High-TcSuperconductivity: Present Status of Fundamental Research and Applications

In 1986, Bednorz and MOiler discovered superconductivity around T 30 K in a ceramic compound of composition (La,Ba)2CuO4 [1]. Soon afterwards, superconductivity below T 92 K was found in a related compound of composition YBa2Cu307. For the first time, the possibility was opened up to maintain superconductivity at T 77 K, the boiling point of liquid nitrogen (LN2). The discovery of these "high-temperature superconductors" (HTSCs) initiated an unprecedented boom in research aiming at both the physical understanding of HTSC and the technical application of these new materials. In particular the latter point, namely the prospect of developing a new superconductivity technology based upon LN2 cryogenics, has attracted wide interest and initiated a wealth of new R&D activities all over the world. In what follows, we will only briefly comment on the physical understanding of the phenomenon of HTSC but mainly concentrate on a review of the present status of applications for these new and challenging materials.