Low-angle grain boundaries (LAGBs) bring an effective scattering of phonons while maintaining a weak effect on charge carrier transport, which could be utilized for enhancing the thermoelectric performance of solid materials. In the Bi2Te3-based materials fabricated by hot extrusion (HE) technique, however, the formation of the LAGBs is evitably accompanied by severe recrystallization, resulting in texture loss and hindering further zT improvement. Here, we demonstrate a feasible strategy utilizing the grain recovery to maintain dense LAGBs with high grain orientation by the optimized HE technique. As a result, a low thermal conductivity of about 1 W m−1 K−1 and a high power factor of 4.2 mW m−1 K−2 are achieved at 300 K for p-type Bi0.5Sb1.5Te3 alloys, leading to a high room-temperature zT of 1.3. Further, with a decent flexural strength of 25.3 MPa, a 23-pair TE cooling module with the dice dimensions of 0.63 × 0.63 × 1.00 mm3 is assembled, which exhibits a maximum temperature difference of 87.8 K at a hot-side temperature Th of 350 K. These results highlight the important role of grain-recovery manipulation in simultaneously optimizing the thermal and electrical properties toward high-performance Bi2Te3-based TE materials.

中文翻译：

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晶粒恢复有助于高性能 BiSbTe 合金的低角度晶界和织构


低角度晶界 （LAGBs） 带来声子的有效散射，同时保持对电荷载流子传输的微弱影响，可用于增强固体材料的热电性能。然而，在通过热挤压 （HE） 技术制造的 Bi2Te3 基材料中，LAGB 的形成不可避免地伴随着严重的再结晶，导致织构损失并阻碍 zT 的进一步改进。在这里，我们展示了一种可行的策略，利用晶粒回收通过优化的 HE 技术保持具有高晶粒取向的致密 LAGB。因此，对于 p 型 Bi0.5Sb1.5Te3 合金，在 300 K 时实现了约 1 W m-1 K-1 的低热导率和 4.2 mW m-1 K-2 的高功率因数，从而导致 1.3 的高室温 zT。此外，凭借 25.3 MPa 的良好弯曲强度，组装了一个 23 对 TE 冷却模块，芯片尺寸为 0.63 × 0.63 × 1.00 mm3，在热侧温度 Th 为 350 K 时，最大温差为 87.8 K。这些结果突出了晶粒回收操作在同时优化高性能 Bi2Te3 基 TE 材料的热和电性能方面的重要作用。