ICT2014 Abstracts

Mg₂(Si,Sn)-based compounds are promising candidate materials for thermoelectric power generation applications in the 500 - 800 K temperature range. High power factors (~ 50 μW·K^-2·cm^-1) have previously been reported in the Mg₂Si_0.4Sn_0.6 compounds by adjusting the carrier concentrations to ~ 2 x 10²⁰ cm^-3 with Sb-doping. This work reports on the effect of Bi-doping on the thermoelectric properties in the Mg₂Si_0.4-xSn_0.6Bi_x materials (0 ≤ x ≤ 0.030). At a comparable carrier concentration level, the power factors of the Bi-doped materials were similar to those of the reported Sb-doped samples while the lattice thermal conductivities of the Bi-doped materials were 15 - 20 % lower. Hall measurements show high mobilities around 60 cm²·V^-1·s^-1 even in the heavily doped (x = 0.030) materials. The lattice thermal conductivities and Hall mobilities were fitted to existing models to study the effect of Bi on the scattering mechanisms in heat and electron transport. A peak ZT of 1.55 was obtained in the Mg₂Si_0.370Sn_0.6Bi_0.030 compound at 770 K and ZTs between 1.3 - 1.5 were repeatedly obtained in various materials with different compositions.