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

Abstract

A batch process with cold seeding was developed, whichconsiderably reduces the production cost of various melt-processedLREBa2Cu3Oy (where LRE represents a light rare earth element) compounds. The key prerequisite forsuccessful batch production is novel thin film Nd-123 seeds grown on MgO crystals, compatiblewith all LRE-123 materials and verified on large Gd-123 and NEG-123 single grains. Thesamples exhibit a sharp superconducting transition (around 1 K wide) with the onsetTc around 93.5 K. The trapped field measurements showed that all the samples in the batchwere single domain and of good pinning performance. The trapped field of nearly1 and 1.2 T was observed in the best 24 mm single-grain pucks of Gd-123 andNEG-123, respectively. The trapped field in the best 45 mm Gd-123 single-grain pucksreached 1.35 T and 0.35 T at 77 K and 87 K, respectively. Using these batch-processedGd-123 bulks, we constructed a middle-sized levitation disk. This proved that thepresent approach leads to production of melt-processed LRE-123 materials with areasonable cost and high performance suitable for superconducting super-magnets.