Preparation and Thermoelectric Properties of Mg₂Si_1−xGe_x Solid-Solution Semiconductor

Abstract

The Mg₂Si_1−xGe_x solid-solution semiconductors were prepared in the composition range 0≤x≤0.45. The Ham effect, thermoelectric power and electrical conductivity were measured and the maximum figure-of-merit (Z) was estimated for the undoped sample at the composition x=0.45. The carrier concentrations at 300 K were controlled at this compositon to 1.4×10²⁵ m⁻³ electrons and 1.8×10²⁵ m⁻³ holes by doping the nominal amount of 1600 ppm Sb and 20000 ppm Ag at this composition, resulting in the figure-of-merits of 6.8×10⁻⁴ K⁻¹ and 3.8×10⁻⁴ K⁻¹, respectively. The measurement of thermoelectric power showed that these doped samples behaved as extrinsic semiconductors up to 850 K. The maximum figure-of-merits at 700 K were estimated to be 1.5×10⁻⁴ K⁻¹ for the n-type sample and 3.4×10⁻⁴ K⁻¹ for the p-type one. From the fact that the value of the n-type sample was larger than those of the traditional materials, the Mg₂Si_1−xGe_x solid-solution semiconductors can be expected as a new candidate material for thermoelectric energy conversion in the middle-temperature range.