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<p>This study fabricated Nb<sub>3</sub>Al superconducting wires with zinc iodide (ZnI<sub>2</sub>) additions (0 ~ 2.0 wt%) using the powder-in-tube (PIT) method followed by rapid heating, quenching, and transformation (RHQT). The effects of ZnI<sub>2</sub> on the microstructure, phase evolution, and superconducting properties were systematically investigated. It was found that zinc (Zn) and iodine(I<sub>2</sub>) released from ZnI<sub>2</sub> decomposition act synergistically: iodine refines Nb grains through a “Nb/I reaction and decomposition” process, which significantly enhances Nb/Al diffusion, suppresses the formation of Al-rich NbAl<sub>3</sub>, and promotes a composition closer to the ideal Nb<sub>3</sub>Al stoichiometry. Zinc, in turn, likely assists in lowering the phase-formation temperature and may act as additional flux-pinning centers. With appropriate ZnI<sub>2</sub> addition (≤ 1.5 wt%), the purity and homogeneity of the A15 superconducting phase are improved, leading to an increased critical temperature (<i>T</i><sub><i>c</i></sub> ≈ 16.8&#xa0;K) and enhanced high-field current-carrying capability. The optimum performance was achieved at 1.0 wt% ZnI<sub>2</sub>, with a critical current density (<i>J</i><sub><i>c</i></sub>) of 3.67 × 10<sup>4</sup>A/cm<sup>2</sup> at 4.2&#xa0;K and 8 T, and 6.71 × 10<sup>3</sup> A/cm<sup>2</sup> at 10&#xa0;K and 5 T. Excessive addition (2.0 wt%), however, caused pronounced iodine volatilization and void formation, which hindered diffusion and degraded superconducting properties. This work demonstrates that ZnI<sub>2</sub> is an effective composite additive for optimizing the diffusion kinetics, microstructure, and superconducting performance of Nb<sub>3</sub>Al wires, offering a useful strategy for the design of high-performance A15-type superconductors.</p>

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Effect of zinc iodide compound addition on the properties of Nb3Al superconducting wires

  • 期刊论文

  • 发表日期：

    2026年2月13日

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  • Lei Zhang,
  • Yiming Guo,
  • Yong Zhao,
  • Mei Huang,
  • Xuru Duan,
  • Yong Zhang

摘要

This study fabricated Nb3Al superconducting wires with zinc iodide (ZnI2) additions (0 ~ 2.0 wt%) using the powder-in-tube (PIT) method followed by rapid heating, quenching, and transformation (RHQT). The effects of ZnI2 on the microstructure, phase evolution, and superconducting properties were systematically investigated. It was found that zinc (Zn) and iodine(I2) released from ZnI2 decomposition act synergistically: iodine refines Nb grains through a “Nb/I reaction and decomposition” process, which significantly enhances Nb/Al diffusion, suppresses the formation of Al-rich NbAl3, and promotes a composition closer to the ideal Nb3Al stoichiometry. Zinc, in turn, likely assists in lowering the phase-formation temperature and may act as additional flux-pinning centers. With appropriate ZnI2 addition (≤ 1.5 wt%), the purity and homogeneity of the A15 superconducting phase are improved, leading to an increased critical temperature (Tc ≈ 16.8 K) and enhanced high-field current-carrying capability. The optimum performance was achieved at 1.0 wt% ZnI2, with a critical current density (Jc) of 3.67 × 104A/cm2 at 4.2 K and 8 T, and 6.71 × 103 A/cm2 at 10 K and 5 T. Excessive addition (2.0 wt%), however, caused pronounced iodine volatilization and void formation, which hindered diffusion and degraded superconducting properties. This work demonstrates that ZnI2 is an effective composite additive for optimizing the diffusion kinetics, microstructure, and superconducting performance of Nb3Al wires, offering a useful strategy for the design of high-performance A15-type superconductors.