Advances in Bi-Based High-Tc Superconducting Tapes and Wires

Abstract

Since the discovery of high-Tc superconductors (HTSs), especially the Bi-based oxide superconductors (Bi-HTSs) in 1989, much effort has been concentrated on the fabrication of Bi-HTS wires and tapes. Bi-HTSs are interesting materials from the viewpoint of practical applications. One of the interesting applications of Bi-HTSs is the cryogen-free conduction-cooled magnet. Besides having a high transition tem- perature (Tc), Bi-HTSs have high upper critical fields (Bc2) or high irreversibility fields (Birr) at temperatures below ∼30 K. Because ∼30 K can be efficiently main- tained by a cryocooler, a Bi-HTS magnet cooled with a cryocooler has great potential in many technological applications. Another promising application of Bi-HTSs is the high-field magnet. When the temperature is reduced to ∼5 K, Bi-HTSs show a much higher Bc2 or Birr than do conventional metallic superconductors (low-temperature superconductors, LTSs) such as Nb3Sn. This indicates that Bi-HTSs also have great potential for use in a high- field superconducting magnet if the magnet is operated at low temperature.