Fabrication of large grain Nd-Ba-Cu-O by self-seeded melt growth

Large, single grain Nd-Ba-Cu-O (NdBCO) samples containing Nd-422 phase inclusions have been fabricated successfully using NdBCO self-seeds by two melt processing techniques under reduced oxygen partial pressure. The first technique involves hot seeding where the seed crystal is placed onto the sample surface at the peritectic temperature. The second method involves doping precursor powder with Au and Ag to reduce the peritectic decomposition temperature of the material. This enables seeding to be achieved by introducing an undoped Nd-123 seed to the sample surface at room temperature, which simplifies processing significantly. This paper compares the microstructure of large grain NdBCO samples fabricated by the two techniques including the dependence of growth rate on undercooling, processing atmosphere and the size and distribution of Nd-422 in the Nd-123 phase matrix.