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Large Strain Actuation though Electrostriction in Single Crystal Ferroelectrics (Midwest Mechanics Seminar)

G. Ravichandran

2:30 PM on 2008-03-28

209 Akerman Hall


Sensors and actuators based on ferroelectric materials are finding increasing use in applications related to mechanical, aerospace and biomedical fields. Most of the current devices rely on the linear piezoelectric behavior of formulations of PZT which offer high bandwidth, linear actuation and strains of up to 0.2%. The nonlinear electromechanical behavior of ferroelectric materials is largely governed by the motion of domains and is affected by stress as well as electric field. Results from continuum modeling based on energy minimization of ferroelectric single crystals for the structure and behavior are presented. A principle result of the modeling is the mode of actuation in ferroelectric single crystals by 90o domain switching could result in large strains. The mechanical and electrical structure of the domain walls obtained using atomic force (AFM) and piezo force (PFM) response probe microscopy are presented. An experimental setup has been designed to investigate large strain actuation in single crystal ferroelectrics under combined electrical and mechanical loading. Experiments have been performed on single domain bulk crystals of barium titanate with (100) and (001) orientation. The electrostrictive response is shown to be highly dependent on the level of applied stress with a maximum strain of 0.9% measured at a compressive stress of about 2 MPa. The in situ observations of the domain patterns using polarized light microscopy are presented. Continuum modeling and simulations are used to gain insights in to the mechanics and mechanisms of large strain actuation and dynamics of domain switching in ferroelectrics.


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