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<p>The in situ formation of (Sr,Ca)<sub>14</sub>Cu<sub>24</sub>O<sub>x</sub>(14:24AEC) phase in Bi-2212 precursor powders has long been recognized as crucial for enhancing Bi-2212 wires’ critical current density (<i>J</i><sub><i>c</i></sub>). However, the underlying generation mechanism of 14:24AEC has remained unclear. In this study, it is established for the first time that the in situ generation of 14:24AEC is governed by both the Sr/Ca ratio in the precursor powders and the heating atmosphere. When the Sr/Ca ratio ranges from 2.217 to 2.278, the 14:24AEC secondary phase is preferentially formed and more readily detected in Bi-2212 precursor powders. Furthermore, oxygen annealing significantly promotes the in situ formation of this phase. In contrast, when the Sr/Ca ratio exceeds 2.278, secondary phases such as Bi-2201 and Cu/CuO are more frequently observed. Notably, Bi-2212 wires fabricated from powders exhibiting exclusive in situ formation of the 14:24AEC phase exhibited the highest <i>J</i><sub><i>c</i></sub> at 4.2&#xa0;K under self-field. This work presents a reliable approach to synthesize Bi-2212 precursor powders with selective in situ generation of the 14:24AEC phase, offering a promising pathway toward improving <i>J</i><sub><i>c</i></sub> and advancing the commercial viability of Bi-2212 wires.</p>

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The in situ generation mechanism of (Sr,Ca)14Cu24Ox secondary phase in Bi-2212 precursor powder

  • 期刊论文

  • 发表日期：

    2026年6月15日

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  • Zhenbao Li,
  • Guoqing Liu,
  • Xiaoyan Xu,
  • Gaofeng Jiao,
  • Qingbin Hao,
  • Kai Yao,
  • Shengnan Zhang,
  • Chengshan Li,
  • Jianfeng Li,
  • Pingxiang Zhang

摘要

The in situ formation of (Sr,Ca)14Cu24Ox(14:24AEC) phase in Bi-2212 precursor powders has long been recognized as crucial for enhancing Bi-2212 wires’ critical current density (Jc). However, the underlying generation mechanism of 14:24AEC has remained unclear. In this study, it is established for the first time that the in situ generation of 14:24AEC is governed by both the Sr/Ca ratio in the precursor powders and the heating atmosphere. When the Sr/Ca ratio ranges from 2.217 to 2.278, the 14:24AEC secondary phase is preferentially formed and more readily detected in Bi-2212 precursor powders. Furthermore, oxygen annealing significantly promotes the in situ formation of this phase. In contrast, when the Sr/Ca ratio exceeds 2.278, secondary phases such as Bi-2201 and Cu/CuO are more frequently observed. Notably, Bi-2212 wires fabricated from powders exhibiting exclusive in situ formation of the 14:24AEC phase exhibited the highest Jc at 4.2 K under self-field. This work presents a reliable approach to synthesize Bi-2212 precursor powders with selective in situ generation of the 14:24AEC phase, offering a promising pathway toward improving Jc and advancing the commercial viability of Bi-2212 wires.