Synergistic effects on thermoelectric properties of Sn0.5Ge0.4875Te with Pb alloying

Abstract

In this contribution, we report a significant enhancement of thermoelectric properties of Sn0.5Ge0.4875Te alloy through three synergistic effects with Pb alloying: the significant reduction of the lattice thermal conductivity of the high entropy alloy (HEA) main phase (Sn, Ge, Pb)Te and lamellae microstructures produced from the spinodal decomposition in the alloy; the significant reduction of the carrier thermal conductivity and the significant increases of the Seebeck coefficient by decreasing the carrier concentration with Pb alloying. The high entropy random solid solution (Sn, Ge, Pb)Te single phase with NaCl-type structure forms in the alloys (Sn0.5Ge0.4875)1-xPbxTe with x = 0.2 and 0.8, while the minor cubic GeTe-based phase arises in the (Sn, Ge, Pb)Te matrix in the alloys with x = 0.33, 0.5 and 0.6, forming the lamellae microstructures. All alloys keep p-type conduction. The hole concentration decreases, but carrier mobility increases and carrier thermal conductivity decreases with Pb content x increasing. The thermoelectric properties of the alloys can be enhanced significantly with synergistic effects with proper Pb alloying. We eventually obtained the maximum figure of merit ZT of 1.61 at 773 K in the alloy (Sn0.5Ge0.4875)1-xPbx with x = 0.5.