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

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 CuTe are introduced into an n-type base material (PbTe)-SbTe. 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 CuTe 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 ≈ 1.6 @ 823K and simultaneously an average ZT ≈ 1.0 (323–823 K) are realized in the (PbTe)SbTe-0.6Sb-2CuTe 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 CuTe alloyed PbTe are unambiguously clarified with aberration-corrected scanning transmission electron microscopy (C-STEM).