Theoretical calculation of the surface acoustic wave characteristics of GdCOB single crystals

Fabrication and crystalline characteristics for various piezoelectic materials have been studied. In particular, quartz, LiNbO3, LiTaO3 and LiB4O7 crystals have been investigated, and their piezoelectric properties for applications such as surface acoustic wave (SAW) devices have been evaluated in detail; however, there has been interest in new materials with improved properties. Recently, new rare earth crystalline materials, such as ReCa4O(BO3)(3) (Re: Y, Gd, La and others) have been grown, and excellent nonlinear optical properties have been reported. It is expected that these materials may also have good piezoelectric properties; however, few studies of the piezoelectricity of these materials have been performed. Of particular interest is that a large electric-mechanical coupling coefficient may be obtained in GdCa4(BO3)(3) (GdCOB). In this study, a theoretical analysis of the SAW characteristics, and investigation of the piezoelectric properties is reported in detail. The analysis was performed using material constants obtained from resonance-anti-resonance method by Wang et al. [J. Wang, X. Hu, X. Yin, R. Song, J. Wei, Z. Shao, Y. Liu, M. Jiang, J. Mater. Res. 16 (2001) 790-796]; SAW velocities and coupling constants were calculated at several crystalline cuts and propagation directions. In particular, the result calculated at the Z-cut of GdCOB was substantially in accordance with the measured results. Two SAW propagation modes (lower and higher) existed on the cut. From comparison between measured and calculated results, the lower and higher modes were identified as the Rayleigh mode and the leaky mode, respectively. From the theoretical analysis of Rayleigh SAW for all crystalline cuts and propagation directions, the maximum velocity and coupling coefficients were obtained for GdCOB Y-cuts, revealing that the Y-cut will be suitable for SAW device applications. (c) 2005 Elsevier B.V All rights reserved.