Enhanced thermoelectric figure of merit in nanocrystalline Bi2Te3 bulk

Nanocrystalline Bi2Te3 bulks were synthesized via a nanostructuring method that included steps of ball milling, cold pressing, and sintering. In the temperature range of 325–525 K, nanocrystalline Bi2Te3 bulks exhibit good thermoelectric properties with a peak ZT of 0.94. The experimental results suggest that the partially coherent boundaries allow the maintenance of low grain growth rate and low resistivity. The enhancement of ZT comes from a large reduction in the phonon thermal conductivity and a strong suppression of the bipolar effect at high temperature.