Stress-Enhanced Displacements in PLZT Rainbow Actuators

The newly developed Rainbow actuator features high displacement and good load‐bearing capability, which are considered to be associated with Rainbow's unique dome‐shaped configuration and high internal stress created during processing. The effects of the internal stress on the field‐induced displacements of a series of PLZT Rainbow samples were investigated. It was found that the displacements were significantly enhanced for the samples having a reduced/total thickness ratio around 0.3 due to the interaction of the internal stress with ferroelectric domains. Finite element modeling was used to analyze the internal stress of the Rainbow actuators. The stress distribution revealed by the X‐ray diffraction (XRD) technique agreed well with the modeling. Enhancement of domain reorientation by the internal stress was observed from the behavior of the XRD peaks in the presence of applied electric fields. The Rainbow samples with maximum stress‐enhanced domain reorientation were found to exhibit maximum field‐induced displacements. A finite element model incorporating the stress‐enhancing mechanism with the displacement calculation was developed. This model yielded displacement values which were in good agreement with the experimental data.