Stress Dependence of the Piezoelectric, Dielectric and Elastic Properties of PZT Ceramics

Abstract

This study describes the experimental development of techniques to determine the transverse and longitudinal properties of piezoelectric materials under static uniaxial stress at low drive levels (<1 V) based on the resonant (IEEE) analysis, This technique offers the significant advantage that it is the only viable route that affords the possibility of calculating the full elasto-piezo-dielectric tensor, and therefore allows the development of predictive models of materials performance in high power devices. Mechanical stress and its direction of application with respect to the polarisation axis dramatically affect piezoelectric materials. In most transducers the uniaxial compressive stress is applied parallel to the polarisation and this study shows that under these conditions the piezoactivity is enhanced ( 40% in 4 MPa stress) in the polarisation direction but decreases laterally (ie. a reduction in d(31)) These changes are accompanied by similar anisotropic variations in the elastic moduli, with c(33)(E) and s(11)(E) decreasing by similar to 25%. These results can be explained by a consideration of the microscopic domain processes that occur under uniaxial compressive stress where the formation of 90 degrees domain walls is enhanced, This new data is important in understanding the variation in materials properties that occur under operational conditions, and this information is essential in both materials selection and the design of high power devices,