Aliovalent Dilute Doping and Nano‐Moiré Fringe Advance the Structural Stability and Thermoelectric Performance in β‐Zn4Sb3. Issue 26 (26th June 2022)

• Record Type: Journal Article
• Authors: Jen, I‐Lun; Wang, Kuang‐Kuo; Wu, Hsin‐Jay
• Is Part Of: Advanced science. Volume 9:Issue 26(2022)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2022-06-26
• Subjects: β‐Zn4Sb3 thermoelectrics -- aliovalent dilute doping -- figure‐of‐merit (zT) -- nano‐moiré fringes; Science -- Periodicals; 505
• DOI: 10.1002/advs.202201802
• Languages: English
• ISSNs: 2198-3844

Abstract

Abstract: Thermoelectric (TE) generators have come a long way since the first commercial apparatus launched in the 1950s. Since then, the β ‐Zn4 Sb3 has manifested its potential as a cost‐effective and environmentally friendly TE generator compared with the tellurium‐bearing TE materials. Although the β ‐Zn4 Sb3 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 ‐Zn4 Sb3 lattice, which elicits an ultralow lattice thermal conductivity κ L = 0.2 W m −1 K −1 in a (Zn0.992 Ga0.008 )4 Sb3 alloy. Hence, a fully dense β ‐Zn4 Sb3 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 ‐Zn4 Sb3 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. Abstract : Aliovalent cation substitution between Zn 2+ and Ga 3+ diminishes the highly mobile Zn 2+ and optimizes the hole carriers, leading to an ultrahigh PF = 1.6 mW m −1 K −2 . The interstitial Ga 0 induces the formation of nano‐moiré fringes and thus elicits an ultralow κ L = 0.2 W m −1 K −1 . A light‐doped (Zn0.992 Ga0.008 )4 Sb3 crystal attains a peak zT of 1.4 in the β ‐Zn4 Sb3 single‐phase region.