主講人介紹：Dr. Yanzhong Pei became a professor in 2012 at the School of Materials Science and Engineering, Tongji University, Shanghai, China. His research mainly focuses on advanced thermoelectric semiconductors, from synthesis to understanding the materials physics and chemistry. He holds a B.E. from Central South University in China, a Ph.D from the Shanghai Institute of Ceramics, CAS, and postdoctoral research experience for about 5 years from Michigan State University and the California Institute of Technology. Dr. Pei has published ~100 papers on thermoelectrics, which received a total citation of ~7700 with a H-index of 41. Dr. Pei was also the recipient of 2017 Goldsmid and 2013 Young Investigator Awards from the International Thermoelectric Society.
內容介紹：As an alternative strategy for advancing thermoelectrics by engineering the band structure, a minimization of lattice thermal conductivity (KL) has been proven to be successful as well. 0D vacancy (either intrinsic or extrinsic) and interstitial defects are effective on scattering phonons. Moreover, the possible clustering of vacancy or interstitial, which forms 1D dislocations, may lead to additional phonon scattering, which opens new possibilities. It is recently revealed that phonon scattering due to these defects essentially stems from a broadening in phonon dispersion through changing the mass of lattice vibrators (atoms) and the interaction force between and in-grain dislocations are particularly effective for such dispersion broadening. In addition, the most popular approximation on the phonon dispersion, the linear dispersion of Debye, statistically leads to a significant deviation between predicted and measured KL for solids. Thus, a development of a more accurate and physically meaningful phonon dispersion for phonon transport would provide a more powerful guidance for minimizing KL. Further than that, focusing on the phonon dispersion and speed of phonon propagation, low sound velocity in complex crystal structures with diffusive species is also desired for a low lattice thermal conductivity. This talk involves our recent efforts on understanding/manipulating the phonon dispersion and phonon scattering for a successful minimization of KL of thermoelectrics.