There is provided a piezoelectric stack including: a substrate having a main surface with a diameter of 3 inches or more; and a piezoelectric film on the substrate, comprising a perovskite-type alkali niobium oxide containing potassium, sodium, niobium, and oxygen, wherein, a half-value width of an X-ray rocking curve of (001) is within a range of 0.5? or more and 2.5? or less over an entire area of an inside of a main surface of the piezoelectric film excluding its periphery when performing X-ray diffraction measurement on the piezoelectric film.

An object is to provide an organic piezoelectric film with a high level of piezoelectricity, a high level of transparency, and a low level of retardation. The organic piezoelectric film of the present disclosure has a total light transmittance of 90% or more, an internal haze value of 0.2%/?m or less per unit film thickness or an internal haze value of 4% or less, piezoelectric constant d.sub.33 of 13 pC/N or more, and a retardation within the range of 0.01 to 10 nm/?m per unit film thickness or a retardation within the range of 0.1 to 900 nm.

In the piezoelectric film including a perovskite oxide which is represented by General Formula P, 0.1?x?0.3 and 0<y?0.49x are satisfied, A.sub.1+?[(Zr,Ti).sub.1-x-yNb.sub.xSc.sub.y]O.sub.z . . . General Formula P, in General Formula P, A is an A-site element primarily containing Pb, ?=0 and z=3 are standard values, but ? and z may deviate from standard values in a range in which a perovskite structure is capable of being obtained.

An acoustic wave device includes: a piezoelectric thin film resonator that is connected between a first node and a second node; and a resonant circuit that is connected in parallel with the piezoelectric thin film resonator between the first node and the second node, and has a resonant frequency f0 that meets a condition of 2?fa?0.92?f0 where fa represents an antiresonant frequency of the piezoelectric thin film resonator.

Provided are a pickup sensor and a biological sensor that are small-sized and can detect micro vibration efficiently and stably with high accuracy. The pickup sensor includes an electroacoustic converter film including: a piezoelectric polymer composite in which piezoelectric particles are dispersed in a viscoelastic matrix that is formed of a polymer material having viscoelasticity at normal temperature; two thin film electrodes that are laminated on opposite surfaces of the piezoelectric polymer composite, respectively; and a protective layer that is laminated on at least one of the two thin film electrodes, in which at least a part of a surface of the electroacoustic converter film is an abutting surface that abuts against a test object, and the thin film electrode on a surface opposite to the abutting surface is grounded.

Highly deformable heterostructures utilizing liquid metals and nanostructures that are suitable for various applications, including but not limited to stretchable electronic devices that can be worn, for example, by a human being. Such a deformable heterostructure includes a stretchable substrate, a conductive liquid metal on the substrate, and nanostructures forming a solid-liquid heterojunction with the conductive liquid metal.

An omnidirectional electroacoustic transducer capable of reproducing a sound with high acoustic quality and sufficient sound volume in a wide frequency band is provided with a small number of components. The electroacoustic transducer includes: two or more electroacoustic transduction units each including an electroacoustic transduction film and an elastic supporter, the electroacoustic transduction film having a polymer composite piezoelectric body in which piezoelectric body particles are dispersed in a viscoelastic matrix formed of a polymer material having viscoelasticity at a normal temperature, and two thin film electrodes laminated on both surfaces of the polymer composite piezoelectric body, and the elastic supporter being disposed to be closely attached to one principal surface of the electroacoustic transduction film so as to cause the electroacoustic transduction film to be bent, in which the two or more electroacoustic transduction units are disposed so that the electroacoustic transduction films face outward and form some or all of faces of a polyhedron.

There is provided a ferroelectric thin-film laminated substrate, including a substrate, and further including a lower electrode layer, a ferroelectric thin-film layer, an upper electrode adhesive layer, and an upper electrode layer being sequentially stacked on the substrate, in which: the lower electrode layer is made of platinum or a platinum alloy; the ferroelectric thin-film layer is made of a sodium potassium niobate (typical chemical formula of (K.sub.1-xNa.sub.x)NbO.sub.3, 0.4?x?0.7); the upper electrode layer is made of gold; the upper electrode adhesive layer is made of a metal that has less oxidizability than titanium and can make a solid solution alloy without generating an intermetallic compound with gold; and a part of the upper electrode adhesive layer and a part of the upper electrode layer are alloyed.

A film structure (10) includes a substrate (11), a piezoelectric film (14) formed on the substrate (11) and containing first composite oxide represented by a composition formula Pb(Zr.sub.1?xTi.sub.x)O.sub.3, and a piezoelectric film (15) formed on the piezoelectric film (14) and containing second composite oxide represented by a composition formula Pb(Zr.sub.1?yTi.sub.y)O.sub.3. In the composition formulae, x satisfies 0.10<x?0.20, and y satisfies 0.35?y?0.55. The piezoelectric film (14) has tensile stress, and the piezoelectric film (15) has compressive stress.

A piezoelectric tactile sensor includes a support body having one or more openings, a diaphragm formed on a surface of the support body, one or more piezoelectric films respectively formed above the openings and on a surface of the diaphragm, and two electrodes that sandwich each of the piezoelectric films. Each of the piezoelectric films has a diameter smaller than a diameter of a corresponding one of the openings and outputs a voltage to the two electrodes in response to a deflection of the diaphragm.