Anion Engineering Enables Concurrent Optimization of Phonon and Carrier Transport in AMg2X2 Zintl Thermoelectrics
Abstract
The simultaneous suppression of lattice heat transport and enhancement of carrier transport is central to the development of high-performance thermoelectric materials. Here, we investigate the microscopic mechanisms governing phonon and carrier transport in CaAl2Si2-type AMg2X2 (A = Ca, Sr, Ba; X = P, As, Sb, Bi) Zintl compounds using first-principles calculations, machine-learning interatomic potentials, and Boltzmann transport theory. As X changes from P to Bi, the widening phonon band gap restricts three-phonon scattering channels and increases the relative importance of four-phonon processes. In CaMg2Bi2 and BaMg2Bi2, four-phonon scattering dominates the relaxation of low-frequency heat-carrying modes at 900 K. The Bi-based series also exhibits an anomalous increase in lattice thermal conductivity from Ca to Ba despite the increasing cation mass. Mode-resolved analysis links the lower thermal conductivity of CaMg2Bi2 to reduced low-frequency group velocities and stronger anharmonic scattering, with Ca-related mid-frequency vibrations providing additional four-phonon scattering channels. Including both particle-like and coherent contributions, its lattice thermal conductivity reaches 0.23 W·m−1K−1 at 900 K. Meanwhile, the increasing covalent character of the vertical Mg-X bonds is accompanied by enhanced band-edge dispersion and reduced carrier effective masses. These electronic changes, together with conduction-band convergence, favor n-type transport and yield a predicted peak ZT of 3.68 at 900 K in CaMg2Bi2. These results elucidate the interplay of phonon spectral structure and higher-order anharmonicity in thermal transport, alongside the distinct electronic response to anion substitution.
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BibTeX
@misc{wang2026anion,
title = {{Anion Engineering Enables Concurrent Optimization of Phonon and Carrier Transport in AMg$_2$X$_2$ Zintl Thermoelectrics}},
author = {Ning Wang and Jincheng Yue and Hui Zhang and Xingchen Shen and Wenling Ren and Shuyao Lin and Yanhui Liu and Yue-Wen Fang and Tian Cui},
howpublished = {arXiv},
year = {2026},
month = nov,
doi = {10.48550/arxiv.2611.02961},
eprint = {2611.02961},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2611.02961},
}
RIS
TY - UNPB
TI - Anion Engineering Enables Concurrent Optimization of Phonon and Carrier Transport in AMg_2X_2 Zintl Thermoelectrics
AU - Ning Wang
AU - Jincheng Yue
AU - Hui Zhang
AU - Xingchen Shen
AU - Wenling Ren
AU - Shuyao Lin
AU - Yanhui Liu
AU - Yue-Wen Fang
AU - Tian Cui
PY - 2026
DA - 2026/11/02
PB - arXiv
DO - 10.48550/arxiv.2611.02961
UR - https://arxiv.org/abs/2611.02961
AB - The simultaneous suppression of lattice heat transport and enhancement of carrier transport is central to the development of high-performance thermoelectric materials. Here, we investigate the microscopic mechanisms governing phonon and carrier transport in CaAl_2Si_2-type AMg_2X_2 (A = Ca, Sr, Ba; X = P, As, Sb, Bi) Zintl compounds using first-principles calculations, machine-learning interatomic potentials, and Boltzmann transport theory. As X changes from P to Bi, the widening phonon band gap restricts three-phonon scattering channels and increases the relative importance of four-phonon processes. In CaMg_2Bi_2 and BaMg_2Bi_2, four-phonon scattering dominates the relaxation of low-frequency heat-carrying modes at 900 K. The Bi-based series also exhibits an anomalous increase in lattice thermal conductivity from Ca to Ba despite the increasing cation mass. Mode-resolved analysis links the lower thermal conductivity of CaMg_2Bi_2 to reduced low-frequency group velocities and stronger anharmonic scattering, with Ca-related mid-frequency vibrations providing additional four-phonon scattering channels. Including both particle-like and coherent contributions, its lattice thermal conductivity reaches 0.23 W·m^−1K^−1 at 900 K. Meanwhile, the increasing covalent character of the vertical Mg-X bonds is accompanied by enhanced band-edge dispersion and reduced carrier effective masses. These electronic changes, together with conduction-band convergence, favor n-type transport and yield a predicted peak ZT of 3.68 at 900 K in CaMg_2Bi_2. These results elucidate the interplay of phonon spectral structure and higher-order anharmonicity in thermal transport, alongside the distinct electronic response to anion substitution.
ER -