Natural SuperlatticeCompounds for High-Temperature Thermoelectrics
Prof David Clarke, John A. Paulson School of Engineering and Applied Sciences, Harvard University
Although the semiconductor physics underlying the thermoelectric effect have been known for several decades, identifying which materials will exhibit the best thermoelectric performance is a challenge for two main reasons. The first is that almost all materials, with the exception of highly conducting metals, exhibit some thermoelectric response when placed in a temperature gradient so there are a huge number of candidate materials to explore. The second is that the physical parameters that enter into the generally accepted figure of merit, ZT, for a material are contra-indicated. This, in turn, has led to the development of nanostructuringof existing materials in order to increase ZT by decreasing phonon thermal conductivity; a highly successful strategy except for long-term applications at high temperatures. Under these conditions, microstructural coarsening occurs destroying the nanostructuring.In this seminar, I will introduce a different approach for high-temperature applications: the exploration of oxide compounds that have a natural superlatticestructure so that the thermoelectric properties will not degrade over time.