Dual-modulation doping effects advance n-type Mg3(Sb, Bi)2 thermoelectrics

N-type Mg 3 (Sb, Bi) 2 compounds suffer from low carrier mobility at low to mid-range temperatures due to strong ionized impurity scattering from uniform doping. Here, we successfully synthesized compounds comprising by Zr, Zr-doped Mg 3( Sb, Bi) 2 , and intrinsic Mg 3( Sb, Bi) 2 by employing a dual-modulation doping strategy. This approach leverages Zr nanoparticles and Zr-doped Mg 3( Sb, Bi) 2 as electron donors, supplying charge carriers to the intrinsic Mg 3( Sb, Bi) 2 , which serves as electronic high-speed channels. By integrating the Zr-doped and intrinsic phases through a synergistic process, we construct an efficient transport network that facilitates rapid electron conduction along these channels. Such a process optimizes carrier concentration, enhances mobility, and shifts the main scattering mechanism to phonon scattering, leading to a significant increase in Hall mobility from 30.7 to 155.3 cm 2 V −1 s −1 . Consequently, the power factor at room temperature rises from 11.6 to 35.9 µW cm −1 K −2 , achieving a peak ZT value over 2.0 at 573 K and an exceptionally high average ZT of 1.7 over 323∼773 K, the highest reported to date. Device-level demonstrations confirm practical applicability, with a single-leg module reaching 13.6% efficiency under 467 K and a two-pair p-n module incorporating p-type GeTe achieving 7.5% at Δ T = 320 K. This dual-modulation doping strategy provides a generalizable design paradigm for optimizing transport and thermal management in n-type Zintl thermoelectrics for scalable mid-temperature waste heat recovery.