Increased efficiency of batch-processed melt-textured YBCO

摘要

Results on an established batch process preparing melt-textured YBCO in high quality and quantity will be reported. We used a standard composition Y_(1.5)Ba_2Cu_3O_(7-x) + 1 wt percent CeO_2 without further doping to fabricate single-domain YBCO monoliths in different sizes and shapes (cylindrical, quadratic) as well as rectangular multi-seeded YBCO monoliths. Up to 2-3 kg melt-textured YBCO blocks are grown reproducibly in one box furnace run. Top seeding by self-made SmBCO was improved and rationalized. Optimization of oxygen annealing treatment leads to macro-crack free YBCO monoliths. Each YBCO monolith was characterized by integral levitation force and field mapping. In a single-domain quadratic monolith with an edge length of 38 mm a maximum induction of 1.44 T at 77 K and a distance of 0.5 mm was frozen. The reproducibility of the batch process is guaranteed. Mean maximum induction from 1.1 to 1.2 T at 77 K per batch was reached. A trapped magnetic field of 2.5 T was achieved between two single-domain monoliths in a gap of 1.5 mm at 77 K. Depending on the application function, elements with different sizes, designs and more or less complex geometry are constructed in several working steps by cutting, machining, bonding and passivation. Selected function elements were checked with field mapping at 77 K. Results of our function elements in HTSC reluctance motors using single-domain material are shown. We will report on a fly-wheel system and a system to levitate persons.