Energy trapping characteristics of the second harmonic thickness extensional vibration in a two-layered monolithic piezoelectric plate

Energy trapping characteristics of two-layered piezoelectric ceramic resonators hae been studied around their second-harmonic thickness-extensional vibration. The vibration was excited through external and internal electrodes; the latter was prepared in a monolithic plate utilizing the common process of manufacturing multilayered monolithic capacitors. The energy trapping of the frequency-lowering-type was observed in agreement with the calculation. If the unelectroded region is not polarized, energy trapping is not sufficiently realized because of its slight frequency-lowering. When the inner electrode is not placed at the middle of thickness, levels of the resonance response are dependent on harmonic order of the vibration.