Lateral-field-excitation properties of LiNbO₃ single crystal

LiNbO_3 has been found attractive for lateral field excitation (LFE) applications due to its high piezoelectric coupling. In this paper, bulk acoustic wave propagation properties for LiNbO_3 single crystal excited by a lateral electric field have been investigated using the extended Christoffel--Bechmann method. It is found that the LFE piezoelectric coupling factor for c mode reaches its maximum value of 95.46\% when \psi = 0^\circ for both (yxl)-58^\circ and (yxwl)\pm 60^\circ/58^\circ LiNbO_3. The acoustic wave phase velocity of c mode TSM (thickness shear mode) changes from 3456 m/s to 3983 m/s as a function of \psi. Here \psi represents the angle between the lateral electric field and the crystallographic X-axis in the substrate major surface. A 5 MHz LFE device of (yxl)-58^\circ LiNbO_3 with \psi=0^\circ was designed and tested in air. A major resonance peak was observed with the motional resistance as low as 17 \rm \Omega and the Q-factor value up to 10353. The test result is well in agreement with the theoretical analysis, and suggests that the LFE LiNbO_3 device can be a good platform for high performance resonator or sensor applications.