Principal Investigator Yet-Ming Chiang
Recent measurements of high actuation strain doped Na1/2 Bi1/2 TiO3 single crystals have revealed unusual behavior in which the field-induced strain and polarization are decoupled in the time domain, contrary to the behavior of classical piezoelectrics. In order to describe this behavior, we introduce an electrorheological model in which independent time constants enter the kinetic equations for polarization, strain, and domain state parameter. Using this minimal set of time constants along with static electromechanical constants, we are able to simulate all observed time dependent behavior.
The microscopic mechanisms of electrorheological behavior in selected high actuation strain single crystals are being studied using single crystal X-ray diffraction, hot-stage TEM, HREM, and STEM mapping of composition distributions. Periodic nanodomains have been observed in a crystal exhibiting exceptionally high field-induced strain (0.85%). The structural and compositional origin of this nanostructure, and its response under applied electric field and stress, are under study.