Processing of GdBa₂Cu₃O_7-y bulk superconductor and its trapped magnetic field

Large c-axis oriented GdBa₂Cu₃O_7-y (Gd-123) bulk superconductors, which contain Gd₂BaCuO₅ (Gd-211) secondary phase and Ag, were melt textured under controlled oxygen partial pressure of 1.0%. Nd-123 was used as a seed crystal for the growth of large-grain bulk. Single-domain Gd-123 samples 32 mm in diameter were successfully fabricated with no macro-sized cracks. The employment of fine starting Gd-211 powders led to a reduction in the mean diameter of Gd-211 particles dispersed in the bulk, which resulted in an improvement in both J_c and field-trapping capability. The trapped magnetic field of the bulk Gd-Ba-Cu-O/Ag made from Gd-211 particles 0.8 μm in diameter reached 1.5 T at 77 K. Furthermore, the trapped magnetic field could be improved by the enlargement of bulk diameter and the optimization of Gd-211 content. The maximum trapped field of 2.0 T at 77 K was achieved for the Gd-Ba-Cu-O/Ag bulk sample 48 mm in diameter with the composition of Gd-123:Gd-211 = 10:5.