Patent ID: 7999441

Claim:
A piezoelectric actuator, comprising: a diaphragm; and a piezoelectric element provided on the diaphragm, including a pair of electrode layers and a piezoelectric film sandwiched between the pair of electrode layers, wherein each elastic coefficient of the pair of electrode layers, the piezoelectric film and the diaphragm is isotropic in three-dimensional directions, an amount of distortion of the piezoelectric film which is caused by an electric field is isotropic in all in-plane directions of the piezoelectric film, a point, which is located on a principal surface of the diaphragm and has a maximum displacement amount when a predetermined electric field is applied between the pair of electrode layers and the piezoelectric film is distorted to bend the diaphragm by distortion, is expressed by Pδ MAX , and a point, which is located on the surface of the diaphragm and on a circumference of a circle having the point Pδ MAX as a center and a radius smaller than a distance between an end portion of the diaphragm and the point Pδ MAX , and has a minimum difference in displacement amount from the point Pδ MAX , is expressed by Pδ A , the diaphragm has a shape capable of uniquely determining an axis A 1 located on the principal surface of the diaphragm when the diaphragm is not bent, and set in a direction of a straight line joining the point Pδ MAX and the point Pδ A , the diaphragm comprises a single-orientation or a single-crystalline material in which a plane orthogonal to the axis A 1 and perpendicular to an axis A 2 located on the principal surface of the diaphragm is a {110} plane, and the piezoelectric film comprises a single-orientation or a single-crystalline piezoelectric film including a {100} plane perpendicular to the axis A 2 .