Effects of Ge and B substitution on thermoelectric properties of CoSi

The effects of substitution of Ge and B for Si on the thermoelectric properties of CoSi were studied. The electrical resistivity, Seebeck coefficient, and thermal conductivity of CoSi, CoSi0.98Ge0.02 and CoSi0.995B0.005 were measured from room temperature to 973 K, and the power factor and figure of merit were evaluated. It was found that the substitution causes a decrease in the electrical resistivity and lattice thermal conductivity, as well as an increase in the absolute value of Seebeck coefficient and power factor. A theoretical analysis indicates the influence of substitution arises mainly from the increased carrier density and point-defect scattering of phonons. The thermoelectric figure of merit is enhanced 25-40% by substitution as compared with that of the nondoped CoSi.