VIBRATION DEVICE, AND PIEZOELECTRIC PUMP

Warping of a piezoelectric layer is eliminated, and even if a tensile stress is applied to the piezoelectric layer due to vibration, a risk that the piezoelectric layer will break is reduced. A piezoelectric pump (100) includes a piezoelectric element (54), an intermediate plate (53), and a vibrating plate (51). The piezoelectric element (54) has a flat-plate-like shape. The intermediate plate (53) is bonded to a principal surface of the piezoelectric element (54) and applies a residual stress in a compressive direction to the piezoelectric element (54). The vibrating plate (51) is bonded to the intermediate plate (53) such that the vibrating plate (51) faces a principal surface of the piezoelectric element (54) and receives a residual stress in a compressive direction from the intermediate plate (53). In addition, the vibrating plate (51) forms a portion of a wall surface of a pump chamber (41) having an open hole (31). A fluid passage is formed in the piezoelectric pump (100). The fluid passage communicates with the outside of the chamber at one end thereof, and communicates with the pump chamber (41) through the open hole (31) at the other end.