FRG: Novel Approaches to the Search for Advanced Thermoelectric Materials

这个合作的重点研究小组(FRG)项目的目标是发明一种新型的热电(TE)材料，这种材料将显著提高制冷和电力应用的效率。基于固体中的电子和热输运理论，半导体材料的理论模型已经有几十年的历史了。然而，没有一种已知的材料具有所有需要的电学和热学特性。此次合作的目的是设计、合成和表征新型半导体热电材料，这些材料表现出作为器件材料的高效率。电子结构理论将为寻找这类材料提供一般指导。主要的障碍是科学家无法预测新化合物的组成或结构，除非它们在化学上与已知化合物相似。然而，一旦发现了一种新的材料并确定了它的晶体结构，就可以计算出它的电子能带结构和输运性质。因此，本研究既有较强的理论基础，又有较强的实验基础。通过季度会议、互访和互联网交流，化学家、物理学家和理论家与他们的学生之间的密切互动将为下一步的实验和计算提供快速的反馈和规划。这个跨学科项目的教育和研究部分被很好地整合在一起，这个复杂项目的全面成功将通过特殊的协同作用实现。%热电(TE)材料允许建造小型纯电子设备，这些设备在通过电流时提供热冷却，或者直接从热中产生电能。TE冷却器消除了对压缩机和气体的需求，如氟利昂。然而，目前的TE冷却器的效率很低(仅为允许的最大效率的10%，而家用冰箱的运行效率约为卡诺效率的30%)。然而，这些设备用于效率不如小尺寸或可靠性重要的应用中。如果能将效率提高到30%或更高，从而改善环境和产生经济效益，则它们的用途将大大扩大。对于学生来说，这是一个理想的训练场地。这个实验和理论项目是高度互动和跨学科的，在参与的化学家和物理学家以及他们的研究生和博士后之间展示了很强的协同性。

The objective of this collaborative Focused Research Group (FRG) project is to invent a new class of thermoelectric (TE) materials that will significantly enhance the efficiency of cooling and power applications. Based on the theory of electronic and heat transport in solids, a theoretical model of semiconducting TE materials has been available for several decades. However, no known material has all the needed electronic and thermal characteristics. The purpose of this collaboration is to design, synthesize and characterize new classes of semiconducting thermoelectric materials that exhibit high efficiency as device materials. Electronic structure theory will provide general guidelines in the search for such materials. The main impediment is the inability of scientists to predict the composition or structure of new compounds, unless they are chemically similar to known compounds. However, once a new material is found and its crystal structure determined, its electronic band structure as well as transport properties can be calculated. Thus this research has both strong theoretical and experimental components. A close interaction between the chemists, physicists and theorists and their students through quarterly meetings, exchange visits, and internet communication, will provide rapid feedback and planning of the next experiments and calculations. The education and research components of this interdisciplinary project are well integrated, and overall success in this complex project will be realized through exceptional synergy.%%%Thermoelectric (TE) materials allow the construction of small, purely electronic devices that provide thermal cooling on passing a current, or that produce electricity directly from heat. TE coolers eliminate the need for compressors and gasses, such as freons. However, current TE coolers have low efficiency (only 10 % of the maximum allowed, while home refrigerators operate at about 30 % of Carnot efficiency.). Yet these devices are used in applications where efficiency is less important than small size or reliability. Their use would greatly expand if the efficiency could be raised to 30 % or more, resulting in environmental improvements and economic benefits. This is an ideal training ground for students. This experimental and theoretical project is highly interactive and interdisciplinary with strong synergy exhibited among the participating chemists and physicists and their graduate and postdoctoral students.