Mukherjee B.

Piezoelectric transducers are frequently used as acoustic sensors and actuators as well as in active methods of noise and vibration control and in other smart applications. The increasing range of these applications requires the piezoelectric materials to be used under a variety of conditions that include large applied AC fields, DC bias fields, applied stresses and a large range of frequencies and temperatures. It is therefore necessary to understand the behaviour of the materials under these conditions. This presentation reviews our work on the non-linear characterization of these materials and takes off from an earlier review presented at the ICSV-5 (1997) conference. A Zygo laser Doppler interferometer has been used to measure the quasi-static strains of soft and hard piezoelectric ceramics, made by EDO Ceramics, as a function of frequencies and applied fields up to 1 MV/m. Significant non-linear behaviour is observed and the piezoelectric coefficients of both soft and hard ceramics have been expressed as polynomial functions of the applied fields. The dependence of the piezoelectric coefficients under the application of DC bias fields has also been studied under both quasi-static and resonance conditions. An experiment to find the dynamic and static values of the piezoelectric coefficient as a function of uni-axial applied stress up to 160 MPa has been developed. Again significantly non-linear behaviour is observed and these will be discussed. Other experiments have allowed us to find the temperature and time-dependence of the piezoelectric response in soft and hard piezoceramics. Almost all the non-linear phenomena can be understood on the basis of domain motions in the material that lead to extrinsic effects. Our observations point to the need to characterize piezoceramic materials under conditions approximating the conditions under which they will be used in applications.