Properties of GdBCO bulk superconductors melt-processed in air using a Mg-doped Nd-Ba-Cu-O generic seed crystal

A Mg-doped Nd-Ba-Cu-O (NdBCO) generic seed crystal has been developed recently for the fabrication of any type of rare earth (RE) based (RE)-Ba-Cu-O single grain bulk superconductor. The new generic seed significantly simplifies the top seeded melt growth (TSMG) process for light RE based (Nd, Sm, Gd or mixed rare earth elements) bulk superconductors in particular. In this paper we report that single domain, bulk GdBCO samples have been fabricated successfully in air using the new seed in a cold seeding process. In this study, precursor powders were enriched with different amounts of BaO2 to investigate the extent of substitution of Gd for Ba in the Gd1+xBa2-xCu3O7-delta (Gd-123) solid solution phase. The particle size of the Gd2BaCuO5 (Gd-211) phase inclusions in the Gd-123 phase matrix and the spatial variation of T-c and Delta T-c along the a/b and c-axes of single grains fabricated with varying amounts of externally added BaO2 have been investigated as a function of BaO2 content. J(c) values as high as 7.2 x 10(4) A cm(-2) at 77 K and 0 T have been observed in large GdBCO grains processed under air.