The Influence of Functionally Graded Layer on the Band Structures of One-Dimensional Phononic Crystals

In this paper, the propagation of surface acoustic waves in a periodic structure which consists of periodic domain inversion piezoelectric substrate covered by a functionally graded layer is studied. We calculated the band structures using the finite element method. The effects of the gradient variation of material constants on the band structures are discussed in detail. Numerical analysis shows that the band gap shifts to lower frequency and the bandwidth decreases with increase of the positive gradient factor β, whereas the band gap shifts to higher frequency and the bandwidth increase with increase of the negative gradient factor β. Besides, the thickness of the layer also has a significant effect on the first band gap.