Atomic-Level Crystal Lattice Chemistry for Ultrahigh-Performance Thermoelectric Materials

The incorporation of foreign atoms or vacancies into crystal matrices tends to induce atomic-level point defects, consequently forming unique defect structures based on coordination chemistry and sizes of the involving atoms. These defects can further evolve into more complex forms, such as one-dimensional dislocations or nanostructures, which uniquely interact with charge carriers and phonons. This interaction significantly influences properties of bulk solids. The introduced atoms can frequently manipulate both the electronic and phonon structures of bulk materials, providing an effective means to control charge and thermal transport properties in beneficial ways. Understanding the formation mechanisms of defects in bulk matrices is crucial for developing design principles with high predictability and stabilizing defect structures for specific applications of bulk crystals.

In this talk, I will present our recent research achievements in the atomic-resolution design of complex, multiscale defect structures stabilized in various types of crystal lattices. To elucidate their formation mechanisms, we conducted direct observations of the resulting defect structures using atomic-resolution scanning transmission electron microscopy (STEM) and atom probe tomography. This work has led to innovative strategies that decouple key parameters of the thermoelectric figure of merit (ZT), including electrical conductivity, Seebeck coefficient, and thermal conductivity. As a result, we have developed several record-high thermoelectric materials.

Biography Dr. In Chung holds a BSc and MSc from Seoul National University, Korea, and a Ph.D. in Chemistry from Michigan State University with Prof. Mercouri G. Kanatzidis. He was a postdoctoral research fellow at Northwestern University. He joined the Korea Advanced Institute of Science and Technology as an assistant professor in 2013. He moved to Seoul National University in 2015 and is currently a full professor. His research interests include the design and synthesis of novel inorganic and inorganic/organic hybrid materials based on chemical principles, the understanding of formation mechanisms of defect structure and bulk inorganic solids by direct observations, energy harvesting and storage materials, and metamaterials. He authored numerous scholarly articles in publications including Nature, Nature Materials, Joule, and the Journal of the American Chemical Society (JACS), while consistently serving as a peer reviewer for leading journals such as Nature and Science over the years.