CRYSTALLOGRAPHIC CHANGES IN ELECTRICALLY FATIGUED ACTUATORS

Abstract

Many new applications are emerging for piezoelectric ceramics, including adaptive structures, vibration isolation, and nano-robotics. In these instances, actuators will likely be operated at higher electric fields than in conventional applications in order to achieve maximum displacement. However, under such relatively harsh driving conditions, there is an increased possibility of property degradation and fatigue. Tailoring the ceramic microstructure through sintering control offers one possible route to improve fatigue resistance. Changes in the crystallographic orientation of ceramic actuators during long-term exposure to electric fields and as a function of sintering temperature can provide considerable insight on fatigue mechanisms and their prevention. In this study, the microstructure of multilayer PbTixZr1-xO3 (PZT) specimens processed at temperatures from 1175-1325 degrees C was examined by scanning electron microscopy (SEM) and X-ray diffraction (XRD) line broadening analysis. Observed grain sizes were 2.5-4 micrometers; coherently diffracting domain sizes were 20-80 nm. A reorientation of c- and a-domains as a result of electrical poling and fatigue was observed, together with changes in the amount of secondary phases. Results showed that domain wall movement was facilitated in specimens processed at lower sintering temperatures (