Characterization of loss mechanisms in piezoelectric ceramic microresonators

Piezoelectric ceramic microresonators possess the very attractive attributes of low cost and high piezoelectric coupling; these make them potentially suitable for high-volume telecommunications applications such as cellular radio/comm-on-the-move. Actuators for microelectromechanical structures (MEMS) applications using bimorph cantilevers are also envisioned using piezoceramics for the same reasons. One problem impeding development is an adequate treatment of loss; it is often the case that devices are designed that do not fulfil their promise because insufficient attention has been addressed to the various dissipation mechanisms involved. For piezoceramics especially, because of the high values attained by the coupling coefficient, it is frequently unjustified to make simplistic assumptions concerning the incorporation and treatment of loss. We explore the incorporation of complex material coefficients into a complex electromechanical coupling coefficient, k*=k'-jk". Resulting from this is a complex resonance frequency of the resonator. We also propose a method for more accurately characterizing lossy ceramic resonators.