Effect of initial composition of precursor powder on transport properties of Ag-Cu alloy sheathed Bi2223 tapes

In this study, we fabricated mono, 7, 19, 37 and 61 filamentary Bi2223 tapes sheathed with the Ag-Cu alloy, and several compositions with different Cu content were selected for precursor powders. The effect of the filament thickness and the initial composition of the precursor powder on the microstructure as well as the Jc properties was investigated. It was found that the multifilamentary tapes with the thin filament had the high sensitivity by controlling the Cu content in precursor powder compared to the monocore tapes with the thick filament. The improvement of the Jc values by controlling the Cu content was achieved in the multifilamentary tapes using the Cu deficient precursor powder comparing to that using the normal composition precursor. However, the formation and growth of large 14:24 particles were observed after the 1st sintering process. These large impurity particles caused the low Jc compared with the tape sheathed with pure Ag. Hence the suppression of the growth in the early stage of sintering should be required for further improvement of Jc of Ag-Cu alloy tape.