MgAgSb基新型低温热电材料电声输运的本征特性

One of the central themes for thermoelectrics study is to develop novel high performance thermoelectric materials.The extensively studied various new thermoelectric materials in recent years aim for the thermoeletric power generation in the medium and high temperature range of 550-1100K.In our pilot work, we found that MgAgSb compound with eco-friendly and abundantly available constituent elements exhibit excellent thermoelectric properties below 550K, and can be a promising candidate for Bi2Te3 based alloys, which are the best thermoelectrics below 550K but the sparsity of Te element limits their large-scale applications. This project will develop the controllable fabrication technique of MgAgSb alloys and investigate the band structure and the intrinsic features of electron and phonon transport by the combination of theoretical calculation, physical modeling and experimental characterization. The thermoelectric transport related key phycial parameters will be derived. The effect of deformation potential and alloy scattering potential on electrical properties will be elucidated. The contributions of various phonon scattering, including Umklapp process, alloy scattering, electron-phonon interaction and boundary scattering to the lattice thermal conductivity will be discussed.Based on the in-depth understanding of the dominant electron and phonon transport mechanisms, the compositon and microstructure of MgAgSb alloys will be rationally designed and optimized to realize the significant improvement of thermoelectric performance. The work can be desirable to providing an effective approach for the development of new high efficiency thermoelectric materials and the thermoelectric property opitimiazation of established materials.

开发新型高性能热电材料是热电学研究的一项核心内容。目前受到广泛关注的各类新型热电材料主要针对中温和高温区（550-1100K）温差发电领域。近来发现环境友好，组成元素来源丰富的低热导MgAgSb化合物在550K以下的低温区表现出优良的热电性能，具有取代因Te资源匮乏而规模化应用受限制的Bi2Te3基低温合金的巨大潜力，但其热电传输机制还不清楚。本项目针对MgAgSb合金的热电特性，通过理论计算、物理建模和实验表征相结合，研究该体系的能带结构特点和电声输运本征特性，获取电声输运相关的基本物理参数，重点理解其变形势和合金散射势对电输运性能的影响，以及Umklapp散射、合金散射、电声散射、晶界散射等对晶格热电率的贡献。在深入了解和阐明该体系中电子和声子输运主导机制的基础上，对其进行优化设计，获得热电性能显著改善的MgAgSb基合金，并为新型高效热电材料的设计开发以及材料性能优化提供指导。

开发新型高性能热电材料是热电学研究的一项核心内容。环境友好，组成元素来源丰富的低热导MgAgSb化合物在550K以下的低温区表现出优良的热电性能，具有取代因Te资源匮乏而规模化应用受限制的Bi2Te3基低温合金的巨大潜力，但其热电传输机制还不清楚。本项目针对MgAgSb合金的热电特性，通过理论计算、物理建模和实验表征相结合，研究该体系的能带结构特点和电声输运本征特性，获取电声输运相关的基本物理参数，理解其多晶型转变以及本征低晶格热电率的机理。.本项目利用变形势理论结合实验结果得到该体系的变形势，In掺杂的α-MgAgSb在525K获得最高zT~1.1。基于晶格动力学和声子传输理论，从化学键角度解释了α-MgAgSb本征低晶格热导率的起因，即全局和局域弱化学键共同存在是非笼状结构Nowotny-Juza化合物α-MgAgSb本征低晶格热导的物理机制。这类分级化学键特征可以推广到其他Nowotny-Juza化合物。通过变温高分辨同步辐射粉末X射线衍射分析了MgAgSb的多晶型晶体结构特征与相变。理论计算和热电性能测量表明γ-MgAgSb具有半导体特征，与II型结构模型结果更加相符合。.本项目在Energy Environm. Sci., Adv. Mater., Adv. Energy Mater.等高水平期刊上发表标注本基金资助的SCI论文39篇。