Band engineering and crystal field screening in thermoelectric Mg3Sb2. Issue 15 (25th March 2019)

• Record Type: Journal Article
• Authors: Tan, Xiaojian; Liu, Guo-Qiang; Hu, Haoyang; Shao, Hezhu; Xu, Jingtao; Jiang, Jun
• Is Part Of: Journal of materials chemistry. Volume 7:Issue 15(2019)
• Page Start: 8922
• Page End: 8928
• Publication Date: 2019-03-25
• Subjects: Materials -- Research -- Periodicals; Chemistry, Analytic -- Periodicals; Environmental sciences -- Research -- Periodicals; 543.0284
• DOI: 10.1039/c9ta00288j
• Languages: English
• ISSNs: 2050-7488

Abstract

Abstract : Based on careful analysis of local chemical bonding, valence band convergence is designed in Mg3 Sb2 by crystal field screening. Abstract : Recently, Mg3 Sb2 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 Mg3 Sb2 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 Mg3 Sb2 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 Mg3 Sb2, where a significantly improved ZT = 1.2 at 800 K is predicted. This study provides an applicable scheme for improving the thermoelectric performance of Mg3 Sb2, and also it enriches the concept of band engineering for thermoelectrics.