High-performance thermoelectric materials at room temperature are eagerly pursued due to their promising applications in the Internet of Things for sustainable power supply. Reducing sound velocity by softening chemical bonds is considered an effective approach to lowering thermal conductivity and enhancing thermoelectric performance. Here, different from softening chemical bonds at the atomic scale, we introduce a global softening strategy, which macroscopically softens the overall material to manipulate its sound velocity. This is demonstrated in MgAgSb, one of the most promising p-type thermoelectric materials at room temperature to replace (Bi,Sb)₂Te₃, that the addition of inherently soft organic compounds can easily lower its sound velocity, leading to an obvious reduction in lattice thermal conductivity. Despite a simultaneous reduction of the power factor, the overall thermoelectric quality factor B is enhanced, enabling softened MgAgSb by C₁₈H₃₆O₂ addition to achieve a figure of merit zT value of ∼0.88 at 300 K and a peak zT value of ∼1.30. Consequently, an impressive average zT of ∼1.17 over a wide temperature range has been realized. Moreover, this high-performance MgAgSb is verified to be highly repeatable and stable. With this MgAgSb, a decent conversion efficiency of 8.6% for a single thermoelectric leg and ∼7% for a two-pair module have been achieved under a temperature difference of ∼276 K, indicating its great potential for low-grade heat harvesting. This work will not only advance MgAgSb for low-grade power generation, but also inspire the development of high-performance thermoelectrics with global softening in the future.

中文翻译：

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全局软化以控制声速，实现可靠的高性能 MgAgSb 热电技术


由于室温下的高性能热电材料在物联网中可用于可持续供电，因此人们热切追求这些材料。通过软化化学键来降低声速被认为是降低热导率和增强热电性能的有效方法。在这里，与在原子尺度上软化化学键不同，我们引入了一种全局软化策略，该策略从宏观上软化整个材料以控制其声速。这在 MgAgSb 中得到了证明，MgAgSb 是室温下最有希望替代 （Bi，Sb）₂Te₃ 的 p 型热电材料，添加固有柔软的有机化合物很容易降低其声速，导致晶格热导率明显降低。尽管同时降低了功率因数，但整体热电品质因数 B 得到了提高，使 MgAgSb 能够通过添加 C₁₈H₃₆O₂ 来软化，从而在 300 K 时达到 ∼0.88 的品质因数 zT 值和 ∼1.30 的峰值 zT 值。因此，在较宽的温度范围内实现了令人印象深刻的 ∼1.17 平均 zT。此外，这种高性能 MgAgSb 被验证为高度可重复性和稳定性。借助这种 MgAgSb，在 ∼276 K 的温差下，单热电臂的转换效率为 8.6%，两对模块的转换效率为 ∼7%，表明其在低品位热收集方面具有巨大潜力。 这项工作不仅将推进 MgAgSb 在低品位发电中的应用，还将激发未来全球软化的高性能热电技术的发展。