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Tailoring thermoelectric properties of Zr0.43Hf0.57NiSn half-Heusler compound by defect engineering

Gałązka, Krzysztof and Xie, Wenjie and Populoh, Sascha and Aguirre, Myriam H. and Yoon, Songhak and Büttner, Gesine and Weidenkaff, Anke (2020):
Tailoring thermoelectric properties of Zr0.43Hf0.57NiSn half-Heusler compound by defect engineering.
In: Rare Metals, (6), 39. Springer, pp. 659-670, ISSN 1001-0521,
DOI: 10.1007/s12598-020-01392-7,
[Online-Edition: https://doi.org/10.1007/s12598-020-01392-7],
[Article]

Abstract

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.

Item Type: Article
Erschienen: 2020
Creators: Gałązka, Krzysztof and Xie, Wenjie and Populoh, Sascha and Aguirre, Myriam H. and Yoon, Songhak and Büttner, Gesine and Weidenkaff, Anke
Title: Tailoring thermoelectric properties of Zr0.43Hf0.57NiSn half-Heusler compound by defect engineering
Language: English
Abstract:

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.

Journal or Publication Title: Rare Metals
Journal volume: 39
Number: 6
Publisher: Springer
Uncontrolled Keywords: Thermoelectric, Half-Heusler, Interstitial, Defect engineering
Divisions: 11 Department of Materials and Earth Sciences
11 Department of Materials and Earth Sciences > Material Science
11 Department of Materials and Earth Sciences > Material Science > Materials and Resources
Date Deposited: 10 Jun 2020 05:40
DOI: 10.1007/s12598-020-01392-7
Official URL: https://doi.org/10.1007/s12598-020-01392-7
Projects: This work was financially supported by German Research Foundation Priority Programme 1386 (No.WE 2803/2-2) and the European Union under Marie Skłodowska-Curie Program (W. J. X.).
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