Coherent Sb/CuTe Core/Shell Nanostructure with Large Strain Contrast Boosting the Thermoelectric Performance of n‐Type PbTe

Abstract The exploration of n‐type PbTe as thermoelectric materials always falls behind its p‐type counterpart, mainly due to their quite different electronic band structure. In this work, elemental Sb and Cu₂Te are introduced into an n‐type base material (PbTe)₈₁‐Sb₂Te₃. The introduction of extra Sb can effectively tune the concentration of electrons; meanwhile, Sb precipitates can also scatter low‐energy electrons (negatively contribute to the Seebeck coefficient) thus enhance the overall Seebeck coefficient. The added Cu₂Te is found to always co‐precipitate with Sb, forming an interesting Sb/CuTe core/shell structure; moreover, the interface between core/shell precipitates and PbTe matrix simultaneously shows coherent lattice and strong strain contrast, beneficial for electron transport but adverse to phonon transport. Eventually, a peak figure of merit ZT_max ≈ 1.6 @ 823K and simultaneously an average ZT ≈ 1.0 (323–823 K) are realized in the (PbTe)₈₁Sb₂Te₃‐0.6Sb‐2Cu₂Te sample, representing the state of the art for n‐type PbTe‐based thermoelectric materials. Moreover, for the first time the three existing forms of Cu atoms in Cu₂Te alloyed PbTe are unambiguously clarified with aberration‐corrected scanning transmission electron microscopy (C_s‐STEM).