Pressure Tuning of Intermediate Valence and Multiband Semiconductor Thermoelectric Materials

摘要

The conventional means of searching for new materials, in this case efficient thermoelectrics, is to synthesize a large number of compounds and investigate each in detail as a function of materials parameters, such as preparation conditions and doping levels. Each compound thus represents one point in a phase space determined by electronic and structural parameters. With the use of pressure one can continuously adjust the interaction parameters and follow the change in properties for each compound. During the period of this grant, we demonstrated that antimony bismuth telluride can be pressure tuned to exhibit a thermoelectric figure of merit that is at least a factor of two higher than any known material at ambient pressure. This demonstration that higher ZT is possible under pressure is a valuable 'existence proof'. We have developed an understanding of origin of the increase in the thermoelectric power associated with an electronic topological transition. This new understanding suggests future research directions for ambient pressure chemical tuning.