Mg sub(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: 01.05.2016
• Subjects: Carrier density; Intermetallics; Magnesium compounds; Semiconductors; Silicides; Thermoelectric materials; Thermoelectricity; Tin
• ISSN: 2046-2069
• DOI: 10.1039/c6ra04986a

The electronic structure and the thermoelectric properties of Mg sub(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 sub(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 sub(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 ZTvalue of 1.1 for p-type Mg sub(2)Sn can be achieved at 800 K with a carrier concentration of 9.8 10 super(19) cm super(-3), which is higher than that of Mg sub(2)Si (0.8) and Mg sub(2)Ge (1.0). The high ZTof Mg sub(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 sub(2)Sn is a promising mid-temperature thermoelectric material.