Multi-filling approach for the improvement of thermoelectric properties of skutterudites

Several skutterudite antimonides filled with atoms of different kinds, (Ba, M)_yCo₄Sb₁₂ (M=Ce, La, Sr), have been synthesized by the combination of solid state reaction and melting methods. Thermal conductivity of (Ba,Sr)_yCo₄ Sb₁₂ samples shows a behavior similar to that of Ba_yCo₄Sb₁₂. Adding a small amount of Ce or La to the Ba_yCo₄Sb₁₂ system is effective in further reducing the lattice thermal conductivity. The difference in the ionic radii of the two co-filler atoms is the most sensitive factor for scattering of phonons. The multi-filled (Ba, M)_yCo₄Sb₁₂ (M=Sr, Ce, La) show lower Seebeck coefficients as compared to the single-filled Ba_yCo ₄Sb₁₂ having the same total filling fraction. It is expected that higher thermoelectric performance could be realized by further optimization of the composition of filler species