A multilayer piezoelectric ceramic structure

Abstract

This utility model relates to the field of functional materials technology, specifically to a multilayer piezoelectric ceramic structure. It includes a porous ceramic layer and piezoelectric ceramic layers disposed on both sides of the porous ceramic layer. In this application, the pores of the porous ceramic layer contain air. During polarization, the air is ionized to form a conductive layer in the porous ceramic layer, thereby significantly increasing the piezoelectric coefficient. Furthermore, by replacing the silver electrode layer of the Schottky contact with a porous ceramic layer, this application effectively reduces leakage current and extends the service life of the piezoelectric ceramic structure.

Description

Technical Field

[0001] This utility model relates to the field of functional materials technology, specifically to a multilayer piezoelectric ceramic structure. Background Technology

[0002] Piezoelectric ceramics are functional ceramic materials capable of converting mechanical energy and electrical energy into each other. In addition to piezoelectricity, piezoelectric ceramics also possess dielectric and elastic properties, making them suitable for high-performance piezoelectric devices such as actuators, sensors, and transducers. Piezoelectric ceramics are manufactured by utilizing the piezoelectric effect, where the material's internal positive and negative charge centers are polarized under mechanical stress, resulting in bound charges of opposite signs appearing on the surfaces at both ends of the material.

[0003] Traditional lead-free piezoelectric ceramics have low piezoelectric coefficients, limiting their application in high-performance piezoelectric devices. Doping modification methods offer limited improvement in piezoelectric coefficients. Furthermore, the traditional piezoelectric ceramic structure involves coating the upper and lower surfaces of the insulating piezoelectric ceramic with silver paste as electrodes. This contact is a Schottky contact, which suffers from high reverse leakage current. Utility Model Content

[0004] In view of this, the present invention provides a multilayer piezoelectric ceramic structure to solve the problem of relatively high reverse leakage current in traditional piezoelectric ceramic structures.

[0005] This invention provides a multilayer piezoelectric ceramic structure, including a porous ceramic layer and piezoelectric ceramic layers disposed on both sides of the porous ceramic layer, wherein the side of the piezoelectric ceramic layer away from the porous ceramic layer is coated with silver paste.

[0006] In this application, the porous ceramic layer contains air in its pores. During the polarization process, the air is ionized and forms a conductive layer in the porous ceramic layer, thereby significantly improving the piezoelectric coefficient. Furthermore, by replacing the silver electrode layer of the Schottky contact with a porous ceramic layer, this application can effectively reduce leakage current and extend the service life of the piezoelectric ceramic structure.

[0007] In one alternative embodiment, the piezoelectric ceramic layer employs a lead-containing system.

[0008] In this application, the piezoelectric coefficient of the lead-containing system is higher than that of the lead-free material, making it suitable for applications requiring extremely high sensitivity. The preparation process of the lead-containing system is highly standardized, which can reduce the cost of industrial production.

[0009] In one alternative implementation, the piezoelectric ceramic layer employs a lead-free system.

[0010] In this application, the use of a lead-free system complies with environmental regulations such as RoHS, avoiding lead pollution issues and making it suitable for sensitive fields such as medical and food equipment. The low piezoelectric coefficient of lead-free materials can be compensated for through a multi-layer structure, and the overall performance can be improved by combining it with a porous ceramic layer.

[0011] In one alternative embodiment, the porous ceramic layer is alumina ceramic.

[0012] In this application, alumina is heat-resistant and provides structural support, preventing deformation during sintering or operation. It does not react with the piezoelectric layer, ensuring interlayer interface stability.

[0013] In one alternative embodiment, the porosity of the porous ceramic layer is 5% to 20%.

[0014] In this application, the pores can absorb mechanical stress, reduce fatigue crack propagation in the piezoelectric layer, and extend device life. A porous ceramic layer with suitable porosity can be selected according to actual needs, which can optimize the electric field distribution and enhance piezoelectric driving efficiency.

[0015] In one alternative embodiment, the thickness of the porous ceramic layer is 0.5 mm to 1.5 mm.

[0016] In one alternative embodiment, the porous ceramic layer and the piezoelectric ceramic layer are integrally formed using a casting process.

[0017] In this application, interlayer co-firing is performed using a tape casting process, which enables chemical bonding between the porous ceramic layer and the piezoelectric ceramic layer, reducing interface defects and improving mechanical strength and electrical stability. This also avoids the misalignment risks associated with traditional lamination processes, improving production yield and consistency.

[0018] In one alternative embodiment, the pores in the porous ceramic layer are uniformly distributed.

[0019] In this application, uniform porosity ensures the uniformity of stress dispersion and electric field distribution, avoiding local performance fluctuations. It also reduces local stress concentration and delays crack initiation and propagation. Attached Figure Description

[0020] To more clearly illustrate the specific embodiments of this utility model or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this utility model. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0021] Figure 1 This is a schematic diagram of the structure of an embodiment of the present utility model;

[0022] Figure 2 This is a schematic diagram of the traditional structure of piezoelectric ceramic components.

[0023] Explanation of reference numerals in the attached figures:

[0024] 1. Porous ceramic layer; 2. Piezoelectric ceramic layer; 3. Pores; 4. Silver electrode layer. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of the embodiments of this utility model clearer, the technical solutions of the embodiments of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this utility model, not all embodiments. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this utility model.

[0026] In existing technologies, due to the low piezoelectric coefficient (d33) of lead-free piezoelectric ceramics (BT, KNN, BNT, etc.), most piezoelectric ceramics currently used in actual production are lead-containing PZT systems. Traditional doping modification methods have limited effectiveness in improving the piezoelectric coefficient, thus limiting the widespread application of lead-free piezoelectric ceramics as a replacement for PZT-based piezoelectric ceramics. Traditional piezoelectric ceramic structures consist of silver paste electrode seats on the upper and lower surfaces of an insulating piezoelectric ceramic. This contact is a Schottky contact, which has high reverse leakage current and a limited barrier height. The uneven stress distribution in traditional single-layer piezoelectric ceramic structures easily leads to fatigue crack propagation.

[0027] The following is combined with Figures 1 to 2 The following describes embodiments of the present invention.

[0028] According to an embodiment of this utility model, a multilayer piezoelectric ceramic structure is provided, including a porous ceramic layer 1 and piezoelectric ceramic layers 2 disposed on both sides of the porous ceramic layer 1. The side of the piezoelectric ceramic layer 2 away from the porous ceramic layer 1 is coated with silver paste to form a silver electrode layer 4, the thickness of which can be less than 10 μm. The ceramic layer in this application is a multilayer structure (ABA), i.e., a "sandwich" structure, with piezoelectric ceramic layer 2 (layer A) and porous ceramic layer 1 (layer B) having porosity alternating. The porous ceramic layer 1 has air pores and a certain porosity.

[0029] like Figure 2 The diagram shows the traditional structure of a piezoelectric ceramic component, with silver electrodes coated on the upper and lower surfaces of the piezoelectric ceramic layer 2 after polishing. Figure 1 The novel piezoelectric ceramic component of this application has a multilayer structure with a porous dielectric layer containing 3 (5%-20%) pores, the thickness of which is adjustable and optimally controlled between 0.5mm and 1.5mm.

[0030] In this application, the pores 3 of the porous ceramic layer 1 contain air. During the polarization process, the air is ionized and forms a conductive layer in the porous ceramic layer 1, thereby significantly improving the piezoelectric coefficient. Furthermore, by replacing the silver electrode layer of the Schottky contact with the porous ceramic layer 1, this application can effectively reduce leakage current and extend the service life of the piezoelectric ceramic structure.

[0031] In one alternative embodiment, the piezoelectric ceramic layer 2 employs a lead-containing system.

[0032] In this application, the piezoelectric coefficient of the lead-containing system is higher than that of the lead-free material, making it suitable for applications requiring extremely high sensitivity. The preparation process of the lead-containing system is highly standardized, which can reduce the cost of industrial production.

[0033] In an optional embodiment, the piezoelectric ceramic layer 2 uses a lead-free system. Lead-free piezoelectric powder can be selected.

[0034] In this application, the use of a lead-free system complies with environmental regulations such as RoHS, avoids lead pollution issues, and is suitable for sensitive fields such as medical and food equipment. The low piezoelectric coefficient of lead-free materials can be compensated for through a multi-layer structure, and the overall performance can be improved by combining it with a porous ceramic layer 1.

[0035] In one optional embodiment, the porous ceramic layer 1 is alumina ceramic.

[0036] In this application, alumina is heat-resistant and provides structural support, preventing deformation during sintering or operation. It does not react with the piezoelectric layer, ensuring interlayer interface stability.

[0037] In one alternative embodiment, the porosity of the porous ceramic layer 1 is 5% to 20%.

[0038] In this application, the pores 3 can absorb mechanical stress, reduce fatigue crack propagation in the piezoelectric layer, and extend device life. A porous ceramic layer 1 with suitable porosity can be selected according to actual needs to optimize the electric field distribution and enhance piezoelectric driving efficiency.

[0039] In one alternative embodiment, the thickness of the porous ceramic layer 1 is 0.5 mm to 1.5 mm.

[0040] In one optional embodiment, the porous ceramic layer 1 and the piezoelectric ceramic layer 2 are integrally formed using a casting process. First, the powder of the piezoelectric ceramic layer 2 and the powder of the porous ceramic layer 1 are mixed to form a suitable slurry, which is then cast and coated at different doctor blade heights. Second, the layers are alternately stacked according to the designed ABA layer structure and brought into close contact through isostatic pressing. Finally, chemical bonding is formed through an interlayer co-firing process.

[0041] In this application, interlayer co-firing is performed using a tape casting process, which enables chemical bonding between the porous ceramic layer 1 and the piezoelectric ceramic layer 2, reducing interface defects and improving mechanical strength and electrical stability. This also avoids the misalignment risks associated with traditional lamination processes, improving production yield and consistency.

[0042] In one alternative embodiment, the pores 3 in the porous ceramic layer 1 are uniformly distributed.

[0043] In this application, uniform porosity 3 ensures the uniformity of stress dispersion and electric field distribution, avoiding local performance fluctuations. This reduces local stress concentration and delays crack initiation and propagation.

[0044] The piezoelectric ceramic multilayer structure of this application can further improve the piezoelectric performance of existing PZT system piezoelectric ceramics; the piezoelectric performance of this application is improved by improving the structure of the piezoelectric ceramic to increase the piezoelectric coefficient, d33>650pC / N; the piezoelectric ceramic multilayer structure of this application can effectively reduce leakage current by replacing the Schottky contact silver electrode layer with a porous ceramic layer in the middle.

[0045] The detailed preparation method for this application is as follows:

[0046] BT-based lead-free piezoelectric powder can be used to prepare a water-based slurry. The casting blade height is adjusted to prepare a 3mm piezoelectric ceramic layer 2 (layer A). Alumina porous ceramic powder with a porosity of 20% is selected, and a water-based slurry is prepared. The casting blade height is adjusted to prepare a 1mm dielectric layer (layer B). The ceramic green body is dried and stacked in an ABA manner. Isostatic pressing is used to achieve tight bonding, and the bonded green body is then trimmed. The multi-layered piezoelectric ceramic green body is then debinded and sintered to form a ceramic body. The sintering curve is as follows: heating at 2℃ / min to 600℃, holding for 2 hours, heating at the same rate to 1325℃, holding for 2 hours, cooling at 1.5℃ / min to 500℃, and then allowing natural cooling. After sintering, the upper and lower surfaces of the sample are polished, cleaned, dried, and then coated with silver paste to solidify the electrodes. The total thickness of the three ABA layers can be 7mm.

[0047] High voltage polarization was tested, and the piezoelectric coefficient d33 was found to be 700 pC / N.

[0048] Comparison Cases

[0049] BT-based lead-free piezoelectric powder can be used to prepare a water-based slurry. The height of the casting squeegee is adjusted to prepare a 7mm piezoelectric ceramic layer 2 (layer A). After drying, isostatic pressing is used to densify the material. The densified green body is then cut to the same dimensions as the multilayer piezoelectric ceramic green body, following a consistent binder removal sintering curve. The sintering curve is as follows: heating at 2℃ / min to 600℃, holding for 2 hours, heating at the same rate to 1325℃, holding for 2 hours, and then cooling at 1.5℃ / min to 500℃ before natural cooling. After sintering, the upper and lower surfaces of the sample are polished, cleaned, dried, and then coated with silver paste to solidify the electrodes.

[0050] High voltage polarization was tested, and the piezoelectric coefficient d33 was found to be 280 pC / N.

[0051] Therefore, it can be seen that the piezoelectric coefficient of the multilayer piezoelectric ceramic structure of this application is significantly higher than that of the traditional piezoelectric ceramic structure.

[0052] Although embodiments of the present invention have been described in conjunction with the accompanying drawings, those skilled in the art can make various modifications and variations without departing from the spirit and scope of the present invention, and such modifications and variations all fall within the scope defined by the appended claims.

Claims

1. A multilayer piezoelectric ceramic structure, characterized by, It includes a porous ceramic layer (1) and piezoelectric ceramic layers (2) disposed on both sides of the porous ceramic layer (1), wherein the side of the piezoelectric ceramic layer (2) away from the porous ceramic layer (1) is coated with silver paste.

2. The multilayered piezoelectric ceramic structure according to claim 1, characterized by The piezoelectric ceramic layer (2) adopts a lead-containing system.

3. The multilayered piezoelectric ceramic structure according to claim 1, characterized by The piezoelectric ceramic layer (2) adopts a lead-free system.

4. The multilayered piezoelectric ceramic structure according to claim 1, characterized by The porous ceramic layer (1) is alumina ceramic.

5. The multilayered piezoelectric ceramic structure according to claim 1, characterized by, The porosity of the porous ceramic layer (1) is 5% to 20%.

6. The multilayer piezoelectric ceramic structure according to claim 1, characterized in that, The thickness of the porous ceramic layer (1) is 0.5 mm to 1.5 mm.

7. The multilayered piezoelectric ceramic structure according to claim 1, characterized by The porous ceramic layer (1) and the piezoelectric ceramic layer (2) are formed into one piece by a casting process.

8. The multilayered piezoelectric ceramic structure according to claim 1, characterized by, The thickness of the piezoelectric ceramic layer (2) is 3 to 10 mm.

9. The multilayered piezoelectric ceramic structure according to claim 1, characterized by, The pores (3) in the porous ceramic layer (1) are uniformly distributed.

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