Important Correlations Between Local Structure and Thermoelectric Properties

* 非技术摘要 * 热电效应是电压差与温度差的转换，反之亦然。 表现出大的热电效应的材料被称为热电材料。 衡量材料表现出多大效果的指标称为材料的“品质因数”，并指定为ZT。 开发具有高ZT值的新型热电材料是能源和冷却应用的重要国家目标，并且需要在原子和宏观尺度上理解新材料的行为。 该个人研究者奖支持一个项目，该项目将对一系列热电材料进行局部结构研究，以更好地了解控制决定ZT的重要参数的局部（原子级）物理学，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，晶体中原子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团队工作的重要经验。技术摘要 * 开发具有高品质因数ZT的新热电材料是一个重要的国家目标，并且需要在局部和宏观水平上详细表征新材料。 这个个人研究项目将使用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（原子级）物理学，这决定了不寻常的低热导率和最近观察到的功率因数增强当一些特定的稀释杂质添加到一些系统中时。 低热导率归因于每种材料内的各种类型的局部无序，这很容易使用XAS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条件，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团队工作的重要经验。

****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.