FRG: Novel Approaches to the Search for Advanced Thermoelectric Materials

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.

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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.