Band engineering and crystal field screening in thermoelectric Mg3Sb2

Recently, Mg3Sb2 attracted much research interest due to its competitive thermoelectric performance of ZT = 1.7 observed in n-type materials at 700 K. On the other hand, the thermoelectric performance of p-type Mg3Sb2 is found to be limited (ZT < 0.7) by the low power factor, originating in the l...

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Published inJournal of materials chemistry. A, Materials for energy and sustainability Vol. 7; no. 15; pp. 8922 - 8928
Main Authors Tan, Xiaojian, Guo-Qiang, Liu, Hu, Haoyang, Shao, Hezhu, Xu, Jingtao, Jiang, Jun
Format Journal Article
LanguageEnglish
Published Cambridge Royal Society of Chemistry 2019
Subjects
Band structure of solids
Banded structure
Conduction
Conduction bands
Engineering
Power factor
Screening
Thermoelectricity
Valleys
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Summary:Recently, Mg3Sb2 attracted much research interest due to its competitive thermoelectric performance of ZT = 1.7 observed in n-type materials at 700 K. On the other hand, the thermoelectric performance of p-type Mg3Sb2 is found to be limited (ZT < 0.7) by the low power factor, originating in the less degenerate valence valleys. In this paper, we report a systematic theoretic investigation on the thermoelectric properties of Mg3Sb2 by using band structure and transport calculations. Starting with the careful analysis of the band structure, the characteristics of the valence and conduction bands are clarified. By raising the concept of crystal field screening, a scheme to increase the degeneracy of valence valleys is proposed. The expected band convergence is numerically confirmed in Ba-doped p-type Mg3Sb2, where a significantly improved ZT = 1.2 at 800 K is predicted. This study provides an applicable scheme for improving the thermoelectric performance of Mg3Sb2, and also it enriches the concept of band engineering for thermoelectrics.
ISSN:2050-7488
2050-7496
DOI:10.1039/c9ta00288j