Dispersive Rayleigh Type Waves in Layered Systems Consisting of Piezoelectric Crystals Bismuth Silicate and Bismuth Germanate

The lowest-order modes of the dispersive six-partial waves of Rayleigh type (RTW6) have been numerically obtained for two layered systems consisting of a layer on a substrate in [100] propagation direction of (001)-cut for both cubic crystals of class 23. Dispersion relations are shown for both a layer of on a substrate of and vice versa. Dispersion relations show one mode in each case with clear maxi-mum and minimum, at which it is analytically shown that the group velocity is equal to the phase velocity. It was concluded that in corresponding highly-symmetric cases, the obtained "non-dispersive" six-partial surface waves in the treated layered systems are a new non-dispersive type, termed Rayleigh-Zakharenko type (RZTW6) "non-dispersive" six-partial surface waves. These can exist in layered systems consisting of a layer on a sub-strate. The possibility of the existence in layered systems of "non-dispersive" waves of both the nine-partial Za-kharenko type (ZTW9) for centrosymmetrical crystals, and the thirteen-partial Zakharenko type waves (ZTW13) for non-centrosymmetrical crystals is suggested. In addition, it is shown that dependence of the phase velocity in a multi-layered system can be reduced to dependence for a layered system consisting of a layer on a substrate. Thus, both systems can be studied in the same way.