Novel seeds applicable for mass processing of LRE-123 single-grain bulks

A batch process with cold seeding was developed, which considerably reduces the production cost of various melt-processed LREBa₂Cu₃O_y (where LRE represents a light rare earth element) compounds. The key prerequisite for successful batch production is novel thin film Nd-123 seeds grown on MgO crystals, compatible with all LRE-123 materials and verified on large Gd-123 and NEG-123 single grains. The samples exhibit a sharp superconducting transition (around 1 K wide) with the onset T_c around 93.5 K. The trapped field measurements showed that all the samples in the batch were single domain and of good pinning performance. The trapped field of nearly 1 and 1.2 T was observed in the best 24 mm single-grain pucks of Gd-123 and NEG-123, respectively. The trapped field in the best 45 mm Gd-123 single-grain pucks reached 1.35 T and 0.35 T at 77 K and 87 K, respectively. Using these batch-processed Gd-123 bulks, we constructed a middle-sized levitation disk. This proved that the present approach leads to production of melt-processed LRE-123 materials with a reasonable cost and high performance suitable for superconducting super-magnets.