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MATERIALS ENGINEERING

SEMINAR

“Electric Field Induced Strain and Switching Behavior in Ferroelectric Materials”

By

Keisuke Yazawa

Purdue MSE Ph.D. Preliminary Exam

Advisors: Professors Carol A. Handwerker and John E. Blendell

ABSTRACT

Ferroelectric materials have been used for actuator and sensor devices due to the electromechanical coupling property. The electromechanical coupling of ferroelectrics is attributed to piezoelectric lattice strain and polarization axis exchange (non-180^o switching). It has been observed that non-180^o switching plays a significant role in electric field induced strain. In addition, grain-grain interaction contributes to the effects in polycrystalline ferroelectrics. However, how the grain-grain interaction contribution affects non-180^o switching is not fully understood yet.
Recently, it has been observed that the grain-grain interaction induced a local elastic strain field due to inhomogeneous piezoelectric response throughout grains. Also, it has been confirmed that ferroelectric switching (180^o switching) was hindered/facilitated by crystal distortion due to the elastic strain field. Considering the interaction mechanism, it can be expected that the elastic strain field by the grain-grain interaction can also influence non-180^o switching, which contributes to electric field induced strain. Further experiments will be direct observations of non-180^o switching and misorientation angle to a neighboring grain, which may affect the local elastic field. This experimental result will provide an insight for the grain-grain interaction contribution to the non-180^o switching as well as a guideline for microstructure design for polycrystalline ferroelectrics to control the non-180^o switching.

Date: Tuesday, December 12, 2017

Time: 1:00 P.M.

Place: ARMS 1028