Measurement of material constants and theoretical calculation of surface acoustic wave characteristics of GdCOB crystal

Various piezoelectric materials have been previously investigated in order to improve their surface acoustic (SAW) characteristics. ReCa/sub 4/O(BO/sub 3/)/sub 3/ (Re: Y, Gd, La etc.) crystals are new materials, and their optical and nonlinear optical properties have been evaluated in earlier studies. In particular, since GdCa/sub 4/O(BO/sub 3/)/sub 3/ (GdCOB) crystal has excellent nonlinear optical properties, good piezoelectric properties are also expected for the material. However, only a few studies on the piezoelectric properties of this material have been reported thus far. We have previously evaluated the properties of GdCOB, and have measured the SAW properties, but only for the X, Y and Z, cuts. However, in order to evaluate whole cuts and propagation directions, computer simulations of the SAW characteristics are required. In this study, calculations of SAW properties of velocity and coupling coefficient have been performed. The results obtained substantially agree with measured results reported previously. The lower (0th) and higher (1st) modes of SAW propagation velocity measured were identified as Rayleigh and leaky modes, respectively. In order to simulate SAW characteristics accurately, material constants were also measured using a resonance-antiresonance method. Resonators of GdCOB crystal in various cut directions were fabricated, and their resonance measurements and vibration mode identification were performed to obtain the material constants. The results of the SAW calculations were markedly improved by using the newly obtained constants. In particular, it was revealed that errors in the calculated velocities markedly decreased by using the new constants.