Effect of addition of the elements Cr, V, Mo, Ge, Re and Ru on the thermoelectric properties of higher manganese silicides MnSi∼1.74

Consisting of light and non-toxic elements, higher manganese silicides (HMS) allow to be substituted with various elements. In the present study, elements Cr, V, Mo, Ge, Re and Ru have been added to HMS to improve the thermoelectric properties. Substitution of 2% Re only influences the thermal conductivity without affecting the carrier concentration and mobility. In all other substitutions, carrier concentration changes systematically and the carrier mobility shows weak temperature dependence due to additional alloy scattering. In addition, due to the effect of doping, substituted elements modify Resistivity (rho) more dramatically than the Seebeck coefficient (alpha) behavior. Thermal conductivity (kappa) is low for all compositions and the maximum value stays impressively at similar to 3.3 W m(-1) K-1 . Thermoelectric Power factor (PF = alpha(2)/rho) and the figure merit (ZT = alpha(2) T rho kappa(-1) ) show a correlation with the carrier concentration measured at low temperatures (80-300 K). The highest PF similar to 2.2 mW m(-1) K--(2) and ZT similar to 0.7 is measured for X + 2 mol%V17Ge31 (X = Mn0.95Cr0.05Si1.74) which is doped to the highest extent.