Structural Dynamics and Thermal Transport in Bismuth Chalcogenide Alloys
Structural Dynamics and Thermal Transport in Bismuth Chalcogenide Alloys
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DOI：
10.33774/chemrxiv-2021-8487n
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发表时间：
2021-08
影响因子：
8.6
通讯作者：
J. Cen;Ioanna Pallikara;J. Skelton
中科院分区：
文献类型：
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作者：
J. Cen;Ioanna Pallikara;J. Skelton
本文详细研究了铋硫系化合物Bi_2S_3、Bi_2Se_3和Bi_2Te_3及其合金的结构动力学、能量和动力学稳定性以及热输运性质。Bi 2S 3、Bi 2Se 3和Bi 2 Te 3中Bi阳离子孤对的不同活性导致正交Pnma和菱面体R-3 m相之间的竞争，后者受到较重硫族元素原子的青睐，而Bi 2Se 3和Bi 2 Te 3的非环境相在环境条件下显示声子不稳定性。Pnma结构具有比R-3 m相更弱的化学键和更强的声子非谐性，从而导致本质上更低的晶格热导率。Bi 2 [Se（1-x）S（x）]3的热力学模型表明，R-3 m结构仅在低S含量时才具有能量优势，但在较低的形成温度下，稳定窗口可能会延长。Bi 2 [Se（1-x）Te（x）]3在R-3 m相中显示出与理想固溶体行为的实质性偏离，这是由于Se和Te原子分别占据组成五重层中的内部和外部位置的强烈能量偏好。在化学键的不均匀性引起的应变场波动所示出的合金系统中的热输运的确定中发挥了重要的作用，和硫属无序远离优选的对称结构被发现是一个重要的因素，在降低的热导率的Bi 2SeTe 2相比，Bi 2 Te 3的端点。这些建模研究的微观洞察力为铋硫属化物及其合金提供了新的见解，这可能会为正在进行的研究提供信息，以优化这些材料和相关材料的热电性能。
We present a detailed study of the structural dynamics, energetic and dynamical stability and thermal transport of the bismuth chalcogenides Bi2S3, Bi2Se3 and Bi2Te3 and their alloys. The differing activities of the Bi cation lone pairs in Bi2S3, Bi2Se3 and Bi2Te3 lead to competition between orthorhombic Pnma and rhombohedral R-3m phases, with the latter favored by heavier chalcogen atoms, while the reported non-ambient phases of Bi2Se3 and Bi2Te3 show phonon instabilities under ambient conditions. The Pnma structure has weaker chemical bonding and stronger phonon anharmonicity than the R-3m phase, resulting in an intrinsically lower lattice thermal conductivity. A thermodynamic model of Bi2[Se(1-x)S(x)]3 indicates that the R-3m structure is energetically favored only for low S content, but the stability window can potentially be extended at lower formation temperatures. Bi2[Se(1-x)Te(x)]3 in the R-3m phase shows substantial deviation from ideal solid-solution behavior, due to a strong energetic preference for the Se and Te atoms to occupy the interior and exterior sites, respectively, in the constituent quintuple layers. Strain-field fluctuations induced by inhomogeneities in the chemical bonding are shown to play a significant role in determining the heat transport in the alloy systems, and chalcogen disorder away from the preferred symmetric structure is found to be an important factor in the reduced thermal conductivity of Bi2SeTe2 compared to the Bi2Te3 endpoint. The microscopic insight from these modelling studies provides new insight into the bismuth chalcogenides and their alloys, which may inform ongoing research to optimize the thermoelectric performance of these and related materials.