From Dislocation to Nano-Precipitation: Evolution to Low Thermal Conductivity and High Thermoelectric Performance inn-Type PbTe

Abstract

PbTe-based alloys have been widely used as mid-temperature thermoelectric (TE) materials since the 1960s. Years of endeavor spurred the tremendous advances in their TE performance. The breakthroughs forn-type PbTe have been somewhat less impressive, which limits the overall conversion efficiency of a PbTe-based TE device. In light of this obstacle, ann-type Ga-doped PbTe via an alternative thermodynamic route that relies on the equilibrium phase diagram and microstructural evolution is revisited. Herein, a plateau ofzT= 1.2 is achieved in the best-performing Ga0.02Pb0.98Te in the temperature range of 550-673 K. Notably, an extremely high averagezT(ave)= 1.01 is obtained within 300 - 673 K. The addition of gallium optimizes the carrier concentration and boosts the power factorPF = S-2 rho(-1). Meanwhile, the kappa(L)of Ga-PbTe reveals a significantly decreasing tendency owing to the defect evolution that changes from dislocation loop to nano-precipitation with increasing Ga content. The pathway for both the kappa(L)reduction and defect evolution can be probed by an equilibrium phase diagram, which opens up a new avenue for locating highzTTE materials.