Understanding the Role of Potassium Doping in PbTe-PbS Thermoelectrics

Abstract

Thermoelectric materials, capable of scavenging electric power from sources of waste heat, are one of promising choices for relaxing global energy problems [1]. However, the low energy conversion efficiency limits such smart materials to put into use widely. We achieved an excellent thermoelectric performance in 2.5% K doped PbTe0.7S0.3 sample: one of the highest dimensionless figure of merit (ZT) of 2.2 at 923 K and the highest energy conversion efficiency of ~20.7% (i.e. the highest average ZT of 1.56) for non-segmented thermoelectric devices. Hopefully, this work highlights a realistic prospect of wide thermoelectric application with high ZT (above 3). In order to obtain the above high performance, we subtly tuned K doping level in spinodal decomposed PbTe0.7S0.3 system to firstly realize a simultaneous enhancement of electrical conductivity and Seebeck coefficient and a reduction of thermal conductivity [2]. Accordingly, a precise characterization and analysis of microstructure as they relate to thermoelectric performance are vitally important for the fundamental understanding of this peculiar thermoelectric material. The presentation will cover S/TEM microscopy and microanalysis strategy to unravel microstructural influence on thermoelectric properties and associated phenomena.