Thermoelectric properties of some phosphorus-based skutterudite compounds

The synthesis and thermoelectric properties of some phosphorus-based skutterudites have been investigated. These compounds were made by both a flux technique using tin as the solvent and direct synthesis from pure elements. Thermoelectric measurements showed that CoP/sub 3/, CeFe/sub 4/P/sub 12/ and CeRu/sub 4/P/sub 12/ have semiconducting properties. The difference between the thermal conductivity of binary and ternary compounds can be primarily attributed to the additional phonon scattering by Ce atoms rattling inside the empty cages in the skutterudite unit cell. The thermal conductivity values for CeFe/sub 4/P/sub 12/ and CeRu/sub 4/P/sub 12/ are compared and discussed. Thermoelectric figures of merits for these compounds were calculated and the highest value was obtained for CeFe/sub 4/P/sub 12/ with a ZT of about 0.15 at 850 K. Two other compounds, CeCo/sub 4/Si/sub 3/P/sub 9/ and Ce/sub 0.3/Co/sub 4/Ge/sub 1.2/P/sub 10.8/ were made in order to compare their properties to those of CoP/sub 3/ and to attempt to determine the effect of both atomic rattling and anion substitution on the lattice thermal conductivity. Comparisons to some antimonide skutterudite compounds are also briefly discussed.