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

Abstract

An Yb 1 Ba 2 Cu 3 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 Yb 1 Ba 2 Cu 3 O 6.8 at temperatures above about 540 K. The Yb 1 Ba 2 Cu 3 O 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/cm 2 in the absence of applied field and 0.4 A/cm 2 at H =7 T.