Effect of Bi2223 addition in precursor on the formation and J_c property of Bi2223 tapes sheathed with the Ag–Cu alloy

The use of an alloy sheath is effective in improving the mechanical strength of Bi2223 tapes although it easily decreases J(c) properties. In the case of the tape sheathed with Ag-Cu alloy, the Jc value was decreased by the formation of non-superconducting (Sr, Ca)(14)Cu24Ox ( 14: 24) particles. In this study, the effect of Bi2223 addition in precursor on the formation and the properties of Bi2223 tapes was investigated. The addition of Bi2223 in precursor was found to be effective in reducing the number and size of the 14: 24 particles and in increasing the formation speed of the Bi2223 phase. This rapid formation of Bi2223 is probably due to the skipping of nucleation of Bi2223 since the Bi2223 crystals added in precursor act as nuclei. In addition, the crystal size after the first sintering decreased on increasing the content of 2223 powder. Due to the reduction of 14: 24 particles, J(c) values of about 2 x 10(4) A cm(-2) were attained in the tapes with 2223 up to 5%, although the J(c) values were decreased by further addition of 2223 to more than 10%. This reduction of J(c) would be caused by the poor alignment of Bi2223 crystals because of the small size in the rolling step.