Top seeded melt growth of Gd-Ba-Cu-O single grain superconductors

Top seeded melt growth (TSMG) has been used extensively to fabricate large, single grain Y-Ba-Cu-O (YBCO) bulk superconductors that can trap large magnetic fields. The TSMG method is relatively economical and has enabled the development of batch processes for the fabrication of a large number of bulk single grain superconductors in a single furnace. In addition, the technique allows the fabrication of complex-shaped bulk samples with controlled and strongly connected grains by using a novel, multi-seeding process. A practical processing route for processing of LRE-Ba-Cu-O (where LRE represents a light rare earth element) single grain superconductors (which have superior properties to YBCO) has been developed at Cambridge over the past three years, based on the development of a generic seed of melt textured Mg-doped Nd-123 and suppression of solid solution phase formation in air by enriching the precursor composition with excess Ba. In this paper we report the successful application of a practical TSMG process in the fabrication of high performance Gd-Ba-Cu-O (GdBCO) single grain superconductor. This method has enabled the development of a batch process for GdBCO and we demonstrate for the first time the fabrication of a large number of high performance single grains of this material in a single process. Finally, we report the processing of bulk GdBCO in the form of complex geometries with controlled grain orientation for bespoke engineering applications.