Thermoelectric Figure-of-Merit of Fully Dense Single-Crystalline SnSe

Wei, Pai-Chun; Bhattacharya, Sriparna; Liu, Yu Fei; Liu, Fengjiao; He, Jian; Tung, Yung Hsiang; Yang, Chun Chuen; Hsing, Cheng Rong; Nguyen, Duc Long; Wei, Ching Ming; Chou, Mei Yin; Lai, Yen Chung; Hung, Tsu Lien; Guan, Syu You; Chang, Chia Seng; Wu, Hsin Jay; Lee, Chi Hung; Li, Wen Hsien; Hermann, Raphael P.; Chen, Yang Yuan; Rao, Apparao M.

Thermoelectric Figure-of-Merit of Fully Dense Single-Crystalline SnSe

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Type

Article

Authors

Wei, Pai-Chun
Bhattacharya, Sriparna
Liu, Yu Fei
Liu, Fengjiao
He, Jian
Tung, Yung Hsiang
Yang, Chun Chuen
Hsing, Cheng Rong
Nguyen, Duc Long
Wei, Ching Ming
Chou, Mei Yin
Lai, Yen Chung
Hung, Tsu Lien
Guan, Syu You
Chang, Chia Seng
Wu, Hsin Jay
Lee, Chi Hung
Li, Wen Hsien
Hermann, Raphael P.
Chen, Yang Yuan
Rao, Apparao M.

KAUST Department

Computer, Electrical and Mathematical Sciences and Engineering (CEMSE) Division

Online Publication Date

2019-03-19

Print Publication Date

2019-03-31

Date

2019-03-19

Abstract

Single-crystalline SnSe has attracted much attention because of its record high figure-of-merit ZT ≈ 2.6; however, this high ZT has been associated with the low mass density of samples which leaves the intrinsic ZT of fully dense pristine SnSe in question. To this end, we prepared high-quality fully dense SnSe single crystals and performed detailed structural, electrical, and thermal transport measurements over a wide temperature range along the major crystallographic directions. Our single crystals were fully dense and of high purity as confirmed via high statistics 119Sn Mössbauer spectroscopy that revealed <0.35 at. % Sn(IV) in pristine SnSe. The temperature-dependent heat capacity (Cp) provided evidence for the displacive second-order phase transition from Pnma to Cmcm phase at Tc ≈ 800 K and a small but finite Sommerfeld coefficient γ0 which implied the presence of a finite Fermi surface. Interestingly, despite its strongly temperature-dependent band gap inferred from density functional theory calculations, SnSe behaves like a low-carrier-concentration multiband metal below 600 K, above which it exhibits a semiconducting behavior. Notably, our high-quality single-crystalline SnSe exhibits a thermoelectric figure-of-merit ZT ∼1.0, ∼0.8, and ∼0.25 at 850 K along the b, c, and a directions, respectively.

Citation

Wei P-C, Bhattacharya S, Liu Y-F, Liu F, He J, et al. (2019) Thermoelectric Figure-of-Merit of Fully Dense Single-Crystalline SnSe. ACS Omega 4: 5442–5450. Available: http://dx.doi.org/10.1021/acsomega.8b03323.

Acknowledgements

The authors wish to acknowledge Prof. Terry Tritt (Clemson University) for providing access to low temperature measurement facilities in his laboratory, and Prof. Julian Goldsmid, Dr. Pooja Puneet, and Prakash Parajuli for valuable discussions. We also thank National Institute of Standards and Technology and Dr. Jeffrey W. Lynn for providing the neutron beam time that made the neutron rocking curve measurements possible. R.P.H. thanks Dipanshu Bansal and Jiawang Hong for numerical phonon data in refs (11) and (26).