IMX Seminar Series - Emergence of forbidden properties in complex materials

In materials with complex chemistry and even a small concentration of defects, properties are often different from those that are expected when considering material's crystal structure. In complex materials the structure may not be the same when looked at different spatial scales. The properties (electric, magnetic, mechanic, and coupled susceptibilities) are dependent on boundary conditions, sample history and time. Material constants in such systems are never constant. What we see in an experiment is just a snapshot of the sample's behavior at a given time and the next observer may see something else. While such behavior may be frustrating during an investigation, it is exciting because it offers an opportunity to study manifestations and coupling of many mechanisms operating concurrently in the material. One result of this complexity is emergence of properties that are forbidden by the material's nominal, average symmetry. I will present several examples of emergence of forbidden electrical polarity and electro-opto-chemo-thermo-mechanical coupling in organometallic halide perovskites, oxide perovskites and in oxides with fluorite structure, which are nominally centrosymmetric. It will be shown that emergent properties can be sometimes order(s) of magnitude higher than those in standard materials. Origins and application potential of such effects will be discussed.    

 

Park, D.-S. et al.  "Induced Giant Piezoelectricity in Centrosymmetric Oxides". Science 2022, 375, 653. doi: 10.1126/science.abm749

Bencan, A.;  et al. "Atomic Scale Symmetry and Polar Nanoclusters in the Paraelectric Phase of Ferroelectric Materials.”,  Nat Commun 2021, 12 (1), 3509, . https://doi.org/10.1038/s41467-021-23600-3.

Bio: Dragan Damjanovic was a professor at the Institute of Materials, Swiss Federal Institute of Technology in Lausanne (EPFL). He lead the Group for Ferroelectrics and Functional Oxides and taught undergraduate and graduate courses on structure and electrical properties of materials. Damjanovic received his BSc degree in Physics from the Faculty of Natural Sciences and Mathematics at the University of Sarajevo and his PhD degree in Ceramics Science and Engineering from The Pennsylvania State University.
The research activities include fundamental and applied investigations of piezoelectric, ferroelectric and dielectric properties of a broad class of materials. In his research, he covers a wide range of spatial (atomic to macroscopic) and time (mHz to GHz) scales.The current focus is on effects of polar nanoclusters on the properties of ferroelectrics and related materials,emergence of electro-chemo-thermo-opto-mechanical coupling in organometallic halide perovskites and effects of charge transport on the electrostrictive and induced piezoelectric response in oxides with fluorite structure. He is an IEEE Fellow and a Fellow of the American Ceramic Society.