ICT2014 Abstracts

Mg₂Si is an attractive thermoelectric material, since it exhibits high thermoelectric performance and consists of abundant and non-toxic elements. For further improvement of the figure of merit of Mg₂Si, nano-dispersion of other compounds in Mg₂Si is one of the effective approaches because it can reduce the thermal conductivity. In this study, we prepare Mg₂Si-Mg₂Sn-Si nanocomposites by ball-milling and sintering of Mg₂Si and Sn and investigate the thermoelectric properties. A mixture of Mg₂(Si,Sn) and Si is obtained via Si-Sn replacement reaction in ball-milling of n-type Mg₂Si with 5 at% of Sn. Mg₂(Si,Sn) separates into Mg₂Si and Mg₂Sn after sintering, resulting in the formation of a nanocomposite containing these two compounds and Si. The nanocomposite shows low thermal conductivity (3.1 W m^-1 K^-1) compared to nanostructured Mg₂Si (5.6 W m^-1 K^-1) at room temperature. On the other hand, the carrier mobility is significantly reduced from 72.2 to 27.6 cm² V^-1 s^-1 by adding Sn in the nanostructuring process. It suggests that Si atoms, which are replaced by the additional Sn atoms, segregate at grain boundaries and form incoherent interfaces. Other thermoelectric properties and preparation of nanocomposites with different Sn contents will be also presented.