A Deterioration Mechanism on Critical Current Densities of High Temperature Superconductors

Abstract

Deterioration of oxide superconductors has been investigated by evaluating the critical current densities at 77K and the resistivity at room temperature. The oxide superconductors were exposed to moisture or heat cycle between 77K and room temperature. The experimental results indicate that the external substance penetrates into the superconductors and brings about chemical reactions to form non-superconductive products so that it involves volume expansion at the site to cause micro-cracks. An analysis of the relation between the critical current density and the conductivity has been carried out and we have estimated the mechanism of the deterioration by the analysis.