High Tc Superconductor Prepared by Oxidization of a Liquid-Quenched Yb1Ba2Cu3 Alloy Foil in Air

Abstract

An Yb₁Ba₂Cu₃ alloy foil with a nonequilibrium structure including an amorphous phase was prepared by splat-quenching. Heating of the alloy foil in air resulted in the structural change to a crystalline metallic phase at about 490 K, followed by the oxide formation of Yb₁Ba₂Cu₃O_6.8 at temperatures above about 540 K. The Yb₁Ba₂Cu₃O_6.8 prepared by oxidization of the liquid-quenched alloy foil was found to exhibit high T _c superconductivity with onset at 91 K and zero resistance at 85 K, even though the J _c value at 4.2 K was as low as about 1.9 A/cm² in the absence of applied field and 0.4 A/cm² at H=7 T.