High Critical Current Density of Y-Ba-Cu Oxide Wire without a Metal Sheath

A critical current density of around 1000 A ·cm -2 in Y-Ba-Cu oxide wire sheathed with silver has previously been reported. In order to obtain a higher critical current density, it has been found that the metal sheath of a wire must be dissolved and thereafter the core heat-treated in ambient flowing oxygen. The maximum critical current density of a 0.72 mm diameter wire was found to be 3900 A ·cm -2 at the nitrogen temperature.