Abstract :
A numerical analysis of non-leaky surface waves propagating in crystals at the supersonic velocity has been performed. These waves were found to be composite bulk waves (CBWs), in general three-partial and comprising incident quasi-longitudinal and two reflected quasi-transverse bulk modes. A projection of the subspace, in which the CBW satisfies the stress-free boundary condition, was calculated for orientations of LiNbO3, defined by the Euler angles (90°, 90°, ψ). The angle ψ=163.3°, for which CBW satisfies both mechanical and electrical boundary conditions, agrees with known propagation direction for non-leaky wave, and the angular dependence of velocity for CBW is very close to that of leaky waves, when the surface is nonmetallized. Application of the same technique to quartz cuts (0°,θ,ψ) gave the lines of supersonic non-leaky waves. These lines include exceptional waves, which correspond to degeneration of the three-partial CBW into one-partial exceptional wave
Keywords :
acoustic materials; lithium compounds; piezoelectric materials; quartz; surface acoustic waves; ultrasonic propagation; ultrasonic velocity; Euler angles; LiNbO3; SiO2; angular dependence; composite bulk waves; electrical boundary conditions; exceptional waves; mechanical boundary conditions; propagation direction; quasi-longitudinal leaky surface waves; reflected quasi-transverse bulk modes; stress-free boundary condition; supersonic velocity; Anisotropic magnetoresistance; Attenuation; Boundary conditions; Crystallography; Crystals; Iron alloys; Metallization; Numerical analysis; Steel; Surface waves;
