SUPERCONDUCTIVITY ABOVE LIQUID NITROGEN TEMPERATURE IN NEW OXIDE SYSTEMS

An important discovery of the superconductivity in Ba-La-Cu-O system with transition temperature 30-35 K has been made by Bednorz and Miiller.After that extensive studies in searching for the new series of related superconducting compounds have been well stimu-lated. New systems with even higher transition temperatures have been found one after another. Bulk superconductivity was confirmed in the LaMCuOsystem with M=Ba, Sr, Ca and 0.1<x<0.3, and the transition temperature T’s were 40 K in single phase compounds and 48.6 K in multi-phase materials. An even higher value of T= 52 K has been reported under hydrostatic pressuret. More recently, superconductivity above 90 K has been claimed bv C. W. Ghu et al. and the superconductivity in Ba-Y-