Overview of Possible Applications of High Tc Superconductors

Abstract

The history of high-Tc superconductors (HTS) begins in 1986 with the famous discovery of superconductors of the system Ba-La-Cu-O (Bednorz & Muller, 1986). Practical applications of superconductivity are steadily improving every year. However, the actual use of superconducting devices is limited by the fact that they must be cooled to low temperatures to become superconducting. For example, superconducting magnets used in most particle accelerators and in Magnetic Resonance Imaging (MRI) are cooled with liquid helium, that is, it is necessary to use cryostats that should produce and maintain temperatures of the order of 4 K. Helium is a very rare and expensive substance. On the other hand, because helium reserves are not great, the world's supply of helium can be wasted in a near future. Thus, because liquid nitrogen is not expensive and the reserves of nitrogen could not be wasted, it is important to use high-Tc superconductors cooled with liquid nitrogen. Superconductors with critical temperatures greater 77 K may be cooled with liquid nitrogen. Copper oxide superconductors are the most important high-Tc superconductors (Cava, 2000). Up to the present time, after one hundred years of the first Kamerlingh Onnes discovery, the highest Tc is approximately equal to 135 K at 1 atm (Schilling & Cantoni, 1993), in superconductors of the Hg-Ba-Ca-Cu-O system. The discovery of a room temperature superconductor should trigger a great technological revolution. Nevertheless, in the meantime, waiting for this revolution, it is necessary to be prepared to apply existing technologies and develop new applications of HTS. The objective of this chapter is to give an overview of the most important applications of HTS. We shall discuss actual applications of HTS as well as possible applications of HTS in a near future. Depending on the strength of the applied magnetic field, applications of HTS may be divided in two groups: large scale applications (large magnetic fields) and small scale applications (small magnetic fields). Because HTS materials are brittle, the future of applications of HTS depends on the discovery of new radical solutions for this difficulty. You will find in this chapter only discussions about practical applications of HTS. If you are interested in theoretical aspects of such applications, you may read a review book (Orlando & Delin, 1991). The plan of this chapter is as follows: