Berche Alexandre, Jund Philippe
Institut Charles Gerhardt Montpellier (ICGM), Centre National de la Recherche Scientifique (CNRS), Université de Montpellier, Ecole Nationale Supérieure de Chimie de Montpellier, UMR 5253, Montpellier, France.
Materials (Basel). 2018 May 23;11(6):868. doi: 10.3390/ma11060868.
For thermoelectric applications, methods generally fail to predict the transport properties of the materials because of their inability to predict properly the carrier concentrations that control the electronic properties. In this work, a methodology to fill in this gap is applied on the NiTiSn half Heusler phase. For that, we show that the main defects act as donor of electrons and are responsible of the electronic properties of the material. Indeed, the presence of Ni interstitial defects explains the experimental valence band spectrum and its associated band gap reported in the literature. Moreover, combining the DOS of the solid solutions with the determination of the energy of formation of charged defects, we show that Ni defects are also responsible of the measured carrier concentration in experimentally supposed "pure" NiTiSn compounds. Subsequently the thermoelectric properties of NiTiSn can be calculated using a fully description and an overall correct agreement with experiments is obtained. This methodology can be extended to predict the result of extrinsic doping and thus to select the most efficient dopant for specific thermoelectric applications.
对于热电应用而言，由于无法准确预测控制电子性质的载流子浓度，现有方法通常难以预测材料的输运性质。在这项工作中，一种填补这一空白的方法被应用于NiTiSn半赫斯勒相。为此，我们表明主要缺陷充当电子供体，并决定了材料的电子性质。事实上，镍间隙缺陷的存在解释了实验价带光谱及其文献中报道的相关带隙。此外，将固溶体的态密度与带电缺陷形成能的测定相结合，我们表明镍缺陷也是实验假设的“纯”NiTiSn化合物中测量的载流子浓度的原因。随后，可以使用完整描述来计算NiTiSn的热电性质，并获得与实验总体上正确的一致性。这种方法可以扩展到预测非本征掺杂的结果，从而为特定的热电应用选择最有效的掺杂剂。
