Thermoelectric properties of the incommensurate layered semiconductor GexNbTe2

The compounds GexNbTe2 (0.39 less than or equal to x less than or equal to 0.53) have been studied for their thermoelectric properties. By changing x the carrier concentration can be adjusted so that the material changes from a p-type metal to a p-type semiconductor. The maximum germanium concentrat ion at about Ge0.5NbTe2 is also the most semiconducting composition. High- and low-temperature electrical resistivity, Hall effect, Set beck coefficie nt, and thermal conductivity were measured. Evidence of electronic ordering was found in some samples. The thermal conductivity is reasonably low and glasslike with room temperature values around 20-25 mW/cm K. However, the p ower factor is too low to compete with state-of-the-art materials. The maxi mum thermoelectric figure of merit, ZT found in these compounds is about 0. 12. The low ZT can be traced to the low carrier mobility of about 10 cm(2)/ Ns. The related compounds Si0.5NbTe2 and Ge0.5TaTe2 were also studied.