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

Large, single grain Nd-Ba-Cu-O (NdBCO) composite samples of NdBa2Cu3O7-delt a (Nd-123) containing 15 and 20 mol. % non-superconducting Nd4Ba2Cu2O10 (Nd -422) phase inclusions have been fabricated successfully by a variety of te chniques based on top-seeded melt growth under reduced oxygen partial press ure. Specifically, individual grains up to 2cm in diameter have been grown using (100) oriented MgO seeding, self(NdBCO) seeding at elevated temperatu re and self-seeding of Ag and Au doped precursor pellets. The latter exhibi t a reduced peritectic decomposition temperature compared with the undoped compound. These techniques, which vary in degree of difficulty and hence re liability, yield grains with a range of microstructural homogeneity. This p aper describes the general aspects of large NdBCO grain fabrication and pre sents the results of the different fabrication techniques.