Chapter 2　Superconducting Materials

Jia-Su Wang and Su-Yu Wang

Superconductors are divided into conventional and unconventional superconduc-tors, and can also be divided into high temperature superconductor（HTSC）and low temperature superconductor（LTSC）. The HTSCs can be cooled with liquid nitrogen（77 K）instead of liquid helium（4.2 K）.This is commercially important be cause liquid nitrogen is much cheaper, which makes HTSCs particularly attractive for practical applications.

The superconducting material can be produced in the forms of single crystals, films, wires, and tapes. The most common LTSCs in applications are the Nb-Ti（niobium-titanium）and the Nb3Sn（niobium-tin）wires and tapes.Superconducting films are mainly used for electronic devices.In principle, for the HTSC materials, there are bulk and wire materials for the electrical engineering applications.The HTSC bulks are mainly used for the HTS Maglev train, Maglev bearings, Maglev flywheel energy storage devices, and so on.