Influence of the Precursor Powder on the Processing Window and Current-Carrying Property of Bi-2212 Wires

Four batches of Bi-2212 precursor powders prepared by both the co-precipitation method (CP) and the spray pyrolysis technology (SP) with two compositions (Bi:Sr:Ca:Cu = 2.17:1.94:0.89:2.00, 2.07:1.94:0.89:2.00) were obtained. The feature of the powder was firstly characterized. The faster phase evolution and lower melting temperature range (△T) of the precursor powder prepared by SP proved that Bi-2212 powder can be obtained by SP with both a higher preparation efficiency and better composition homogeneity. Then the current-carrying property and microstructure of these wires made from these powders were analyzed comprehensively. The property of the wires was proved to be influenced by the feature of these precursor powders a lot. Wires made by the precursor powder with the better composition homogeneity and higher phase purity were confirmed to hold a larger processing window (T_p). In addition, the decrease of the planar size of Bi-2212 crystals was discovered to improve both the machining homogeneity and texture of the wire. What’s more, both the better composition homogeneity of the precursor powder and the larger width of Bi-2212 crystals were found to improve both the interior texture and connectivity of Bi-2212 filaments. For the first time, the article provided quite specific directions to improve the quality of the precursor powder so as to both broaden T_p and enhance the current-carrying property of Bi-2212 wires.