Investigation of Al substitution on the thermoelectric properties of SrSi2

We report the results of aluminum substitution on the temperature-dependent electrical resistivity, Seebeck coefficient, as well as thermal conductivity of SrSi_2−xAl_x alloys with 0 ≤ x ≤ 0.20. It is found that the substitution of Al onto the Si sites of SrSi₂ causes a significant decrease in the electrical resistivity and the Seebeck coefficient. The observations are associated with the downward shift of the Fermi level, due to hole-doping via Al substitution within a rigid-band scenario. The low-temperature thermal conductivity decreases markedly with increasing Al content. Analysis of the lattice thermal conductivity from the contribution of various thermal scattering mechanisms reveals that the reduction in the lattice thermal conductivity mainly arises from the grain-boundary and point-defect scattering of the phonons through chemical substitution.