ELECTRON-MICROPROBE ANALYSIS AND SYNCHROTRON DIFFRACTION STUDY OF CRYSTALLINE (ND0.5Y0.5)BA2CU3O7-DELTA

A melt-textured growth process, starting with the composite material ( Nd0.5Y0.5)Ba2Cu3O7-delta as feedstock, was used to grow large intergro wth crystals containing 97% (Nd/Y)Ba2Cu3O7-delta[(Nd/Y)123] and 3% (Nd /Y)(2)BaCuO5 [(Nd/Y)211]. Electron microprobe analysis and synchrotron diffraction studies showed the detailed compositions to be Nd0.55Y0.4 3Ba1.95Cu3.00Sr0.10O7-delta and Nd0.60Y0.40Ba2.00Cu2.95O6.76 for the ( Nd/Y)123 phase and Nd0.57Y1.37Ba0.99Cu1.00Sr0.01O5-x and Nd0.65Y1.35Ba 1.00Cu1.00O4.95 for the (Nd/Y)211 phase, respectively. The small stron tium impurity detected arose from contamination of the high purity bar ium carbonate used to prepare the feedstock. The (Nd/Y)211 structure s howed a significant variation in the occupancy of one of the rare-eart h sites, while no evidence was found for the substitution of Nd3+ or Y 3+ on the Ba2+ sites in either phase, These intergrowth crystals showe d a significantly lower critical current density when compared with th e unusually large value for the pure melt processed material which has been found to contain Nd3+ substituting on the Ba2+ sites.