Effect of composition control of precursor and pre-oxidation of alloy sheath on Jc properties of Ag–Cu alloy sheathed Bi2223 tapes

Abstract

When an Ag–Cu alloy is used as inner sheath material of Bi2223 tape, the formation of many large (Sr,Ca)14Cu24Ox (14:24) particles in the early stage of sintering degraded the Jc values. To suppress this formation reaction for the improvement of Jc, the effects of composition control of precursor and the pre-oxidation of Ag–Cu alloy sheath were investigated in this study. The Jc value of the tape controlling precursor composition, in which tape the amount of impurity particles was slightly decreased, was recovered up to 1.2×104A/cm2. On the other hand, the tape sheathed with pre-oxidized alloy could suppress the formation of the 14:24 particles in the early stage of sintering through the reduction of Cu potential in alloy sheath. As a result, the size and number of 14:24 particles were decreased in the final tape and improved the Jc value. Based on these results, the composition control of precursor and pre-oxidation of alloy sheath were applied simultaneously to fabricate the tape. This combination of both processes resulted further reduction of the number and size of the 14:24 particles in the final tape, and the best Jc value of 1.8×104A/cm2 was achieved. This proves that the high Jc can be achieved in the Ag–Cu alloy sheathed tape by the suppression of impurity particles.