A bnt-based composite ceramic material, a ferroelectric multilayer device, and a preparation method and application thereof

Abstract

The application belongs to the technical field of functional ceramic materials and devices, and particularly relates to a BNT-based composite ceramic material, a ferroelectric multilayer device and a preparation method and application. The BNT-based composite ceramic material provided by the application has a chemical composition of (0.97-0.99){1-x[(Bi 0.5 Na 0.5 )(Ti 0.995 Mn 0.005 )]O3-xBiAlO3}-(0.01-0.03)NaNbO3, wherein 0 The application obtains a ferroelectric ceramic material with high energy storage density, high remanent polarization and high breakdown field strength through the design of element composition. Through the combined action of the design of the composite ceramic material and the multilayer structure, the energy storage density of the ferroelectric ceramic device can be greatly improved, which is an effective technical approach to realize the miniaturization of the ferroelectric multilayer device, and is expected to output higher energy density under the condition of the same volume, and meets the development trend requirement of the high-power pulse field.

Description

Technical Field

[0001] This invention belongs to the field of functional ceramic materials and devices, specifically relating to a BNT-based composite ceramic material, a ferroelectric multilayer device, its preparation method, and its application. Background Technology

[0002] Ferroelectric materials exhibit rich response behaviors and multi-field coupling effects under external fields due to their spontaneous polarization, leading to their widespread application in numerous technological fields. Ferroelectric high-power pulsed power supplies, a significant application of ferroelectric materials, operate primarily on the principle of pressure-induced phase transition depolarization. By applying a shock wave, the ferroelectric ceramic is depolarized, releasing surface bound charges and releasing the polarization energy stored during polarization within microseconds. This generates strong current pulses (for low-impedance loads) or voltage pulses (for high-impedance loads), outputting megawatt-level pulsed energy. The theoretical energy density formula for ferroelectric ceramics is W = P. r 2 / 2ε0ε r P r ε is the remanent polarization intensity, ε0 ​​is the vacuum permittivity, ε r As the relative permittivity is affected by breakdown, the actual energy density is usually much lower than the theoretical energy density, and the output formula is W = P. r E b Residual polarization intensity P r The magnitude of the electric field reflects the amount of bound charge after polarization, affecting the release of charge under pressure; while the breakdown field strength E b The residual polarization intensity and electrical breakdown resistance determine the energy output in practical applications. Therefore, the residual polarization intensity and electrical breakdown resistance are extremely important for high-power ferroelectric pulse power supplies.

[0003] Due to their superior dielectric and ferroelectric properties and high Curie temperature, lead-based materials such as Pb(Zr,Ti)O3(PZT)95 / 5 are currently the main commercial materials for high-power pulse power supplies. However, with the implementation of environmental protection and human health policies worldwide, the use of lead in electronic devices is restricted, making lead-free materials an inevitable trend in future materials research and development. 0.5 Na 0.5 TiO3(BNT) ferroelectric materials exhibit strong ferroelectric properties (P... r ~38μC / cm 2 BNT possesses unique relaxation characteristics, with a density only 66% that of PZT. Pure BNT has a depolarization temperature of approximately 190℃, but it suffers from drawbacks such as high coercivity and high leakage conductivity, failing to meet the requirements for electrical resistance and polarization. Modification through elemental doping or second-component solid solution is often necessary. However, current research on BNT-based solid solution compositions focuses primarily on piezoelectricity and energy storage, often achieving relaxation through doping with certain amounts of rare earth elements, Zr, Ba, Sr, etc. A typical characteristic is a narrow, sloping hysteresis loop, indicating high polarization intensity P.max High, remanent polarization P r The remanent polarization is extremely low, typically lower than that of pure BNT. Therefore, the preparation of BNT-based ferroelectric ceramics with high remanent polarization requires further exploration by selecting appropriate solid solution components.

[0004] Furthermore, in practical applications, current high-power ferroelectric pulse power supplies typically employ a multi-layer ceramic sheet stacked in series structure to achieve high-voltage outputs of several hundred kilovolts. The problems of large size and weight urgently need to be addressed. The trend towards miniaturization places higher demands on the energy storage density and size of ferroelectric ceramic devices. Traditional bulk ferroelectric ceramics, limited by electrode area, cannot store large amounts of charge, and consequently, the surface-bound charge that can be released during stress-induced depolarization is relatively limited. Summary of the Invention

[0005] Therefore, the technical problem to be solved by the present invention is to overcome the defects of existing ferroelectric ceramic materials, such as difficulty in simultaneously possessing high actual energy density, remanent polarization intensity, and breakdown field strength, thereby providing a BNT-based composite ceramic material, ferroelectric multilayer device, preparation method, and application.

[0006] Therefore, the present invention provides the following technical solution:

[0007] This invention provides a BNT-based composite ceramic material with the following chemical composition: (0.97-0.99){1-x[(Bi 0.5 Na 0.5 (Ti) 0.995 Mn 0.005 )]O3-xBiAlO3}-(0.01-0.03)NaNbO3, where, 0 <x≤0.02。

[0008] Optionally, in the chemical composition of the BNT-based composite ceramic material, the value of x is 0.01≤x≤0.02.

[0009] In this invention, preferably, x = 0.01.

[0010] This invention also provides a method for preparing a BNT-based composite ceramic material, comprising the following steps:

[0011] S1, according to the chemical composition of BNT-based composite ceramic materials (0.97-0.99){1-x[(Bi 0.5 Na 0.5 (Ti) 0.995 Mn 0.005 Weigh the raw materials according to the stoichiometric ratio in O3-xBiAlO3}-(0.01-0.03)NaNbO3;

[0012] S2, mix the raw materials, press them into blocks, calcine them, and pulverize them to obtain the BNT-based composite ceramic material.

[0013] Optionally, in step S2, the calcination temperature is 700–900°C and the calcination time is 1–3 hours.

[0014] And / or, the pulverization to an average particle size of 10 nm to 20 μm;

[0015] And / or, the pulverization step includes ball milling and stirred milling for fine grinding. The pulverization step may also employ sand milling and planetary ball milling. This invention uses a ball milling + stirred milling method to achieve the required particle size in a shorter time.

[0016] In this invention, the raw materials used to prepare BNT-based composite ceramic materials are conventional in the field, and are compounds containing corresponding metal elements. Typically, and not specifically, they can be at least one of oxides, carbonates, bicarbonates, etc., containing these metal elements. Optionally, the purity of the raw material powder is >99%.

[0017] Optionally, in step S1, ball milling is used to mix the raw materials. The parameters of the ball milling include: a mass ratio of raw material: milling medium: alcohol = 1:(1.8~2.2):(0.6~1.0), the milling medium is zirconium balls or agate balls, the milling speed is 280~360 rpm, and the time is 4~8h.

[0018] Optionally, the heating rate during calcination shall not exceed 2°C / minute.

[0019] Optionally, in the pulverization step after calcination, the ball milling is performed for 6 to 12 hours with a powder:milling medium:alcohol mass ratio of 1:(1.8-2.2):(0.6-1.0), using zirconium balls or agate balls as the milling medium and a milling speed of 280-360 rpm; the parameters for the stirred milling include: fine grinding with a powder:milling medium:alcohol mass ratio of 1:(8-12):(1.0-2.5), a milling speed of 400-500 rpm, using zirconium balls with a diameter of 0.9-1.2 mm, and a grinding time of 3-6 hours.

[0020] The present invention also provides a ferroelectric multilayer device, comprising the above-described BNT-based composite ceramic material or the BNT-based composite ceramic material prepared by the above-described preparation method.

[0021] The present invention also provides a method for fabricating the above-mentioned ferroelectric multilayer device, comprising the following steps:

[0022] S11, BNT-based composite ceramic material, solvent, binder, plasticizer and dispersant are mixed to obtain ceramic slurry;

[0023] S12, the ceramic slurry is cast into a film, the inner electrode is screen printed, the layers are stacked, the film isostatically pressed, the adhesive is removed, the film is sintered, and the outer electrode is drawn on to obtain the ferroelectric multilayer device.

[0024] Optionally, the thickness of the ferroelectric multilayer device is 0.01 mm to 0.15 mm;

[0025] And / or, the material type of the inner electrode and the outer electrode is at least one of Pt, Ag / Pd, Cu, and Ni.

[0026] Optionally, in step S11, the BNT-based composite ceramic material accounts for 39% to 46% of the total mass of the ceramic slurry.

[0027] And / or, the amount of the adhesive used is 3.5% to 4.5%;

[0028] And / or, the amount of the plasticizer is 1.65% to 1.75%;

[0029] And / or, the amount of the dispersant is 0.4% to 0.6%;

[0030] And / or, the amount of the solvent used is 45% to 55%.

[0031] Optionally, in step S12, the glue removal step is carried out in an oxygen-containing atmosphere, with the temperature increased to 300-500°C at a rate of less than 1°C / min, and held at that temperature for 1-3 hours.

[0032] And / or, the sintering step is carried out in an oxygen-containing atmosphere, with the temperature increased to 1000-1200°C at a heating rate of 0.1-10°C / min, and held for 1-3 hours.

[0033] In this invention, the binder is selected from at least one organic compound such as polyvinylpyrrolidone, sucrose, polyvinyl alcohol (PVA), and polyvinyl butyral (PVB). The plasticizer is selected from at least one organic compound such as polyethylene glycol and dioctyl phthalate. The solvent is selected from at least one organic solvent such as ethanol, methanol, acetone, ethyl acetate, butanone, and glycerol. The organic solvents used in this invention have high volatility, which is beneficial for the curing of the film after casting. The dispersant used in this invention is conventional in the art and is not specifically limited herein.

[0034] In this invention, the oxygen-containing atmosphere in the debinding and sintering steps can be an oxygen atmosphere or an air atmosphere.

[0035] The present invention also provides an application of the above-described ferroelectric multilayer device or the ferroelectric multilayer device prepared by the above-described preparation method in a high-power pulse power supply.

[0036] In the art, high power is generally calculated from the current and voltage in the circuit, and varies with the resistance selected for the circuit. In practical applications, it is obtained by connecting a plurality of ceramic sheets in series, and is not directly reflected by the performance of a single device. For a single unit, W=P r E b The higher the value is, the more beneficial it is to the realization of high power.

[0037] The technical solution of the present invention has the following advantages:

[0038] The BNT-based composite ceramic material provided by the present invention has a chemical composition of: (0.97-0.99){1-x[(Bi 0.5 Na 0.5 )(Ti 0.995 Mn 0.005 )]O3-xBiAlO3}-(0.01-0.03)NaNbO3, wherein 0<x≤0.02. The present invention obtains a ferroelectric ceramic material having simultaneously high energy storage density, high remanent polarization and high breakdown field strength through the design of elemental composition. Functional ceramic materials in the prior art often achieve relaxation by doping more than a certain amount of elements such as rare earth elements, Zr, Ba, Sr, etc., and the typical feature is that the hysteresis loop is often in a narrow and oblique shape, that is, the polarization intensity P max is relatively high, while the remanent polarization P r is extremely low, and the depolarization temperature is usually at room temperature or lower than room temperature. In XRD, it can be observed that the rhombohedral phase decreases and the pseudocubic phase increases. The present invention is based on the high-power pulse application principle based on pressure depolarization. The high energy storage density is achieved through high remanent polarization and high breakdown field strength. Appropriate doping is used to increase rhombohedral distortion without significantly reducing the rhombohedral phase, so as to increase the remanent polarization P r . The adopted ceramic powder has obvious ferroelectricity, and the typical feature is that the hysteresis loop is square-shaped, that is, the remanent polarization P r is close to the polarization intensity P max . Specifically, bismuth aluminate (BA) has strong ferroelectricity, and a small amount of doping is beneficial to improving the ferroelectricity of the powder. Doping of low-valent elements in the BNT-BA system can also enhance ferroelectricity, and strong ferroelectricity means high remanent polarization. After Mn replaces Ti, it forms a dipole pair with oxygen vacancies, reducing the concentration of movable oxygen vacancies in the material, thereby increasing the resistivity of the ceramic. The reduction of oxygen vacancies can effectively increase the breakdown field strength; in addition, appropriate Mn doping can reduce the loss of the sample. Domain wall vibration is an important source of loss in ferroelectrics, and dipoles will pin domain walls and hinder domain wall vibration. Nb 5+ ions tend to replace Ti 4+This leads to the formation of A-site cation vacancies. The combination of A-site cation vacancies with Nb ions hinders mass transport, thereby reducing the grain growth rate. This results in the formation rate of ceramic nuclei exceeding the grain growth rate, leading to a smaller grain size. Smaller grain sizes are beneficial for increasing the breakdown field strength. Simultaneously, sodium niobate (NN), as an antiferroelectric phase, can regulate phase boundaries, giving the ceramic material a certain degree of temperature stability. After polarization, the ferroelectric domains are stable and not easily depolarized.

[0039] The method for preparing BNT-based composite ceramic materials provided by this invention uses a ball milling + stirred milling method to achieve the required particle size in a shorter time, thereby improving the device fabrication efficiency.

[0040] The ferroelectric multilayer device provided by this invention can significantly improve the energy storage density of ferroelectric ceramic devices through the combined effect of composite ceramic material design and multilayer structure design. It is an effective technical approach to achieve miniaturization of ferroelectric multilayer devices and is expected to output higher energy density under the same volume conditions, which meets the development trend requirements of the high-power pulse field.

[0041] The ferroelectric multilayer device provided by this invention can further improve the breakdown field strength by designing the layer thickness and effective layer area; by limiting the parameters of steps such as debinding and sintering, it is more conducive to obtaining fine, uniform and dense grains, thereby further improving the performance of the device. Attached Figure Description

[0042] To more clearly illustrate the specific embodiments of the present invention 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 the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0043] Figure 1 The images shown are scanning electron microscope images of the dielectric layer and electrode layer of the ferroelectric multilayer device prepared in Example 3.

[0044] Figure 2 The hysteresis loop diagram of the ferroelectric multilayer device prepared in Example 1 at room temperature;

[0045] Figure 3 The image shows the pyroelectric curve of the polarized ferroelectric multilayer device prepared in Example 1.

[0046] Figure 4 Hysteresis loops of the ferroelectric multilayer device prepared in Example 2 at different temperatures;

[0047] Figure 5 Hysteresis loops of the ferroelectric multilayer device prepared in Example 3 at different temperatures;

[0048] Figure 6 is a hysteresis loop diagram of the ferroelectric multilayer device prepared in Example 1 under isostatic pressure;

[0049] Figure 7 is a hysteresis loop diagram of the ferroelectric multilayer device prepared in Example 2 under isostatic pressure;

[0050] Figure 8 is a hysteresis loop diagram of the ferroelectric bulk devices prepared in Comparative Examples 1 and 2 at room temperature. DETAILED DESCRIPTION

[0051] The present invention is further illustrated by the following embodiments, it should be understood that the following embodiments are only used to illustrate the present invention, not to limit the present invention.

[0052] The present invention provides a manganese-doped BNT-BA-NN lead-free ferroelectric ceramic material with a chemical composition of (0.97-0.99){1-x[(Bi 0.5 Na 0.5 )(Ti 0.995 Mn 0.005 )]O3-xBiAlO3}-(0.01-0.03)NaNbO3, wherein 0<x≤0.02. The ceramic material is a BNT-based lead-free ceramic material with high remanent polarization based on ferroelectric-relaxor phase transition. It has the characteristic of stress-induced rhombohedral ferroelectric-relaxor phase transition, and the selection of x value is based on the position of the phase boundary (on the ferroelectric phase-biased side). Compared with commercial PZT 95 / 5 ceramics, this ceramic material has the characteristics of low density and high energy storage volume density. Ferroelectric-relaxor phase transition can occur and bound charges can be released within the isostatic pressure range of 200 to 450 MPa. When 0.01≤x≤0.02, the remanent polarization of the ferroelectric bulk ceramic is as high as 38 to 44 μC / cm 2 . Preferably, x=0.01, at this time, the remanent polarization P of the manganese-doped BNT-BA-NN lead-free ferroelectric bulk ceramic material at 8.0 kV / mm r can reach 44 μC / cm 2 , and this component is selected as the powder material for multilayer devices.

[0053] A BNT device with an internal electrode multilayer structure is prepared by a tape-casting lamination co-firing method, followed by binder removal and sintering. The ferroelectric ceramic device not only has high remanent polarization and energy storage density, but also can undergo pressure-induced ferroelectric-relaxor phase transition and release surface bound charges under the action of small isostatic pressure. Compared with commercial PZT ceramics, this ceramic material has the characteristics of low density and high energy storage volume density. The bulk density of the lead-free ferroelectric multilayer device provided by the present invention is 4.7 to 5.3 g / cm 3The actual energy storage volume density after polarization at room temperature reaches 10.6 J / cm³. 3 It approaches its theoretical energy storage volume density. It can undergo a ferroelectric-relaxation phase transition and release bound charges within the isostatic pressure range of 200–450 MPa. The following exemplarily illustrates the fabrication method of the BNT-based ferroelectric multilayer device of the present invention, which mainly includes the following steps.

[0054] This invention prepares BNT-based composite ceramic materials via a solid-state method. In this invention, oxides, carbonates, or bicarbonates of the various metal elements in the chemical composition, such as Bi₂O₃, NaHCO₃, TiO₂, Al₂O₃, Nb₂O₅, and MnCO₃ powders, are used as raw materials, according to a ratio of 0.99{0.99[(Bi 0.5 Na 0.5 (Ti) 0.995 Mn 0.005 The ceramic powder is prepared using the stoichiometric ratio of O3-0.01BiAlO3-0.01NaNbO3. It is mixed using a single ball milling (wet ball milling) at a mass ratio of raw material:ball:alcohol = 1:(1.8~2.2):(0.6~1.0) for 4~8 hours, with zirconium or agate balls as the milling media. After drying, the powder is sieved, pressed into blocks, and calcined at a rate not exceeding 2℃ / min to 700~900℃ for 1~3 hours, then cooled to room temperature in the furnace. The ceramic powder is then subjected to a second ball milling (wet ball milling) and fine grinding at a mass ratio of ceramic powder:ball:alcohol = 1:(1.8~2.2):(0.6~1.0) for 6~12 hours to achieve a small particle size and narrow distribution, with zirconium or agate balls as the milling media. After drying, the powder is sieved and then finely ground in a stirred mill for 3-6 hours at a mass ratio of ceramic powder:balls:alcohol = 1:(8-12):(1.0-2.5). The milling media are zirconium balls or agate balls. After drying, the BNT-based composite ceramic material is obtained by sieving.

[0055] This invention prepares ferroelectric multilayer devices using a ceramic casting and co-firing technique. The BNT-based ceramic powder (44 wt%) obtained in step 1, a mixed solvent of alcohol and ethyl acetate (ethanol to ethyl acetate mass ratio 1:2.15, 50 wt%), and a dispersant (0.5 wt%) are ball-milled for 4 hours. Then, a binder, polyvinyl butyral (PVB) (3.8 wt%), and a plasticizer, dioctyl phthalate (DOP) (1.7 wt%) are added, and ball milling continues for another 4 hours. After vacuum degassing of the slurry, it is cast into a film, screen-printed with internal electrodes, stacked, subjected to warm isostatic pressing (60–70 MPa / 60–75 °C), cut, and after debinding at 330 °C, sintered at 1080 °C for 2 hours at a heating rate of 0.2–6 °C / min. External electrodes are then attached, and electrical performance testing can be performed.

[0056] The following embodiments are provided to better understand the present invention and are not limited to the preferred embodiments described. They do not constitute a limitation on the content and scope of protection of the present invention. Any product that is the same as or similar to the present invention, derived by any person under the guidance of the present invention or by combining the features of the present invention with other prior art, falls within the protection scope of the present invention.

[0057] For experiments not specifically described in the examples, the procedures or conditions should be followed according to the conventional experimental procedures described in the literature in this field. Reagents or instruments whose manufacturers are not specified are all commercially available conventional reagent products.

[0058] Example 1

[0059] This embodiment provides a ferroelectric multilayer device, the composition, fabrication method, and specific operating parameters of which are as follows:

[0060] Step (1): Preparation of BNT-based ceramic composite material: The material composition is 0.99{0.99[(Bi 0.5 Na 0.5 (Ti) 0.995 Mn 0.005 The mixture, consisting of Bi₂O₃, NaHCO₃, TiO₂, Al₂O₃, Nb₂O₅, and MnCO₃ powders, was prepared according to the stoichiometric ratio of the above materials. It was mixed using a wet ball milling method at a mass ratio of raw material:ball:alcohol = 1:2:0.9, and milled at 360 r / min for 4 hours to ensure uniform mixing. After drying, the mixture was passed through a 40-mesh sieve, pressed into large blocks under 5 MPa pressure, and heated to 750℃ at a rate not exceeding 2℃ / min, holding at that temperature for 2 hours. The calcined powder was then subjected to a second ball milling (wet ball milling) and fine grinding at 360 r / min for 12 hours, with a powder:ball:alcohol mass ratio of 1:2:0.9, resulting in ceramic powder with a small particle size and narrow particle size distribution. The milling media were agate balls. After drying, the powder is sieved and then placed in a stirred mill for fine grinding. The powder is ground for 4 hours at a mass ratio of powder:ball:alcohol = 1:10:2, with zirconium balls as the grinding media.

[0061] Step (2): Preparation of ferroelectric multilayer devices: Slurry preparation: BNT-based ceramic composite powder (44wt%), a mixed solvent of alcohol and ethyl acetate (mass ratio of alcohol to ethyl acetate is 1:2.15, 50wt%), and dispersant AKM0531 (0.5wt%) were ball-milled for 4h. Then, binder polyvinyl butyral (PVB, Aladdin, molecular weight 90,000 to 120,000) (3.8wt%) and plasticizer dioctyl phthalate (DOP) (1.7wt%) were added, and ball-milling continued for 4h. After vacuum degassing of the slurry, it was cast into a film, Ag / Pd internal electrodes were screen-printed, and after stacking, it was isostatically pressed (65MPa / 75℃) at a speed of 0.12cm. 2 The dimensions are cut to a thickness of 0.03mm. The material is heated to 330℃ in air and held for 5 hours. After the adhesive is removed, a multi-layer ceramic body is obtained.

[0062] Sintering: Place the ceramic blank into an alumina crucible. To prevent the volatilization of elements such as bismuth and sodium, cover the blank with ceramic powder having the same composition as in step (1), cover it with a ground glass plate, and heat it to 1080℃ at a heating rate of 0.5℃ / min, and hold it for 2 hours.

[0063] The temperature was increased to 700℃ at a rate of 2℃ / min, and the temperature was held for 0.5 hours to obtain silver for calcination, thus obtaining a ferroelectric multilayer device.

[0064] The obtained ferroelectric multilayer device was DC polarized under the following conditions: an electric field strength of 8 kV / mm and a holding voltage of 10 min in silicone oil. Hysteresis loop tests, pyroelectric tests, isostatic depolarization, and hysteresis loop tests were then performed on the polarized ferroelectric multilayer device. The test results are as follows: Figure 2-3 and Figure 6 As shown, from Figure 2 It can be seen that the ferroelectric multilayer device prepared in Example 1 has a withstand voltage as high as 26 kV / mm, which is much higher than the bulk breakdown field strength (10 kV / mm), and a remanent polarization of 39.4 μC / cm. 2 The theoretical energy storage density is 11.0 J / cm³. 3 The breakdown field strength reaches 27 kV / mm, and the actual energy storage density reaches 10.6 J / cm³. 3 The temperature corresponding to the pyroelectric peak is the depolarization temperature (T). d ),from Figure 3 It can be seen that T d Approximately 88℃. From Figure 6 As can be seen, under isostatic pressure, the polarized samples can release surface bound charges in the range of 0-450 MPa. As the pressure increases, the depolarization discharge increases, and the corresponding hysteresis loop shows a waisting phenomenon, indicating that the threshold of pressure-induced ferroelectric-relaxation phase transition is low.

[0065] Example 2

[0066] This embodiment provides a ferroelectric multilayer device, which differs from Embodiment 1 only in that the sintering step is heated to 1080°C at a faster heating rate of 5°C / min.

[0067] The obtained ferroelectric multilayer device was subjected to DC polarization under the following conditions: an electric field strength of 8 kV / mm and a holding voltage of 10 min in silicone oil. Hysteresis loop tests were performed on the ferroelectric multilayer device at different temperatures and under isostatic pressure. The test results are as follows: Figure 4 and Figure 7 As shown in the figure, the hysteresis loop of Example 2 exhibits a waisting phenomenon at around 90℃, which is basically consistent with the depolarization temperature of Example 1. Under isostatic pressure, the polarized samples can release surface bound charges within the range of 0-450 MPa. Figure 7 As can be seen, with the increase of pressure, the depolarization discharge increases, and the corresponding hysteresis loop shows a waisting phenomenon, indicating that the threshold of pressure-induced ferroelectric-relaxation phase transition is low.

[0068] Example 3

[0069] This embodiment provides a ferroelectric multilayer device, which differs from Embodiment 1 only in that the cutting size of the ferroelectric multilayer device is 1cm. 2 The device layer thickness is 0.08 mm.

[0070] Figure 1 The diagram shows the dielectric and electrode layers of the ferroelectric multilayer device obtained in this embodiment. As can be seen from the diagram, the electrode layers are clearly defined and uniformly distributed among the dielectric layers. The obtained ferroelectric multilayer device was DC polarized under the following conditions: an electric field strength of 8 kV / mm and a holding voltage in silicone oil for 10 min. Hysteresis loop tests were performed on the ferroelectric multilayer device at different temperatures, and the test results are as follows. Figure 5 As shown in the figure, the hysteresis loop of Example 3 still exhibits typical ferroelectric characteristics at 120℃. With increasing temperature, the remanent polarization intensity changes very little, indicating good temperature stability.

[0071] Example 4

[0072] This embodiment provides a ferroelectric multilayer device, which differs from Embodiment 1 only in the composition of the BNT-based ceramic composite material, specifically as follows: 0.97{0.99[(Bi 0.5 Na 0.5 (Ti) 0.995 Mn 0.005 )]O3-0.01BiAlO3}-0.03NaNbO3.

[0073] Example 5

[0074] This embodiment provides a ferroelectric multilayer device, which differs from Embodiment 1 only in the composition of the BNT-based ceramic composite material, specifically as follows: 0.98{0.99[(Bi 0.5 Na 0.5 (Ti) 0.995 Mn 0.005 )]O3-0.01BiAlO3}-0.02NaNbO3.

[0075] Example 6

[0076] This embodiment provides a ferroelectric multilayer device, which differs from Embodiment 1 only in that the calcination temperature is 850℃ and the holding time is 1.5h.

[0077] Comparative Example 1

[0078] This comparative example provides a bulk ceramic device using the same BNT-based composite ceramic material as in Example 1. The bulk ceramic device is prepared using a traditional solid-state method. The specific steps are as follows: 9 wt% polyvinyl alcohol (PVA) is weighed and mixed with BNT powder for granulation, aging, and passing through a 40-mesh sieve. The mixture is then pressed into small cylinders with a diameter of 13 mm and a height of 1 mm under a pressure of 200 MPa. After debinding at 750°C for 2 hours, the blank is sintered. The sintering process conditions are: heating to 1080°C at a rate of 2°C / min, holding for 2 hours, cooling to room temperature in the furnace, smoothing, and coating with a silver external electrode before silver firing.

[0079] Comparative Example 2

[0080] This comparative example provides a bulk ceramic device, which differs from Comparative Example 1 only in that its composition is 0.99{0.98[(Bi) 0.5 Na 0.5 (Ti) 0.995 Mn 0.005 The device was prepared using the same method as Comparative Example 1. Hysteresis loop testing was performed on the ferroelectric ceramic device. Figure 8 The hysteresis loops of Comparative Examples 1 and 2 under an alternating electric field of 8.0 kV / mm and 1 Hz show that both hysteresis loops exhibit ferroelectricity, and the residual polarization is higher when BiAlO3 is 0.01. Therefore, in terms of powder selection, powder with x = 0.01 is selected for the fabrication of ferroelectric multilayer devices.

[0081] Test case

[0082] The devices obtained in the comparative example were tested using the same testing methods as those used in the embodiments. The specific test results are shown in the table below:

[0083] Table 1

[0084]

[0085] The data in the table above show that, under the same conditions of preparing BNT-based composite ceramic materials, the bulk ceramic device (Comparative Example 1) often fails to achieve its optimal theoretical energy storage density and has a low breakdown field strength. In contrast, the ferroelectric multilayer devices prepared in Examples 1-3 all have better breakdown field strengths than Comparative Example 1, with Example 2 achieving an actual energy storage density of 7.4 J / cm². 3 The actual energy storage density of Example 3 reached 5.7 J / cm³. 3 In particular, the actual energy storage density of Example 1 is close to its theoretical energy storage density, reaching 10.6 J / cm³. 3 This demonstrates its enormous application potential.

[0086] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A ferroelectric multilayer device, characterized in that, This includes BNT-based composite ceramic materials, the chemical composition of which is: 0.99{0.99[(Bi 0.5 Na 0.5 (Ti) 0.995 Mn 0.005) ]O3-0.01BiAlO3}-0.01NaNbO3; The ferroelectric multilayer device has a layer thickness of 0.01mm to 0.03mm; The preparation method of the BNT-based composite ceramic material includes the following steps: S1, Weigh the raw materials according to the stoichiometric ratio in the chemical composition of BNT-based composite ceramic materials; S2, the raw materials are mixed, pressed into blocks, calcined, and pulverized to obtain the BNT-based composite ceramic material; the calcination temperature is 750℃ and the calcination time is 2h; The method for fabricating the ferroelectric multilayer device includes the following steps: S11, BNT-based composite ceramic material, solvent, binder, plasticizer, and dispersant are mixed to obtain a ceramic slurry; the mass percentage of each component in the ceramic slurry is as follows: The composition of BNT-based composite ceramic material is as follows: 44% solvent, 50% binder, 3.8 wt% plasticizer, 1.7 wt% plasticizer, and 0.5 wt% dispersant. The solvent is a mixture of alcohol and ethyl acetate in a mass ratio of 1:2.

15. The dispersant is AKM0531. The binder is polyvinyl butyral, and the plasticizer is dioctyl phthalate. S12, the ceramic slurry is cast into a film, the inner electrode is screen-printed, the layers are stacked, the film isostatically pressed, the binder is removed, the film is sintered, and the outer electrode is drawn on to obtain the ferroelectric multilayer device. The sintering step is performed at a heating rate of 0.1 to 0.5 °C / min to 1000 to 1200 °C.

2. The ferroelectric multilayer device according to claim 1, characterized in that, In step S12, the glue removal step is carried out in an oxygen-containing atmosphere, with the temperature increased to 300~500℃ at a heating rate of less than 1℃ / min, and held at that temperature for 1~3 hours. The sintering step is carried out in an oxygen-containing atmosphere and held at that temperature for 1 to 3 hours.

3. The application of the ferroelectric multilayer device according to any one of claims 1-2 in a high-power pulse power supply.

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