Abstract
Aiming at the improvement of current capacity in Bi<sub>2</sub>Sr<sub>2</sub>Ca<sub>2</sub>Cu<sub>3</sub>O<sub>10+δ</sub> (Bi-2223) superconducting tapes, both the calcination process of precursor powders and the sintering process of Bi-2223 tapes have been modified to tune the intergrain connections. By adopting different calcination atmosphere of air and oxygen during the pre-calcination process, the phase composition of final precursor powder kept almost the same, while the particle size decreased in oxygen pre-calcinated powders, which thus led to the appearance of more secondary phases. On the other hand, due to the optimization of crystallization process of Bi-2223 phase, the microstructure with less pore density has been obtained, which proved that the increase of heating rate could obviously lead to the enhancement of intergrain connections of Bi-2223 tapes. Finally, critical current of 116 A has been achieved with the air pre-calcinated powders and 400 °C /h heating rate during HT2, which was ∼40% increase comparing with the <i>I</i><sub>c</sub> of Bi-2223 tape with oxygen pre-calcinated powders and 100 °C/h heating rate in HT2 process.
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