As a new method of alloying, entropy engineering has proven to be an effective strategy to decrease the lattice thermal conductivity (). However, the majority of entropy engineering applications of half-Heusler alloys (HHs) are suboptimal. The poor Seebeck coefficients () and obscure underlying electron and phonon transport mechanisms of medium- and high-entropy HHs hinder the further optimization of their thermoelectric properties. Herein, a systematic synthesis of -type ZrCoSb-based medium-entropy HHs is reported, along with a corresponding structural, theoretical, and thermoelectric study. It is demonstrated that the effectively decreased in medium-entropy HHs was mainly due to the scattering of atomic disorder, in addition to the vacancies, stacking faults, dislocations, and nano-domains/precipitates. Using density functional theory calculations, we attribute the lower to the lower density-of-states (DOS) effective mass and the slowly changing DOS at Fermi level. By optimizing the spark plasma sintering temperature, an ultralow of 1.27 W m K was achieved in the Zr(NbTa)CoSb medium-entropy HH alloy at 923 K. In conjunction with the improved power factor, the highest peak figure-of-merit value of ∼0.42 was achieved for the Zr(NbTa)CoSb medium-entropy HH alloy. This study provides a guidance for the design and further optimization of the thermoelectric properties for medium-entropy HH alloys.

中文翻译：

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熵驱动的多尺度缺陷增强了ZrCoSb基半霍斯勒合金的热电性能


作为一种新的合金化方法，熵工程已被证明是降低晶格热导率的有效策略（）。然而，半霍斯勒合金（HH）的大多数熵工程应用都不是最理想的。中熵和高熵 HH 较差的塞贝克系数 () 以及模糊的电子和声子传输机制阻碍了其热电性能的进一步优化。在此，报道了 型 ZrCoSb 基中熵 HH 的系统合成，以及相应的结构、理论和热电研究。结果表明，中熵HHs的有效降低主要是由于原子无序的散射，此外还有空位、堆垛层错、位错和纳米域/析出物。使用密度泛函理论计算，我们将其归因于较低的态密度（DOS）有效质量和费米能级缓慢变化的 DOS。通过优化放电等离子烧结温度，Zr(NbTa)CoSb 中熵 HH 合金在 923 K 下实现了 1.27 W m K 的超低值。结合改善的功率因数，最高峰值品质因数Zr(NbTa)CoSb 中熵 HH 合金实现了~0.42。该研究为中熵HH合金热电性能的设计和进一步优化提供了指导。