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Atomic-Scale Chemical Inhomogeneity as a Determinant of Thermoelectric Transport in Bi2Te3-Based Materials

Wu Wang1,2,*,†, Juan Cui3,*, Zhongbin Wang1,*, Jianrui Wang1, Mingyuan Hu1, Lin Xie4, Lin Gan5, and Jiaqing He1,6,‡

  • *These authors contributed equally to this work.
  • †Contact author: wangwu@sztu.edu.cn
  • ‡Contact author: hejq@sustech.edu.cn
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Phys. Rev. X 16, 011044 – Published 3 March, 2026

DOI: https://doi.org/10.1103/qqrq-ths7

Abstract

The local structure and chemical environment critically govern transport properties in quantum and energy materials, but their atomic-scale manifestations remain elusive. Here we uncovered the atomic characteristics, intrinsic origin, and thermoelectric implications of chemical inhomogeneity in Bi2Te3-based materials with varying Se alloying. Using aberration-corrected electron microscopy, chemical bonding analysis, and thermodynamic modeling, we revealed pronounced Se enrichment in the central layer of a quintuple structure and constructed precise atomic models for this intrinsic inhomogeneity. Atomic-scale charge-density and valence-state measurements provided direct experimental evidence for chemical bonding disparity in Bi2Te3, with more covalent bonding in central layers and greater ionic bonding in outer layers. We also showed that this bonding disparity, coupled with entropy-enthalpy competition, drove the observed site preference and local chemical segregation in Bi2Te3−xSex (x=0.5, 1.0, 1.5, 2.0, and 2.5). The site-resolved bonding analyses further demonstrated that selective Se occupation tuned both ionic and covalent components of Bi–X bonds in Bi2Te3−xSex. Therefore, this intrinsic chemical inhomogeneity modulated bonding polarity, the electronic band gap, and the Seebeck coefficient, serving as a fundamental determinant of thermoelectric performance. Our findings highlight atomic-scale chemical inhomogeneity as a key factor in tailoring functional properties of layered quantum materials beyond thermoelectrics.

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Popular Summary

Bismuth telluride (Bi2Te3)-based materials are widely used as near-room-temperature thermoelectrics, but how local atomic configuration controls the transport properties remains unclear. Using atomic-resolution electron microscopy, we directly visualize where Se atoms sit and find that they preferentially accumulate in the central layer of each quintuple. By combining these site-resolved images with bonding analysis and quantum-mechanical calculations, we reveal why this site preference arises and demonstrate how it tunes chemical bonding, band gap, and ultimately the Seebeck coefficient. This intrinsic chemical inhomogeneity emerges not as an imperfection, but rather as a built-in, adjustable feature that can be leveraged to optimize thermoelectric performance. This clarifies how microscopic chemistry governs macroscopic transport and may also influence the material’s plasticity and topological behavior, offering a broadly useful strategy for engineering layered quantum materials.

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Phys. Rev. X 16, 011044– Published 3 March, 2026
  • Received 7 September 2025
  • Accepted 28 January 2026
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Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.

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