Thermoelectric properties of the incommensurate layered semiconductor Ge/sub x/NbTe/sub 2/

The compounds Ge/sub x/NbTe/sub 2/ (0.39/spl les/x/spl les/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 concentration at about Ge/sub 0.5/NbTe/sub 2/, is also the most semiconducting composition. High and low temperature electrical resistivity, Hall effect, Seebeck coefficient, and thermal conductivity were measured. The thermal conductivity is reasonably low and glasslike with room temperature values around 20-25 mW/cm K. However, the power factor is too low to compete with state of the art materials. The maximum ZT found in these compounds is about 0.12. The low ZT can be traced to the low carrier mobility of about 10 cm/sup 2//Vs. The related compounds Si/sub 0.2/NbTe/sub 2/ and Ge/sub 0.5/TaTe/sub 2/ were also studied.