Fabrication of high performance light rare earth based single-grain superconductors in air

Abstract

Large, single-grains of (LRE)-Ba–Cu–O (LRE=light rare earth: Nd, Sm, and Gd) bulk high-temperature superconductors with significantly improved properties have been fabricated in an air atmosphere using a practical processing technique based on seeded infiltration growth. This process involves the use of a generic seed crystal, developed recently at the IRC in Superconductivity, to promote epitaxial grain nucleation. The formation of a solid-solution phase within the nucleated single grain is then suppressed effectively by providing excess Ba to the growth front under an air processing atmosphere. Critical current densities in excess of 105A∕cm2 at 77K have been observed in the resulting large grain samples, with an associated and significant improvement in trapped magnetic field. This air-based seeded-infiltration-growth process offers a significant degree of freedom both in terms of the processing parameters and the reproducibility in growth of oriented single grains.