Love waves propagation in functionally graded piezoelectric materials with quadratic variation

The propagation behavior of Love waves in a semi-infinite functionally graded piezoelectric material (FGPM) with a quadratic variation is addressed. The coupled electromechanical field equations are solved, and the dispersion relations, displacement, electric potential, and stress fields are obtained analytically for both electrically open and short conditions. The effects of gradient coefficient on phase velocity, group velocity, and electromechanical coupling factor are plotted and discussed. It is shown that the phase velocity associated with the non-piezoelectric case coincides with that of the corresponding piezoelectric material under electrically open conditions. Because of gradual variation in electromechanical properties, the initial stress during manufacturing process is negligible. Therefore, this model serves as an excellent substitute for the typical layered piezoelectric structures used in surface acoustic wave (SAW) devices. This work provides with a theoretical foundation for the design and practical applications of SAW devices with high performance.