A stacked piezoelectric device and its fabrication method

Abstract

This invention belongs to the field of piezoelectric device technology, specifically relating to a stacked piezoelectric device and its fabrication method. The piezoelectric device includes: a piezoelectric element comprising multiple piezoelectric segments arranged along the length direction and isolated from each other, and polymer segments disposed between adjacent piezoelectric segments and separating them along the length direction. Each piezoelectric segment is composed of multiple layers of ceramic substrate and multiple layers of internal electrodes stacked alternately. The electrode ports of the internal electrodes of the even-numbered layers in the piezoelectric segment are exposed in the same direction on one end face of the piezoelectric element, while the electrode ports of the internal electrodes of the odd-numbered layers are exposed in the opposite direction on the other end face of the piezoelectric element; a first electrode layer electrically connected to the electrode ports of the internal electrodes of the even-numbered layers; and a second electrode layer electrically connected to the electrode ports of the internal electrodes of the odd-numbered layers. This invention can improve stress distribution characteristics and achieve higher flexibility while ensuring reliable electrical connection and high driving efficiency of the stacked piezoelectric device.

Description

Technical Field

[0001] This invention belongs to the field of piezoelectric device technology, specifically relating to a stacked piezoelectric device and its preparation method. Background Technology

[0002] Piezoelectric materials can convert mechanical energy into electrical energy through the piezoelectric effect, and are therefore widely used in fields such as ultrasonic motors, energy harvesting, piezoelectric sensors, and non-destructive testing. Among them, piezoelectric ceramic materials have become one of the most commonly used functional materials in piezoelectric devices due to their excellent piezoelectric properties, mature manufacturing processes, and high driving force.

[0003] In the prior art, Chinese invention patent CN101547875B discloses a stacked piezoelectric element, which achieves large strain output performance at a relatively low driving voltage by staggering multiple layers of piezoelectric ceramic preforms and multiple layers of internal electrodes in the thickness direction and applying an electric field in the stacking direction. This type of stacked piezoelectric device has a compact structure and high output force, and is widely used in precision driving and other fields.

[0004] However, due to the inherent brittleness, high density, and low allowable strain of piezoelectric ceramic materials, the aforementioned monolithic laminated piezoelectric elements typically form a continuous rigid structure along the length orthogonal to the lamination direction. During operation or when subjected to external impacts or vibrations, the mechanical strain generated on the piezoelectric element is difficult to release, easily leading to stress concentration in localized areas. This negatively impacts the long-term reliability and impact resistance of the piezoelectric element. Furthermore, as the size of the piezoelectric element increases, the monolithic continuous structure is also susceptible to uneven sintering shrinkage during manufacturing, increasing the difficulty of controlling dimensional and performance consistency.

[0005] Furthermore, to overcome the problems of insufficient flexibility and difficulty in adapting to large deformations or curved structures in piezoelectric ceramic materials, a piezoelectric composite material solution has been proposed in the prior art. For example, Chinese invention patent CN108428783A discloses a typical piezoelectric fiber composite material structure, which uses unidirectional and uniformly distributed piezoelectric fibers and encapsulates the piezoelectric fibers with interdigitated electrodes. This structure can, to a certain extent, combine the driving force advantages of piezoelectric ceramics with the flexible characteristics of composite materials, enabling the device to have large driving strain, high flexibility, and low thickness. It is suitable for applications such as drones, helicopter rotor health monitoring, flutter suppression, and smart wearables that can be bent and attached to complex structural surfaces.

[0006] However, the interdigitated electrode structure, because the electrodes do not cover the entire surface of the piezoelectric material but are distributed in an alternating pattern, results in a non-uniform electric field distribution. Specifically, the electric field is stronger in the region directly above the finger electrodes and weaker in the central region between adjacent electrodes. This causes some piezoelectric fibers to be in areas with insufficient electric field strength, making it difficult to obtain an electric field strength exceeding their coercive field, thus failing to achieve sufficient polarization and forming so-called polarization dead zones. Furthermore, to ensure sufficient effective actuation, this type of piezoelectric fiber composite material typically requires the application of high polarization and operating voltages (above 1000V, typically 1500V), which is detrimental to device miniaturization and low-power applications.

[0007] In summary, in the existing technology, on the one hand, although the integral layered piezoelectric ceramic device has a large driving force and mature electrical connection method, it has certain limitations in terms of structural flexibility, stress release and impact resistance reliability; on the other hand, although the piezoelectric fiber composite material with interdigitated electrodes has high flexibility, it has problems such as low electric field utilization, polarization dead zone and high driving voltage. Summary of the Invention

[0008] To address the aforementioned technical problems, the present invention aims to provide a stacked piezoelectric device and its fabrication method. Therefore, the present invention can improve stress distribution characteristics and achieve higher flexibility while ensuring reliable electrical connection and high driving efficiency of the stacked piezoelectric device, and avoid the problem of uneven electric field caused by the interdigitated electrode structure.

[0009] In a first aspect, the present invention provides a stacked piezoelectric device, comprising: A piezoelectric element comprising a plurality of piezoelectric segments arranged along the length direction and isolated from each other, and polymer segments disposed between adjacent piezoelectric segments and separating adjacent piezoelectric segments along the length direction, wherein each piezoelectric segment is composed of multiple layers of ceramic substrate and multiple layers of internal electrodes stacked alternately. A first electrode layer, disposed on the upper surface of the piezoelectric element, and electrically connected to the internal electrodes of the even-numbered layers of the plurality of piezoelectric segments; and The second electrode layer is disposed on the lower surface of the piezoelectric element and is electrically connected to the internal electrodes of the odd-numbered layers of the plurality of piezoelectric segments.

[0010] Furthermore, the piezoelectric element further includes: a first external electrode that electrically connects the internal electrodes of the even-numbered layers in each piezoelectric segment to each other, and a second external electrode that electrically connects the internal electrodes of the odd-numbered layers in each piezoelectric segment to each other; the first electrode layer is electrically connected to a plurality of first external electrodes, and the second electrode layer is electrically connected to a plurality of second external electrodes.

[0011] Further, the piezoelectric segment also includes a first end face and a second end face located at one end and the other end in the width direction, respectively, wherein the width direction is orthogonal to both the height direction, which is the stacking direction of the piezoelectric segment, and the length direction; one end of the internal electrode of the even-numbered layers in the piezoelectric segment is exposed on the first end face, and the other end is spaced apart from the second end face; one end of the internal electrode of the odd-numbered layers in the piezoelectric segment is spaced apart from the first end face, and the other end is exposed on the second end face; the first external electrode includes a first main body segment disposed on the uppermost ceramic substrate of the piezoelectric segment, and a lower folded segment that folds down from the first main body segment along one side of the piezoelectric segment and extends to the first end face to be electrically connected to the exposed end of the even-numbered internal electrode; the second external electrode includes a second main body segment disposed on the lowermost ceramic substrate of the piezoelectric segment, and an upper folded segment that folds up from the second main body segment along the other side of the piezoelectric segment and extends to the second end face to be electrically connected to the exposed end of the odd-numbered internal electrode; the first electrode layer is electrically connected to the first main body segment, and the second electrode layer is electrically connected to the second main body segment.

[0012] Furthermore, the piezoelectric segment also includes a first end face and a second end face located at one end and the other end in the width direction, respectively; one end of the internal electrode of the even-numbered layers in the piezoelectric segment is exposed on the first end face; one end of the internal electrode of the odd-numbered layers in the piezoelectric segment is exposed on the second end face; the first electrode layer is electrically connected to the exposed end of the internal electrode of the even-numbered layers, and the second electrode layer is electrically connected to the exposed end of the internal electrode of the odd-numbered layers.

[0013] Furthermore, a first polymer layer is disposed between the first electrode layer and the upper surface of the piezoelectric element, and a second polymer layer is disposed between the second electrode layer and the lower surface of the piezoelectric element.

[0014] Furthermore, the first electrode layer includes a first contact electrode sheet and a first positioning strip, the first positioning strip being used to align the first contact electrode sheet with the upper surface of the piezoelectric element to contact the first main body segment of each of the first external electrodes; the second electrode layer includes a second contact electrode sheet and a second positioning strip, the second positioning strip being used to align the second contact electrode sheet with the lower surface of the piezoelectric element to contact the second main body segment of each of the second external electrodes.

[0015] In a second aspect, the present invention provides a method for fabricating a stacked piezoelectric device as described in the first aspect, comprising: Fabrication of an integral piezoelectric element composed of a multilayer ceramic matrix and a multilayer internal electrode stacked in an alternating manner; The piezoelectric element is divided into multiple piezoelectric segments along a length direction orthogonal to the stacking direction; A polymer segment is formed between adjacent piezoelectric segments, thereby isolating the adjacent piezoelectric segments from each other in the length direction; A first electrode layer is disposed on the upper surface of the piezoelectric element and electrically connected to the internal electrodes of the even-numbered layers of the plurality of piezoelectric segments; A second electrode layer is disposed on the lower surface of the piezoelectric element and electrically connected to the internal electrodes of the odd-numbered layers of the plurality of piezoelectric segments.

[0016] Furthermore, in the fabrication of the piezoelectric element, a first external electrode for electrically connecting the even-numbered inner electrodes is formed on the uppermost ceramic substrate, and a second external electrode for electrically connecting the odd-numbered inner electrodes is formed on the lowermost ceramic substrate.

[0017] Furthermore, the step of dividing the piezoelectric element along its length includes dividing the piezoelectric element into multiple piezoelectric segments at predetermined intervals along its length.

[0018] Furthermore, forming a polymer segment between adjacent piezoelectric segments includes: introducing a polymer material into the gap between adjacent piezoelectric segments and molding the polymer material through a curing process, thereby fixing and isolating adjacent piezoelectric segments from each other in the length direction.

[0019] Compared with the prior art, the present invention has at least the following beneficial effects: This invention divides a piezoelectric element into multiple piezoelectric segments along its length and places polymer segments between adjacent piezoelectric segments. This allows the piezoelectric element to form a segmented structure along its length while maintaining its original stacked structure and internal electrode arrangement. Because adjacent piezoelectric segments are isolated by polymer segments, the mechanical deformation generated by each segment during operation can be decoupled and buffered, thereby reducing stress concentration in the overall stacked piezoelectric element along its length. This improves the structural stability and reliability of the device. Furthermore, this invention, by setting a first electrode layer and a second electrode layer on the upper and lower surfaces of the stacked piezoelectric element, electrically connects the internal electrodes of multiple piezoelectric segments as a whole. This ensures that the electric field is mainly formed along the stacking direction of the piezoelectric segments, thus avoiding the problem of uneven electric field distribution caused by changes in electrode spacing in interdigitated electrode structures. This also helps reduce the possibility of generating locally underpolarized regions during polarization. Simultaneously, this invention uses stacked piezoelectric segments as the basic driving unit and achieves structural segmentation through polymer segments. While maintaining high driving capability, it also ensures structural reliability, expanding the application applicability of stacked piezoelectric devices in complex working conditions (such as bending and large-size structures). On the other hand, filling the spaces between piezoelectric segments with polymer can enhance the overall flexibility of the material, effectively maintaining the strength and dynamics of the piezoelectric ceramic while overcoming its brittleness. Attached Figure Description

[0020] Figure 1 This is an exploded view of a stacked piezoelectric device according to a specific embodiment of the present invention.

[0021] Figure 2 for Figure 1 A schematic diagram of the piezoelectric segment in the image.

[0022] Figure 3 This is a flowchart of the fabrication process for piezoelectric elements.

[0023] Figure 4 This is a plan view of a piezoelectric device.

[0024] Figure 5 The figure shows the test results of strain values ​​of stacked piezoelectric devices using the cantilever beam method.

[0025] Figure label: 100, piezoelectric element; 110, piezoelectric segment; 111, ceramic matrix; 112, internal electrode; 112a, first internal electrode; 112b, second internal electrode; 113, external electrode; 113a, first external electrode; 113b, second external electrode; 120, polymer segment. 200, First electrode layer; 210, First contact electrode sheet; 220, First positioning strip; 300, second electrode layer; 310, second contact electrode sheet; 320, second positioning strip; 400, First polymer layer, 500, Second polymer layer. Detailed Implementation

[0026] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Furthermore, it should be understood that the specific embodiments described herein are only for illustration and explanation of the present invention and are not intended to limit the present invention.

[0027] In this invention, the following length direction, width direction, and height direction are named to facilitate clarifying the relative positional relationship of each component, and are not intended to limit the relative size of the length or dimensions in each direction. That is to say, it is not required that the length dimension of the component is necessarily greater than the dimensions in other directions. Unless otherwise stated, the directional terms such as "up," "down," "left," "right," "front," and "back" generally refer to up, down, left, and right in the actual use or working state of the device, specifically the directions shown in the accompanying drawings.

[0028] It should be noted that the order of description of the following embodiments is not intended to limit the preferred order of the embodiments of this application. Furthermore, the descriptions of each embodiment in the following embodiments have their own emphasis; for parts not described in detail in a certain embodiment, please refer to the relevant descriptions in other embodiments.

[0029] This invention relates to the fabrication of a piezoelectric device, specifically to a multilayer piezoelectric ceramic fiber composite material (i.e., a piezoelectric element) composed of two materials: multilayer piezoelectric ceramic fiber and epoxy resin (the polymer described later), as well as a piezoelectric device comprising a piezoelectric element, an external electrode layer, and a polyimide encapsulation layer (the polymer layer described later), belonging to the field of smart materials and functional device fabrication.

[0030] like Figures 1 to 4 As shown, a specific embodiment of the present invention provides a stacked piezoelectric device, which includes a piezoelectric element 100, a first electrode layer 200, and a second electrode layer 300. The first electrode layer 200 and the second electrode layer 300 are used to connect the piezoelectric element 100 to the positive and negative terminals of an external power source or external electrical equipment, respectively, so as to realize the mutual conversion between mechanical energy and electrical energy through the piezoelectric effect of the piezoelectric element.

[0031] Specifically, the piezoelectric element 100 includes a plurality of piezoelectric segments 110 arranged sequentially and spaced apart from each other along its length, and polymer segments 120 disposed between adjacent piezoelectric segments 110. It should be understood that the plurality of piezoelectric segments 110 and the plurality of polymer segments 120 are arranged alternately to form the piezoelectric element 100, with the arrangement direction being the length direction of the piezoelectric element. Each polymer segment 120 separates adjacent piezoelectric segments 110 from each other in the length direction, thereby forming a structure in the length direction of the piezoelectric element 100 composed of alternating arrangements of the plurality of piezoelectric segments 110 and the plurality of polymer segments 120. Preferably, in the height direction perpendicular to the length direction, the thickness (height) of each piezoelectric segment 110 and polymer segment 120 is substantially the same. Alternatively, the thickness of the polymer segment 120 in the height direction of the piezoelectric element may be greater than that of the piezoelectric segment 110, so as to separate adjacent piezoelectric segments 110 in the length direction.

[0032] Furthermore, each piezoelectric segment 110 is composed of multiple layers of ceramic substrate 111 and multiple layers of internal electrodes 112 stacked alternately in the height direction. The ceramic substrate 111 is made of piezoelectric ceramic material, and the internal electrodes 112 are disposed between adjacent ceramic substrates 111 and are staggered along the height direction.

[0033] Specifically, such as Figure 3As shown, the internal electrode 112 includes a plurality of even-numbered layers of first internal electrodes 112a and a plurality of odd-numbered layers of second internal electrodes 112b. The first internal electrodes 112a and second internal electrodes 112b are alternately arranged in the height direction, thereby forming a multi-layer electrode structure in the stacking direction. The first electrode layer 200 is electrically connected to the even-numbered layers of the multiple piezoelectric segments 110, and the second electrode layer 300 is electrically connected to the odd-numbered layers of the multiple piezoelectric segments 110. The first electrode layer 200 and the second electrode layer 300 can be configured to be directly electrically connected to the internal electrodes 112, or they can be indirectly connected to the internal electrodes 112 through the external electrode 113 described later; the present invention is not limited thereto.

[0034] Therefore, this invention divides the stacked piezoelectric element into multiple piezoelectric segments along its length and places polymer segments between adjacent piezoelectric segments, thus forming a structure in the length direction of the piezoelectric element composed of alternating piezoelectric segments and polymer segments. This achieves segmentation of the piezoelectric element's mechanical structure while maintaining the stacked structure. Because polymer segments are placed between adjacent piezoelectric segments, the mechanical deformation generated by each piezoelectric segment during operation or under impact can be buffered by the polymer segments, thereby reducing stress concentration in the piezoelectric ceramic material along its length. This is beneficial for improving the structural stability and reliability of the stacked piezoelectric device.

[0035] Furthermore, such as Figure 2 and Figure 3 As shown, in this embodiment, each piezoelectric segment 110 has a first end face and a second end face disposed opposite to each other in the width direction, wherein the width direction is a direction orthogonal to both the stacking direction (height direction) and the length direction of the piezoelectric segment 110.

[0036] In the piezoelectric segment 110, a first internal electrode 112a extends along the width of the piezoelectric segment 110, with one end of its electrode port exposed on a first end face to form an electrical connection with the first external electrode 113a (described later); the other end of its electrode port is spaced apart from the second end face to prevent it from contacting the second external electrode 113b (described later). Similarly, one end of the second internal electrode 112b exposes on a second end face to form an electrical connection with the second external electrode 113b (described later); the other end of its electrode port is spaced apart from the first end face to prevent it from contacting the first external electrode 113a (described later). It should be understood that either the first internal electrode 112a or the second internal electrode 112b is electrically connected to one of the first external electrodes 113a and 113b via one of the first end faces and the second end face; conversely, the other of the first internal electrode 112a or the second internal electrode 112b is connected to the other of the first external electrodes 113a and 113b via the other of the first end face and the second end face. It should be understood that the first internal electrodes 112a and 112b do not contact each other; if one is electrically connected to the first external electrode 113a, then the other is electrically connected to the second external electrode 113b. For ease of explanation, in the following text, the first internal electrode 112a forms electrical contact with the first external electrode 113a via the first end face, and the second internal electrode 112b forms electrical contact with the second external electrode 113b via the second end face.

[0037] Each piezoelectric segment 110 is provided with a first external electrode 113a and a second external electrode 113b, which are used to electrically connect the first internal electrodes 112a and the second internal electrodes 112b of each layer within the same piezoelectric segment 110. In one specific embodiment, the first external electrode 113a is attached to the first end face of each piezoelectric segment 110 to electrically connect the first internal electrodes 112a of each piezoelectric segment 110 extending beyond the first end face; the second external electrode 113b is attached to the second end face of each piezoelectric segment 110 to electrically connect the second internal electrodes 112b of each piezoelectric segment 110 extending beyond the second end face.

[0038] In one specific embodiment, a first external electrode 113a is disposed on the uppermost ceramic substrate 111 in the height direction of the piezoelectric segment 110, and a second external electrode 113b is disposed on the lowermost ceramic substrate 111. For example, the first external electrode 113a may include a first main body segment disposed on the uppermost ceramic substrate 111, and a lower folded segment that folds down from one side of the first main body segment along the width direction of the piezoelectric segment 110 and extends to a first end face, the lower folded segment being electrically connected to the exposed electrode port of the first internal electrode 112a.

[0039] The second external electrode 113b includes a second main body segment disposed on the lowest ceramic substrate 111, and an upward folded segment that folds upward from the other side of the second main body segment along the width direction of the piezoelectric segment 110 and extends to the second end face. The upward folded segment is electrically connected to the exposed electrode port of the second internal electrode 112b.

[0040] With the above structural arrangement, the first internal electrodes 112a within the same piezoelectric segment 110 are electrically connected to each other, and the second internal electrodes 112b within the same piezoelectric segment 110 are electrically connected to each other. This facilitates electrical connection with the first electrode layer 200 and the second electrode layer 300.

[0041] Alternatively, the first electrode layer 200 and the second electrode layer 300 may each have a main body segment and a folded segment, and be directly electrically connected to the internal electrodes through the first electrode layer 200 and the second electrode layer 300.

[0042] like Figure 1 As shown, in this embodiment, the first electrode layer 200 and the second electrode layer 300 are respectively attached to opposite sides of the piezoelectric element 100 and electrically connected to the first external electrode 113a and the second external electrode 113b of the plurality of piezoelectric segments 110. In one specific embodiment, the first electrode layer 200 is configured to be attached to the first main body segment of the first external electrode 113a on the upper surface of the piezoelectric element 100 in the height direction; the second electrode layer 300 is disposed on the lower surface of the piezoelectric element 100 and attached to the second main body segment of the second external electrode 113b. In another specific embodiment, the first electrode layer 200 is disposed on the first end face side of the piezoelectric element 100 in the width direction and attached to the first external electrode 113a to form an electrical connection with the first internal electrode 112a; the second electrode layer 300 is disposed on the second end face side and attached to the second external electrode 113b to form an electrical connection with the second internal electrode 112b.

[0043] Specifically, the first electrode layer 200 includes a first contact electrode sheet 210 and a pair of first positioning strips 220. The first positioning strips 220 are used to align the first contact electrode sheet 210 with the upper surface of the piezoelectric element 100, so that the first contact electrode sheet 210 can simultaneously contact the first main body segment of the first external electrode 113a of each piezoelectric segment 110.

[0044] The second electrode layer 300 includes a second contact electrode sheet 310 and a pair of second positioning strips 320. The second positioning strips 320 are used to align the second contact electrode sheet 310 with the lower surface of the piezoelectric element 100, so that the second contact electrode sheet 310 can simultaneously contact the second main body segment of the second external electrode 113b of each piezoelectric segment 110.

[0045] Preferably, electrode layers 200 and 300 are polyimide electrodes.

[0046] Through the above structural arrangement, the electrical connections of multiple piezoelectric segments 110 form a unified driving structure.

[0047] Therefore, multiple piezoelectric segments are each composed of multiple layers of ceramic matrix and multiple layers of internal electrodes stacked alternately. They are uniformly electrically connected through a first electrode layer disposed on the upper surface of the piezoelectric element and a second electrode layer disposed on the lower surface of the piezoelectric element. This makes the electrical connection of multiple piezoelectric segments form an integral driving structure, avoiding the structural complexity caused by wiring multiple independent piezoelectric elements separately. Furthermore, by using the first electrode layer 200 and the second electrode layer 300 disposed on the upper and lower surfaces of the piezoelectric element to be electrically connected to the internal electrode 112, the electric field is mainly formed along the stacking direction of the piezoelectric segments. Compared with piezoelectric composite materials using interdigitated electrode structures, this helps to reduce the uneven distribution of the electric field inside the piezoelectric material, thereby reducing the possibility of generating locally underpolarized regions during polarization.

[0048] In this embodiment, as Figure 1 As shown, a first polymer layer 400 is disposed between the first electrode layer 200 and the upper surface of the piezoelectric element 100, and a second polymer layer 500 is disposed between the second electrode layer 300 and the lower surface of the piezoelectric element 100.

[0049] The first polymer layer 400 and the second polymer layer 500 are used to improve the adhesion between the electrode layer and the piezoelectric element 100 and provide a certain buffering effect during the assembly process, thereby helping to improve the stability of the electrical connection.

[0050] like Figure 3 As shown, this embodiment provides a method for fabricating a stacked piezoelectric device, which includes the following steps.

[0051] First, suitable piezoelectric ceramic material components are selected, and the piezoelectric ceramic raw materials are pre-fired to prepare ceramic powder with the corresponding components. The piezoelectric ceramic material can be either a lead-based piezoelectric ceramic system or a lead-free piezoelectric ceramic system.

[0052] Subsequently, a uniform-thickness ceramic green film is prepared from ceramic powder using a casting process, and internal electrode patterns are formed on the ceramic green film using a screen printing process. The ceramic green film with printed internal electrodes is then cut into multiple ceramic substrates with internal electrodes. The ceramic substrates with printed internal electrodes are then stacked in a predetermined order, and subjected to hot pressing, warm isostatic pressing, debinding, and co-firing treatments to prepare an integral stacked piezoelectric element 100 composed of multiple layers of ceramic substrates 111 and multiple layers of internal electrodes 112.

[0053] The ceramic substrate prepared by the casting method can have a single-layer ceramic substrate thickness ranging from 20 to 120 μm. The total thickness of the stacked piezoelectric element 100 can range from 0.1 mm to 2 mm.

[0054] In this embodiment, a first external electrode 113a for electrically connecting the even-numbered inner electrodes is provided on the uppermost ceramic substrate 111. The first external electrode 113a is flanged so that its lower folded section fits against the first end face and is electrically connected to the end of the first inner electrode 112a. A second external electrode 113b for electrically connecting the odd-numbered inner electrodes is provided on the lowermost ceramic substrate 111. The second external electrode 113b is flanged so that its upper folded section fits against the second end face and is electrically connected to the end of the second inner electrode 112b. By providing external electrodes, subsequent overall electrical connection can be facilitated.

[0055] Next, while keeping the internal electrode stacking direction of the piezoelectric element 100 unchanged, the entire piezoelectric element 100 is divided along a length direction orthogonal to the stacking direction to form a plurality of piezoelectric segments 110 at predetermined intervals.

[0056] Subsequently, polymer material is filled into the gaps formed between adjacent piezoelectric segments 110, and the polymer material is cured to form multiple polymer segments 120 along the length direction, thereby fixing and isolating adjacent piezoelectric segments 110 from each other. The polymer material can be any of thermosetting resins such as epoxy resin, polyester resin, or phenolic resin.

[0057] Then, a first electrode layer 200 is disposed on the upper surface of the piezoelectric element 100, which is electrically connected to the first external electrode 113a, and thus electrically connected to the first internal electrode 112a of the even-numbered layers of the plurality of piezoelectric segments 110; a second electrode layer 300 is disposed on the lower surface of the piezoelectric element 100, which is electrically connected to the second external electrode 113b, and thus electrically connected to the second internal electrode 112b of the odd-numbered layers of the plurality of piezoelectric segments 110. The first electrode layer 200 and the second electrode layer 300 can be disposed in the form of a polyimide electrode film and encapsulated and connected to the piezoelectric element 100 by thermosetting curing.

[0058] After the electrode layer is set, the stacked piezoelectric device can be polarized as needed. The polarization treatment can be performed after the overall stacked piezoelectric element is fabricated, or it can be performed after the polymer segments 120 are divided and formed and the electrode layers are encapsulated, as long as the piezoelectric segments 110 are sufficiently polarized.

[0059] The stacked piezoelectric device of the present invention can be prepared by the above steps. An example of its physical structure is shown below. Figure 4 As shown.

[0060] The above-mentioned casting and stacking method can be used to prepare multilayer piezoelectric ceramic materials. The co-firing technology can effectively reduce polarization and driving voltage to between a few V and 100 V, effectively improving the piezoelectric coefficient while significantly reducing the driving voltage. Since it is almost all-electrode, polarization can be fully and completely achieved.

[0061] In one specific embodiment, the piezoelectric ceramic material is selected from the lead nickel niobate-lead zirconate titanate (PNN-PZT) material system.

[0062] Specifically, PNN-PZT piezoelectric ceramic powder was first used as raw material, and a sintering aid was added before pre-firing. The powder particle size was then controlled by sieving through a 200-mesh sieve. Subsequently, a ceramic green film was prepared using a casting process, and the single-layer thickness of the ceramic green film was approximately 40±3μm.

[0063] After screen printing the internal electrode pattern onto a ceramic green film, the ceramic green film is cut according to the position of the internal electrodes, and the cut ceramic substrates are stacked together. The resulting composite piezoelectric element is then prepared through hot pressing, debinding, and co-firing. Subsequently, the internal electrodes are led out to the upper and lower surfaces of the piezoelectric element by flanging the external electrodes.

[0064] Subsequently, the integral stacked piezoelectric element is divided along its length with 50μm slits to form multiple 350μm wide piezoelectric segments. Polymer material is then filled and cured between adjacent piezoelectric segments to form polymer segments, thus obtaining a segmented piezoelectric element structure.

[0065] Finally, the segmented piezoelectric element is encapsulated and connected to the upper and lower electrode layers. Using a DC power supply, it is polarized for 15 minutes at a room temperature electric field of 2.5 kV / mm (per layer of piezoelectric ceramic) to obtain the stacked piezoelectric device of this embodiment.

[0066] In another specific embodiment, the piezoelectric ceramic material is selected from the PZT-5H material system, and the rest of the preparation process is basically the same as in the above embodiment.

[0067] Specifically, a ceramic green film is prepared by a casting process to form a multi-layer internal electrode structure, and then co-fired to obtain an integrally stacked piezoelectric element. Subsequently, the integral piezoelectric element is divided along its length, and polymer segments are formed between adjacent piezoelectric segments.

[0068] After completing the segmented structure, the piezoelectric element is encapsulated and connected to the upper and lower electrode layers, and polarization treatment is performed under appropriate electric field conditions according to the polarization characteristics of the piezoelectric ceramic material, thereby obtaining the stacked piezoelectric device of this embodiment.

[0069] A cantilever beam structure was used to fix the aforementioned stacked piezoelectric device onto the cantilever beam. By adjusting the acceleration and driving frequency of the cantilever beam, and using a strain acquisition device to measure the strain value of the stacked piezoelectric device in real time, the maximum strain value of the stacked piezoelectric device of this invention was found to exceed 2000 με. The maximum strain value test curve is shown below. Figure 5 As shown, using the same PNN-PZT composition as described above, a multilayer ceramic piezoelectric element with the same structure as CN101547875B was prepared. The strain value was tested using the above method, and the maximum strain value was measured to be 1580 με. A single-layer piezoelectric fiber composite device with the same structure as CN108428783A was tested using the above method, and its maximum strain value was measured to be approximately 1800 με. Therefore, it can be seen that the multilayer piezoelectric device with the above structure of the present invention can effectively enhance the overall flexibility of the material.

[0070] This invention obtains a piezoelectric element by dividing it into segments and filling the spaces between the piezoelectric segments after the integrally stacked piezoelectric element is formed. This fabrication method is highly compatible with existing processes for manufacturing stacked piezoelectric devices, requiring no changes to the internal stacked structure of the piezoelectric segments or the arrangement of the internal electrodes, thus facilitating processing and manufacturing. Furthermore, by setting polymer layers on the upper and lower surfaces of the piezoelectric element and then placing electrode layers on top of them, the adhesion between the electrode layers and the piezoelectric element is improved, thereby enhancing the stability of the electrical connection and reducing the risk of poor contact during assembly or use.

[0071] like Figure 3 As shown, the present invention also prepares piezoelectric elements and subsequent piezoelectric devices through the following steps.

[0072] By selecting a suitable piezoelectric ceramic composition, a piezoelectric ceramic film is prepared by casting. Using interdigitated electrodes (the internal electrodes mentioned above), a multilayer piezoelectric ceramic is prepared. After the positive and negative electrodes of the multilayer ceramic are connected by the side through a ceramic electrode flanging process, they are introduced into the top and bottom layers respectively to obtain a layered multilayer piezoelectric ceramic element.

[0073] According to the requirements of the piezoelectric fiber composite element, the above-mentioned layered multilayer piezoelectric ceramic element is cut to obtain multilayer ceramic fibers. The fiber gaps are filled with polymer adhesive (forming the above-mentioned polymer segments). After a suitable temperature and time, the polymer adhesive has been semi-cured. A suitable polymer adhesive is coated on the surface of the multilayer fibers (forming the above-mentioned polymer layer). Then, the piezoelectric multilayer fiber composite material is stacked with the corresponding upper and lower polyimide electrode films and hot-pressed to obtain the multilayer piezoelectric fiber composite element.

[0074] Furthermore, the piezoelectric ceramic is either a lead-based or lead-free piezoelectric ceramic system.

[0075] Furthermore, the polarization of the multilayer piezoelectric fiber composite element is generally room temperature polarization, and the piezoelectric ceramic material is generally selected from material systems with low coercivity, that is, material components that can be fully polarized at room temperature.

[0076] Furthermore, the piezoelectric multilayer ceramics prepared by the casting method have a single-layer thickness ranging from 20 to 120 μm, with no other size limitations.

[0077] Furthermore, the piezoelectric multilayer ceramics prepared by the casting method have a total thickness ranging from 0.1 mm to 2 mm, with no other size restrictions.

[0078] Furthermore, the width of the polymer between the piezoelectric fibers in the multilayer piezoelectric fiber composite structure layer can be precisely adjusted according to design requirements to prepare piezoelectric fiber composite structure layers with a series of piezoelectric fiber volume fractions, ranging from 0-100%.

[0079] Furthermore, the polymer adhesive is any one of thermosetting resins such as epoxy resin, polyester resin, or phenolic resin.

[0080] The upper and lower polyimide electrodes of the multilayer piezoelectric fiber composite element adopt an all-electrode mode, and are respectively connected to the positive and negative electrodes of the multilayer piezoelectric ceramic fiber. Furthermore, the polarization of the multilayer piezoelectric fiber composite element can be achieved either after the multilayer piezoelectric ceramic is prepared, or after cutting it into multilayer fibers and encapsulating the polyimide electrodes, ensuring sufficient polarization.

[0081] The polarization voltage of the multilayer piezoelectric fiber composite element is related to the thickness of its single-layer ceramic film. The thickness of the single-layer ceramic film can be determined based on the total thickness and number of layers of the fiber composite element. The thickness of the single-layer ceramic film is the total thickness ÷ the number of layers.

[0082] The method for preparing multilayer piezoelectric fiber composite elements provided by this invention combines the advantages of casting multilayer piezoelectric ceramics and piezoelectric fiber composite materials. The multilayer interdigitated electrode structure can effectively reduce the polarization and driving voltage to below 100 V, effectively avoiding the problem of high polarization / driving voltage in traditional methods for preparing piezoelectric fiber composite elements.

[0083] By employing a multilayer ceramic electrode flanging process, followed by cutting, organic material filling, and electrode encapsulation, piezoelectric multilayer fiber composite elements can be fabricated. This allows for full electrode coverage polarization / drive, effectively polarizing while avoiding polarization dead zones. Using a casting process, the piezoelectric multilayers exhibit uniform thickness and precise dimensional control, with single-layer thicknesses ranging from 20-120 μm and total thicknesses from 0.1-2 mm. The cutting-organic material filling process allows for control over the width of the polymer between the multilayer piezoelectric fibers, enabling precise adjustment according to design requirements. This allows for the fabrication of piezoelectric fiber composite structures with a series of adjustable piezoelectric fiber volume fractions, ranging from 0-100%.

[0084] In addition, when fabricating piezoelectric devices, it is necessary to ensure that the dimensions of the multilayer piezoelectric ceramic substrate match the electrodes in the length direction (interdigitated electrode direction), because the machining allowance of the interdigitated electrodes in the length direction is limited, while there is more machining allowance in the width direction.

[0085] When filling the piezoelectric element with polymer after cutting, the amount of filling needs to be appropriate. Too little or too much filling will result in an uneven final device, making it difficult to fit well with the cantilever beam and causing performance loss.

[0086] In addition, too much polymer filling can also lead to poor contact between the piezoelectric element and the outer polyimide film electrode (electrode layer), making it difficult to polarize or drive it by an external electric field.

[0087] The present invention will be described in more detail below, and the following embodiments are not intended to further limit the present invention.

[0088] Example 1 In this embodiment 1, the ceramic material for the piezoelectric segment is lead nickel niobate-lead zirconate titanate-based (Pb(Ni) 1 / 3 Nb 2 / 3 The piezoelectric device is prepared by using a composition of O3-Pb(Zr, Ti)O3, PNN-PZT, and the specific process is as follows.

[0089] 1. Using PNN-PZT piezoelectric ceramic powder as raw material, an appropriate amount of lithium carbonate was added as a sintering aid. After pre-firing, the powder was sieved through a 200-mesh sieve to control the particle size of the ceramic powder. If the material was suitable, a casting process was used to prepare a ceramic green film with a film thickness of 40±3 μm.

[0090] 2. Interdigitated electrodes were fabricated on a ceramic film with a length of 40 mm and a width of 28 mm using screen printing. Multiple layers were stacked, and after hot pressing and warm isostatic pressing, the binder was removed, and the film was co-fired (1000℃, 3 hours) to obtain a sheet-like multilayer piezoelectric segment ceramic composed of alternating layers of ceramic substrate and electrodes. The co-fired ceramics were 0.29 mm and 0.55 mm thick. After post-processing such as flanging, the positive and negative electrodes were connected to the upper and lower surfaces of the ceramic.

[0091] 3. The sheet-like multilayer piezoelectric ceramic segments are cut along their length with a kerf of 50 μm. The cutting distance is adjusted so that the cut multilayer piezoelectric ceramic fibers are 350 μm long. An epoxy resin adhesive is uniformly coated between and on the surface of the multilayer piezoelectric ceramic fibers to prepare PNN-PZT-based piezoelectric ceramic fiber composite materials with dimensions of 36×24.8×0.37 mm and 36×24.8×0.63 mm, with a piezoelectric ceramic fiber volume fraction of approximately 87.5%.

[0092] 4. The piezoelectric ceramic fiber composite material is placed centrally on the upper and lower polyimide electrodes and hot-pressed. After encapsulation, the positive and negative electrodes of the composite material are led out through the two sides in the width direction using wires. Using a DC power supply, the material is polarized for 15 minutes at room temperature under an electric field of 2.5 kV / mm (per layer of piezoelectric ceramic) to complete the fabrication of the stacked piezoelectric device.

[0093] Example 2 In this embodiment 2, the piezoelectric ceramic material used is PZT-5H material, and the piezoelectric device is prepared using the following process.

[0094] 1. Using PZT-5H piezoelectric ceramic powder as raw material, an appropriate amount of lithium carbonate was added as a sintering aid. After pre-firing, the powder was sieved through a 200-mesh sieve to control the particle size of the ceramic powder. If the material was suitable, a casting process was used to prepare a ceramic green film with a film thickness of 100±5 μm.

[0095] 2. Interdigitated electrodes were fabricated on a ceramic film with a length of 40 mm and a width of 28 mm using screen printing. Three layers (two blank layers) and five layers (four blank layers) were stacked respectively. After hot pressing and warm isostatic pressing, the binder was removed and co-fired (1000℃, 3 hours) to obtain multilayer piezoelectric ceramics with thicknesses of 0.38 mm and 0.74 mm. After post-treatment such as flanging, the positive and negative electrodes were connected to the upper and lower surfaces of the ceramic.

[0096] 3. Polarize for 15 minutes at room temperature under an electric field of 2.5 kV / mm (per layer of piezoelectric ceramic).

[0097] 4. Cut the sheet-like multilayer piezoelectric ceramic along its length with a kerf of 80 μm. Adjust the cutting distance to make the multilayer piezoelectric fibers 250 μm. Coat the interlayer piezoelectric fibers and the surface with a layer of epoxy resin to obtain PNN-PZT-based piezoelectric fiber composite structure layers with dimensions of 35.2×24.3×0.46 mm and 35.2×24.3×0.82 mm. The volume fraction of the multilayer fibers is approximately 71.4%.

[0098] 5. The multilayer piezoelectric composite material is placed centrally on the upper and lower polyimide electrodes, and then hot-pressed. After encapsulation, the positive and negative electrodes of the multilayer piezoelectric composite material are led out through the two sides in the width direction by wires to complete the fabrication of the multilayer piezoelectric fiber composite device.

[0099] This invention selects suitable piezoelectric ceramic material components, obtains ceramic films using a casting method, and prepares multilayer piezoelectric ceramics through firing. Further, it utilizes a cutting-casting-encapsulation technique to prepare high-performance multilayer piezoelectric fiber composite structural elements. The multilayer piezoelectric ceramics undergo a ceramic electrode flanging process, connecting the positive and negative electrodes through side connections, and then introducing them into the top and bottom layers respectively to obtain a layered multilayer piezoelectric ceramic element. This layered multilayer piezoelectric ceramic element is then cut to obtain multilayer ceramic fibers, allowing polymer adhesive to form in the fiber gaps. The polymer adhesive, already semi-cured, is heated and coated onto the surface of the multilayer fibers. Then, the piezoelectric multilayer fiber composite material is stacked with corresponding upper and lower polyimide electrode films and subjected to hot pressing and curing to obtain the multilayer piezoelectric fiber composite element.

[0100] The solution of this application has been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of this application. The description of the above embodiments is only for the purpose of helping to understand the method and core ideas of this application. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of this application. Therefore, the content of this specification should not be construed as a limitation of this application.

[0101] Throughout this specification, the terms "an embodiment," "embodiment," or "specific embodiment" refer to a particular feature, structure, or characteristic described in connection with an embodiment that is included in at least one embodiment of this application, but not necessarily in all embodiments. Therefore, the various representations of the phrases "in one embodiment," "in an embodiment," or "in a specific embodiment" in different places throughout this specification do not necessarily refer to the same embodiment. Furthermore, a particular feature, structure, or characteristic of any specific embodiment of this application may be combined with one or more other embodiments in any suitable manner. It should be understood that other variations and modifications of the embodiments described and illustrated herein may be based on the teachings herein and will be considered part of the spirit and scope of this application.

[0102] It should also be understood that one or more of the elements shown in the figures may be implemented in a more separate or more integrated manner, or may even be removed because they are inoperable in certain circumstances or provided because they may be useful for a particular application.

[0103] Furthermore, unless otherwise expressly stated, any arrows in the accompanying drawings should be considered illustrative only and not limiting. Additionally, unless otherwise stated, the term "or" as used herein is generally intended to mean "and / or". Where a term is anticipated to provide a separation or combination capability that is unclear, a combination of components or steps will also be considered as indicated.

Claims

1. A stacked piezoelectric device, characterized in that, include: A piezoelectric element includes a plurality of piezoelectric segments arranged along a length direction and isolated from each other, and polymer segments disposed between adjacent piezoelectric segments and separating adjacent piezoelectric segments along a length direction. Each piezoelectric segment is composed of multiple layers of ceramic substrate and multiple layers of internal electrodes stacked alternately. The electrode ports of the internal electrodes of the even-numbered layers of the piezoelectric segment are exposed in the same direction on one end face of the piezoelectric element, and the electrode ports of the internal electrodes of the odd-numbered layers are exposed in the opposite direction on the other end face of the piezoelectric element. The first electrode layer is electrically connected to the electrode ports of the internal electrodes of the even-numbered layers; as well as The second electrode layer is electrically connected to the electrode ports of the internal electrodes of the odd-numbered layers.

2. The stacked piezoelectric device according to claim 1, characterized in that, The piezoelectric segment further includes a first end face and a second end face located at one end and the other end in the width direction, respectively, wherein the width direction is a direction orthogonal to the stacking direction of the piezoelectric segment; The electrode ports of the internal electrodes of the even-numbered layers are exposed on the first end face, and the electrode ports of the internal electrodes of the odd-numbered layers are exposed on the second end face.

3. The stacked piezoelectric device according to claim 2, characterized in that, The first electrode layer includes a first main body segment disposed on the uppermost ceramic substrate of the piezoelectric segment, and a lower folded segment that folds down from the first main body segment along one side of the piezoelectric segment and extends to the first end face to be electrically connected to the electrode port of the internal electrode of the even-numbered layer in the piezoelectric segment; The second electrode layer includes a second main body segment disposed on the lowest ceramic substrate of the piezoelectric segment, and an upper folded segment that folds upward from the second main body segment along the other side of the piezoelectric segment and extends to the second end face to be electrically connected to the electrode ports of the internal electrodes of the odd-numbered layers in the piezoelectric segment.

4. The stacked piezoelectric device according to claim 2, characterized in that, The piezoelectric element also includes: A first external electrode, disposed on each piezoelectric segment, electrically connects the electrode ports of the even-numbered layers of internal electrodes to each other, and A second external electrode is provided on each piezoelectric segment to electrically connect the electrode ports of the internal electrodes of the odd-numbered layers to each other. The first electrode layer is electrically connected to the internal electrodes of the even-numbered layers through a plurality of first external electrodes, and the second electrode layer is electrically connected to the internal electrodes of the odd-numbered layers through a plurality of second external electrodes.

5. The stacked piezoelectric device according to claim 4, characterized in that, The first external electrode includes a first main body segment disposed on the uppermost ceramic substrate of the piezoelectric segment, and a lower folded segment that folds down from the first main body segment along one side of the piezoelectric segment and extends to the first end face to be electrically connected to the electrode port of the internal electrode of the even-numbered layers in the piezoelectric segment; The second external electrode includes a second main body segment disposed on the lowest ceramic substrate of the piezoelectric segment, and an upper folded segment that folds upward from the second main body segment along the other side of the piezoelectric segment and extends to the second end face to be electrically connected to the electrode port of the internal electrode of the odd-numbered layers in the piezoelectric segment.

6. The stacked piezoelectric device according to any one of claims 1 to 5, characterized in that, A first polymer layer is disposed between the first electrode layer and the piezoelectric element. A second polymer layer is disposed between the second electrode layer and the piezoelectric element.

7. The stacked piezoelectric device according to claim 5, characterized in that, The first electrode layer includes a first contact electrode sheet and a first positioning strip. The first positioning strip is used to align the first contact electrode sheet with the upper surface of the piezoelectric element so as to contact the first body segment of each of the first external electrodes. The second electrode layer includes a second contact electrode sheet and a second positioning strip. The second positioning strip is used to align the second contact electrode sheet with the lower surface of the piezoelectric element to contact the second body segment of each of the second external electrodes.

8. A method for fabricating a stacked piezoelectric device as described in any one of claims 1 to 7, characterized in that, include: Fabrication of piezoelectric elements consisting of alternating layers of multilayer ceramic substrates and multilayer internal electrodes; The piezoelectric element is divided into multiple piezoelectric segments along a length direction orthogonal to the stacking direction. The electrode ports of the internal electrodes of the even-numbered layers in the piezoelectric segments are exposed in the same direction on one end face of the piezoelectric element, while the electrode ports of the internal electrodes of the odd-numbered layers are exposed in the opposite direction on the other end face of the piezoelectric element. A polymer segment is filled between adjacent piezoelectric segments to isolate the adjacent piezoelectric segments from each other in the length direction; Electrically connect the electrode ports of the first electrode layer to the internal electrodes of the even-numbered layers; and The second electrode layer is electrically connected to the electrode ports of the internal electrodes of the odd-numbered layers.

9. The method for preparing a stacked piezoelectric device according to claim 8, characterized in that, In the fabrication of the piezoelectric element, a first external electrode is formed on the uppermost ceramic substrate and electrically connected to the electrode ports of the even-numbered internal electrodes, and a second external electrode is formed on the lowermost ceramic substrate and electrically connected to the electrode ports of the odd-numbered internal electrodes.

10. The method for preparing a stacked piezoelectric device according to claim 8 or 9, characterized in that, The step of filling polymer segments between adjacent piezoelectric segments includes: The polymer material is filled into the gap between adjacent piezoelectric segments, and the polymer material is cured to form polymer segments, thereby fixing and isolating adjacent piezoelectric segments from each other in the length direction.

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