Piezoelectric single crystal device and fabrication method thereof

Abstract

The present invention provides a piezoelectric single crystal device excellent in heat resistance and capable of stably maintaining the electromechanical coupling factor kin a lateral vibration mode at a high value of 50% or more without a decrease even in an operating environment in which the temperature changes from room temperature to a high temperature (specifically, 150° C.), and also provides a fabrication method thereof. Specifically, assuming that the [101] axis of a tetragonal system having the [001] axis as a C axis (with the largest lattice constant) is a polarization direction, a normal directionto an edge face T of the piezoelectric device is within the solid-angle range of ±25° with respect to the [-101] axis substantially orthogonal to the polarization direction, the range including the [-101] axis. Assuming that the [011] axis of the tetragonal system is the polarization direction, the normal directionto the edge face T of the piezoelectric device is within the solid-angle range of ±25° with respect to the [0-11] axis substantially orthogonal to the polarization direction, the range including the [0-11] axis. In any case, the electromechanical coupling factor kin the direction orthogonal to the polarization direction, i.e., in the lateral vibration mode, is 50% or more.