Title: Multiscale Crystal Lattice Chemistry for Unusual Bulk Inorganic Solids

Abstract

Inorganic solids inevitably involve a certain level of either intrinsic or extrinsic crystal imperfections, which are embedded in the bulk crystal matrix. They can be atomic-level point defects generated by incorporating vacancies and atoms for doping and alloying. They can be further extended to form one-dimensional dislocations or multi-dimensional nanostructures. According to the local structure and dimension of such defects ranging from Å to micron scale, they uniquely interact with charge carrier and heat-carrying phonon, decisively affecting physical properties of bulk solids. Understanding how they form can help design and stabilize desirable defect structures with high predictability, thereby leading to discovering unusual properties. This may ultimately contribute to understanding formation mechanisms of bulk inorganic solids. However, their formation mechanisms are little understood.

In this talk, I will discuss our recent efforts on rational design of complex defect structures stabilized in bulk crystal matrice. Direct observations on their local defect structures employing atomic-resolution scanning transmission electron microscopy and atom probe tomography reveal how they form and how new chemical interactions consequently evolve. These results help understand defect formation mechanisms, thereby giving highly predictable design principles for desirable defect structures. They uniquely serve as an innovative tool to control physical quantities regarding charge and thermal transports independently against fundamental physics rules. In this context, I will discuss how to synthesize record-breaking performance thermal-to-electric energy transforming materials. Afterward, I will show several examples of how to manipulate crystal lattices in a predictable way, thereby realizing exotic physical properties such as negative refractions in bulk materials.

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