General properties of the Anisimkin Jr.´ plate modes

For materials of different symmetry and orientation three types of plate modes are found at velocity v_n close to the velocity v_L of the longitudinal BAW - the Lamb, Anisimkin Jr.´, and quasi-longitudinal. Shorting plate faces and avoiding piezoelectric effect do not transform one type of the mode to the other. The Lamb modes approach v_n = v_L at irregular plate thickness (h/¿)_n and large dispersion dv_n/d(h/¿) ¿ 10³ m/s (h - thickness, ¿ - wavelength, n - mode order). Other modes are characterized by less dispersion dv_n/d(h/¿) ¿ 10³ m/s and regular (h/¿)_n, forming strict succession of the whole numbers, which are close to periodic plate thickness for transverse BAW resonance. It is these general properties satisfied simultaneously rather than anisotropy and piezoelectric stiffening of the plates play an important role in existence of the Anisimkin Jr.´ and QL-modes. As the modes possess negligible elastic displacement perpendicular to the plate faces, they are attractive candidates for liquid sensing.