Mg 2 Sn: a potential mid-temperature thermoelectric material

• Published in: RSC advances Vol. 6; no. 54; pp. 48728 - 48736
• Main Authors: Jin, Yu Rong, Feng, Zhen Zhen, Ye, Ling Yun, Yan, Yu Li, Wang, Yuan Xu
• Format: Journal Article
• Language: English
• Published: 2016
• ISSN: 2046-2069; 2046-2069
• DOI: 10.1039/C6RA04986A

The electronic structure and the thermoelectric properties of Mg 2 X (X = Si, Ge, and Sn) were studied using the density functional theory and the semi-classical Boltzmann transport theory. The three compounds of Mg 2 X (X = Si, Ge, and Sn) were found to be indirect band-gap semiconductors with gap magnitudes of 0.66, 0.63, and 0.29 eV, respectively. By studying the carrier concentration dependence of the transport properties, we find that the p-type Mg 2 X exhibit superior thermoelectric performance originating from a large density-of-states effective mass due to the large valley degeneracy of valence bands. In particular, a maximum ZT value of 1.1 for p-type Mg 2 Sn can be achieved at 800 K with a carrier concentration of 9.8 × 10 19 cm −3 , which is higher than that of Mg 2 Si (0.8) and Mg 2 Ge (1.0). The high ZT of Mg 2 Sn is mainly attributed to its low lattice thermal conductivity that is a consequence of the low velocity of the optical modes caused by the large mass density. These findings suggest that Mg 2 Sn is a promising mid-temperature thermoelectric material.