of superconducting wires for superconducting electric power apparatus reviewing the recent progress in RE123 and Bi2223 superconducting wires and their applications.