From Dislocation to Nano‐Precipitation: Evolution to Low Thermal Conductivity and High Thermoelectric Performance in n‐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 for n‐type PbTe have been somewhat less impressive, which limits the overall conversion efficiency of a PbTe‐based TE device. In light of this obstacle, an n‐type Ga‐doped PbTe via an alternative thermodynamic route that relies on the equilibrium phase diagram and microstructural evolution is revisited. Herein, a plateau of zT = 1.2 is achieved in the best‐performing Ga_0.02Pb_0.98Te in the temperature range of 550–673 K. Notably, an extremely high average zT_ave = 1.01 is obtained within 300 − 673 K. The addition of gallium optimizes the carrier concentration and boosts the power factor PF = S²ρ⁻¹. Meanwhile, the κ_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 κ_L reduction and defect evolution can be probed by an equilibrium phase diagram, which opens up a new avenue for locating high zT TE materials.