Grain growth behavior and enhanced thermoelectric properties of PbTe consolidated by high-density pulse current

Spark plasma sintering is a popular metallurgical process for making thermoelectric materials via solid-state reaction. Such a current-assisted sintering process enables the consolidation of compacted powders within a short duration owing to electrically and thermally enhanced atomic diffusion. Herein, we explore the grain growth behavior and thermoelectric properties of compacted PbTe powders under a high-density sintering current. The electrically sintered PbTe exhibits a 10-times larger grain size and a 7-fold increase in electrical conductivity compared to its counterpart treated at the same temperature without current introduction. The influence of electric current on grain growth behavior, lattice defect concentration and thermoelectric transport properties of the sintered PbTe is investigated. The enlarged grain size is beneficial for improving carrier mobility. Moreover, the preferential Pb migration driven by the high-density pulse current enhances the formation of V-pb defects and dispersed Pb-rich precipitates, leading to the increased carrier concentration and decreased lattice thermal conductivity for the electrically sintered PbTe. This study demonstrates the way of improving thermoelectric properties through multiscale microstructure engineering. (C) 2019 Elsevier B.V. All rights reserved.