Microstructural Kinetics and Failure Mechanisms of Ferroelectric Ceramics
Graduate Student: Wei Lin Tan
Ferroelectric ceramics are most commonly exploited for their piezoelectric effect which is utilized in sensors and actuators. Their ability to switch polarization under large electric fields has also led to applications in memory devices like FERAMs. However, the regime between the small e-field, linear region and the high e-field, on-off region is not fully understood.
If we can exploit the domain switching mechanism in ferroelectrics, this opens up new possibilities in electrically-tunable mechanical properties, such as high stiffness and damping. Ferroelectric ceramics, like most brittle materials, have high static stiffness, but when brought close to their coercive field, can exhibit anomalously high dissipation and damping due to the domain switching process. However, domain switching also generates high internal stresses within the ceramic, leading to fatigue and subsequent failure.
In this project, we seek to understand the kinetics of the domain switching process in bulk ferroelectric ceramics. We use a combination of Broadband Electromechanical Spectroscopy (BES) and Digital Image Correlation (DIC), to measure the dynamic stiffness and damping of ferroelectrics under combined mechanical, electrical, and thermal loads. We further investigate mechanisms of fatigue and failure with the BES and Focused Ion Beam SEM. In addition, we develop material models that help us understand the experimental data and predict the response of new materials and composites.