Microstructures and thermoelectric properties of higher manganese silicide prepared by rapid solidification and hot pressing

Polycrystalline higher manganese silicide （HMS） with the chemical composition of MnSi_1.75-x （x=0, 0.02, 0.04） were prepared by rapid solidification （RS） and hot uniaxial pre.ssing （HUP）. It is shown that the microstructures of the samples consist of locally parallelly distributed MnSi thin flakes in the semiconductor Mn₄Si₇ matrix due to a quasi-directional solidification during RS. It is found that electric conductivities decrease and Seebeck coefficients increase with the increase of silicon content in the material. The thermoelectric properties are controlled by carrier scattering below 400℃ and electron excitation above 500℃. The highest thermoelectric power factor obtained is 1.3×10^-3Wm^-1K^-1 at 570℃.