Investigation of the bipolar effect in the thermoelectric material CaMg2Bi2 using a first-principles study

J. J. Gong; A. J. Hong; J. Shuai; L. Li; Z. B. Yan; Z. F. Ren; J.-M. Liu

doi:10.1039/C6CP02057G

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Investigation of the bipolar effect in the thermoelectric material CaMg₂Bi₂ using a first-principles study†

J. J. Gong,*^a A. J. Hong,^a J. Shuai,^b L. Li,^a Z. B. Yan,^a Z. F. Ren^b and J.-M. Liu*^a

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* Corresponding authors

^a Laboratory of Solid State Microstructure and Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
E-mail: liujm@nju.edu.cn, gongjijun@163.com

^b Department of Physics and TcSUH, University of Houston, Houston, TX 77204, USA

Abstract

The bipolar effect in relatively narrow band-gap thermoelectric (TE) compounds is a negative process deteriorating the TE properties particularly at higher temperatures. In this work, we investigate the TE performance of the compound CaMg₂Bi₂ using the first-principles calculation and semi-classical Boltzmann transport theory in combination with our experimental data. It is revealed that this compound exhibits a remarkable bipolar effect and temperature-dependent carrier concentration. The bipolar effect imposes remarkable influence on all the electron-transport related TE parameters. An effective carrier concentration n_eff as a function of temperature is proposed to account for the bipolar effect induced carrier excitations. The as-evaluated TE parameters then show good consistency with measured results. This work may shed light on our understanding of the bipolar effect in TE compounds.

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Article information

DOI: https://doi.org/10.1039/C6CP02057G
Article type: Paper
Submitted: 29 Mar 2016
Accepted: 20 May 2016
First published: 20 May 2016

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Phys. Chem. Chem. Phys., 2016,18, 16566-16574

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Investigation of the bipolar effect in the thermoelectric material CaMg₂Bi₂ using a first-principles study

J. J. Gong, A. J. Hong, J. Shuai, L. Li, Z. B. Yan, Z. F. Ren and J.-M. Liu, Phys. Chem. Chem. Phys., 2016, 18, 16566 DOI: 10.1039/C6CP02057G

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