Theoretical study on guided wave propagation in (1 −x)Pb(Mg1/3Nb2/3)O₃–xPbTiO₃(x= 0.29 and 0.33) single crystal plates

The propagation of guided waves in free standing (1 − x)Pb(Mg1/3Nb2/3)O3–xPbTiO3 [PMN–xPT] (x = 0.29 or 0.33) single crystal plates has been studied theoretically. The polar directions are in the 111 family directions of the cubic reference coordinates but the crystals are being polarized along [0 0 1]c, [0 1 1]c and [1 1 1]c of the cubic reference directions so that the effective microscopic symmetries are 4mm, mm2 and 3m, respectively. Multiple mode couplings appear in the dispersion curves for both the symmetric and the antisymmetric Lamb and shear horizontal modes. The velocities of most guided waves decrease rapidly with frequency. Then, after passing a minimum, they begin to increase with frequency and eventually saturate to the shear wave velocity vsz (or v1 = 3507 m s−1 for [1 1 1]c polarized sample). For a [1 1 1]c polarized single domain PMN–0.33PT sample, the S1 mode instead of the S0 mode approaches the Rayleigh velocity vR at high frequencies.