Acoustoionic interaction of SH surface waves with dilute ionic solutions

A theory describing the acoustoionic interaction of shear horizontal (SH) surface waves with viscous conductive ionic liquid is presented. A Green's function formulation that accounts for the acoustoelectric interaction with ions and dipoles in the solution is obtained for the surface potential in terms of the liquid and piezoelectric crystal parameters. For dilute ionic solutions, simple closed-form expressions for the velocity change and attenuation are obtained in terms of liquid conductivity and dielectric constant and the piezoelectric coupling coefficient. It is shown that SH surface waves in particular and acoustic waves in general can be used to perform microanalysis of dilute ionic solutions, detecting conductivity, dielectric constant, and relaxation frequency. The analysis, which was done for a simple crystal class, the hexagonal (6 mm), shows results which compare very well with exact numerical computations.