Theoretical and Computational Modeling of Ferroelectric Materials

Monday, April 27, 2009
9:00 - 10:00 AM
Room 229, Norris Hall

Dr. Antonios Kontsos
Department of Aerospace Engineering and Engineering Mechanics,
The University of Texas at Austin

The talk presents a novel theoretical and numerical framework to model domain structure morphologies, their evolution and interactions with arrays of dislocations in ferroelectric materials. This is the first study of its kind that investigates interactions of domain walls with defects. The approach consists of a diffuse interface model which is consistent with the principles of continuum thermodynamics and relies on selecting an appropriate form for the material free energy. The governing model equations are condensed into a statement for the principal of virtual work, which is implemented in a non-linear finite element scheme to obtain solutions to boundary value problems. The results show that for no externally applied electromechanical loads, the dislocations deform 180o and 90o domain wall configurations in ferroelectric crystals. It is also demonstrated that dislocations locally pin domain walls that would otherwise move due to the application of electric field and/or shear stresses on the crystal. In addition, results are presented on energetically favorable domain structures and their evolution in ferroelectric thin films. These results verify the Kittel law for different values of applied strain. Changes in the morphology of the domain structure from polydomain to 180o domain wall or monodomain configurations are associated with the domain width and amount of applied strain. Finally, results are presented to investigate the effect of applied electric field for given film geometry, on the evolution of vortex structures that have been theoretically predicted to exist.

Biography: Dr. Antonios Kontsos is a Post-doctoral Fellow in the Center for Mechanics of Solids, Structures and Materials and a Lecturer in the Department of Aerospace Engineering & Engineering Mechanics in The University of Texas at Austin. Dr. Kontsos received his PhD and Masters degrees from Rice University and his undergraduate Diploma from University of Patras in Greece, all in Mechanical Engineering. His research interests are in the areas of theoretical and computational modeling of multifunctional, multiscale, random and heterogeneous materials.

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