Characterizing the performance of piezoelectric ceramic as a function of stress, electric field, and thermal history

The relatively recent development of large flextensional and other low-frequency, high-power transducers has stimulated renewed interest in the performance of piezoelectric ceramic under conditions of high stress and electric field. This paper addresses the development of special fixturing for the assembly and testing of structures emulating the use of PZT-8 material in high-power projectors. The test fixtures themselves are Tonpilz oscillators. Using a system of four tie rods, axial loads as high as 2.2×105 N (50 000 lbf) can be applied. The tie rods are fitted with strain gauges so that load can be monitored as often as desired during the course of aging and stress and electrical drive sensitivity studies. Initially data were acquired for combined static and dynamic stress in a controlled thermal environment. The performance characteristics of the piezoelectric ceramic are inferred from electrical admittance measurements. Providing for the incorporation of extensometers and closed-loop control of axial stress allows the fixtures to be used for a number of broader applications such as measurement of the viscoelastic properties of ceramic. [Work supported by SPAWAR.]