Refinement of Nd-422 phase trapped in a Nd1+delta Ba2-delta Cu3O7-y superconducting matrix

The possibility of controlling Nd-422 phase dimension and morphology, both in the partially melted state and in the final superconducting matrix, was investigated. Nd-Ba-Cu-O samples were prepared by the melt powder melt growth (MPMG) technique, Precursor materials containing Nd as either Nd2O3 or Nd-422, formed during precursor quenching, were used. The role of Pt in Nd-422 refining was analyzed. The effect on Nd-422 nucleation and growth, of stoichiometries with increasing Nd-422 molar excesses (0%, 10%, 20%, and 40%) combined with different heating processes, up to the partially melted state, were examined. Uniformly distributed needle-like particles (1 mu m diameter and 10-15 mu m length) were obtained at 1120 degrees C and resulted in a further refined distribution trapped in completely processed samples.