A shear vibration-based piezoelectric composite material and a preparation method thereof are disclosed. The piezoelectric composite material includes a piezoelectric material and the passive material. The piezoelectric material includes a piezoelectric material polarized along the x-axis positive and a piezoelectric material negatively polarized along the x-axis. The piezoelectric materials in the two polarization directions are alternately arranged along the x-axis direction. The passive material includes a filling layer, a transition layer, and a planar layer. The filling layer is disposed between every two adjacent piezoelectric materials. The planar layer is located outer two surfaces perpendicular to the z-axis of the piezoelectric material. The planar layer on one side is fixedly connected to the filling layer in the odd-numbered position via the transition layer. The planar layer on the other side is fixedly connected to the filling layer in the even-numbered position via the transition layer. The piezoelectric composite material can be used to prepare an underwater acoustic transducer, a hydrophone, piezoelectric energy harvesters, and the like. The invention innovatively converts shear vibrations into the thickness vibrations of the upper and lower surfaces of the composite material, thereby improving the performance of the composite material.

A method for repolarizing a piezoelectric actuator associated with an injector mounted on an internal combustion engine of a vehicle, the piezoelectric actuator having undergone initial polarization before the vehicle was used, includes with the engine stopped: applying a first polarization voltage to the terminals of the piezoelectric actuator during a first specified time interval of not less than ten minutes, stopping the application of the first polarization voltage during a second time interval, following the first time interval and at least equal to the latter, applying a second polarization voltage to the terminals of the piezoelectric actuator during a third specified time interval, following the second time interval, stopping the application of the second polarization voltage to the terminals of the piezoelectric actuator after the third time interval,
the successive first, second and third time intervals defining a repolarization sequence of the piezoelectric actuator.

A multi-layer piezoelectric microactuator assembly has at least one poled and active piezoelectric layer and one poled but inactive piezoelectric layer. The poled but inactive layer acts as a constraining layer in resisting expansion or contract of the first piezoelectric layer thereby reducing or eliminating bending of the assembly as installed in an environment, thereby increasing the effective stroke length of the assembly. Poling only a single layer would induce stresses into the device; hence, polling both piezoelectric layers even though only one layer will be active in use reduces stresses in the device and therefore increases reliability.

A piezoelectric polyvinylidene fluoride (PVDF) material, a method for manufacturing the same, and a fingerprint recognition module are provided. The polyvinylidene PVDF material includes PVDF, a first solvent, a second solvent, a fluorosurfactant, and an inducing material. Material of the inducing material is one of carbon nanotubes, carbon black, and gold nanorods. Because of the high anisotropy of the inducing material, molecular orientation of the PVDF material is induced, thereby improving piezoelectric performance of the piezoelectric PVDF material. Problems of conventional piezoelectric PVDF materials, which are used in ultrasonic fingerprint recognition modules, such as poor piezoelectric performance and high-energy loss are improved.

A transparent optical element may include a layer of an electroactive ceramic disposed between transparent electrodes, such that the electrodes are each oriented perpendicular to a non-polar direction of the ceramic layer. Optical properties of the optical element, including transmissivity, haze, and clarity may be improved by the application of a voltage to the electroactive ceramic, and an associated phase transformation.

Among other things, piezoelectric materials and methods of their manufacture are described; particularly methods of forming regions of varying crystal structure within a relaxor piezoelectric substrate. Such methods may including heating the piezoelectric substrate above the transition temperature and below the Curie temperature such that a first phase transition occurs to a first crystal structure; rapidly cooling the piezoelectric substrate below the transition temperature at a cooling rate that is sufficiently high for the first crystal structure to persist; and applying an electric field through one or more selected regions of the piezoelectric substrate, such that within the one or more selected regions, a second phase transition occurs and results in a second crystal structure.

A method is provided for manufacturing a piezoelectric device including a piezoelectric element that is disposed above a diaphragm and that has a multilayer structure including a first electrode disposed above the diaphragm, a piezoelectric layer disposed on the first electrode, and a second electrode disposed on the piezoelectric layer. The method includes forming the multilayer structure including the first electrode, the piezoelectric layer, and the second electrode above the diaphragm, forming a voltage application electrode extending outwardly from an end of the second electrode to cover a region located above the piezoelectric layer in an inactive section having no second electrode, applying a voltage between the first electrode and the second electrode, and removing the voltage application electrode.

The present invention provides an ultrasonic fingerprint recognition module and a display panel. Advantages of the present invention are that a vibration absorbing layer can absorb mechanical energy of a piezoelectric thin film layer such that a number of cycles of later ultrasound is significantly reduces to extremely increase a vertical resolution of ultrasound fingerprint recognition and overall recognition effect and precision.

In manufacturing method of a cylindrical piezoelectric element, a cylindrical piezoelectric material is formed by molding a piezoelectric material into a cylindrical shape and subjecting the molded piezoelectric material to calcination. A reference electrode is provided on an inner circumferential surface of the cylindrical piezoelectric material. Drive electrodes are provided in a circumferential direction so that the drive electrodes are extending in an axial direction from one end to the other end on an outer circumferential surface. A polarization electrode is provided at a part of the circumferential surface in the vicinity of the one end. A predetermined voltage is applied between the polarization electrode and the reference electrode. The polarization electrode is removed from the cylindrical piezoelectric material.

A pyroelectric device, comprising a plurality of layers of a polar dielectric material having a pyroelectric coefficient, p, wherein each layer exhibits pyroelectric properties; a plurality of conductive electrodes, wherein each conductive electrode is substantially in contact with at least a portion of one surface of a respective at least one of said plurality of layers of polar dielectric material, wherein said electrodes are electrically connected in a parallel configuration as to form a series of capacitors comprised of said plurality of layers of polar dielectric material and plurality of conductive electrodes.