ICT2014 Abstracts

The magnesium compounds Mg₂X (X = Si, Ge, Sn) and their solid solutions have attracted much attention as superior thermoelectric materials in the temperature range of 500 K to 800 K. Their thermoelectric properties are compatible with PbTe and CoSb₃, and they have competitiveness considering the economical and environmental aspects as well as thermoelectric performance. In this study, a solid-state reaction with elemental Mg, Si, Ge and Sb was performed to obtain pre-synthesized Mg₂Si_0.5Ge_0.5Sb_m (m = 0, 0.005, 0.01, 0.02 and 0.03) solid solutions. The resulting powder was hot pressed to synthesize Mg₂Si_0.5Ge_0.5Sb_m solid solusions. All specimens were identified as single phases with anti-fluorite structure. Mg₂Si_0.5Ge_0.5Sb_m showed n-type conduction, and the carrier concentration was increased from 7.3x10¹⁷ cm^-3 to 2.3x10²¹ cm^-3 by the doped Sb acting as donors. The absolute value of the Seebeck coefficient was decreased by Sb-doping. Mg₂Si_0.5Ge_0.5Sb_0.02 showed the lowest thermal conductivity of 2.3 W/mK at 723 K, and exhibited a maximum ZT of 0.56 at 823 K.