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 nH 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 κL = 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.

Thermoelectrics In article number 2201802 by I‐Lun Jen, Kuang‐Kuo Wang, and Hsin‐Jay Wu, aliovalent cation substitution fulfilling by dilute gallium (Ga) ions diminishes the highly‐mobile zinc (Zn) ions in zinc antimonide (Zn4Sb3) and optimizes the hole carriers, leading to an ultrahigh thermoelectric power factor. The interstitial metallic Ga elicits formation of nano‐moiré fringes, resulting in an ultra‐low lattice thermal conductivity. A light‐doped Ga‐Zn4Sbx crystal performs high thermoelectric performance with superior structural stability by leveraging the ionic and electronic conduction.