Achieving band convergence by tuning the bonding ionicity in n-type Mg                         3                         Sb                         2

Xin Sun; Xin Li; Jiong Yang; Jinyang Xi; Ryky Nelson; Christina Ertural; Richard Dronskowski; Weishu Liu; Gerald J. Snyder; David J. Singh; Wenqing Zhang

doi:10.1002/jcc.25822

Achieving band convergence by tuning the bonding ionicity in n-type Mg ₃ Sb ₂

Xin Sun, Xin Li, Jiong Yang^*, Jinyang Xi, Ryky Nelson, Christina Ertural, Richard Dronskowski, Weishu Liu, Gerald J. Snyder, David J. Singh, Wenqing Zhang

^*Corresponding author for this work

Materials Science and Engineering

Research output: Contribution to journal › Article › peer-review

67 Scopus citations

Abstract

Identifying strategies for beneficial band engineering is crucial for the optimization of thermoelectric (TE) materials. In this study, we demonstrate the beneficial effects of ionic dopants on n-type Mg ₃ Sb ₂ . Using the band-resolved projected crystal orbital Hamilton population, the covalent characters of the bonding between Mg atoms at different sites are observed. By partially substituting the Mg at the octahedral sites with more ionic dopants, such as Ca and Yb, the conduction band minimum (CBM) of Mg ₃ Sb ₂ is altered to be more anisotropic with an enhanced band degeneracy of 7. The CBM density of states of doped Mg ₃ Sb ₂ with these dopants is significantly enlarged by band engineering. The improved Seebeck coefficients and power factors, together with the reduced lattice thermal conductivities, imply that the partial introduction of more ionic dopants in Mg ₃ Sb ₂ is a general solution for its n-type TE performance.

Original language	English (US)
Pages (from-to)	1693-1700
Number of pages	8
Journal	Journal of computational chemistry
Volume	40
Issue number	18
DOIs	https://doi.org/10.1002/jcc.25822
State	Published - Jul 5 2019

Funding

This work was supported by the National Key Research and Development Program of China (No. 2017YFB0701600), the Natural Science Foundation of China (Grant Nos. 11674211 and 51632005), and the 111 project D16002. W. Q. Zhang acknowledges the support from program of Shanghai Subject Chief Scientist (16XD1401100), the support from Guangdong Innovation Research Team Project (No. 2017ZT07C062), and Shenzhen Pengcheng-Scholarship program. Work at the University of Missouri is supported by the U.S. Department of Energy. Office of Science, Basic Energy Sciences through grant number DE-SC0019114. GJS acknowledges the support from NASA Jet Propulsion Laboratory. Contract Grant sponsor: Guangdong Innovation Research Team Project; Science Foundation of China; Contract Grant number: Nos. 11674211 and Grant number: No. 2017YFB0701600; Contract Grant sponsor: Natural 51632005; Contract Grant sponsor: Program of Shanghai Subject Chief

Keywords

Mg Sb
band engineering
band-resolved COHP
bonding ionicity
thermoelectric

ASJC Scopus subject areas

Computational Mathematics
General Chemistry

Access to Document

10.1002/jcc.25822

Cite this

Sun, X., Li, X., Yang, J., Xi, J., Nelson, R., Ertural, C., Dronskowski, R., Liu, W., Snyder, G. J., Singh, D. J., & Zhang, W. (2019). Achieving band convergence by tuning the bonding ionicity in n-type Mg ₃ Sb ₂. Journal of computational chemistry, 40(18), 1693-1700. https://doi.org/10.1002/jcc.25822

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abstract = " Identifying strategies for beneficial band engineering is crucial for the optimization of thermoelectric (TE) materials. In this study, we demonstrate the beneficial effects of ionic dopants on n-type Mg 3 Sb 2 . Using the band-resolved projected crystal orbital Hamilton population, the covalent characters of the bonding between Mg atoms at different sites are observed. By partially substituting the Mg at the octahedral sites with more ionic dopants, such as Ca and Yb, the conduction band minimum (CBM) of Mg 3 Sb 2 is altered to be more anisotropic with an enhanced band degeneracy of 7. The CBM density of states of doped Mg 3 Sb 2 with these dopants is significantly enlarged by band engineering. The improved Seebeck coefficients and power factors, together with the reduced lattice thermal conductivities, imply that the partial introduction of more ionic dopants in Mg 3 Sb 2 is a general solution for its n-type TE performance.",

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Sun, X, Li, X, Yang, J, Xi, J, Nelson, R, Ertural, C, Dronskowski, R, Liu, W, Snyder, GJ, Singh, DJ & Zhang, W 2019, 'Achieving band convergence by tuning the bonding ionicity in n-type Mg ₃ Sb ₂', Journal of computational chemistry, vol. 40, no. 18, pp. 1693-1700. https://doi.org/10.1002/jcc.25822

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AB - Identifying strategies for beneficial band engineering is crucial for the optimization of thermoelectric (TE) materials. In this study, we demonstrate the beneficial effects of ionic dopants on n-type Mg 3 Sb 2 . Using the band-resolved projected crystal orbital Hamilton population, the covalent characters of the bonding between Mg atoms at different sites are observed. By partially substituting the Mg at the octahedral sites with more ionic dopants, such as Ca and Yb, the conduction band minimum (CBM) of Mg 3 Sb 2 is altered to be more anisotropic with an enhanced band degeneracy of 7. The CBM density of states of doped Mg 3 Sb 2 with these dopants is significantly enlarged by band engineering. The improved Seebeck coefficients and power factors, together with the reduced lattice thermal conductivities, imply that the partial introduction of more ionic dopants in Mg 3 Sb 2 is a general solution for its n-type TE performance.

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