Important Correlations Between Local Structure and Thermoelectric Properties

*非技术摘要*热电效应是将电压差转换为温差，反之亦然。具有很大热电效应的材料称为热电材料。衡量一种材料表现出多大影响的一种指标被称为该材料的“品质系数”，并被命名为ZT。开发具有高ZT值的新型热电材料是能源和制冷应用的重要国家目标，需要在原子和宏观尺度上了解新材料的行为。这一个人研究人员奖支持一个项目，该项目将对一系列热电材料进行局部结构调查，以更好地了解控制决定ZT的重要参数的局部(原子级)物理，例如非常低的热导率和高功率因数。这些测量将确定局部扭曲，原子在晶体中的分布，以及电子结构的变化；这些结果为理论模型提供了约束，并为正在开发新材料的项目合作者提供了重要的反馈。该项目将为本科生(高级论文)和研究生(博士论文)提供教育和研究机会；学生还将获得在国家同步加速器设施作为团队工作的重要经验。*技术摘要*开发具有高优值系数ZT的新热电材料是一个重要的国家目标，需要在地方和宏观层面对新材料进行详细的表征。这个单独的研究项目将使用X射线吸收光谱(XAS)来研究一系列新材料的局部结构，以阐明局部(原子水平)物理，这决定了当一些特定的稀薄杂质添加到一些系统中时，异常低的热导率和最近观察到的功率因数的提高。低导热系数归因于每种材料中各种类型的局部无序，这很容易用XAS来确定。缺陷原子的电子结构的变化将通过吸收边形状的变化来探测。这些结果将为理论模型提供重要的约束，并为正在开发新材料的项目合作者提供重要的反馈。该项目将为本科生(高级论文)和研究生(博士论文)提供教育和研究机会；这些学生还将获得在国家同步加速器设施作为团队工作的丰富经验。

****NON-TECHNICAL ABSTRACT****The thermoelectric effect is the conversion of a voltage difference to a temperature difference and vice versa. A material that exhibits a large thermoelectric effect is called a thermoelectric material. A measure of how big an effect a material exhibits is called the material's 'figure of merit' and is designated ZT. Developing new thermoelectric materials with a high value of ZT is an important national goal for both energy and cooling applications and requires an understanding of the behavior of new materials at both atomic and macroscopic scales. This individual investigator award supports a project that will carry out local structure investigations for a series of thermoelectric materials to better understand the local (atomic-level) physics that controls important parameters that determine ZT, such as a very low thermal conductivity and a high power factor. These measurements will determine local distortions, distributions of atoms in the crystals, and changes in the electronic structure; such results provide constraints for theoretical models and important feedback to the project's collaborators who are developing new materials. This project will provide educational and research opportunities for both undergraduate (Senior theses) and graduate students (PhD theses); the students will also gain important experience working as a team at national synchrotron facilities.****TECHNICAL ABSTRACT****Developing new thermoelectric materials with a high figure of merit, ZT, is an important national goal and will require detailed characterizations of new materials at both the local and macroscopic levels. This individual investigator project will use X-ray absorption spectroscopy (XAS) to investigate the local structure of a series of new materials to elucidate the local (atomic-level) physics, which determines the unusual low thermal conductivity and the recently observed enhancement of the power factor when a few specific dilute impurities are added to some systems. The low thermal conductivity is attributed to various types of local disorder within each material which is easily determined using XAS. Changes in the electronic structure about defect atoms will be probed via changes in the shape of the absorption edges. These results will provide important constraints for theoretical models and crucial feedback to the project's collaborators who are developing new materials. This project will provide educational and research opportunities for both undergraduate (Senior theses) and graduate students (PhD theses); these students will also gain significant experience working as a team at national synchrotron facilities.