Synthesis and thermoelectric properties of Bi2Te3 based nanocomposites

Nanocrystalline binary Bi2Te3 powders were synthesized by a hydrothermal method from BiCl3 and pure tellurium at different temperature. XRD analysis and TEM observation showed that the average grain sizes increase from 15 to 35 nm with the increase of the synthesis temperature from 120 to 250 °C. Novel Bi2Te3 based nanocomposites were prepared by hot pressing from 90 wt.% zone-melted alloys and 10 wt.% hydrothermally synthesized nanopowders. It was found that the nanosized powders are effective to reduce the thermal conductivity stronger than the electrical conductivity, a result that improves the figure of merit of a nanocomposite. A maximal ZT value of 0.83 has been obtained. Further improvement on the figure of merit of the nanocomposites are considered to be possible by doping the nanopowders and optimizing the composition of the base alloys.