Perspectives of new materials research for thermoelectric applications

A possibility of increasing the thermoelectric figure-of-merit of materials has bent definitely identified by the use of different fabrication techniques. An attempt at rf-plasma processing has been made to improve the figure-of-merit of iron disilicides β-FeSi₂ . In addition, our recent results on the skutterudites CoSb₃ and related-materials are reported. The lattice thermal conductivity κ_L of CoSb₃ is a factor of 7 to 10 higher than that of a state-of-art thermoelectric material such as Bi ₂Te₃/Sb₂Te₃. This can be lowered to some degree by mixed-valence alloying. The κ_L of n-type Co_0.9(PdPt)_0.1Sb₃ was 0.025 W/cmK, which was one-fifths smaller than that of CoSb₃, which led to a ZT value of 0.9 at 800 K. However, the reduction in the lattice thermal conductivity by the mixed-valence alloying is limited. The lattice thermal conductivity is strongly affected by the Debye temperature Θ_D of materials; therefore, the first matter to be settled may be to lower the value of Θ_D for improving the figure-of-merit