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Fully Ab-Initio Determination of the Thermoelectric Properties of Half-Heusler NiTiSn: Crucial Role of Interstitial Ni Defects

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
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Materials 2018, 11(6), 868; https://doi.org/10.3390/ma11060868
Received: 25 April 2018 / Revised: 16 May 2018 / Accepted: 18 May 2018 / Published: 23 May 2018
(This article belongs to the Special Issue Half-Heusler, Silicide and Zintl-type Thermoelectric Materials)
For thermoelectric applications, ab initio 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 Nii 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 Nii 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 ab initio 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. View Full-Text
Keywords: thermoelectric materials; half-Heusler phase; point defects thermoelectric materials; half-Heusler phase; point defects
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Berche, A.; Jund, P. Fully Ab-Initio Determination of the Thermoelectric Properties of Half-Heusler NiTiSn: Crucial Role of Interstitial Ni Defects. Materials 2018, 11, 868.

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