Occupied Outer Cationic Orbitals in Dimeric MX2-Type BaSe2 Compound Lead to Reduced Thermal Conductivity and High Thermoelectric Performance

IF 13 2区 材料科学 Q1 MATERIALS SCIENCE, MULTIDISCIPLINARY
Jie Zhang, Li Zhou, Xiaohong Xia, Yun Gao, Zhongbing Huang
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Abstract

Decoupling electrical and thermal properties to enhance the figure of merit of thermoelectric materials underscores an in-depth understanding of the mechanisms that govern the transfer of charge carriers. Typically, a factor that contributes to the optimization of thermal conductivity is often found to be detrimental to the electrical transport properties. Here, we systematically investigated 26 dimeric MX2-type compounds (where M represents a metal and X represents a nonmetal element) to explore the influence of the electronic configurations of metal cations on lattice thermal transport and thermoelectric performance using first-principles calculations. A principled scheme has been identified that the filled outer orbitals of the cation lead to a significantly lower lattice thermal conductivity compared to that of the partly occupied case for MX2, due to the much weakened bonds manifested by the shallow potential well, smaller interatomic force constants, and higher atomic displacement parameters. Based on these findings, we propose two ionic compounds, BaAs and BaSe2, to realize reasonable high electrical conductivities through the structural anisotropy caused by the inserted covalent X2 dimers while still maintaining the large lattice anharmonicity. The combined superior electrical and thermal properties of BaSe2 lead to a high n-type thermoelectric ZT value of 2.3 at 500 K. This work clarifies the structural origin of the heat transport properties of dimeric MX2-type compounds and provides an insightful strategy for developing promising thermoelectric materials.

Abstract Image

二聚 MX2 型 BaSe2 化合物中被占据的外阳离子轨道可降低热导率并提高热电性能
将电学特性和热学特性分离,以提高热电材料的性能,这就要求深入了解电荷载流子的传输机制。通常情况下,有助于优化热导率的因素往往不利于电传输特性。在此,我们系统地研究了 26 种二聚 MX2- 型化合物(其中 M 代表金属,X 代表非金属元素),利用第一性原理计算探讨了金属阳离子的电子构型对晶格热传输和热电性能的影响。我们确定了一个原则性方案,即对于 MX2 而言,阳离子的外层轨道填满会导致晶格热传导率显著低于部分填满的情况,这是由于浅势阱、较小的原子间力常数和较高的原子位移参数大大削弱了键的作用。基于这些发现,我们提出了两种离子化合物--BaAs 和 BaSe2,通过插入的共价 X2 二聚体引起的结构各向异性实现了合理的高电导率,同时仍然保持了较大的晶格非谐调性。这项研究阐明了二聚 MX2- 型化合物热传输特性的结构起源,并为开发前景广阔的热电材料提供了富有洞察力的策略。
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来源期刊
Energy & Environmental Materials
Energy & Environmental Materials MATERIALS SCIENCE, MULTIDISCIPLINARY-
CiteScore
17.60
自引率
6.00%
发文量
66
期刊介绍: Energy & Environmental Materials (EEM) is an international journal published by Zhengzhou University in collaboration with John Wiley & Sons, Inc. The journal aims to publish high quality research related to materials for energy harvesting, conversion, storage, and transport, as well as for creating a cleaner environment. EEM welcomes research work of significant general interest that has a high impact on society-relevant technological advances. The scope of the journal is intentionally broad, recognizing the complexity of issues and challenges related to energy and environmental materials. Therefore, interdisciplinary work across basic science and engineering disciplines is particularly encouraged. The areas covered by the journal include, but are not limited to, materials and composites for photovoltaics and photoelectrochemistry, bioprocessing, batteries, fuel cells, supercapacitors, clean air, and devices with multifunctionality. The readership of the journal includes chemical, physical, biological, materials, and environmental scientists and engineers from academia, industry, and policy-making.
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