High-Tc Superconductor Prepared by Oxidation of a Mechanically Alloyed Nonequilibrium fcc Ba2YCu3 Phase

Abstract
A nonequilibrium fcc Ba2YCu3 phase was prepared in an immiscible Ba-Y-Cu system by mechanical alloying (MA). Heating of the nonequilibrium phase powder in air resulted in the structural change to an equilibrium metallic phase at about 440 K, followed by the oxidation into Ba2YCu3O y at temperatures above 470 K. The Ba-Y-Cu oxide prepared by oxidation of the pressed product of the fcc alloy powder exhibited high-T c superconductivity with zero resistance at 89 K. Thus, MA is useful for the preparation of a high-T c oxide superconductor through the formation of the homogeneously mixed fcc phase of immiscible elements.