Processing and microstructure of single grain, uranium-doped Y-Ba-Cu-O superconductor

摘要

Large grain Y-Ba-Cu-O (YBCO) superconductor doped with various amounts of depleted UO_2 and containing excess Y_2BaCuO_5 (Y-211) and Y_2O_3 have been fabricated by top seeded melt growth (TSMG). The effect of depleted UO_2 on the large grain microstructure has been studied systematically in samples with and without added Pt. It is found that UO_2 refines the size of the second phase particles in the superconducting YBa_2Cu_3O_(7-delta) (Y-123) matrix to dimensions of a few hundred nanometres with an approximately spherical morphology. Addition of Y_2O_3 to the uranium-doped precursor powder, rather than Y-211, yields a significantly finer distribution of second phase particles and an associated higher critical current density J_c at increased magnetic field.