Tuning the Relative Strengths of Electromechanical Resonances Using Non-Uniform Polarization of Piezoelectric Wafers

A free piezoelectric disc with uniform polarization shows multiple radial modes of vibration that occur in the low-frequency range. The strength of these radial mode resonances is fixed and reduces with increasing frequency or mode number. In this article, we show that piezoelectric wafers can be designed with appropriate non-uniform polarization profiles to selectively excite single or any combination of multiple radial modes with an additional capability of altering the relative strengths of electromechanical resonances that is not possible with uniform polarization. We first discuss the theory behind our approach based on a Fourier-Bessel expansion technique. Then, we present several examples demonstrating the capability of tuning the relative strengths of electromechanical resonances in a piezoelectric disc using axisymmetric, non-uniform polarization profiles. The methodology presented in this article finds application in the design of single element transducers with multi-frequency operation, frequency-tuned sensors/receivers, collimated beam sources for underwater acoustics, and other non-traditional applications such as information storage.