Thermoelectric (TE) generators have come a long way since the first commercial apparatus launched in the 1950s. Since then, the β-Zn4Sb3 has manifested its potential as a cost-effective and environmentally friendly TE generator compared with the tellurium-bearing TE materials. Although the β-Zn4Sb3 features an intrinsically low thermal conductivity κ, it suffers from a long-lasting structural instability issue arising from the highly mobile zinc ions. Herein, the dilute Ga dopant gives rise to the aliovalent substitution, lowers the mobile zinc ions, and optimizes the hole carrier concentration n H simultaneously. Meanwhile, the formation of nano-moiré fringes suggests the modulated distribution of point defect that results from soluble Ga in a β-Zn4Sb3 lattice, which elicits an ultralow lattice thermal conductivity κ L = 0.2 W m-1 K-1 in a (Zn0.992Ga0.008)4Sb3 alloy. Hence, a fully dense β-Zn4Sb3 incorporated with the dilute Ga doping reveals superior structural stability with a peak zT > 1.4 at 623 K. In this work, the aliovalent dilute doping coupled with phase diagram engineering optimizes the fluxes of moving electrons and charged ions, which stabilizes the single-phase β-Zn4Sb3 while boosting the TE performance at the mid-temperature region. The synergistic strategies endow the ionic crystals with a thermodynamic route, which opens up a new category for high-performance and thermal robust TE alloys.
Keywords: aliovalent dilute doping; figure‐of‐merit (zT); nano‐moiré fringes; β‐Zn4Sb3 thermoelectrics.
© 2022 The Authors. Advanced Science published by Wiley‐VCH GmbH.