Designing high-performance Yb(Mg,Zn)2(Bi,Sb)2 Zintls for power generation through anion framework engineering

Balancing electronic and phonon transport remains a central challenge for Zintl thermoelectrics. Here we show that complex anion framework engineering in provides concurrent control over both. Progressive substitution of Mg by Zn tunes the anion p -states at the Γ -point, driving valence-band p -orbital overlap and thereby enhancing weighted mobility and the power factor toward the Zn-rich end ( x = 2 ). In parallel, alloy disorder introduces strong phonon point-defect scattering, suppressing lattice thermal conductivity. Therefore, the optimal performance is realized at the intermediate composition x = 1 . 3 , despite a modest power factor at 773 K ( µ ∼ 10 µW cm −1 K −2 ), the low κ l a t ( ∼ 0.58 W m −1 K −1 ) yields a peak z T ≈ 0 . 9 at 773 K. We further demonstrate device-level feasibility by fabricating a two-pair module using as the p -type leg, achieving an efficiency of ∼ 8.5 % at a temperature difference of 420 K. These results establish anion framework engineering as a practical route to couple band convergence with phonon scattering and deliver competitive, environmentally acceptable thermoelectric performance.