Diamond films have been widely investigated for various scientific and technological applications because of their superior properties such as high hardness, good wear resistance, and low thermal expansion coefficient. By employing diamond films as acoustic media, the operation frequency could be increased without stringent requirements on the lithographic resolution. Accordingly, this paper aims at proposing a theoretical analysis of Lamb wave characteristics in multilayered piezoelectric plates including a diamond layer. First, the formulae of effective permittivity were derived based on the transfer matrix method and further was employed to calculate the phase velocity dispersion of the Lamb wave devices. The electromechanical coupling coefficients (ECCs) were further calculated exactly by the Green's function method. Meanwhile, the influences of the diamond film thickness on the phase velocity dispersion and ECC are also discussed. The calculation results can provide useful guidelines for designing Lamb wave devices with a diamond layer. The Lamb wave device based on a ZnO/diamond composite plate is a highly promising candidate for radio-frequency filter in modern communication systems
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