Broadband Electromechanical Spectroscopy: A Method for Measuring the Dynamic Electromechanical Response of Ferroelectrics
To gain a better understanding of the dynamic response of thermo-electro-mechanically coupled materials, in particular stiffness and mechanical damping, an experimental apparatus and method called Broadband Electromechanical Spectroscopy (BES) has been developed. The motivation for creating BES was to study the behavior of ferroelectric materials (and other electro-active materials) over wide ranges of frequencies of simultaneously-applied electric fields and mechanical stresses under accurate temperature control. By precisely controlling electric fields and mechanical loading, the effect of microstructural changes, in particular domain switching in ferroelectrics, on the material's dynamic mechanical response is measured. Experiments show large increases in mechanical damping during domain switching that can be tuned by appropriate electrical loading. Results obtained using the new capabilities brought by BES can be used to better understand the damping associated with domain wall motion to be able to create ceramic materials with both high stiffness and high damping—an elusive combination of properties in typical engineering materials. The design and use of the apparatus along with results obtained from tests on a particular ferroelectric, viz. lead zirconate titanate, are presented.