THEORETICAL-ANALYSIS OF HORIZONTAL SHEAR MODE PIEZOELECTRIC SURFACE ACOUSTIC-WAVES IN POTASSIUM NIOBATE

The propagation characteristics of the pure SH (horizontal shear) mode piezoelectric surface acoustic wave (SAW) on rotated Y-cuts about the Z-axis of potassium niobate (KNbO3) are theoretically analyzed. The r esults show that there exists a SH mode SAW which has a velocity lower than the piezoelectrically inactive Rayleigh mode SAW for most of the rotated cuts. Differing from the so-called Bleustein-Gulyaev wave in 6 mm crystals, the particle displacement of the SH mode SAW on the met alized surface of Y-cut KNbO3 decays with slow oscillation as a functi on of depth from the substrate surface, while that on the free surface oscillates with a slight decay. The electromechanical coupling factor K-2 ranges from a very large value of 0.53 to a relatively small valu e of 0.026, depending on substrate orientation. (C) 1997 American Inst itute of Physics.