Non-linear properties of piezoelectric ceramics.

摘要

The adaptability and lightweight properties of piezoelectric ceramics make them highly desirable materials for use in actuation. Some actuator applications require the piezoelectric material to support large mechanical loads and produce high strain output. In order to accomplish this requirement of higher strains, large electric fields must be applied. The design of piezoelectric smart structures is limited by the accuracy to which the material properties of the sensor/actuator materials are determined. Transducer designers have long suspected that the small-signal material parameters supplied by piezoelectric ceramic manufacturers do not adequately describe the performance of the material under conditions where the application requires large applied field or stress. This results from the non-linear behaviour exhibited by the material under such operating conditions. In order to characterise piezoelectric materials such as Lead Zirconate Titanate (PZT) ceramics under these conditions, it is useful to be able to measure the strain directly as a function of applied field and frequency. Although such performance measuring techniques as impedance analysis provide an effective measure at high frequencies, measurements at low frequencies (1 Hz–3 kHz) are required for underwater sonar transducers and for noise/vibration control applications. Strain measurements using optical methods have proven to be very successful.; In this work, a ZMI 2000 laser interferometer system from Zygo Corporation has been installed and modified to measure the strains of ceramics. The piezoelectric constants of soft PZT (EC-65, EC-76) and hard PZT (EC-69) piezoelectric ceramics, manufactured by EDO Electroceramic Products, were measured as a function of frequency and applied field. The dependence of the piezoelectric constants under an applied DC bias voltage as well as the time dependence of the piezoelectric response in the piezoelectric ceramics has also been studied. The results are examined within the context of extrinsic contributions to the piezoelectric response.