The propagation behavior of Love waves in a functionally graded layered piezoelectric structure is investigated in this paper. It involves a thin piezoelectric layer, in which the parameters vary linearly in the thickness direction, bonded perfectly to an elastic substrate. By the WKB method, the phase velocity equations are obtained for both electrical open and short cases on the free surface, respectively. The results show that the circular frequency and cut-off frequency increase as the elastic modulus and dielectric constant vary linearly respectively; meanwhile, the number of vibration modes decreases, and the coupled electromechanical factor increases with the decrease of the dielectric constant. Undoubtedly, this is useful for the design of surface acoustic wave (SAW) devices.

In this paper, the propagation behavior of Love waves in a smart functionally graded piezoelectric structure is analyzed. The smart structure consists of three layers, in which the piezoelectric plate serves as the upper layer accompanied by a sandwiched graded layer and a metal substrate. In the graded layer, all the parameters and the elastic modulus are respectively assumed to vary after two mathematical forms, i.e. an exponential function and a linear function. The WKB method is adopted to analytically solve the propagation problem of Love waves for both electrical open and short cases on the free surface, respectively. The phase velocity curves demonstrate that the number of modes is greater than in the non-graded layer structure. Furthermore, the influence of graded variation on coupled electromechanical factor is presented.