The influence of viscous and conducting liquid on the characteristics of the slot acoustic wave

The influence of the liquid with the different values of conductivity, permittivity, and viscosity on the characteristics of the slot mode in the structure consisting of delay line with propagating shear - horizontal acoustic wave of zero order (SH0) and upper piezoelectric plate separated by the air gap was experimentally investigated. The delay line made of the Y-X lithium niobate plate 0.2 mm thick contained two interdigital transducers for the excitation and reception of acoustic wave in the frequency range of 2.6-3.8 MHz. The upper plate represented the 0.5 mm thick plate of Z-X lithium niobate. The excitation of the slot mode led to the appearance of the sharp resonant peaks on the frequency dependencies of insertion loss and phase of the output signal. It has been found that the depth and frequency of these peaks depend on the parameters of liquid contacting with the upper plate. The possibility of the use of the slot mode in the pointed structure for the identification of liquids with the different values of the conductivity, viscosity, and permittivity was shown. The qualitative explanations of the obtained experimental results are presented.