Thermoelectric materials are capable of converting waste heat into electricity. Half-Heusler materials, as one of the promising candidates for thermoelectrics, have a relatively low figure of merit due to their high thermal conductivity. Here, we propose an effective strategy to lower the lattice thermal conductivity of half-Heusler materials guided by the first principles calculations and Boltzmann transport equation. The strategy was inspirited by regulating the phonon dispersion with a combination of two heavy and one light atoms, which introduced the absence of acoustic-optic phonon gap (a–o gap) and promoted the phonon–phonon scattering phase space, and therefore a small lattice thermal conductivity. Taking half-Heusler LuNiBi as an example, we found that it possessed an ultralow lattice thermal conductivity (0.7 W m⁻¹ K⁻¹ at 300 K after two-channel phonon transport model correction), which was two orders of magnitude smaller than that of usual half-Heusler materials. Our findings provide an effective strategy to design half-Heusler materials with low thermal conductivities and serve as a guide for the further improvement of the thermoelectric performance of half-Heusler compounds.

中文翻译：

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半赫斯勒LuNiBi中没有声子间隙驱动的超低晶格热导率

热电材料能够将废热转化为电能。半赫斯勒材料作为热电材料的一种有前途的候选材料，由于其高导热性而具有相对较低的品质因数。在这里，我们提出了一种有效的策略，以降低半赫斯勒材料的晶格热导率，以第一性原理计算和玻尔兹曼传输方程为指导。该策略的灵感来自于用两个重原子和一个轻原子的组合来调节声子色散，这引入了声光声子间隙（a-o 间隙）的缺失并促进了声子 - 声子散射相空间，因此一个小的晶格热导率。以半赫斯勒 LuNiBi 为例，我们发现它具有超低的晶格热导率（0.7 W m^-1 K ^-1在 300 K 时经过双通道声子传输模型校正），比通常的半赫斯勒材料小两个数量级。我们的研究结果为设计具有低热导率的半赫斯勒材料提供了一种有效的策略，并为进一步提高半赫斯勒化合物的热电性能提供了指导。