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<p>Bi-Sb alloy, as a promising thermoelectric material at cryogenic temperatures, has seen stagnant progress due to challenges in understanding the transport behaviors of energy carriers, and difficulties in synthesizing high-homogeneity, large-grain samples. In this study, an inherent electron-phonon decoupling in Bi-Sb is revealed using the first-principles calculations based on the virtual crystal approximation. The mean free path of the dominant electrons (<i>λ</i><sub>ele</sub> ~ 10<sup>3</sup> nm) is found of two orders of magnitude larger than that of phonons (<i>λ</i><sub>ph</sub> ~ 10<sup>1 </sup>nm), suggesting that a grain size greater than 10 μm would be favorable for thermoelectric transport. Bulk Bi-Sb polycrystals with highly elemental homogeneity and large grain size (~80 μm) are successfully synthesized through an ultra-fast quenching method combined with annealing, delivering superior thermoelectric performance. A prototype module based on the Bi<sub>0.88</sub>Sb<sub>0.12</sub> polycrystal, with a <i>ZT</i><sub>max</sub> of 0.48 at 150 K, is fabricated and demonstrates a Δ<i>T</i><sub>max</sub> of 4 K at a <i>T</i><sub>h</sub> of 75 K. This marks the first report of n-p paired thermoelectric cooling modules operating below liquid nitrogen temperature.</p>

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Bulk Bi-Sb polycrystals underpinned by high electron/phonon mean free path ratio enabling thermoelectric cooling under 77 K

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2025年4月14日

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  • Xiaowei Wu,
  • Zhen Fan,
  • Hangtian Zhu,
  • Tianyu Wang,
  • Meng Liu,
  • Jun Li,
  • Nan Chen,
  • Qiulin Liu,
  • Zhen Lu,
  • Guodong Li,
  • Xin Qian,
  • Te-Huan Liu,
  • Ronggui Yang,
  • Xiaoyan Niu,
  • Qi Zhao,
  • Zhiliang Li,
  • Shufang Wang,
  • Huaizhou Zhao

摘要

Bi-Sb alloy, as a promising thermoelectric material at cryogenic temperatures, has seen stagnant progress due to challenges in understanding the transport behaviors of energy carriers, and difficulties in synthesizing high-homogeneity, large-grain samples. In this study, an inherent electron-phonon decoupling in Bi-Sb is revealed using the first-principles calculations based on the virtual crystal approximation. The mean free path of the dominant electrons (λele ~ 103 nm) is found of two orders of magnitude larger than that of phonons (λph ~ 101 nm), suggesting that a grain size greater than 10 μm would be favorable for thermoelectric transport. Bulk Bi-Sb polycrystals with highly elemental homogeneity and large grain size (~80 μm) are successfully synthesized through an ultra-fast quenching method combined with annealing, delivering superior thermoelectric performance. A prototype module based on the Bi0.88Sb0.12 polycrystal, with a ZTmax of 0.48 at 150 K, is fabricated and demonstrates a ΔTmax of 4 K at a Th of 75 K. This marks the first report of n-p paired thermoelectric cooling modules operating below liquid nitrogen temperature.