The possibility of preparing bulk Nd-123 by the partial-melting technique in air is reported for the first time. The effects of the starting composition and of processing conditions (temperature, annealing time) on the superconducting properties of the system were investigated. The electrical properties were found to depend critically on the starting composition as well as on the annealing times and the cooling rates. The best results (zero-resistance temperature with an onset ) were obtained starting with the stoichiometric composition (x = 0) by annealing at for 24 h and cooling to RT at . The results are discussed in terms of competition between the nucleation of Nd-123 and as secondary phase, variation of the Nd content in the 123 phase and kinetics of oxygen intercalation during the cooling process. .

The application of partial melting techniques to the densification of BSCCO 2223 ceramics is presented. A new method has been developed, that avoids the peritectic decomposition of the 2223 phase and exploits the existence of a limited region of the phase diagram, occurring for composition richer in Ca and Cu, in which this phase is the only BSCCO phase coexisting with the liquid. This allows the densification process assisted by the liquid phase, limiting at the same time the formation of undesired intergrowths of lower To phases. In comparison with the usually adopted processes, the new method results in a dramatic decrease of the post-treatment times, which are typically limited to a few hours. By optimising the thermal as well as the temporal parameters governing a standard two-steps procedure, values of .J c of the order of 10 3 Acm-2 , at 77 K, can be obtained for a global process time not exceeding 6 hours.PACS 74.62.Bf -Effects of material synthesis, crystal structure and chemical composition. PACS 01.30.Cc -Conference proceedings.

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