Band gap of piezoelectric/piezomagnetic phononic crystal with graded interlayer (Q2016591)

This paper studies the dispersion curves and the band gaps of the SH-wave in a one-dimensional phononic crystal with piezoelectric or piezomagnetic components and graded interlayer. The graded interlayer with different gradient profiles is modeled as a system of homogeneous sublayers with both piezoelectric and piezomagnetic effects simultaneously. The variation of material properties is taken to obey the power law in the graded interlayer. The secular equation of the dispersion relation of waves is obtained by means of the transfer matrix method and the Bloch theorem, and it is solved numerically. The dispersive curves are found in the Brillouin zone. Both the propagation directions normal and oblique to the interface are studied. Numerical results are obtained for the graded interlayer between PZT-4H (piezoelectric) and CoFe2O4 (piezomagnetic) materials and that between PZT-5H (piezoelectric) and polythene (non-piezoelectric) material. The band gaps of the phononic crystal with and without graded interlayers are compared. The low- and high-frequency band gaps are found to be more sensitive to the propagation direction of the SH-wave and the graded profiles of the interlayer, respectively.