The present disclosure relates to a piezoelectric single-crystal element, a MEMS device using same, and a method for manufacturing same, wherein the piezoelectric single-crystal element includes a wafer, a lower electrode stacked on the wafer, a piezoelectric single-crystal thin film stacked on the lower electrode, and an upper electrode stacked on the piezoelectric single-crystal thin film, wherein the piezoelectric single-crystal thin film is composed of PMN-PT, PIN-PMN-PT or Mn:PIN-PMN-PT, and the piezoelectric single-crystal thin film has a polarization direction set to a <001> axis, a <011> axis or a <111> axis, and a MEMS device using same.

A power factor improvement and power generation apparatus using a piezoelectric element may include: a first piezoelectric element having first and second electrodes, and vibrating when voltage is applied from a power line; and a second piezoelectric element having first and second electrodes, and generating electricity in accordance with vibration of the first piezoelectric element. This apparatus is possible to improve a power factor of a power line and generate power using the inherent condenser component, which a piezoelectric element has, instead of a power factor compensation condenser, and it is also possible to generate power.

A piezo-electric actuator on the side of a mobile device will enable pressure exerted by the user to be sensed at the conventional button locations, while providing a haptic feedback. Unfortunately, mechanical integration of piezo-electric actuators at the side of a mobile device is challenging. A mobile device in accordance with the present disclosure comprises a PCB; an outer frame surrounding the PCB; and a switch. The switch comprises: a first piezo-electric actuator configured to generate a first actuator voltage signal in response to a first force applied by a user, and to generate a first haptic feedback to the user in response to a first haptic voltage signal transmitted from the controller thereto; and a first virtual button in the outer frame configured to transmit the first force to the first piezo-electric actuator, and to transmit the first haptic feedback to the user.

A force sensing device is mounted on a tool to sense force, particularly quasi-static and static forces. The force sensing device includes at least one a sensor. A piezoelectric element in the sensor includes a driving portion and a sensing portion. A first voltage is input to the driving portion to generate a vibration in the piezoelectric element and a second voltage in response to the vibration is output from the sensing portion. The second voltage output from the sensing portion is changed as the vibration in the piezoelectric element is suppressed by an external force acting on the force sensing device so variation of the second voltage can be used to measure the external force.

Pressure/strain piezoresistive are described that include a poled piezoelectric polymer such as PVDF or P(VDF-TrFE) and graphene. The poled piezoelectric polymer and the graphene are electronically coupled to form a heterojunction and provide an ultra-high sensitivity pressure/strain sensor. The sensors can be carried on a flexible supporting substrate such as PDMS or PET to exhibit high flexibility. The materials of formation can be biocompatible and the sensors can be wearable or implantable.

There are provided a piezoelectric film-attached substrate and piezoelectric element, which include, on a substrate in the following order, a lower electrode layer, a piezoelectric film containing a perovskite-type oxide containing lead as a main component of an A site, and a buffer layer, where the buffer layer contains a metal oxide represented by M.sub.dN.sub.1-dO.sub.e. Here, M consists of one or more metal elements substitutable for the A site of the perovskite-type oxide and has an electronegativity of less than 0.95. In a case of 0<d<1 and in a case where the electronegativity is denoted by X, 1.41X−1.05≤d≤A1.Math.exp(−X/t1)+y0, where A1=1.68×10.sup.12, t1=0.0306, and y0=0.59958.

An entangled-photon pair emitting device according to an embodiment of the inventive concept includes a piezoelectric structure having a first surface and a second surface, which face each other, wherein the piezoelectric structure includes an opening passing through the piezoelectric structure from the first surface to the second surface, a stress transfer medium that fills the opening, a light source emitting part disposed on the stress transfer medium, an upper electrode disposed on the first surface of the piezoelectric structure, and a lower electrode disposed on the second surface of the piezoelectric structure. Here, the light source emitting part includes a semiconductor thin-film and a quantum dot in the semiconductor thin-film.

An entangled-photon pair emitting device according to an embodiment of the inventive concept includes a piezoelectric structure having a first surface and a second surface, which face each other, wherein the piezoelectric structure includes an opening passing through the piezoelectric structure from the first surface to the second surface, a stress transfer medium that fills the opening, a light source emitting part disposed on the stress transfer medium, an upper electrode disposed on the first surface of the piezoelectric structure, and a lower electrode disposed on the second surface of the piezoelectric structure. Here, the light source emitting part includes a semiconductor thin-film and a quantum dot in the semiconductor thin-film.

Provided is a piezoelectric material filler including alkali niobate compound particles having a ratio (K/(Na+K)) of the number of moles of potassium to the total number of moles of sodium and potassium of 0.460 to 0.495 in terms of atoms and a ratio ((Li+Na+K)/Nb) of the total number of moles of alkali metal elements to the number of moles of niobium of 0.995 to 1.005 in terms of atoms. The present invention can provide a piezoelectric material filler having excellent piezoelectric properties, and a composite piezoelectric material including the piezoelectric material filler and a polymer matrix.

Provided is a piezoelectric material filler including alkali niobate compound particles having a ratio (K/(Na+K)) of the number of moles of potassium to the total number of moles of sodium and potassium of 0.460 to 0.495 in terms of atoms and a ratio ((Li+Na+K)/Nb) of the total number of moles of alkali metal elements to the number of moles of niobium of 0.995 to 1.005 in terms of atoms. The present invention can provide a piezoelectric material filler having excellent piezoelectric properties, and a composite piezoelectric material including the piezoelectric material filler and a polymer matrix.