Trace Yb doping-induced cationic vacancy clusters enhance thermoelectrics in P-type PbTe

Abstract

Alloying has been widely used to enhance thermoelectric (TE) performance, but achieving high TE performance remains challenging due to strong coupling between electrical and thermal transport in lead telluride-based materials. In this Letter, trace doping of the rare earth element Yb in a Pb0.95Na0.04Te matrix effectively regulates charge carriers by competing with cation vacancies. This mechanism optimizes carrier concentration and phonon scattering, resulting in a high power factor of ∼27 μW cm−1 K−2 and a low lattice thermal conductivity of ∼0.42 W m−1 K−1 at 823 K in Pb0.94Na0.04Yb0.01Te. First-principles calculations reveal that Yb doping induces local lattice distortions in PbTe, potentially forming pseudo-nanostructures in localized regions. This strategy leads to a peak zT of ∼2.4 at 823 K and an average zT of ∼1.4 from 303 to 823 K in Pb0.94Na0.04Yb0.01Te. Our findings suggest that the competition between dopant cations and cation vacancies reduces thermal conductivity via local lattice distortions while simultaneously improving electrical conductivity at high temperatures. This synergistic control of electrical and thermal transport offers an approach for boosting zT in TE materials.