One type of transverse surfacewaves in piezoelectric layered solids for electro-acoustic devices

Layered solids are extensively-used structures for the design of electro-acoustic wave devices in which surface waves are excited and propagate. Transverse surface waves existing in such structures are attractive to the electro-acoustic device designers due to their unique features like high performance and simple particle motion and so on. One kind of the transverse surface wave is the so-called Love wave which exists only when the bulk-shear-wave velocity in the layer material is less than that in the substrate. Besides the well-known Love wave, another type of the transverse surface wave can exist in such layered structures under some specific condition. This type of transverse surface wave could be regarded as a modified version to the conventional Bleustein-Gulyaev (BG) wave which exists and propagates only at the free surface of a piezoelectric half-space due to the interconnection between elastic and electric fields. It is closely related to a bulk shear wave, and though little reported and used at present it may have certain advantages over the traditional surface wave utilized for electro-acoustic devices. This chapter presents a brief overview on this type of transverse surface wave based on the recent work in our group. Furthermore, the propagation of such modified B-G wave in layered structures with initial stresses and/or material gradient is also introduced.