Thermoelectric properties on antimonide skutterudites and filled skutterudites

We study thermoelectric properties on IrSb/sub 3/ and the electronic structure of YbFe/sub 4/Sb/sub 12/. The band structure of IrSb/sub 3/ is calculated by the full-potential linearized augmented plane wave (FLAPW) method with and without the consideration of the spin-orbit(SO) interaction. The calculated valence and conduction band structures near the band gap are fitted well by a simple band model, i.e., the Kane's nonparabolic bands and the parabolic bands. Using the simple band model, thermoelectric properties are calculated easily. In the calculation the relaxation time is dealt with the two types of the approximation, i.e. a constant relaxation time and a relaxation time which is inversely proportional to the electronic density of states (DOS). The results indicate that the detailed consideration of the scattering mechanism is necessary. In YbFe/sub 4/Sb/sub 12/ the DOS is obtained by the ab initio band calculation. The DOS at the Fermi energy is in good agreement of the experimental value, and thus the correlation effect of electron-electron interaction due to the localized f-orbital seems to be weak in the system.