Canadian Journal of Pure & Applied Sciences

Abstract: In this paper, calculations of the phase velocity Vph of the dispersive nine-partial Rayleigh type waves (RTW9) were introduced in dependence on the kh (k is the wavenumber, and h is the layer thickness). The layered systems, consisting of a layer of Bi12SiO20 on a substrate of Bi12GeO20, and the reverse configurations were investigated. The calculated dispersion curves of the RTW9 lowest-order modes with both metallized and free surfaces have shown the existence of the non-dispersive nine-partial Zakharenko type waves (ZTW9) polarized like the Rayleigh waves. The non-dispersive ZTW9-waves split the RTW9 lowest-order modes into sub-modes with different dispersions, Vph > Vg and Vph < Vg, where Vg is the group velocity. The RTW9 phase velocity Vph is confined within a narrow Vph-range that can be convenient for some technical devices. Also, cubic crystals with strong piezoelectric effect can be used for different cubic-structure magnetoelectric devices. It was found that the coefficient of electromechanical coupling (CEMC) K2 for the RTW9 first type has its maximum value at kh ~ 5 for the structure Bi12SiO20/Bi12GeO20. The second type of RTW9- waves was also studied, which can propagate only in the structure Bi12SiO20/Bi12GeO20, because there is the condition Vt(Bi12GeO20) > Vt(Bi12SiO20) for the speed Vt of the bulk transverse wave, Vt = [(C55/?)(1 + K0 2)]1/2 with 55 11 2 15 2 0 K = e /C ? . It was also discussed the existence possibility of new supersonic surface waves with the in-plane polarization and Vph ~ Vl, where Vl represents the speed of the bulk longitudinal wave. Also, a calculation method with short computer program is described introducing the transverse and longitudinal dynamic CEMCs KDt and KDl. For comparison with [110] direction, the 200-x2-rotated direction was also studied concerning propagation of the first and second types of pure RTW9-waves. Here, the existence of RTW9 second type depends on the velocity equivalents of the layer and substrate, but not on the corresponding velocities Vt, and solutions for the Vph > Vt were also found.