Effect of Sintering on the Thermoelectric Transport Properties of Bulk Nanostructured Bi0.5Sb1.5Te3 Pellets Prepared by Chemical Synthesis

Abstract

Considerable research effort has gone into improving the performance of traditional thermoelectric materials such as Bi2−x Sb x Te3 through a variety of nanostructuring approaches. Bottom-up, chemical approaches have the potential to produce very small nanoparticles (≪100 nm) with narrow size distribution and controlled shape. For this study, nanocrystalline powder of Bi0.5Sb1.5Te3 was synthesized using a ligand-assisted chemical method, and consolidated into pellets with cold pressing followed by sintering in Ar atmosphere. The thermoelectric transport properties were measured from 7 K to 300 K as a function of sintering temperature. Sintering is found to increase ZT and to move the maximum in ZT to lower temperatures due to a reduction in the free charge concentration. Hall mobility studies indicate that sintering increases the electron mean free path more than it increases the phonon mean free path up to sintering temperature of 598 K. A maximum ZT of 0.42 was measured at temperature of 275 K.