Manufacture of bulk superconducting YBa2Cu3O7-δ by a continuous process

Abstract

THE high critical current densities (Jcs) measured in thin films and within grains of the high-transition-temperature (high-MTc) oxide superconductors indicate that low Jc should not prevent the use of high-Tc materials in high-current devices1. Indeed, a Jc of ∼7.5×104 A cm−2 has been obtained in highly textured bulk YBa2Cu3O7 ('123') at 0 T, processed by a melt-textured2 or liquid-phase3 growth technique. Unfortunately, textured materials with this improved Jc comprised only a very small portion (< 1 cm) of the bulk precursor, which had random grain orientations on a larger scale. For high-current applications, one needs bulk materials fabricated in usable shapes of large dimensions with controlled grain orientation to carry a high total current, not just a high current density. Here we report the development of a continuous process for fabricating large bulk superconductors with a pre-determined grain orientation. A bar of the 123 compound with dimensions 5 x 0.5 x ∼0.3 cm with excellent grain alignment (a-b plane along the longest sample dimension) has been fabricated continuously. The bulk 123 thus obtained has magnetically determined Jcs of ∼3 x 104 and 1.2 x 104 A cm−2 at 0 and 1 T, respectively and transport Jcs of 2 x 104, 1.1 x 104 and 7.5 x 103 A cm2 at 0, 0.54 and 0.83 T.