Calculation of Bulk Acoustic Wave Propagation Velocities in Trigonal Piezoelectric Smart Materials

The goal of this paper is to determine the bulk acoustic wave (BAW) propagation velocities (quasi-longitudinal, quasi-shear vertical and quasi-shear horizontal) in two important piezoelectric smart materials, Lithium Niobate (LiNbO3) and Lithium Tantalate (LiTaO3). To determine the BAW propagation velocities, the BAW elemental equations are deduced. The BAW velocities are calculated for each direction by solving the Christoffel's equation systematically based on the theory of acoustic waves in anisotropic solids exhibiting piezoelectricity. The modification of the BAW velocities by the piezoelectric effect are calculated and graphically compared with the velocities in the corresponding non-piezoelectric materials. Furthermore, the electromechanical coupling factors are defined and investigated. The results obtained in this study can be applied to signal processing, sound systems and wireless communication in addition to the improvement of surface acoustic wave (SAW) devices and military defense equipment.