The influence of precursor powder on the microstructure and properties of Bi-2212 blocks

The present work reports our investigations on the partial melt processing of bulk Bi-2212. Commercial and homemade precursor powders with different nominal compositions were melt-processed into silver molds. Samples were analyzed by XRD, SEM/EDS and DC critical current measurements. The main secondary phases forming upon Bi-2212 peritectic decomposition were 14:24 and 91150, besides 2201, which crystallizes from the liquid. The superconducting properties depended mainly on the precursor and on the maximum processing temperature. The commercial precursors provided the best results. Bi-2212 blocks with I c = 90–135 A and J c = 900–1350 A/cm 2, at 77 K, have been obtained. However, reducing the amount of coarse secondary phases and optimizing the 2212 oxygen content may enhance the performance of bulk Bi-2212.