Phase evolution, microstructure and transport property of (Bi, Pb)-2223/Ag tapes prepared using powders of varying particle size distribution

(Bi, Pb)-2223/Ag sheathed tapes were prepared using precursor powders with different particle size distributions which were obtained by grinding the calcined powder for different durations. DTA results revealed that the reaction temperature of the precursor powder depends on the particle size and is at a minimum for the finest powder. Phase evolution studies, transport current measurement at 77 It with and without the application of an external field, microstuctural examination etc, were carried out in order to evaluate the relative performance of the tapes. The results showed that the particle size has significant effects on the reaction kinetics, ultimate phase fraction, microstructure and transport critical current density. Fdr the tapes fabricated using coarser powder, the reaction kinetics were found to be slower and the microstructure contained smaller grains with many misalignments and voids. On the other hand use of extremely fine precursors yielded tapes with a large fraction of secondary phases due to the degradation of the crystallinity of the precursor and a consequent change in the reaction sequence. The tape prepared using a precursor with an average particle size of 3-4 mum showed the best results with respect to J(c), high-T-c phase fraction, microstructure and J(c)-B characteristics.