A copper inner electrode multilayer co-firing piezoelectric driver based on low-temperature reduction and a preparation method thereof

Abstract

This invention provides a low-temperature reduction-based multilayer co-fired piezoelectric actuator with copper internal electrodes and its fabrication method, belonging to the field of piezoelectric device manufacturing technology. The fabrication method involves thorough debinding under normal air atmosphere, followed by low-temperature reduction treatment of the copper oxide internal electrodes of the multilayer piezoelectric actuator under a reducing atmosphere (e.g., Ar-5%H2, N2-5%H2) (temperature range: 225-425℃). This effectively overcomes the problems of insufficient debinding and easy oxidation of the copper internal electrodes in traditional multilayer copper electrode actuators. Sintering is then performed. Compared with existing technologies, this invention provides a new approach to the fabrication of multilayer ceramic devices with copper internal electrodes, effectively solving the electrode oxidation problem during the co-firing process through a low-temperature reduction process. This method has advantages such as simple operation, low energy consumption, mild process conditions, and low material cost. This method provides a feasible technical solution for the fabrication of high-performance, low-cost multilayer piezoelectric actuators.

Description

Technical Field

[0001] This invention relates to the field of piezoelectric device manufacturing technology, and in particular to a low-temperature reduction-based copper internal electrode multilayer co-fired piezoelectric actuator and its preparation method. Background Technology

[0002] Multilayer piezoelectric actuators utilize the inverse piezoelectric effect of piezoelectric ceramics to generate micro-displacements under the influence of an electric field, thereby achieving driving and positioning. Multilayer piezoelectric actuators have advantages such as fast response speed and high positioning accuracy, and are widely used in optics, precision manufacturing and control, nanotechnology, life sciences, and other fields.

[0003] Multilayer piezoelectric actuators are formed by alternating stacks of thousands of layers of thick ceramic films and metal internal electrodes, followed by co-firing. Perovskite-structured soft PZT (lead zirconate titanate)-based piezoelectric ceramics are commonly used ceramic materials for fabricating piezoelectric actuators due to their high piezoelectric constant and large strain. Because PZT piezoelectric ceramics have high sintering temperatures, Ag-Pd is typically used as the internal electrode in multilayer piezoelectric actuators to achieve co-firing of the PZT piezoelectric ceramic and the metal internal electrode. However, the high cost of Pd metal significantly increases the cost of multilayer piezoelectric actuators. Furthermore, Ag ions in the metal internal electrode easily migrate under an electric field, leading to short-circuit failure after long-term use. In contrast, copper, as a base metal, not only has low manufacturing costs and high conductivity, but also does not easily migrate within ceramics, greatly improving the lifespan of multilayer piezoelectric actuators. Therefore, multilayer piezoelectric ceramic actuators using copper internal electrodes have broad application prospects due to their significant advantages of low cost and long lifespan.

[0004] Compared to Ag or Ag-Pd internal electrodes, the fabrication of multilayer piezoelectric actuators with copper internal electrodes is extremely difficult. The high-temperature oxidation of the copper internal electrode is a key challenge in the manufacturing of multilayer ceramic devices with copper internal electrodes. Currently, TDK Corporation of Japan is the only company in the market that has fully mastered this technology and is conducting large-scale production. No related products are yet sold in China, mainly because the method of co-firing copper internal electrodes with multilayer piezoelectric ceramics has not been fully mastered and scaled up for mass production. Currently, most research in this field focuses on how to prevent oxidation of the copper internal electrode during co-firing. CN118841260A describes a method for preparing multilayer ceramic capacitors by co-firing antiferroelectric materials with copper internal electrodes in a reducing atmosphere; however, this method suffers from long debinding times, incomplete debinding, and high energy consumption. Therefore, the large-scale application of this method faces certain challenges.

[0005] Given the above background, there is an urgent need for a more efficient and simpler method for fabricating multilayer piezoelectric ceramic actuators with copper internal electrodes. Summary of the Invention

[0006] The purpose of this invention is to provide a low-temperature reduction-based multilayer co-fired piezoelectric actuator with copper internal electrodes and its preparation method to solve the above problems. The low-temperature reduction preparation method realizes the multilayer co-firing of copper internal electrodes and ceramics, and the copper internal electrodes in the prepared multilayer co-fired piezoelectric actuator have good conductivity.

[0007] The objective of this invention is achieved through the following solution: The first objective of this invention is to provide a method for preparing a copper internal electrode multilayer co-fired piezoelectric actuator based on low-temperature reduction, the method comprising the following steps: preparation and debinding of copper internal electrode multilayer piezoelectric ceramic preform, low-temperature reduction of the preform, and multilayer co-firing of copper internal electrodes.

[0008] The preparation method includes the following steps: (1) After removing the glue from the copper internal electrode piezoelectric ceramic green blank with a multi-layer structure, it is placed in a first reducing atmosphere for heat treatment to reduce the copper oxide internal electrode to metallic copper in situ, thereby obtaining the copper internal electrode multi-layer piezoelectric ceramic green blank. (2) The prepared copper inner electrode multilayer piezoelectric ceramic blank is sintered in a second reducing atmosphere to achieve co-firing densification of the ceramic layer and the copper inner electrode, and a copper inner electrode multilayer co-fired piezoelectric actuator is obtained.

[0009] Furthermore, the preparation process of the multilayer piezoelectric ceramic green body with a multilayer copper internal electrode includes the following steps: The ceramic powder preparation involves preparing a copper internal electrode piezoelectric ceramic green body with a multi-layer structure by using processes such as casting slurry preparation, casting molding, internal electrode patterning printing, warm isostatic pressing, and precision cutting.

[0010] Furthermore, the raw materials of the ceramic powder include lead oxide (99.5%), zirconium oxide (99.5%), titanium dioxide (99.5%), niobium pentoxide (99.5%), ytterbium oxide (99.9%), and nickel oxide (99%).

[0011] Furthermore, the preparation process of the multilayered piezoelectric ceramic green body with a multilayered copper internal electrode specifically includes the following steps: a) The raw materials are prepared according to the stoichiometric ratio, and then ceramic powder is obtained by ball milling, sieving and synthesis using the traditional solid-phase synthesis method.

[0012] b) The ceramic powder is thoroughly mixed with solvent and binder to obtain a casting slurry. The slurry is cast using a casting machine to obtain a piezoelectric film with a thickness of approximately 48 micrometers. The piezoelectric films are then stacked to obtain a piezoelectric thick film.

[0013] c) Copper internal electrodes are printed on the surface of the piezoelectric thick film using screen printing, and then a layer of piezoelectric thick film is covered. The printing and covering steps are repeated alternately until the required number of electrode layers is obtained to obtain a multilayer piezoelectric thick film sample.

[0014] d) The vacuum-sealed multilayer piezoelectric thick film sample is placed in a warm water isostatic press for warm isostatic pressing. The warm isostatically pressed multilayer piezoelectric thick film is then cut into the required size using an automatic hot cutting machine to obtain a copper internal electrode multilayer piezoelectric ceramic green body (a copper internal electrode piezoelectric ceramic green body with a multilayer structure).

[0015] Further, step a) according to 0.05Pb(Ni 1 / 3 Nb 2 / 3 O3- 0.05Pb(Yb) 1 / 2 Nb 1 / 2 The raw materials were prepared by mixing O3- 0.26PbZrO3-0.39PbTiO3.

[0016] Further, in step b), the solvent is a mixture of toluene, alcohol, isopropanol, and butyl phthalate; the binder is polyvinyl butyral (PVB) commonly used in the preparation of PZT-based ceramics. Further, in step b), the mixing ratio of toluene, alcohol, isopropanol and butyl phthalate in the solvent is (40~50):(35~40):(10~15):5 by mass.

[0017] More preferably, in step b), the mixing ratio of toluene, alcohol, isopropanol and butyl phthalate in the solvent is 45:37.5:12.5:5 by mass.

[0018] Further, in step b), the mass ratio of ceramic powder to solvent and binder is (50~70): (15~25): (20~30).

[0019] More preferably, in step b), the mass ratio of ceramic powder to solvent and binder is 58:20:22.

[0020] Furthermore, in step c), the thickness of the piezoelectric thick film is approximately 1.5 to 2.5 millimeters.

[0021] More preferably, in step c), the thickness of the piezoelectric thick film is about 2 mm.

[0022] Furthermore, in step c), the required number of electrode layers is 8 to 10.

[0023] Furthermore, in step d), during the isostatic pressing process, the isostatic pressing temperature is 65℃, the isostatic pressing pressure is 65MPa, and the isostatic pressing time is 15min.

[0024] Furthermore, the specific fabrication process of the copper internal electrode co-fired multilayer piezoelectric actuator includes: e) Place the copper internal electrode multilayer piezoelectric ceramic green body in a tube furnace with an air atmosphere to fully remove the binder, and then heat treat it in a first reducing atmosphere to reduce the copper oxide internal electrode to metallic copper in situ, thereby obtaining the copper internal electrode multilayer piezoelectric ceramic green body.

[0025] f) Place the obtained blank in a tube furnace under a second reducing atmosphere and co-fire the copper internal electrode with the multilayer ceramic to obtain a copper internal electrode multilayer piezoelectric ceramic device (copper internal electrode multilayer co-fired piezoelectric actuator).

[0026] Further, in step e), the maximum temperature of the adhesive removal is 500-600℃, the holding time is 2-6h, the heating rate is 0.5-2℃ / min, and the atmosphere is air.

[0027] Further, in step e), the first reducing atmosphere is a mixture of an inert atmosphere and a reducing gas.

[0028] Furthermore, the inert atmosphere is argon or nitrogen; the reducing gas is hydrogen.

[0029] Furthermore, the volume ratio of the inert atmosphere to the reducing gas is 90~98:2~10.

[0030] More preferably, the volume ratio of the inert atmosphere to the reducing gas is 95:5.

[0031] Furthermore, the gas flow rate of the first reducing atmosphere is 60-200 cc / min.

[0032] Further, in step e), the heat treatment temperature is 225-425℃, the holding time is 3-6h, and the cooling rate is 1-3℃.

[0033] Further, in step f), the second reducing atmosphere is composed of pure nitrogen and activated carbon, with a nitrogen gas flow rate of 150-350 cc / min and an activated carbon content of 4-6 mg.

[0034] Furthermore, in step f), the co-firing temperature is 880-940℃, the holding time is 2-4h, and the heating rate is 2-3℃ / min.

[0035] Furthermore, "green blank" is a synonym for copper internal electrode multilayer piezoelectric ceramic green blank (copper internal electrode piezoelectric ceramic green blank with multilayer structure) before glue removal, while "plain blank" is a synonym for copper internal electrode multilayer piezoelectric ceramic after glue removal but before sintering.

[0036] Furthermore, the copper internal electrode multilayer ceramic device (copper internal electrode multilayer co-fired piezoelectric actuator) is the sample obtained after sintering the raw blank.

[0037] Furthermore, the multilayer ceramic device with copper internal electrode should achieve ceramic sintering, copper internal electrode sintering, and electrode resistance of less than 0.5Ω.

[0038] The second objective of this invention is to provide a low-temperature reduction-based copper internal electrode multilayer co-fired piezoelectric actuator, which is prepared using the above-described preparation method.

[0039] Furthermore, the copper internal electrode multilayer co-fired piezoelectric actuator is a perovskite-structured lead zirconate titanate (PZT)-based piezoelectric ceramic material.

[0040] Furthermore, PZT-based piezoelectric ceramics include ternary and quaternary soft PZT-based piezoelectric ceramics such as PNN-PZT and PNN-PYN-PZT.

[0041] Furthermore, the electrode resistance of the copper internal electrode multilayer co-fired piezoelectric actuator is less than 0.5Ω, and the Pb content in the piezoelectric ceramic material is... 2+ It was not reduced, and there was no interdiffusion between the electrode material and the piezoelectric ceramic material.

[0042] Furthermore, the resulting copper internal electrode multilayer co-fired piezoelectric actuator is suitable for piezoelectric actuators, piezoelectric transducers, etc., and has broad application prospects.

[0043] This invention discloses a method for fabricating a multilayer co-fired piezoelectric actuator with copper internal electrodes based on low-temperature reduction technology. The method involves thorough debinding under normal air atmosphere, followed by low-temperature reduction treatment of the copper oxide internal electrode of the multilayer piezoelectric actuator under a reducing atmosphere (e.g., Ar-5%H2, N2-5%H2) (temperature range: 225-425℃). This effectively overcomes the problems of insufficient debinding and easy oxidation of the copper oxide internal electrode in traditional multilayer copper internal electrode actuators. The innovation of this method is reflected in two aspects: firstly, it provides a new approach for the fabrication of multilayer ceramic devices with copper internal electrodes; secondly, it effectively solves the electrode oxidation problem during the co-firing process of the copper internal electrode through the low-temperature reduction process. The specific process steps are: ceramic slurry preparation, piezoelectric thick film preparation, internal electrode printing, warm isostatic pressing, cutting, debinding, reduction treatment of the copper oxide internal electrode, and co-firing of the actuator. This method has advantages such as simple operation, low energy consumption, mild process conditions, and low material cost. This method provides a feasible technical solution for the fabrication of high-performance, low-cost multilayer piezoelectric actuators.

[0044] Compared with existing technologies, the present invention has the following characteristics: 1) The preparation method of the copper internal electrode multilayer co-fired piezoelectric actuator based on low temperature reduction technology of the present invention focuses on the reduction problem of copper oxide internal electrode, without having to consider the problem of electrode anti-oxidation during long-term glue removal, and the preparation conditions are more relaxed.

[0045] 2) The preparation method of the copper internal electrode multilayer co-fired piezoelectric actuator based on low temperature reduction technology of the present invention uses an air atmosphere in the glue removal process, which results in shorter glue removal time and more thorough glue removal.

[0046] 3) The method for preparing the copper internal electrode multilayer co-fired piezoelectric actuator based on low-temperature reduction technology of the present invention uses low-temperature atmosphere reduction in the copper oxide internal electrode stage, which has low technical difficulty, low preparation cost and low energy consumption. Attached Figure Description

[0047] The following figures are only used to illustrate the feasibility of embodiments of the present invention and should not be regarded as a limitation on the scope.

[0048] Figure 1 SEM image (a) of the multilayer co-fired ceramic with copper internal electrode and EDS composition test results at the electrode (b).

[0049] Figure 2 The images show the copper internal electrode surface before and after reduction, where (a) is before reduction and (b) is after reduction.

[0050] Figure 3 The results are TGA test results for copper internal electrode multilayer piezoelectric ceramic green bodies, where (a) the test atmosphere is air and (b) the test atmosphere is nitrogen.

[0051] Figure 4 This is a schematic diagram of testing the resistance value of the internal electrode after destroying the intact copper internal electrode multilayer co-fired piezoelectric actuator in Example 7. Detailed Implementation

[0052] The present invention will now be described in detail with reference to specific embodiments, but this is by no means a limitation thereof. Any preparation methods, materials, structures, or composition ratios not explicitly described in this invention are considered common features disclosed in the prior art.

[0053] Unless otherwise specified, the reagents, methods, instruments, and equipment used in this invention are conventional in the art. Unless otherwise specified, the reagents and materials used in the following examples are all commercially available.

[0054] This invention provides a low-temperature reduction preparation method for a multilayer co-fired ceramic actuator with copper internal electrodes, the specific steps of which are as follows: Step 1: A copper internal electrode multilayer piezoelectric ceramic green body, prepared by processes such as ceramic powder preparation, slurry proportioning, tape casting, internal electrode patterning printing, warm isostatic pressing, and precision cutting, is laid flat on an alumina plate. The main crystalline phase of the ceramic powder is lead zirconate titanate, and the sintering aid of the ceramic material is one or more of lead oxide, copper oxide, and lithium carbonate.

[0055] The preparation method of the copper internal electrode multilayer piezoelectric ceramic green body includes the following steps: Ceramic powder preparation: The raw materials, namely lead oxide (99.5%), zirconium oxide (99.5%), titanium dioxide (99.5%), niobium pentoxide (99.5%), ytterbium oxide (99.9%), and nickel oxide (99%), are prepared according to the formula 0.05Pb(Ni 1 / 3 Nb 2 / 3 O3- 0.05Pb(Yb) 1 / 2 Nb 1 / 2 The ceramic powder was prepared by mixing O3-0.26PbZrO3-0.39PbTiO3 according to the stoichiometric ratio and using the traditional solid-phase synthesis method, through ball milling, sieving and synthesis steps.

[0056] Slurry ratio: The ceramic powder was thoroughly ball-milled with 9wt% toluene, 7.5wt% alcohol, 2.5wt% isopropanol, 1wt% butyl phthalate, and 22wt% polyvinyl butyral to obtain a 100% mass fraction slurry. The ball milling parameters were as follows: φ3mm zirconium balls were mixed with the material at a mass ratio of 3:1, and the mixture was ball-milled using a planetary ball mill for 3 hours.

[0057] Casting: The obtained slurry is poured into a casting machine, and the distance between the blade and the conveyor belt is set to about 0.5 micrometers. The slurry passes through the blade, so that it is evenly distributed on the conveyor belt below the blade. After drying, a piezoelectric film with a thickness of about 48 micrometers is obtained. Four layers of piezoelectric films are stacked to obtain a piezoelectric thick film.

[0058] Internal electrode patterning printing: A copper inner electrode with a pattern of φ8mm circle was printed on the surface of the piezoelectric thick film using screen printing. Then, a layer of piezoelectric thick film was covered. The printing and covering steps were repeated 6 times to obtain a multilayer piezoelectric thick film sample with 6 layers of copper inner electrodes and 8 layers of piezoelectric thick film.

[0059] Warm isostatic pressing: The vacuum-sealed multilayer piezoelectric thick film sample was placed in a warm water isostatic press for warm isostatic pressing. The parameters were set as follows: the temperature was increased to 65℃ at 5℃ / min, and then the pressure was increased to 65MPa at 5MPa / min and held for 15min.

[0060] Precision cutting: The multilayer piezoelectric thick film after warm isostatic pressing is cut using an automatic hot cutting machine to a size of φ10mm, resulting in a copper internal electrode multilayer piezoelectric ceramic green body (a copper internal electrode piezoelectric ceramic green body with a multilayer structure).

[0061] Step 2: Place the green body obtained in Step 1 in a tube furnace for debinding. The debinding temperature is 500-600℃, the holding time is 2-6 hours, the heating rate is 1℃ / min, and the debinding atmosphere is air. Immediately afterwards, cool down to 225-425℃ at a rate of 3℃ / min and hold for 3-6 hours to reduce the copper oxide internal electrode, thereby obtaining a copper internal electrode multilayer piezoelectric ceramic green body. The reducing atmosphere is a mixture of inert gas (argon or nitrogen) and reducing gas (hydrogen), with a gas volume ratio of inert gas:reducing gas = 95:5.

[0062] Step 3: Place the unglazed blank obtained in Step 2 into a corundum crucible and cover it with ceramic powder of the same type of ceramic material.

[0063] Step four: The sample obtained in step three is placed in a tube furnace for sintering to obtain a multilayer piezoelectric ceramic device with copper internal electrode; wherein the sintering temperature is 880-940℃, the holding time is 2-4h, the heating rate is 3℃ / min, and the sintering atmosphere is created by inert gas (nitrogen) and 5mg activated carbon.

[0064] Example 1 In this embodiment, the copper internal electrode multilayer piezoelectric ceramic preform uses PNN-PYN-PZT ceramic material (0.05Pb(Ni)). 1 / 3Nb 2 / 3 O3- 0.05Pb(Yb) 1 / 2 Nb 1 / 2 The following embodiments use 0.3 wt% copper oxide (relative to the mass of the ceramic material) and sintering aids (copper oxide, 0.26PbZrO3, 0.39PbTiO3, the same applies below) to prepare a green body of the ceramic material (a copper internal electrode multilayer piezoelectric ceramic green body prepared by the above method, the same applies below). The specific implementation is as follows: the green body is laid flat on an alumina plate and placed in a tube furnace for debinding in an air atmosphere. The debinding temperature is 500℃, the holding time is 4h, and the heating rate is 1℃ / min. Then, the temperature is reduced to 250℃ at 3℃ / min for heat treatment to reduce the copper oxide internal electrode to metallic copper in situ. The temperature is held for 4h in an atmosphere of argon and hydrogen mixed gas with a gas volume ratio of 95:5 and a gas flow rate of 80cc / min to obtain a copper internal electrode multilayer piezoelectric ceramic green body.

[0065] Example 2 In this embodiment, the copper internal electrode multilayer piezoelectric ceramic preform uses PNN-PYN-PZT ceramic material and sintering aid. The sintering aid is added at 0.3 wt% copper oxide. The preform prepared from this ceramic material is debinded to obtain the preform. The specific implementation scheme is as follows: the preform is laid flat on an alumina plate and placed in a tube furnace for debinding in an air atmosphere. The debinding temperature is 500℃, the holding time is 4h, and the heating rate is 1℃ / min. Then, the temperature is reduced to 325℃ at 3℃ / min for heat treatment to reduce the copper oxide internal electrode to metallic copper in situ. The temperature is held for 4h in an atmosphere of argon and hydrogen mixed gas with a gas volume ratio of 95:5 and a gas flow rate of 80cc / min to obtain the copper internal electrode multilayer piezoelectric ceramic preform.

[0066] Example 3 In this embodiment, the copper internal electrode multilayer piezoelectric ceramic preform uses PNN-PYN-PZT ceramic material and sintering aid. The sintering aid is added at 0.3 wt% copper oxide. The preform prepared from this ceramic material is debinded to obtain the preform. The specific implementation is as follows: the preform is laid flat on an alumina plate and placed in a tube furnace for debinding in an air atmosphere. The debinding temperature is 550℃, the holding time is 4h, and the heating rate is 1℃ / min. Then, the temperature is reduced to 325℃ at 3℃ / min for heat treatment to reduce the copper oxide internal electrode to metallic copper in situ. The temperature is held for 4h in an atmosphere of argon and hydrogen mixed gas with a gas volume ratio of 95:5 and a gas flow rate of 80cc / min to obtain the copper internal electrode multilayer piezoelectric ceramic preform.

[0067] Example 4 In this embodiment, the copper internal electrode multilayer piezoelectric ceramic preform uses PNN-PYN-PZT ceramic material and sintering aid. The sintering aid is added at 0.3 wt% copper oxide. The preform prepared from this ceramic material is debonded to obtain the preform. The specific implementation is as follows: the preform is laid flat on an alumina plate and placed in a tube furnace for debonding in an air atmosphere. The debonding temperature is 550℃, the holding time is 4h, and the heating rate is 1℃ / min. Then, the temperature is reduced to 400℃ at 3℃ / min for heat treatment to reduce the copper oxide internal electrode to metallic copper in situ. The temperature is held for 4h in a mixed gas atmosphere of argon and hydrogen with a gas volume ratio of 95:5 and a gas flow rate of 80cc / min to obtain the copper internal electrode multilayer piezoelectric ceramic preform.

[0068] Example 5 In this embodiment, the copper internal electrode multilayer piezoelectric ceramic preform uses PNN-PYN-PZT ceramic material and sintering aid. The amount of sintering aid added is 0.3wt% copper oxide. The green preform prepared by this ceramic material is debinded to obtain the preform. The specific implementation scheme is as follows: the green preform is laid flat on an alumina plate and placed in a tube furnace for debinding in an air atmosphere. The debinding temperature is 600℃, the holding time is 4h, and the heating rate is 1℃ / min. Then, the temperature is reduced to 250℃ at 3℃ / min for heat treatment to reduce the copper oxide internal electrode to metallic copper in situ. The temperature is held for 4h in a mixed gas atmosphere of argon and hydrogen with a gas volume ratio of 95:5 and a gas flow rate of 80cc / min to obtain the copper internal electrode multilayer piezoelectric ceramic preform.

[0069] Example 6 In this embodiment, the copper internal electrode multilayer piezoelectric ceramic preform uses PNN-PYN-PZT ceramic material and sintering aid. The sintering aid is added at 0.3 wt% copper oxide. The preform prepared from this ceramic material is debonded to obtain the preform. The specific implementation is as follows: the preform is laid flat on an alumina plate and placed in a tube furnace for debonding in an air atmosphere. The debonding temperature is 600℃, the holding time is 4h, and the heating rate is 1℃ / min. Then, the temperature is reduced to 400℃ at 3℃ / min for heat treatment to reduce the copper oxide internal electrode to metallic copper in situ. The temperature is held for 4h in a mixed gas atmosphere of argon and hydrogen with a gas volume ratio of 95:5 and a gas flow rate of 80cc / min to obtain the copper internal electrode multilayer piezoelectric ceramic preform.

[0070] Example 7 The copper internal electrode multilayer piezoelectric ceramic preform used in this embodiment was obtained from Example 1 and then sintered in a tube furnace to prepare a copper internal electrode co-fired multilayer piezoelectric actuator. The specific implementation method is as follows: the preform is placed flat in a corundum crucible, covered with about 1.5g of ceramic powder, and sintered in a tube furnace. The sintering temperature is 880℃, the holding time is 4h, the heating rate is 3℃ / min, and the furnace is cooled after the program ends. The sintering atmosphere consists of an inert gas (nitrogen) and 5mg of activated carbon, and the nitrogen flow rate is 200cc / min to obtain the copper internal electrode co-fired multilayer piezoelectric actuator.

[0071] In this embodiment, the electrode resistance of the copper internal electrode multilayer co-fired piezoelectric actuator is less than 0.5Ω. After destroying the intact copper internal electrode multilayer co-fired piezoelectric actuator, its internal electrode resistance value is tested to be less than 0.5Ω. Figure 4 As shown.

[0072] Example 8 The copper internal electrode multilayer piezoelectric ceramic blank used in this embodiment was obtained from Example 3. It was then sintered in a tube furnace to prepare a copper internal electrode co-fired multilayer piezoelectric actuator. The specific implementation method is as follows: the blank is placed flat in a corundum crucible, covered with ceramic powder of the same ceramic material, and sintered in a tube furnace. The sintering temperature is 900℃, the holding time is 3h, the heating rate is 3℃ / min, and the furnace is cooled after the program ends. The sintering atmosphere consists of inert gas (nitrogen) and activated carbon, and the nitrogen flow rate is 250cc / min to obtain the copper internal electrode co-fired multilayer piezoelectric actuator.

[0073] Example 9 The copper internal electrode multilayer piezoelectric ceramic preform used in this embodiment was obtained from Example 6, and then sintered in a tube furnace. The specific implementation method is as follows: the preform is placed flat in a corundum crucible, covered with ceramic powder of the same ceramic material, and sintered in a tube furnace to prepare a multilayer piezoelectric actuator with copper internal electrode co-fired. The sintering temperature is 920℃, the holding time is 3h, the heating rate is 3℃ / min, and the furnace is cooled after the program ends. The sintering atmosphere consists of inert gas (nitrogen) and activated carbon, and the nitrogen flow rate is 200 cc / min, thus obtaining a copper internal electrode co-fired multilayer piezoelectric actuator.

[0074] Multilayer piezoelectric ceramic green bodies contain a large amount of organic matter. This organic matter needs to be exposed to oxygen at high temperatures and decomposed into gases such as carbon dioxide to be released. However, the copper internal electrode is easily oxidized in a high-temperature, oxygen-containing atmosphere. Therefore, Examples 1-6 employ the low-temperature reduction technology proposed in this invention. After the binder in the air is removed from the multilayer piezoelectric ceramic green body, it is kept at a reducing environment formed by argon and hydrogen for several hours. This achieves both the full decomposition of organic matter (i.e., binders, plasticizers, defoamers, etc. in the casting slurry) and the preservation of the conductivity of the copper internal electrode. The weight loss rate is used to evaluate whether the organic matter has been fully decomposed, while the conductivity of the copper internal electrode and the reduction status are explained by the mass change before and after reduction, the performance of the final multilayer piezoelectric device, and the copper and oxygen atom content in the copper internal electrode.

[0075] Table 1 shows the measurement results of the copper internal electrode multilayer piezoelectric ceramic green bodies after debinding and reduction in Examples 1-6. In Examples 1-6, 0.3 wt% copper oxide was used as a sintering aid. The debinding and reduction temperatures for each example were combinations of three debinding temperatures (500℃, 550℃, 600℃) and three reduction temperatures (250℃, 325℃, 400℃). The table shows that the weight loss rate after debinding increases with increasing debinding temperature, indicating that higher temperatures promote the decomposition of organic matter. The comparative results of Examples 1 and 2, Examples 3 and 4, and Examples 5 and 6 show that the weight loss rate after reduction increases with increasing reduction temperature, indicating that within a suitable temperature range, higher reduction temperatures are beneficial for the reduction of the copper internal electrode. The weight loss rate of Example 6 increased by 1.08% compared to Example 1, indicating that the copper internal electrode multilayer piezoelectric ceramic green body of Example 6 had been fully debonded. Furthermore, after being treated with low-temperature reduction technology, the copper internal electrode multilayer piezoelectric ceramic green body underwent a significant weight change, which means that the copper oxide in the copper internal electrode was reduced to copper. The specific reduction effect will be further explained by the test results of the device obtained after sintering.

[0076] Table 1 Measurement results of samples from copper internal electrode multilayer piezoelectric ceramic green bodies after glue removal and reduction in Examples 1-6.

[0077]

[0078] Table 2 shows the test results of the actuators obtained after sintering the copper internal electrode multilayer piezoelectric ceramic green bodies of Examples 7-9. Examples 7-9 used samples obtained from Examples 1, 3, and 6, respectively. The samples of Examples 7-9 all exhibited high piezoelectric coefficients and low dielectric losses, indicating good reduction effects in Examples 1, 3, and 6, with the copper internal electrodes possessing good conductivity. Similarly, Examples 2, 4-5 also showed good reduction effects. Compared to Examples 7-8, Example 9 had the highest piezoelectric coefficient of 2135 pC / N and the lowest dielectric loss of 1.7%. Furthermore, the table shows that the copper atom content in the copper internal electrode layer of Examples 7-9 was much higher than the oxygen atom content. The Cu / O ratio of the reduced copper internal electrode was much higher than that of the unreduced copper internal electrode (Cu oxidizes to form CuO or Cu2O, Cu / O < 1), further indicating that the low-temperature reduction treatment in Examples 1-6 was effective. After debinding, the copper oxide in the copper internal electrode was reduced to copper, and the reduced copper internal electrode exhibited good reduction effects.

[0079] Table 2 Test results of the actuators obtained after sintering the copper internal electrode multilayer piezoelectric ceramic green bodies of Examples 7-9.

[0080]

[0081] In summary, this invention proposes a novel approach to co-firing copper internal electrodes with multilayer piezoelectric ceramics, and provides a method for fabricating copper internal electrode multilayer piezoelectric devices based on low-temperature reduction technology. Combined with examples and experimental results, this method successfully fabricates copper internal electrode multilayer piezoelectric actuators, and the resulting products exhibit good electrode conductivity and piezoelectric properties. This method provides a feasible technical solution for the fabrication of high-performance, low-cost multilayer piezoelectric actuators.

[0082] Furthermore, compared to Example 1, under the same conditions, when only nitrogen was used as the debinding atmosphere, the resulting sample contained a large amount of residual carbon due to insufficient nitrogen debinding. The sintered sample was easily brittle and could not be tested for performance. Compared to Example 1, under the same conditions, without low-temperature reduction after debinding and directly proceeding to subsequent sintering, the copper internal electrode of the sample after air debinding was severely oxidized. Direct sintering resulted in cracking, and the sample exhibited high resistance and non-conductivity.

[0083] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A method for fabricating a multilayer co-fired piezoelectric actuator with copper internal electrodes based on low-temperature reduction, characterized in that, The preparation method includes the following steps: (1) After removing the glue from the copper internal electrode piezoelectric ceramic green blank with multi-layer structure, it is placed in the first reducing atmosphere for heat treatment, so that the copper oxide internal electrode is reduced to metallic copper in situ, and a copper internal electrode multi-layer piezoelectric ceramic green blank is obtained. (2) The prepared copper inner electrode multilayer piezoelectric ceramic blank is sintered in a second reducing atmosphere to achieve co-firing densification of the ceramic layer and the copper inner electrode, and a copper inner electrode co-firing multilayer piezoelectric actuator is obtained.

2. The method for preparing a multilayer co-fired piezoelectric actuator with copper internal electrodes based on low-temperature reduction according to claim 1, characterized in that, The preparation process of the copper internal electrode piezoelectric ceramic green body with multi-layer structure includes the following steps: Ceramic powder preparation involves preparing a copper internal electrode piezoelectric ceramic green body with a multi-layer structure by using a process of casting slurry preparation, casting molding, internal electrode patterning printing, warm isostatic pressing, and precision cutting. The ceramic powder raw materials include lead oxide, zirconium oxide, titanium dioxide, niobium pentoxide, ytterbium oxide, nickel oxide, and the raw material formulation is made according to the proportions of 0.05Pb(Ni 1 / 3 Nb 2 / 3 )O3- 0.05Pb(Yb 1 / 2 Nb 1 / 2 )O3- 0.26PbZrO3- 0.39PbTiO3.

3. The method for preparing a multilayer co-fired piezoelectric actuator with copper internal electrodes based on low-temperature reduction according to claim 1, characterized in that, In step (1), the maximum temperature of the glue removal is 500-600℃, the heat preservation time is 2-6h, the heating rate is 0.5-2℃ / min, and the atmosphere is air.

4. The method for preparing a multilayer co-fired piezoelectric actuator with copper internal electrodes based on low-temperature reduction according to claim 1, characterized in that, In step (1), the heat treatment temperature is 225-425℃, the holding time is 3-6h, and the cooling rate is 1-3℃.

5. The method for preparing a multilayer co-fired piezoelectric actuator with copper internal electrodes based on low-temperature reduction according to claim 1, characterized in that, In step (1), the first reducing atmosphere is a mixture of an inert atmosphere and a reducing gas; The inert atmosphere is argon or nitrogen; The reducing gas is hydrogen.

6. The method for preparing a multilayer co-fired piezoelectric actuator with copper internal electrodes based on low-temperature reduction according to claim 5, characterized in that, The volume ratio of the inert atmosphere to the reducing gas is 90~98:2~10; The gas flow rate of the first reducing atmosphere is 60-200 cc / min.

7. The method for preparing a multilayer co-fired piezoelectric actuator with copper internal electrodes based on low-temperature reduction according to claim 1, characterized in that, In step (2), the sintering temperature is 880-940℃, the holding time is 2-4h, and the heating rate is 2-3℃ / min.

8. The method for preparing a multilayer co-fired piezoelectric actuator with copper internal electrodes based on low-temperature reduction according to claim 1, characterized in that, In step (2), the second reducing atmosphere includes nitrogen and activated carbon; The nitrogen gas flow rate is 150-350cc / min; the activated carbon content is 4-6mg.

9. A copper internal electrode multilayer co-fired piezoelectric actuator based on low-temperature reduction, obtained by the preparation method according to any one of claims 1-8, characterized in that, The copper internal electrode multilayer co-fired piezoelectric actuator is a perovskite-structured lead zirconate titanate-based piezoelectric ceramic material.

10. The low-temperature reduction-based copper internal electrode multilayer co-fired piezoelectric actuator according to claim 9, characterized in that, The electrode resistance of the copper internal electrode multilayer co-fired piezoelectric actuator is less than 0.5Ω.

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