Enhancement of the critical current density in Cu/Ag composite sheathed (Ba, K)Fe₂As₂ tapes by pre-annealing process

Iron-based superconductors, a promising candidate for high-field applications, have aroused rising attentions. In the present study, a pre-annealing method was used to promote the transport critical current density (J _c) in Cu/Ag composite sheathed (Ba,K)Fe₂As₂ tapes. It was found that tapes sintered at 740 °C for 3 h under ambient pressure showed a J _c up to 4.9 × 10⁴ A cm^-2 (4.2 K, 10 T). Also, a transport J _c of 6.5 × 10⁴ A cm^-2 (4.2 K, 10 T) was achieved using a hot-press technique. The factors affecting the J _c of tapes were systematically analyzed. The well-constructed crystallization and grain connectivity obtained in pre-annealed tapes were considered as the major causes of the high J _c. These results highlight the great potential to increase the J _c in multiple metal composite sheathed Ba-122 tapes.