Thermoelectric Performance of Multiple-Doped Co4Sb12-x-y-z Ge x Te y S z Skutterudite Compounds

CoSb3 skutterudites multiply doped with Ge, Te, and S were synthesized by solid-state reaction and spark plasma sintering. x-Ray diffraction studies revealed that Ge, Te, and S entered the lattice of the CoSb3 compounds, and while Te increased the lattice volume, Ge and S decreased it. Compared with the undoped and single-doped CoSb3 compounds, the thermal conductivity and lattice thermal conductivity are significantly suppressed due to greatly increased point defect scattering. It is found that S is more effective for decreasing the lattice thermal conductivity than Te and Ge. The highest thermoelectric figure of merit, ZT, exceeds 1.1 for the Co4Sb11.25Ge0.05Te0.63S0.07 compound at 800 K.