Inorganic Colloidal Solution-Based Approach to Nanocrystal Synthesis of (Bi,Sb)2Te3

There is an interest in higher-ZT thermoelectric materials for high-watt-density cooling of electronics. Reducing thermal conductivity through increased phonon scattering in nanomaterials has been shown to be effective and is being investigated by many groups. Solution-based synthesis is a method for making thermoelectric nanomaterials that can provide particle sizes <20?nm and can be scaled to production quantities of materials. We are exploring an approach that proceeds through formation of an ??ink?? that contains inorganic colloidal nanocrystals of thermoelectric materials. This approach has the advantage that, by adjustments within the basic synthesis process, the size, shape, and composition of the nanocrystals can be tightly controlled to study changes in the transport properties. Currently we are making materials from inks that contain Bi₂Te₃ nanocrystals with Sb₂Te₃ ligands, suspended in a solvent. Powders formed by curing the inks are made into solid pellets by hot pressing, and the pellets are used for characterization and transport property measurements. The best result from our thermoelectric property measurements is ZT?=?0.9 with power factor of 27???W/cm?K², which to our knowledge is the best value for solution-based synthesis.