Enhancement of thermoelectric properties by effective K-doping and nano precipitation in quaternary compounds of (Pb1-xKxTe)(0.70)(PbSe)(0.25)(PbS)(0.05)

Abstract

We investigated thermoelectric properties in K-doped quaternary compounds of (Pb1-xKxTe)(0.70)(PbSe)(0.25)(PbS)(0.05) (x = 0.03). In terms of two valence bands model, we argue that the L-band approaches to the S-band with increasing the K-doping concentration resulting in the increase of carrier concentration and effective mass of carrier due to the increase of band degeneracy. The effective K-doping by x = 0.02 and PbS substitution causes high power factor and low thermal conductivity, resulting in the comparatively high ZT value of 1.72 at 800 K. The low thermal conductivity for (Pb0.98K0.02Te)(0.70)(PbSe)(0.25)(PbS)(0.05) compound is attributed from the lattice distortion and line dislocation in a phase of nano precipitation. By optimizing K-doping and PbS substitution, we achieved the enhancement of practical thermoelectric performance such as average ZT(avg) = 1.08, engineering (ZT)eng = 0.81, maximum efficiency eta max = 11.63%, and output power density P-d = 6.3 W cm(-2), with temperature difference Delta T = 500 K, which has practical applicability in waste heat power generation technologies.