SAW and pseudo-SAW properties using matrix methods

摘要

Pseudo-surface-waves (PSAW's), or leaky SAW's, were firstnrecognized over 25 years ago and the phase velocity (vp) andnattenuation per wavelength (ΑΛ) of PSAW modes fornnonpiezoelectrics were calculated soon after. Since the seventiesnprogress has been made in exploiting the higher velocities andnelectromechanical coupling constants (K2=2Δv/v)nachievable with PSAW's for piezoelectric device applications; this hasnstimulated new interest in the search for piezoelectric materials withnorientations which have low ΑΛ, high K2, high vnp. Procedures for calculating the PSAW properties (vpn, ΑΛ, and K2) are not very explicitlyngiven. In light of the preceding we present in this paper a review ofnthe basic features of SAW and PseudoSAW's using the matrix method. Innthis paper: the mechanically free open-circuited and short-circuitednsurface wave boundary value problems for piezoelectrics are formulatednusing the matrix method; two types of modes (SAW and PSAW) arendescribed; and a number of computationally simple, frequency independentnanalytical functions are derived, from which ΑΛ, vpn, and K2 are calculated for any direction on anynmaterial plane using commercially available PC software. Thenrelationship of these functions to the effective permittivity concept,nfavoured by many researchers, is demonstrated and illustrative numericalnexamples for the PSAW's reveals that low-loss orientations are quitensensitive to material constant values