Bulk Bi-Sb polycrystals underpinned by high electron/phonon mean free path ratio enabling thermoelectric cooling under 77 K.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 40229294.
- Also identified by DOI 10.1038/s41467-025-58491-1 and PMC identifier 11997089.
- Licence recorded as CC BY-NC-ND.
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Abstract
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 (λ<sub>ele</sub> ~ 10<sup>3</sup> nm) is found of two orders of magnitude larger than that of phonons (λ<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 ZT<sub>max</sub> of 0.48 at 150 K, is fabricated and demonstrates a ΔT<sub>max</sub> of 4 K at a T<sub>h</sub> of 75 K. This marks the first report of n-p paired thermoelectric cooling modules operating below liquid nitrogen temperature.