The discovery of superconductivity in copper oxide perovskite (1) has opened a new era of research in superconducting materials. This class of materials not only show high-temperature superconductivity but also show properties that are different from classical superconductors. This offers a great challenge to understanding the basic phenomenon that causes superconductivity in these materials and to developing the appropriate preparation methods so that these can be exploited for a wide range of applications. During the last one and half decades after the discovery of high-Tc materials, several high-Tc superconductors have been discovered which show superconductivity at temperatures higher than liquid-nitrogen temperature (77 K). There has also been great progress.
