Tuesday, 3 October 2017: 15:30
Chesapeake F (Gaylord National Resort and Convention Center)
The thermoelectric (TE) energy-conversion efficiency of TE materials has been steadily improved over recent decades. This efficiency is expressed in terms of a dimensionless number zT = S2σT/k, which is simply referred to as the figure-of-merit, where S is the Seebeck coefficient, σ is the electrical conductivity, k is the thermal conductivity, and T is the absolute temperature. Limited success at increasing zT has been achieved by focusing on k reduction, which is thought to increase phonon scattering by incorporating complex lattice structures, such as superlattices, heterostructures, and nanocomposites, into the material. For some materials, k can be reduced to a minimum by placing the substance in an amorphous state; however, this behavior is typically associated with a substantial decrease in the charge carrier mobility and, therefore, in σ. This strong interdependence among the key parameters of zT has delayed the release of new high-zT TE devices for use in industry. Therefore, this study adopts a different approach, which focuses on controlling the mechanisms and processes that tend to de-couple the key parameters and maximize the zT numerator. Particular attention is paid to mechanisms that optimize the power factor (P.F.), which is equal to σS2. In this work, we tailored nanocomposite embedded structure in Bi-Te and Sb-Te based films, resulting in allowed the realization of intriguing TE performance based on interfacial energy-barrier scattering. The TE performance of nanocrystalline films is optimized by tailoring the Vb employed in the energy-filtering mechanisms in two positions: 1) at the grain boundaries of the single-phase nanocrystalline films and 2) at the interfaces of the hetero-nanocomposites. More details will be presented