Improvement of Thermoelectric Performance of CoSb3−xTex Skutterudite Compounds by Additional Substitution of IVB-Group Elements for Sb

An enhanced ZT value as high as 1.1 at ∼550 °C has been achieved in n-type nanostructured CoSb 3− x Te x skutterudite compounds through additional substitution of IVB-group elements (Si, Ge, Sn, Pb) for Sb. Particularly, Sn was found to be the most effective element to enhance the ZT value by extending the solubility limit of Te in CoSb 3− x Te x, which decreases thermal conductivity more significantly than electrical conductivity. The reduced thermal conductivity is confirmed by the Raman scattering measurement of CoSb 2.86 M 0.02 Te 0.12 (M = Si, Ge, Sn, Pb), which shows that Ge and Sn enter into the Sb-site of CoSb 3 and generate significant changes in the vibration modes, whereas Si and Pb are not likely to get into the lattice of CoSb 3 . Furthermore, nanostructure with fine grains and “nanodots” also contributes to the reduction of thermal conductivity.