Lamb Wave Propagation Characteristics and Transducer Performances in Layered Substrate Composed of Piezoelectric Thin Plate and Glass Thin Plate

Abstract

In a layered substrate composed of a piezoelectric ceramic thin plate and a glass thin plate, Lamb wave propagation characteristics and operation performances of an interdigital transducer (IDT) are described. The numerical analysis results of Lamb wave phase velocities in the form of a function of the product of the frequency and the thickness of the piezoelectric ceramic plate are in good agreement with the measured velocities for various thickness ratios of the two plates used as layered substrates. The electromechanical coupling constant k2 of the IDT on the layered substrate reaches a peak value when the velocity of the respective Lamb wave mode is almost equal to the phase velocity of the zeroth-order symmetrical mode at fd=0. The above condition for the highest k2 value has been experimentally confirmed for two types of layer-structured devices: the double-layer-type and the separation-type.