Electrical properties of PZT piezoelectric ceramic at high temperatures

Advanced aeronautic and space structures need active components that can function at high frequencies and temperatures. Piezoelectric materials can provide frequency response but their use at elevated temperatures is limited. The reason for the lack of insertion of piezoelectric for high temperature active component and sensors are two fold. First, the database of piezoelectric properties that describe the piezoelectric constants is lacking for high temperatures engineering applications. Most studies measure the dielectric constants to determine the Curie temperature but do not provide piezoelectric coefficients as a function of temperature. Second, piezoelectric materials with Curie temperature (T _C) exceeding 500 °C are sought for aeronautics and aerospace applications. This investigation describes a measurement system that captures the impedance dependence upon temperature for piezoelectric materials. Commercially available lead zirconate titanate (PZT) was studied as to determine the piezoelectric activity to define the operating envelope with respect to temperature. The elastic properties , piezoelectric coefficients , dielectric properties , and electro-mechanical coupling factors were determined as a function of temperature. The coupling factor k ₃₃ was found to be relatively constant to 200 °C and exhibit slight temperature dependence above 200 °C. The temperature sensitivity for both piezoelectric coefficient and electromechanical coupling factor were very small; the slopes and Δk ₃₃/k ₃₃ were found to be 0.01 and (−0.07) respectively in the range of 120 to 200 °C. This measurement technique will populate databases that describe the piezoelectric properties of commercially available PZT piezoelectric materials. It can also facilitate the assessment of new piezoelectric materials that are currently being developed for higher temperature applications. This work is supported by US Air Force grant F49620-03-1-0128.