Acoustic waves in two piezoelectric plates separated by a vacuum gap

The experimental study of acoustic waves propagating in the structure “piezoelectric plate I -vacuum gap - piezoelectric plate II” was carried out. The plate I contained two interdigital transducers, which excited and received acoustic wave with shear- horizontal polarization. The piezoelectric plate II was set from above between transducers. For the certain orientation of the plate II the sharp equidistant peaks of the resonant attenuation appeared on the amplitude - frequency characteristics. It has been found that the depth of these peaks decreases with increase of the gap between plates. It has been shown that these peaks are connected with the resonant reflections of the slot acoustic waves in the structure. The experiments allowed to determine the phase velocity and electromechanical coupling coefficient of slot waves for different orientations of the plate II, which are in a good agreement with theory. The comparison theory and experiment allowed to formulate two conditions of existing of slot waves.