Thermal transport in solid materials plays a crucial role in every modern application, ranging from batteries to nuclear technology. In semiconductors, both mobile electrons and lattice vibrations quantifiably contribute to heat transport. In these materials, several engineering principles are known and largely used to tune heat conduction, like nano-structuring, doping, etc. However, the interplay of crystal structure, symmetry and chemical bonding on thermal conduction are still not well understood. In this talk, we will use layered AMX Zintl materials to look closely at how covalent/ionic bonds impact thermal transport properties. We leverage polymorphic phase transitions to systematically probe the relationship between covalent substructure, elastic moduli, and phonon scattering. Next, we will look at electronic contributions to thermal conductivity and Lorenz number in a low lattice thermal conductivity system. The study will reveal the limitations of our current theoretical understanding of heat conduction by charge carriers, while paving the way for another tuning parameter for thermal conductivity.

Bio: Ashiq Shawon is a PhD candidate in the materials science and engineering program at Michigan State University. His research focuses on thermal and elastic properties in thermoelectric materials. He is also currently interning at the Oak Ridge National Laboratory with the Neutron and X-ray scattering group. Before moving to East Lansing, Ashiq received a master’s degree in materials science from Korea National University of Transportation, South Korea and a bachelor’s degree in chemistry from Shahjalal University of Science and Technology, Bangladesh.