The thermoelectric transport properties of Zr0.43Hf0.57NiSn half-Heusler compounds were investigated for samples sintered with different spark plasma sintering (SPS) periods: 8, 32 and 72 min. By means of scanning transmission electron microscopy with a high-angular annular dark-field detector (STEM-HAADF), it was found that sintering time affected the defect concentration, namely the amount of Ni interstitial atoms, and created locally ordered inclusions of full-Heusler phase. The structural information, phase composition and electrical transport properties could be consistently explained by the assumption that Ni interstitials give rise to an impurity band situated about 100 meV below the bottom of the conduction band via a self-doping behavior. The impurity band was found to merge with the conduction band for the sample with intermediate SPS time. The effect was ascribed to the gradual dissolution of full-Heusler phase inclusions and production of interstitial Ni defects, which eventually vanished for the sample with the longest sintering time. It was demonstrated that the modification of the density of states near the edge of the conduction band and enhanced overall charge carrier concentration provided by defect engineering led to overall 26% increase in the thermoelectric figure of merit (ZT) with respect to the other samples.

中文翻译：

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通过缺陷工程定制Zr0.43Hf0.57NiSn半赫斯勒化合物的热电性能

研究了 Zr0.43Hf0.57NiSn 半赫斯勒化合物的热电输运特性，用于用不同的放电等离子体烧结 (SPS) 周期：8、32 和 72 分钟烧结的样品。通过具有高角度环形暗场探测器 (STEM-HAADF) 的扫描透射电子显微镜，发现烧结时间影响缺陷浓度，即 Ni 间隙原子的数量，并产生局部有序的全-赫斯勒相。结构信息、相组成和电传输特性可以通过假设 Ni 间隙通过自掺杂行为产生位于导带底部以下约 100 meV 的杂质带来一致地解释。发现杂质带与具有中间 SPS 时间的样品的导带合并。该效应归因于全赫斯勒相夹杂物的逐渐溶解和间隙镍缺陷的产生，最终在烧结时间最长的样品中消失。结果表明，导带边缘附近状态密度的改变和缺陷工程提供的整体电荷载流子浓度的提高导致热电品质因数 (ZT) 相对于其他样品整体增加了 26%。