Lame-mode piezoelectric resonators and transformers using LiNbO3 crystals

Lame-modes of vibration existing in a ceramic rectangular plate with an integral length-to-width ratio have vibrational nodes at the four corners but cannot be excited piezoelectrically because of their equivoluminal nature. In this paper it is theoretically shown that Lame-modes exist in 155° rotated Y-cut LiNbO₃ rectangular plates and can be efficiently excited piezoelectrically. This is experimentally verified through measurements of the impedance characteristics, displacement distribution, and capacitance ratio. It is also demonstrated that the Q value is not significantly degraded by the support of the resonator on the four corners. As an application, a piezoelectric transformer using the Lame-mode resonator is demonstrated to have excellent characteristics