Characteristics of fundamental acoustic wave modes in thin piezoelectric plates.

Abstract The characteristics of the three lowest order plate waves (A 0 , S 0 , and SH 0 ) propagating in piezoelectric plates whose thickness h is much less than the acoustic wavelength λ are theoretically analyzed. It is found that these waves can provide much higher values of electromechanical coupling coefficient K 2 and lower values of temperature coefficient of delay (TCD) than is possible with surface acoustic waves (SAWs). For example, in 30 Y  −  X lithium niobate, the SH 0 mode has K 2  = 0.46 and TCD = 55 ppm/°C. The corresponding values for SAW in the widely used, strong coupling material of 128 Y  −  X lithium niobate are K 2  = 0.053 and TCD = 75 ppm/°C. Another important advantage of plate waves is that, unlike the case of SAWs, they can operate satisfactorily in contact with a liquid medium, thus making possible their use in liquid phase sensors.