MSE Seminar Series: George Rossetti
Friday, March 5, 2010
Room 2108 Chemical and Nuclear Engineering Bldg.
Thermodynamic Behavior and Electromechanical Properties of Ferroelectric Solid Solutions
Presented by George Rossetti
Materials Science and Engineering Program
Chemical, Materials and Biomolecular Engineering
Institute of Materials Science
University of Connecticut
Ceramics based on ferroelectric solid solutions find applications in a wide array of dielectric, electromechanical and electro-optic devices. In this talk a theory is presented for the generic case of a ferroelectric solid solution wherein different symmetry phases are located at opposing ends of the isobaric, pseudo-binary composition-temperature phase diagram. Disparate physical phenomena that may occur in such systems, including tricritical behavior, the formation of nanodomain and polar glasslike ferroelectric states, and the appearance of two-phase equilibrium fields, are reconciled through a self-consistent application of the Landau theory of phase transitions, the classical theory of domains, and the Gibbs thermodynamics of solutions. Drawing on selected examples from technologically important perovskite-structured solid solution systems that include PZT [Pb(Zr1-xTix)O3], PMN-PT [Pb(Mg1/3Nb2/3)1-xTixO3], BST [(BaxSr1-x)TiO3] and BZT [Ba(Zr1-xTix)O3] interrelations between the polarization anisotropy energy, the topology of the pseudo-binary phase diagram, the ferroelectric-ferroelastic domain structure, and the extrinsic contributions to the dielectric and piezoelectric properties are demonstrated. The close qualitative analogies that exist between the diffusionless composition-temperature phase diagrams of these systems and the pressure-temperature diagrams of the end member compounds are also illustrated. The implications of the theory for the control of microstructure and for the design of ferroelectric solid solution materials with controlled dielectric and electromechanical properties are discussed.
About the Speaker
Dr. George A. Rossetti, Jr. joined UConns Institute of Materials Science in 2006 as Research Professor and was appointed Associate Professor in the Department of Chemical, Materials and Biomolecular Engineering in 2008. He joined UConn from Rutgers University, where he was Research Associate Professor of Ceramic and Materials Engineering. Prior to this he spent nearly a decade in industry where was a Senior Research Engineering at Saint-Gobain Corporation (Worcester, MA) and Director of Functional Materials at Continuum Photonics Inc. (Billerica, MA). During this time he led numerous research programs involving applications of crystal science to the development and commercialization of functional materials for sensing, energy harvesting, vibration attenuation, and active structural/precision motion control systems. His research presently focuses on the crystal growth and processing science, thermodynamics and crystallography of transformational phenomena, and physical properties of dielectric, piezoelectric and ferroelectric materials. He holds a B.S. in Chemical Engineering and M.S. in Materials Engineering, both from Worcester Polytechnic Institute, a Ph.D. in Solid State Science from The Pennsylvania State University, and he carried out post-doctoral work at Princeton University. Dr. Rossetti has authored more than fifty publications and holds two U.S. patents in the area of functional and advanced ceramic materials.