A film structure body has: a substrate that is a silicon substrate including an upper surface composed of a (100) plane; an orientation film including a zirconium oxide film that is cubic crystal (100)-oriented on the upper surface; and a conductive film including a platinum film that is cubic crystal (100)-oriented on the orientation film.

A piezoelectric device including a substrate, a metal-insulator-metal element, a hydrogen blocking layer, a passivation layer, a first contact terminal and a second contact terminal is provided. The metal-insulator-metal element is disposed on the substrate. The hydrogen blocking layer is disposed on the metal-insulator-metal element. The passivation layer covers the hydrogen blocking layer and the metal-insulator-metal element. The first contact terminal is electrically connected to the metal-insulator-metal element. The second contact terminal is electrically connected to the metal-insulator-metal element.

A dielectric elastomer actuator comprising: a plurality of polymer layer; a plurality of stretchable electrode layers, each polymer layer being sandwiched between two electrode layers so as to control the electric field within the polymer layer; at least one stretchable charge distribution layer, each charge distribution layer being adjacent to one stretchable electrode layer and/or to one polymer layer.

In a piezoelectric device, when viewed in a direction perpendicular to one main surface, an outer shape of a recess is a polygonal shape or a circular shape. When n represents a number of sides of the polygonal shape, r represents a radius of a circumscribed circle of an imaginary regular polygon including n sides with a length identical to a length of a shortest of the sides, and d represents a maximum thickness of a membrane portion, which is located above the recess, of a multilayer portion, r≤197.7dn.sup.−0.6698 when 3≤n≤7, and r≤52.69d when 8≤n or when the outer shape of the recess is a circular shape.

In a piezoelectric device, a layered portion includes, at a position at least above a recess, a single crystal piezoelectric layer and a pair of electrode layers to apply voltage to the single crystal piezoelectric layer. At least a portion of the pair of electrode layers includes a lower electrode layer extending along a surface of the single crystal piezoelectric layer, the surface being closer to a base. The lower electrode layer is present only inside the recess.

Provided is a piezoelectric ceramics having a gradual change in piezoelectric constant depending on an ambient temperature. Specifically, provided is a single-piece piezoelectric ceramics including as a main component a perovskite-type metal oxide represented by a compositional formula of ABO.sub.3, wherein an A site element in the compositional formula contains Ba and M.sub.1, the M.sub.1 being formed of at least one kind selected from the group consisting of Ca and Bi, wherein a B site element in the compositional formula contains T1 and M.sub.2, the M.sub.2 being formed of at least one kind selected from the group consisting of Zr, Sn, and Hf, wherein concentrations of the M.sub.1 and the M.sub.2 change in at least one direction of the piezoelectric ceramics, and wherein increase and decrease directions of concentration changes of the M.sub.1 and the M.sub.2 are directions opposite to each other.

There is provided a piezoelectric actuator, including: a vibration plate; a first piezoelectric body; a second piezoelectric body; a first electrode disposed on a first surface of the first piezoelectric body; a second electrode disposed on a second surface of the second piezoelectric body; an intermediate electrode disposed on an intermediate surface of the first piezoelectric body and overlapping with the first and second electrodes; an intermediate trace connected to the intermediate electrode on the intermediate surface and drawn out to one side in a first direction beyond the first piezoelectric body and the second piezoelectric body; a first trace overlapping with the intermediate trace in the thickness direction and being conducted with the intermediate trace; and a second trace overlapping with the intermediate trace in the thickness direction and being conducted with the intermediate trace.

A multilayer piezoelectric element includes a piezoelectric body containing a piezoelectric ceramic material, a first electrode, and a second electrode. The piezoelectric body includes a first main surface and a second main surface opposing each other. The first electrode includes an external electrode formed on the first main surface. The second electrode includes an internal electrode formed inside the piezoelectric body to oppose the external electrode. The piezoelectric body includes an active region between the external electrode and the internal electrode, and includes an inactive region opposite to the active region with the internal electrode interposed therebetween. A stress received by the piezoelectric body from the external electrode is larger than a stress received by the piezoelectric body from the internal electrode. A polarization direction of the active region is a direction directed from the external electrode to the internal electrode.

A lead-free piezoelectric material includes perovskite-type metal oxide containing Na, Nb, Ba, Ti, and Mg and indicates excellent piezoelectric properties. The piezoelectric material satisfies the following relational expression (1): 0.430≤a≤0.460, 0.433≤b≤0.479, 0.040≤c≤0.070, 0.0125≤d≤0.0650, 0.0015≤e≤0.0092, 0.9×3e≤c−d≤1.1×3e, a+b+c+d+e=1, where a, b, c, d, and e denote the relative numbers of Na, Nb, Ba, Ti, and Mg atoms, respectively.

A piezoelectric element includes a stack including a plurality of internal electrodes and a plurality of piezoelectric layers stacked on one another, and a surface electrode located on a side surface of the stack and connected to the plurality of internal electrodes. A second electrode illustrated in FIG. 3B includes a first conductor including a strip extending in a longitudinal direction and an extension having one end continuous with the strip and another end exposed on the side surface of the stack and connected to the surface electrode. The piezoelectric element includes a second conductor located between the extension and an opposite portion of the side surface of the stack opposite to a portion of the side surface on which the other end of the extension is exposed.