Thermoelectric properties of the compounds Tl/sub 9/-X-Q/sub 6/ (X=antimony, bismuth; Q=selenium, tellurium)

The Tl/sub 9/XQ/sub 6/-class of compounds is related to the binary compound Tl/sub 5/Te/sub 3/. It is crystallizing in the tetragonal space group I4/mcm. The compounds were synthesized by mixing the elements in stoichiometric ratios and melting them in quartz ampoules under vacuum. Electrical resistivity, thermopower and thermal conductivity were measured as function of temperature to determine the thermoelectric figure of merit. At 300 K the compounds show thermopowers between 90 /spl mu/V/K (Tl/sub 9/SbTe/sub 6/) and 400 /spl mu/V/K (Tl/sub 9/BiSe/sub 6/). The electrical resistivities range from 2.5 m/spl Omega/cm (Tl/sub 9/SbTe/sub 6/) to 83 m/spl Omega/cm (Tl/sub 9/BiTe/sub 6/). The thermal conductivity at room temperature is less than 1.5 W/mK.