Composite material for constituting stress release layer and method for manufacturing the same, and integrated co-fired piezoelectric ceramic actuator and method for manufacturing the same

Abstract

This invention provides a composite material for constituting a stress-relieving layer and its preparation method, as well as an integrated co-fired piezoelectric ceramic actuator and its preparation method. The method for preparing the composite material for constituting the stress-relieving layer includes: ball milling Bi₂O₃, Fe₂O₃, Pb₃O₄, and TiO₂ to obtain precursor powder; heat-treating the precursor powder to obtain BiFeO₃-PbTiO₃ ceramic powder; and mixing the BiFeO₃-PbTiO₃ ceramic powder with an internal electrode metal slurry to obtain the composite material. This invention utilizes the negative thermal expansion characteristics of BF-PT ceramics to effectively control the internal stress of the actuator. The elasticity of the internal electrode metal ensures the stress-relieving capability of the composite material used as a stress-relieving layer, while its high density creates an effective moisture barrier.

Description

Technical Field

[0001] This invention relates to the field of piezoelectric ceramic device technology, and more specifically, to a composite material for constituting a stress relief layer and its preparation method, and an integrally co-fired piezoelectric ceramic actuator and its preparation method. Background Technology

[0002] Multilayer co-fired piezoelectric ceramic actuators are composed of stacked piezoelectric ceramic dielectric layers and cross-metal electrodes. Utilizing their piezoelectric inverse effect characteristics, they can exhibit micro- and nano-scale displacement. Unlike traditional hydraulic and electromagnetic actuators, piezoelectric ceramic actuators have a wide range of applications in micro-actuation and high-precision instruments due to their nanometer-level resolution, ultrafast response rate, ease of integration, and strong anti-interference capabilities.

[0003] Existing piezoelectric actuators are typically formed by stacking multiple components and then co-firing them together. In order to adapt to applications with large displacement and long stroke, the piezoelectric actuators are stacked to a height of tens of millimeters or even hundreds of millimeters. When the actuator is powered on, the internal part of the actuator, especially the inner electrode layer or the weaker structural parts of the actuator, is prone to tensile deformation and cracking, which in turn creates cracks inside the actuator. After long-term service, due to the cracks inside the piezoelectric actuator, moisture and other substances from the external environment can easily penetrate into the piezoelectric actuator, leading to its failure.

[0004] Therefore, in order to solve the above problems, how to develop an integrated co-fired piezoelectric ceramic actuator that is resistant to water vapor erosion is an important technical problem that needs to be solved in this field. Summary of the Invention

[0005] The main objective of this invention is to provide a composite material for constituting a stress relief layer and its preparation method, as well as an integrated co-fired piezoelectric ceramic actuator and its preparation method, in order to solve the problem that the existing integrated co-fired piezoelectric ceramic actuator is prone to cracking and failure.

[0006] To achieve the above objectives, a first aspect of the present invention provides a method for preparing a composite material for constituting a stress-relieving layer, comprising: step R1, ball milling Bi2O3, Fe2O3, Pb3O4 and TiO2 to obtain precursor powder; step R2, heat-treating the precursor powder to obtain BiFeO3-PbTiO3 ceramic powder; and step R3, mixing the BiFeO3-PbTiO3 ceramic powder with an internal electrode metal paste at a weight ratio of (60~75):(25~35) to obtain the composite material.

[0007] Further, in step R3, the weight ratio of BiFeO3-PbTiO3 ceramic powder to internal electrode metal paste is (63~66):(34~37).

[0008] Furthermore, in step R2, the molar ratio of BiFeO3 to PbTiO3 is (0.6~0.9):(0.4~0.1).

[0009] Further, in step R1, the ball milling speed is 500±50 rpm and the time is 12±2 h; in step R2, the heat treatment holding temperature is 850±20℃ and the time is 1 h~2 h.

[0010] Furthermore, in step R3, the mixing is carried out by ball milling, with a milling speed of 400 rpm to 500 rpm and a time of 12 h to 24 h.

[0011] Furthermore, in step R3, the internal electrode metal paste is a silver-palladium paste, and the weight ratio of silver to palladium in the silver-palladium paste is 90:10.

[0012] A second aspect of the present invention provides a composite material for constituting a stress relief layer, which is composed of BiFeO3-PbTiO3 ceramic powder and internal electrode metal paste, wherein the weight ratio of BiFeO3-PbTiO3 ceramic powder to internal electrode metal paste is (60~75):(25~35).

[0013] A third aspect of the present invention provides a method for preparing an integrated co-fired piezoelectric ceramic actuator, comprising the following steps: S1. providing a plurality of ceramic diaphragms; S2. coating the surface of the ceramic diaphragms with an inner electrode metal paste to form an inner electrode metal diaphragm; S3. coating the surface of the inner electrode metal diaphragm with another ceramic diaphragm; S4. repeating steps S2 and S3 until multiple alternating layers of ceramic diaphragms and inner electrode metal diaphragms are formed; S5. coating the surface of the uppermost ceramic diaphragm in step S4 with the aforementioned composite material to form a stress relief preparative layer; S6. further coating the surface of the inner electrode metal diaphragm with the composite material. A ceramic film is coated on the surface of the stress relief preparation layer, so that the stress relief preparation layer is adjacent to the two adjacent ceramic films above and below; S7. Continue to repeat steps S2 and S3 to form multiple alternating layers of ceramic films and inner electrode metal films on the surface of the ceramic film on the upper side of the stress relief preparation layer, thus forming a stacked blank; S8. Cut the stacked blank to form multiple stacked components; S9. Stack the multiple stacked components and perform heat treatment and external electrode to finally obtain an integrated co-fired piezoelectric ceramic actuator containing a ceramic dielectric layer, an inner electrode metal layer and a stress relief layer.

[0014] Furthermore, in the integrated co-fired piezoelectric ceramic actuator, the number of stacked components is 15 to 20; in each stacked component, the number of ceramic dielectric layers is 24 to 29.

[0015] Furthermore, in step S9, before heat treatment of the stacked multiple stacked components, the steps of stacking and isostatic pressing of the multiple stacked components are included; the heat treatment steps of the stacked multiple stacked components include debinding and sintering, the debinding temperature is 600℃~700℃, the debinding time is 8h~15h; the sintering temperature is 950℃~1050℃, and the sintering time is 2h~8h.

[0016] A fourth aspect of the present invention provides an integrated co-fired piezoelectric ceramic actuator comprising a plurality of stacked assemblies stacked along the vertical direction. Each stacked assembly comprises a stress relief layer made of the aforementioned composite material, a multilayer ceramic dielectric layer, and a multilayer internal electrode metal layer. The stress relief layer is bonded between two adjacent ceramic dielectric layers and is in contact only with the ceramic dielectric layer. The remaining ceramic dielectric layers and multilayer internal electrode metal layers are arranged alternately in pairs.

[0017] Furthermore, the stacked assembly has mutually perpendicular length and width directions, and the stress relief layer has two parts, which are formed between two adjacent ceramic dielectric layers and arranged opposite to each other along the width direction.

[0018] Furthermore, in the length direction, the outer edges of both parts of the stress relief layer are flush with the outer edge of the ceramic dielectric layer, and the lengths of both parts of the stress relief layer are equal to the length of the ceramic dielectric layer.

[0019] Furthermore, in the width direction, the ratio of the total width of the two parts of the stress relief layer to the width of the stacked assembly is 30% to 50%, and the widths of the two parts of the stress relief layer are equal.

[0020] Furthermore, the thickness of a single ceramic dielectric layer is 50μm~100μm, and the thickness of the stress relief layer is 100μm~200μm; the integrated co-fired piezoelectric ceramic actuator also includes multiple internal electrode metal layers with a thickness of 1~10μm.

[0021] The fifth aspect of the present invention provides an integrated co-fired piezoelectric ceramic actuator, comprising a plurality of stacked assemblies stacked along the vertical direction. Each stacked assembly includes two or more stress relief layers made of the aforementioned composite material, multiple ceramic dielectric layers, and multiple internal electrode metal layers. Each stress relief layer is individually bonded between two adjacent ceramic dielectric layers, and each stress relief layer is in contact only with the ceramic dielectric layer. The remaining ceramic dielectric layers and multiple internal electrode metal layers are arranged alternately in pairs.

[0022] The technical solution of this invention has the following technical effects:

[0023] (1) Through a carefully designed composite material preparation process, BiFeO3-PbTiO3 ceramic powder (BF-PT) with a negative coefficient of thermal expansion is mixed with internal electrode metal slurry in a specific ratio to form a uniformly dispersed slurry. This process not only ensures precise control of the material composition, but also optimizes the particle size and lattice structure of the ceramic material through ball milling and heat treatment, enabling BF-PT ceramic to generate prestress during cooling. The addition of internal electrode metal provides good plasticity and elasticity, which provides favorable conditions for the subsequent solid solution of the stress relief layer and the ceramic dielectric layer.

[0024] (2) The negative thermal expansion characteristics of BF-PT ceramics can effectively regulate the internal stress of the actuator and avoid crack formation. The elasticity of the inner electrode metal ensures the stress relief capability of the composite material used as a stress relief layer, while its high density creates an effective water vapor barrier.

[0025] (3) The actuator fabrication method utilizes an integrated co-firing process to tightly bond the stress relief layer made of composite material with the multilayer ceramic dielectric layer stacked assembly, achieving simultaneous sintering and solution treatment of each layer. This method not only simplifies the production process and reduces costs but also ensures good adhesion and performance consistency between the stress relief layer and the ceramic dielectric layer at the interface. In particular, the integrated co-firing process enables the stress relief layer and the ceramic dielectric layer to be tightly integrated, enhancing the interfacial bonding strength between the layers and improving the stability and reliability of the overall structure.

[0026] (4) The completed piezoelectric actuator stack assembly, wherein the stress relief layer is integrally co-fired with the stack assembly, and the silver-palladium metal in the stress relief layer encapsulates the BF-PT ceramic inside, and the stress relief layer and the ceramic dielectric layer undergo solid solution reaction. When the piezoelectric ceramic actuator is energized, it expands and contracts along the height direction based on the inverse piezoelectric effect. Due to the deformation characteristics of the silver-palladium metal, the stress relief layer is stretched and undergoes elastic deformation. The stress relief layer can alleviate the internal stress of the piezoelectric actuator, avoid the generation of cracks, effectively prevent moisture from entering the actuator, and is suitable for working in environments below zero degrees Celsius. Compared with traditional piezoelectric actuators, the integrally co-fired piezoelectric ceramic actuator provided by this invention can adapt to lower temperature working environments, improving the actuator's operating capability and service life under extreme conditions. Attached Figure Description

[0027] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0028] Figure 1A three-dimensional structural schematic diagram of the integrated co-fired piezoelectric ceramic actuator provided by the present invention;

[0029] Figure 2 This is a schematic diagram of the microstructure of the stress relief layer 30 in the integrated co-fired piezoelectric ceramic actuator provided by the present invention, wherein, Figure 2 (a) shows a schematic diagram of the grains in the stress relief layer; Figure 2 (b) shows the direction of internal stress in the BF-PT ceramic grains within the stress relief layer;

[0030] Figure 3 This is a process flow diagram for preparing BiFeO3-PbTiO3 and obtaining the composite material in this invention;

[0031] Figure 4 This is a schematic diagram showing the arrangement of a ceramic diaphragm and a metal internal electrode diaphragm.

[0032] Figure 5 A schematic diagram showing the setup of the ceramic diaphragm and stress relief preparatory layer;

[0033] Figure 6 This is a schematic diagram of the structure of the stacked raw blank provided by the present invention;

[0034] Figure 7 This is a schematic diagram of the structure of the stacked body provided by the present invention;

[0035] Figure 8 A schematic diagram of the integrated co-fired piezoelectric ceramic actuator provided by the present invention;

[0036] Figure 9 This is a process flow diagram of the fabrication process of the integrated co-fired piezoelectric ceramic actuator in this invention;

[0037] The above figures include the following reference numerals:

[0038] 10. Ceramic dielectric layer; 20. Inner electrode metal layer; 30. Stress relief layer; 40. Outer electrode metal layer; 50. Positive electrode line; 60. Negative electrode line. Detailed Implementation

[0039] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the embodiments.

[0040] As described in the background art, existing piezoelectric ceramic actuators suffer from poor performance due to the unavoidable intrusion of moisture into the actuator interior caused by cracks. To address this technical problem, a first aspect of the present invention provides a method for preparing a composite material for constituting a stress-relieving layer, comprising: step R1, ball milling Bi2O3, Fe2O3, Pb3O4, and TiO2 to obtain precursor powder; step R2, heat-treating the precursor powder to obtain BiFeO3-PbTiO3 ceramic powder; and step R3, mixing the BiFeO3-PbTiO3 ceramic powder with an internal electrode metal slurry at a weight ratio of (60~75):(25~35) to obtain the composite material.

[0041] This invention employs a meticulously designed composite material preparation process to mix BiFeO3-PbTiO3 ceramic powder (BF-PT) with a negative coefficient of thermal expansion with an internal electrode metal slurry in a specific ratio, forming a uniformly dispersed slurry. This process not only ensures precise control of the material composition but also optimizes the particle size and lattice structure of the ceramic material through ball milling and heat treatment. This allows the BF-PT ceramic to generate prestress during cooling, while the addition of the internal electrode metal provides good plasticity and elasticity, creating favorable conditions for the subsequent solid solution treatment of the stress relief layer and the ceramic dielectric layer.

[0042] In step R3, the preferred weight ratio of BiFeO3-PbTiO3 ceramic powder to internal electrode metal slurry is (63~66):(34~37). In the resulting composite material, the ceramic itself has a prestress of outward expansion, and the internal electrode metal, wrapped around the BF-PT ceramic, provides a suitable pre-tightening force. Mixing the two in this weight ratio is more conducive to their synergistic effect.

[0043] In step R2, the preferred molar ratio of BiFeO3 to PbTiO3 is (0.6~0.9):(0.4~0.1), which enables the resulting composite material to be used as a stress relief layer material and better avoid cracking.

[0044] In step R1, the preferred ball milling speed is 500±50 rpm and the time is 12±2 h, so as to promote more thorough refinement of each raw material powder; in step R2, the preferred heat treatment holding temperature is 850±20℃ and the time is 1h~2h, so as to further optimize the growth of ceramic grains.

[0045] In step R3, in order to obtain a composite slurry with better uniform dispersion and good rheological properties, and thus form a composite material with a denser structure and more complete functions, it is preferable to mix by ball milling, with a ball milling speed of 400 rpm to 500 rpm and a time of 12 h to 24 h.

[0046] In step R3, the preferred internal electrode metal paste is a silver-palladium paste, with a silver to palladium weight ratio of 90:10. In practical applications, the dispersion medium for the internal electrode metal paste can be ethanol and / or deionized water.

[0047] In practical applications, the preferred particle size of the obtained BiFeO3-PbTiO3 ceramic powder is 0.5μm~1.0μm, which enables the paste formed after mixing with silver-palladium paste to be printed more stably, forming a composite material with more complete functions, and serving as a stress relief layer to significantly enhance the structural integrity and working stability of the obtained actuator.

[0048] A second aspect of the present invention provides a composite material for constituting a stress-relieving layer, comprising a mixture of BiFeO3-PbTiO3 ceramic powder and an internal electrode metal slurry, wherein the weight ratio of BiFeO3-PbTiO3 ceramic powder to internal electrode metal slurry is (60~75):(25~35). The negative thermal expansion characteristics of the BF-PT ceramic effectively regulate the internal stress of the actuator, preventing crack formation. The elasticity of the internal electrode metal ensures the stress-relieving capability of the composite material used as a stress-relieving layer, while its high density creates an effective moisture barrier.

[0049] A third aspect of the present invention provides a method for preparing an integrated co-fired piezoelectric ceramic actuator, comprising the following steps: S1. providing a plurality of ceramic diaphragms; S2. coating the surface of the ceramic diaphragms with an inner electrode metal paste to form an inner electrode metal diaphragm; S3. coating the surface of the inner electrode metal diaphragm with another ceramic diaphragm; S4. repeating steps S2 and S3 until multiple alternating layers of ceramic diaphragms and inner electrode metal diaphragms are formed; S5. coating the surface of the uppermost ceramic diaphragm in step S4 with the aforementioned composite material to form a stress relief preparative layer; S6. further coating the surface of the inner electrode metal diaphragm with the composite material. A ceramic film is coated on the surface of the stress relief preparation layer, so that the stress relief preparation layer is adjacent to the two adjacent ceramic films above and below; S7. Continue to repeat steps S2 and S3 to form multiple alternating layers of ceramic films and inner electrode metal films on the surface of the ceramic film on the upper side of the stress relief preparation layer, thus forming a stacked blank; S8. Cut the stacked blank to form multiple stacked components; S9. Stack the multiple stacked components and perform heat treatment and external electrode to finally obtain an integrated co-fired piezoelectric ceramic actuator containing a ceramic dielectric layer, an inner electrode metal layer and a stress relief layer.

[0050] By employing an integrated co-firing process, the stress-relieving layer made of composite materials is tightly bonded to a multi-layer ceramic dielectric stack assembly, achieving simultaneous sintering and solution treatment of each layer. This method not only simplifies the production process and reduces costs but also ensures good adhesion and performance consistency between the stress-relieving layer and the ceramic dielectric layer at the interface. In particular, the integrated co-firing process ensures a tight fusion between the stress-relieving layer and the ceramic dielectric layer, enhancing the interfacial bonding strength between layers and improving the overall structural stability and reliability. To avoid ambiguity, the "stress-relieving preparatory layer" in the above preparation method, after heat treatment, forms the "stress-relieving layer" in the integrated co-fired piezoelectric ceramic actuator.

[0051] Furthermore, in the integrated co-fired piezoelectric ceramic actuator, the number of stacked components is 15-20; in each stacked component, the number of ceramic dielectric layers is 24-29. In the actuator stacked component provided by this invention, if the number of stress relief layers in the actuator is too large, adjacent stress relief layers will squeeze and consume part of the displacement of the ceramic dielectric layer, thus failing to effectively release stress. Conversely, if the number of stress relief layers is too small, after applying an electric field, the excessive number of dielectric layers will cause excessive stress and lead to cracking. Based on this, the above-mentioned arrangement of ceramic dielectric layers was optimized through extensive experiments, and stress relief layers were also included to achieve a more significant stress relief and moisture isolation effect.

[0052] Furthermore, in step S9, before heat treatment of the stacked multiple stacked components, the steps of stacking and isostatic pressing of the multiple stacked components are included; the heat treatment steps of the stacked multiple stacked components include debinding and sintering.

[0053] In practical applications, the preferred debinding temperature is 600℃~700℃, and the debinding time is 8h~15h; the sintering temperature is 950℃~1050℃, and the sintering time is 2h~8h. The preferred sintering temperature, as described above, promotes the formation of a more uniform structure between the obtained BiFeO3-PbTiO3 ceramic powder and the silver-palladium alloy, thereby more effectively releasing the internal stress of the actuator during its application as a stress-relieving layer material.

[0054] A fourth aspect of the present invention provides an integrated co-fired piezoelectric ceramic actuator comprising a plurality of stacked assemblies stacked along the vertical direction. Each stacked assembly comprises a stress relief layer made of the aforementioned composite material, a multilayer ceramic dielectric layer, and a multilayer internal electrode metal layer. The stress relief layer is bonded between two adjacent ceramic dielectric layers and is in contact only with the ceramic dielectric layer. The remaining ceramic dielectric layers and multilayer internal electrode metal layers are arranged alternately in pairs.

[0055] As previously stated, this invention provides a stress-relieving layer made of composite material within the stacked assembly of a piezoelectric ceramic actuator. Because this stress-relieving layer includes a composite material with a negative coefficient of thermal expansion, the composite material, due to its own pre-stress and the elasticity of the metallic material, can achieve stress relief. Simultaneously, it can prevent the formation of microcracks (such as...) inside the piezoelectric ceramic actuator. Figure 1 It can prevent moisture intrusion; and because it does not have a large-area foreign protective layer, it can be used normally in sub-zero environments.

[0056] The stress relief layer provided by this invention involves mixing a BiFeO3-PbTiO3 (abbreviated as "BF-PT") ceramic material with a negative thermal expansion coefficient into a silver-palladium slurry in a certain proportion. When the mixing proportion exceeds 60%, the conductivity almost disappears. This mixed slurry is then used as the stress relief layer material to fill the stress relief layer positions of an integrally co-fired piezoelectric ceramic actuator (e.g., ...). Figure 2 (a)). After sintering, the stress relief layer will dissolve together with the actuator's dielectric layer at the contact interface. (The stress relief layer dissolves and bonds with the ceramic dielectric layer after sintering. When the actuator works, the stress relief layer is stretched and deformed, releasing internal stress. The stress relief layer is passively stretched and deformed, and in addition, the stress relief layer itself is easy to deform, exhibiting the elastic deformation characteristics of silver-palladium metal. Furthermore, because BF-PT ceramic has a negative coefficient of thermal expansion, the BF-PT ceramic powder will undergo volume expansion during the cooling process of sintering. After sintering, there will be an outward expansion pre-stress (such as...) Figure 2 In (b), this prestress will exert a squeezing effect on the surrounding metal layer and actuator dielectric layer. Before the actuator applies the driving voltage, the metal internal electrode and BF-PT ceramic inside the stress relief layer material are in a state of dynamic equilibrium; after the driving voltage is applied to the piezoelectric ceramic actuator, the stress relief layer is passively subjected to tensile deformation and is in a tensile state. The BF-PT ceramic itself has outward prestress, and the metal is more easily deformed. Therefore, the piezoelectric ceramic actuator proposed in this invention, due to the composite stress relief layer, allows the internal stress of the piezoelectric ceramic actuator to be released when the stress relief layer is subjected to tensile deformation during operation, avoiding the generation of cracks. In addition, the metal's encapsulation and protection of the ceramic effectively isolates moisture, enabling it to work normally in low-temperature environments such as sub-zero temperatures and humid environments.

[0057] The completed piezoelectric actuator stack assembly, in which the stress relief layer is integrally co-fired with the stack assembly, has silver-palladium metal in the stress relief layer encapsulating the BF-PT ceramic, resulting in a solid solution reaction between the stress relief layer and the ceramic dielectric layer. When the piezoelectric ceramic actuator is energized, based on the inverse piezoelectric effect, the ceramic actuator expands and contracts along its height. Due to the deformation characteristics of silver-palladium metal, the stress relief layer undergoes elastic deformation under tension. The stress relief layer can alleviate the internal stress of the piezoelectric actuator, preventing crack formation and effectively preventing moisture intrusion into the actuator, making it suitable for operation in sub-zero environments. Compared to traditional piezoelectric actuators, the integrally co-fired piezoelectric ceramic actuator provided by this invention is not only waterproof and moisture-proof but also adaptable to lower temperature operating environments, improving the actuator's operational capability and service life under extreme conditions.

[0058] In several more preferred embodiments, to avoid cracking and thus better alleviate stress and isolate moisture, it is preferable that: the stacked assembly has mutually perpendicular length and width directions; the stress relief layer has two parts, which are formed between two adjacent ceramic dielectric layers and arranged opposite to each other along the width direction. Furthermore, in the length direction, the outer edges of both parts of the stress relief layer are flush with the outer edges of the ceramic dielectric layers, and the lengths of both parts are equal to the lengths of the ceramic dielectric layers. Even further, in the width direction, the ratio of the total width of the two parts of the stress relief layer to the width of the stacked assembly is 30% to 50%, and the widths of the two parts of the stress relief layer are equal.

[0059] In practical applications, the stress relief layer is positioned between the 15th and 19th ceramic dielectric layers. Furthermore, the thickness of a single ceramic dielectric layer is 50μm to 100μm, and the thickness of the stress relief layer is 100μm to 200μm. The integrated co-fired piezoelectric ceramic actuator also includes multiple internal electrode metal layers with a thickness of 1 to 10μm. This range of stress relief layer thickness allows for sufficient stress relief space while better maintaining the response speed and accuracy of the actuator stack assembly.

[0060] The fifth aspect of the present invention provides an integrated co-fired piezoelectric ceramic actuator, comprising a plurality of stacked assemblies stacked along the vertical direction. Each stacked assembly includes two or more stress relief layers made of the aforementioned composite material, multiple ceramic dielectric layers, and multiple internal electrode metal layers. Each stress relief layer is individually bonded between two adjacent ceramic dielectric layers, and each stress relief layer is in contact only with the ceramic dielectric layer. The remaining ceramic dielectric layers and multiple internal electrode metal layers are arranged alternately in pairs.

[0061] The present application will be further described in detail below with reference to specific embodiments, which should not be construed as limiting the scope of protection claimed in the present application.

[0062] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0063] Example 1

[0064] Fabrication of a monolithic sintered piezoelectric ceramic actuator:

[0065] First, the composite material used in the stress relief layer 30 is prepared:

[0066] (R1) Accurately weigh the required raw material powder and prepare 2 mol of 0.7BiFeO3-0.3PbTiO3 using Bi2O3, Fe2O3, Pb3O4, and TiO2. Transfer the prepared powder to a ball mill jar, using anhydrous ethanol as the dispersion medium. Start the ball mill and control the rotation speed at 500 r / min, continuously grinding for 12 hours to achieve thorough fineness. Pour the slurry obtained from the first ball milling into a clean tray and dry it completely in an oven. After the alcohol has evaporated, manually assisted pulverize the dry powder.

[0067] (R2) The fine powder sample was then sent into a high-temperature sintering furnace, and a solid-state reaction was carried out at a temperature of 850°C for 1-2 hours to synthesize 0.7BiFeO3-0.3PbTiO3 (BF-PT) material with a particle size of 1 μm.

[0068] (R3) The prepared BF-PT ceramic powder is uniformly mixed with the pre-selected metal internal electrode silver-palladium paste (Ag90Pd10). Based on the total weight of the mixture as 100%, the weight ratio of BF-PT ceramic powder is 65% and the weight ratio of silver-palladium paste (anhydrous ethanol as the dispersion medium) is 35%. The two are fully mixed by ball milling (450 rpm, 20 h) to finally obtain a uniform stress relief layer filling slurry, which is the composite material used to form the stress relief layer 30.

[0069] The process diagram for preparing BiFeO3-PbTiO3 ceramic powder and then obtaining the composite material in the above process is shown below. Figure 3 .

[0070] Then, the integrated co-fired piezoelectric ceramic actuator was fabricated:

[0071] (S1) Provides multiple ceramic films (specifically, 80 μm thick PbTiZrO3 ceramic films).

[0072] (S2) First, the internal electrode metal paste is printed using the aforementioned ceramic film (which forms a ceramic dielectric layer 10 after subsequent sintering, hereinafter the same), so as to gradually perform alternating printing of the internal electrode metal paste and stacking of the ceramic film. Specifically, as follows... Figure 4 As shown, an inner electrode metal paste is printed on the ceramic film to form an inner electrode metal film (which forms an inner electrode metal layer 20 with a thickness of 2~5μm after subsequent sintering, the same below).

[0073] (S3) Then, another ceramic film is coated on the surface of the internal electrode metal film.

[0074] (S4) Then, rotate the ceramic diaphragm and the inner electrode metal diaphragm (or inner electrode screen) 180° to ensure that the printed inner electrodes can be cross-aligned. Continue to stack the ceramic diaphragm and print the metal inner electrode diaphragm using a pressure of 100 kg (i.e., repeat steps S2 and S3 above) to form a cross-aligned inner electrode structure.

[0075] (S5) After the 15-layer ceramic membrane is laminated, as follows: Figure 5 As shown, the composite material printed on the surface of the 15th ceramic diaphragm is dried to form a stress relief preparation layer. This stress relief preparation layer includes two parts, which are located on both sides of the 15th ceramic diaphragm along the width direction. In the length direction, the outer edges of both parts are flush with the outer edge of the ceramic diaphragm, and the length of both parts is equal to the length of the ceramic diaphragm. In the width direction, taking the width of the ceramic diaphragm as 100%, the total width of the two parts accounts for 40%, and the widths of the two parts are equal (this stress relief preparation layer forms a stress relief layer 30 with a thickness of 150 μm after subsequent sintering).

[0076] (S6) Then, a ceramic film is applied to the surface of the stress relief preparation layer, so that the stress relief preparation layer is adjacent to the two adjacent ceramic films.

[0077] (S7) Next, continue printing 11 layers of ceramic film and corresponding internal electrode metal film. Finally, a structure like this can be fabricated. Figure 6 The stacked green body shown contains 27 ceramic films and a stress relief preparatory layer (which, after sintering, forms 27 ceramic dielectric layers 10 and a stress relief layer 30).

[0078] (S8) After cutting the stacked blank obtained by the above overprinting, multiple stacked components are formed.

[0079] (S9) Seventeen stacked components are arranged and stacked together in sequence, and then stacked using a stacking press at a pressure of 700N to form the shape of the actuator stack blank; then isostatic pressing is applied to the stack blank at 1500Bar; finally, after debinding and sintering (1000℃×5h), the final structure is obtained as shown. Figure 7 The stacked body shown has a total thickness of 36 mm. The sintered stacked body needs to be ground to achieve specified dimensions (such as 3×3 mm, 5×5 mm, and 7×7 mm; in this embodiment 1, 5×5 mm is used as an example). Subsequently, an external electrode metal layer 40 is plated onto the electrode surface; and positive electrode wire 50 and negative electrode wire 60 are welded onto this electrode layer. Finally, encapsulation and polarization treatment are completed, ultimately forming a stacked body as shown. Figure 8 The piezoelectric ceramic actuator product shown has a multi-layer integrated co-fired structure, and then undergoes subsequent testing.

[0080] The above Figure 7 The stacked body obtained by sintering shown includes multiple stacked components.

[0081] The fabrication process diagram of the above-mentioned integrated co-fired piezoelectric ceramic actuator is shown below. Figure 9 .

[0082] Example 2

[0083] Fabrication of an integrated co-fired piezoelectric ceramic actuator:

[0084] The only difference between this embodiment and Embodiment 1 is that, in the process of preparing the composite material used to form the stress relief layer 30, the weight ratio of BF-PT ceramic powder is changed to 75% and the weight ratio of silver-palladium paste is changed to 25%, with the total weight of the mixture being 100%.

[0085] Examples 3 to 7

[0086] The differences between Examples 3 to 7 and Example 1 are only in the following aspects: in step (S7) of preparing the integrated co-fired piezoelectric ceramic actuator, the number of ceramic diaphragms and corresponding internal electrode metal diaphragms subsequently set are different; and in step (S9), the number of stacked components is different. See Table 2 for details.

[0087] Comparative Example 1

[0088] Fabrication of an integrated co-fired piezoelectric ceramic actuator:

[0089] The only difference between this comparative example and Example 1 is that, in the process of preparing the composite material used to form the stress relief layer 30, the weight ratio of BF-PT ceramic powder is changed to 40% and the weight ratio of silver-palladium paste is changed to 60%, with the total weight of the mixture being 100%.

[0090] Comparative Example 2

[0091] Fabrication of an integrated co-fired piezoelectric ceramic actuator:

[0092] The only difference between this comparative example and Example 1 is that, in the process of preparing the composite material used to form the stress relief layer 30, the weight percentage of BF-PT ceramic powder is changed to 85% and the weight percentage of silver-palladium paste is changed to 15%, based on the total weight of the mixture as 100%.

[0093] At 150V, the leakage current and displacement of the piezoelectric ceramic actuators obtained in each embodiment and comparative example were tested, and the results are shown in Tables 1 and 2 below.

[0094] Table 1 below can be obtained from Examples 1 and 2 and Comparative Examples 1 and 2.

[0095] Table 1

[0096]

[0097] As shown in Table 1, if the silver-palladium paste content is too low, the silver-palladium metal cannot uniformly fill the spaces between BF-BT grains after sintering. When voltage is applied, there is insufficient silver-palladium metal to provide elasticity, so the stress-relief layer will still crack, failing to achieve the effect of preventing moisture intrusion. Conversely, if the silver-palladium paste content is too high, there will be too little BF-BT material with a negative coefficient of thermal expansion after sintering, resulting in insufficient compressive stress on the silver-palladium metal portion. Therefore, when voltage is applied, the stress-relief layer will still crack, failing to achieve the effect of preventing moisture intrusion.

[0098] Based on the comprehensive experimental results, the optimal silver-palladium paste content of about 35% showed the best effect. The stress relief layer proposed in this invention can not only ensure sufficient stress relief without cracking the ceramic, but also prevent moisture intrusion.

[0099] Table 2 can be obtained from Examples 1 and Examples 3 to 7.

[0100] Table 2

[0101]

[0102] Table 2 shows that a stress relief layer is placed for every certain number of dielectric layers. Too many stress relief layers in the actuator will cause adjacent layers to compress and consume some displacement of the dielectric layer, failing to effectively release stress. Too few stress relief layers will result in excessive stress and tearing after an electric field is applied due to the large number of dielectric layers. Based on the experimental results, 24-27 layers can meet the moisture-proof requirements, but placing one stress relief layer at 27 dielectric layers is optimal, avoiding both displacement loss due to excessive layers and tearing due to insufficient layers allowing moisture to enter.

[0103] As can be seen from the above description, the embodiments of the present invention, by setting a special stress relief layer 30 in the actuator, wherein a specific weight ratio of piezoelectric ceramic and silver-palladium alloy work together to achieve effective release of internal stress, while the presence of the silver-palladium alloy ensures the density and waterproofness of the stress relief layer. The resulting piezoelectric ceramic actuator possesses superior performance, can operate normally under harsh environmental conditions, and effectively avoids cracks in the internal dielectric layer caused by stress concentration, as well as electrical breakdown caused by moisture intrusion.

[0104] It should be noted that the terms "first," "second," etc., used in the specification and claims of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such terms can be used interchangeably where appropriate so that the embodiments of this application described herein can be implemented, for example, in a sequence other than those described herein.

[0105] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a composite material for constituting a stress-relieving layer, characterized in that, include: Step R1: Bi2O3, Fe2O3, Pb3O4 and TiO2 are ball-milled to obtain precursor powder; Step R2 involves heat-treating the precursor powder to obtain BiFeO3-PbTiO3 ceramic powder; the molar ratio of BiFeO3 to PbTiO3 is (0.6~0.9):(0.4~0.1). Step R3: The BiFeO3-PbTiO3 ceramic powder and the internal electrode metal slurry are mixed at a weight ratio of (60~75):(25~35) to obtain the composite material.

2. The method according to claim 1, characterized in that: In step R3, the weight ratio of the BiFeO3-PbTiO3 ceramic powder to the internal electrode metal slurry is (63~66):(34~37).

3. The method according to claim 1, characterized in that, In step R1, the ball milling process is performed at a rotation speed of 500±50 rpm for a duration of 12±2 h. In step R2, the heat treatment is held at a temperature of 850±20℃ for 1 to 2 hours.

4. The method according to claim 1, characterized in that, In step R3, the mixing is carried out by ball milling, and the ball milling speed is 400 rpm to 500 rpm, and the time is 12 h to 24 h.

5. The method according to claim 1, characterized in that, In step R3, the internal electrode metal paste is a silver-palladium paste, and the weight ratio of silver to palladium in the silver-palladium paste is 90:

10.

6. A composite material for constituting a stress-relieving layer, characterized in that: The composite material is prepared by mixing BiFeO3-PbTiO3 ceramic powder with internal electrode metal paste, wherein the weight ratio of BiFeO3-PbTiO3 ceramic powder to internal electrode metal paste is (60~75):(25~35); the composite material for constituting the stress relief layer is prepared by the method for preparing the composite material for constituting the stress relief layer according to any one of claims 1 to 5.

7. A method for preparing an integrated co-fired piezoelectric ceramic actuator, characterized in that, Includes the following steps: S1. Provides multiple ceramic diaphragms; S2. An internal electrode metal paste is coated on the surface of the ceramic diaphragm to form an internal electrode metal diaphragm. S3. Then, another ceramic film is applied to the surface of the internal electrode metal film; S4. Repeat steps S2 and S3 until multiple alternating layers of ceramic film and internal electrode metal film are formed; S5. Then, on the surface of the uppermost ceramic membrane in step S4, the composite material described in claim 6 is applied to form a stress relief preparation layer; S6. Then, cover the surface of the stress relief preparation layer with a ceramic film, so that the stress relief preparation layer is adjacent to the two adjacent ceramic films above and below. S7. Continue to repeat steps S2 and S3 to form multiple alternating layers of ceramic films and internal electrode metal films on the surface of the ceramic film above the stress relief preparation layer, thus forming a stacked green blank. S8. Cut the stacked blanks to form multiple stacked components; S9. After stacking multiple stacked components, heat treatment and external electrodes are applied to obtain an integrated co-fired piezoelectric ceramic actuator containing a ceramic dielectric layer, an inner electrode metal layer, and a stress relief layer.

8. The method according to claim 7, characterized in that: In the integrated co-fired piezoelectric ceramic actuator, the number of stacked components is 15 to 20; in each stacked component, the number of ceramic dielectric layers is 24 to 29.

9. The method according to claim 7, characterized in that: In step S9, before heat treatment of the stacked multiple stacked components, the steps of stacking and isostatic pressing of the multiple stacked components are also included. The heat treatment steps for the stacked components include debinding and sintering. The debinding temperature is 600℃~700℃ and the debinding time is 8h~15h. The sintering temperature is 950℃~1050℃ and the sintering time is 2h~8h.

10. An integrated co-fired piezoelectric ceramic actuator, characterized in that: The integrated co-fired piezoelectric ceramic actuator includes multiple stacked components stacked along the vertical direction. Each stacked component includes a stress relief layer made of the composite material described in claim 6, multiple ceramic dielectric layers, and multiple internal electrode metal layers. The stress relief layer is bonded between two adjacent ceramic dielectric layers and is in contact only with the ceramic dielectric layers. The remaining ceramic dielectric layers and multiple internal electrode metal layers are arranged alternately in pairs.

11. The integrated co-fired piezoelectric ceramic actuator according to claim 10, characterized in that: The stacked assembly has mutually perpendicular length and width directions, and the stress relief layer has two parts, which are formed between two adjacent ceramic dielectric layers and arranged opposite to each other along the width direction.

12. The integrated co-fired piezoelectric ceramic actuator according to claim 11, characterized in that, In the length direction, the outer edges of both portions of the stress relief layer are flush with the outer edge of the ceramic dielectric layer, and the lengths of both portions of the stress relief layer are equal to the length of the ceramic dielectric layer.

13. The integrated co-fired piezoelectric ceramic actuator according to claim 12, characterized in that: In the width direction, the ratio of the total width of the two portions of the stress relief layer to the width of the stacked assembly is 30% to 50%, and the widths of the two portions of the stress relief layer are equal.

14. The integrated co-fired piezoelectric ceramic actuator according to any one of claims 10 to 13, characterized in that, The thickness of a single ceramic dielectric layer is 50μm to 100μm, and the thickness of the stress relief layer is 100μm to 200μm; the integrated co-fired piezoelectric ceramic actuator also includes multiple internal electrode metal layers with a thickness of 1 to 10μm.

15. An integrated co-fired piezoelectric ceramic actuator, characterized in that: It includes multiple stacked components stacked along the vertical direction. Each stacked component includes two or more stress relief layers, multiple ceramic dielectric layers, and multiple internal electrode metal layers made of the composite material described in claim 6. Each stress relief layer is individually bonded between two adjacent ceramic dielectric layers, and each stress relief layer is in contact only with the ceramic dielectric layer. The remaining ceramic dielectric layers and multiple internal electrode metal layers are stacked alternately in pairs.

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