A study of loss in piezoelectric ceramic resonators

Abstract

Piezoelectric resonators and filters are important components in many military and commercial communication systems. Standard piezoelectric materials such as quartz have low coupling values and are quite expensive to fabricate. Newer materials like piezoceramics have been developed that are cheaper, have higher values of coupling constant, but can be considerably more lossy than single-crystal materials. The purpose of this work is to explore loss mechanisms through the use of complex elastic coefficients in the piezoelectric constitutive relations and the differential equations for a simple one-dimensional (1-D) resonator. Results will be presented that show how the complex elastic coefficients modify the acoustic wave velocity, the coupling constant, and the resonant frequencies of the resonator. An equivalent circuit model of a resonator will also be presented with and without loss to compare with the calculated results. An experiment has been designed to better characterize loss in devices by applying an exponentially decaying sine wave. In theory this type of signal should be able to excite the complex resonance of the device. Results will be presented for thickness-excited PZT resonators, and the results will be compared to the circuit models and the 1-D calculations.