Lead-free high-energy-storage-density ceramic material with sandwich structure as well as preparation method and application of lead-free high-energy-storage-density ceramic material

Abstract

The invention discloses a lead-free high-energy-storage-density ceramic material with a sandwich structure and a preparation method and application of the lead-free high-energy-storage-density ceramic material with the sandwich structure, according to the method, 0.8 Na < 0.35 > Bi < 0.35 > Sr < 0.3 > TiO3 <-0.2 > CaAl < 0.5 > Ta < 0.5 > O3 (NBST-CAT) layers and 0.8 (Na < 0.5 > Bi < 0.5 >) TiO3 <-0.2 > (Ba0. 7Sr < 0.3 >) (Mg < 1 / 3 > Ta < 2 / 3 >) O3 (NBT-BSMT) layers are subjected to alternate superposition, pressurization, glue discharging and sintering treatment, and the lead-free high-energy-storage-density ceramic material with the sandwich structure is prepared. The technical problem that the maximum polarization intensity and the breakdown electric field intensity of the sodium bismuth titanate ceramic prepared by doping modification and other methods in the prior art cannot be improved at the same time is effectively solved.

Description

Technical Field

[0001] This invention belongs to the field of dielectric energy storage ceramic capacitor technology, and relates to a sandwich structure lead-free high energy density ceramic material, its preparation method and application. Background Technology

[0002] To address the increasingly severe energy and environmental problems worldwide, the clean energy industry is developing rapidly. Against this backdrop, energy storage devices play an indispensable role. Compared to other energy storage devices such as batteries and electrochemical capacitors, dielectric capacitors stand out due to their ultra-high power density and rapid charge / discharge capabilities, and have been widely used in pulse power systems and hybrid vehicles. However, the release density of dielectric capacitors (…) W rec The energy density of energy storage ceramic materials is far lower than that of batteries and electrochemical capacitors, and most traditional dielectric capacitors contain lead, which is harmful to the environment and human health. Therefore, the development of environmentally friendly capacitors with high energy storage performance is urgent. Typically, the energy storage density of energy storage ceramic materials can be measured by the hysteresis loop (…). PE The curve was calculated to obtain this result. W rec The total energy density ( ) is the closed region enclosed by the discharge curve and the Y-axis in the hysteresis loop. W tot () represents the closed region enclosed by the charging curve and the Y-axis in the hysteresis loop. W rec and W tot It can be expressed by the following formula:

[0003] From equations (1) and (2), it can be seen that in order to obtain a high energy storage density, the prepared ceramic material must have a high breakdown electric field strength. E b ), large maximum polarization intensity ( P max ) and small remanent polarization intensity ( P r ).

[0004] Sodium bismuth titanate (Bi) 0.5 Na 0.5 TiO3 (NBT) belongs to the ABO3 type perovskite crystal and is a typical lead-free dielectric and ferroelectric material with high dielectric properties. P max And a lower dielectric loss value, but a breakdown electric field strength ( E b The value of Bi is relatively small, making Bi... 0.5 Na 0.5TiO3-based materials have low energy density. In recent years, researchers have used doping and solid solution techniques to improve the energy density of NBT ceramic systems. E b A series of studies were conducted, but due to limitations in the electrostriction effect, improvements were made. E b Often at the cost of sacrifice P max This comes at a cost. This contradiction makes it difficult to simultaneously achieve high quality in ceramics prepared through methods such as doping modification. P max and high E b Ultimately, this limits the practical value of this material system in energy storage applications. Therefore, the electric field strength, energy density, and energy storage efficiency of lead-free energy storage ceramic dielectric materials need further improvement. Summary of the Invention

[0005] To address the problems existing in the prior art, this invention provides a sandwich-structured lead-free high energy density ceramic material, its preparation method, and its application, thereby solving the technical problem that the maximum polarization intensity and breakdown electric field intensity of sodium bismuth titanate ceramics prepared by doping modification and other methods in the prior art cannot be improved simultaneously.

[0006] This invention is achieved through the following technical solution: A method for preparing a sandwich-structured lead-free high-energy-density ceramic material includes the following steps: S1: Preparation of 0.8Na 0.35 Bi 0.35 Sr 0.3 TiO3-0.2CaAl 0.5 Ta 0.5 O3 powder and 0.8 (Na) 0.5 Bi 0.5 TiO3-0.2(Ba 0.7 Sr 0.3 (Mg) 1 / 3 Ta 2 / 3 )O3 powder; S2: The 0.8Na 0.35 Bi 0.35 Sr 0.3 TiO3-0.2CaAl 0.5 Ta 0.5 O3 powder and 0.8 (Na) 0.5 Bi 0.5 TiO3-0.2(Ba 0.7 Sr 0.3 (Mg) 1 / 3 Ta 2 / 3O3 powder was mixed with organic solvent, binder, emulsifier, dispersant and plasticizer to prepare NBST-CAT casting slurry and NBT-BSMT casting slurry; S3: After forming NBST-CAT casting slurry and NBT-BSMT casting slurry, NBST-CAT casting layer and NBT-BSMT casting layer are obtained respectively. The NBST-CAT casting layer and NBT-BSMT casting layer are alternately stacked, and after pressing and heat treatment, ceramic material green body is obtained. S4: After debinding and sintering the ceramic material green body, the lead-free high energy density ceramic material with sandwich structure is obtained.

[0007] Preferably, in step S2, the organic solvent is a mixture of anhydrous ethanol and butanone.

[0008] Preferably, in step S2, the amounts of anhydrous ethanol and butanone added to the NBST-CAT casting slurry are 0.8Na and 0.8Na, respectively. 0.35 Bi 0.35 Sr 0.3 TiO3-0.2CaAl 0.5 Ta 0.5 45%~55% and 95%~105% of the O3 powder mass; The amounts of anhydrous ethanol and butanone added to the NBT-BSMT casting slurry were 0.8 (Na) 0.5 Bi 0.5 TiO3-0.2(Ba 0.7 Sr 0.3 (Mg) 1 / 3 Ta 2 / 3 )45%~55% and 95%~105% of the O3 powder mass; Preferably, in step S3, when the NBST-CAT casting layer and the NBT-BSMT casting layer are alternately stacked, a total of eight layers are set, wherein the two sides are NBT-BSMT casting layers and the middle is an NBST-CAT casting layer, and the two sides are each provided with 1 to 3 NBT-BSMT casting layers, and the middle is provided with 2 to 6 NBST-CAT casting layers.

[0009] Preferably, in step S3, when the NBST-CAT casting layer and the NBT-BSMT casting layer are alternately stacked, a total of eight layers are set, wherein the two sides are NBT-BSMT casting layers and the middle is an NBST-CAT casting layer, and the two sides are each set with 2 NBT-BSMT casting layers, and the middle is set with 4 NBST-CAT casting layers.

[0010] Preferably, in step S3, the NBST-CAT cast layer and the NBT-BSMT cast layer are alternately stacked, and after pressing and heat treatment, a ceramic material green body is obtained. Specifically, the ceramic material green body is obtained by pressing under a first pressure and then performing a heat treatment, and then pressing under a second pressure and then performing a second heat treatment. The first pressure is less than the second pressure.

[0011] Preferably, in step S4, the glue discharge temperature is 500~600℃ and the glue discharge time is 1~3h.

[0012] Preferably, in step S4, the sintering temperature is 1170~1180℃ and the holding time is 1~3h.

[0013] A lead-free, high-energy-density ceramic material with a sandwich structure is prepared by the method described above; the electric field strength of the ceramic material is greater than 300 kV / cm, and the energy storage density is greater than 5 J / cm². 3 .

[0014] The above-mentioned sandwich structure of lead-free high energy density ceramic material is used in dielectric capacitors.

[0015] Compared with the prior art, the present invention has the following beneficial technical effects: This invention provides a method for preparing a sandwich-structured lead-free high-energy-density ceramic material, wherein the method involves using 0.8Na 0.35 Bi 0.35 Sr 0.3 TiO3-0.2CaAl 0.5 Ta 0.5 O3 (NBST-CAT) layer and 0.8 (Na) 0.5 Bi 0.5 TiO3-0.2(Ba 0.7 Sr 0.3 (Mg) 1 / 3 Ta 2 / 3 By alternating layers of NBT-BSMT (Non-Bipolar Metal-Based Metal-Based Metal) (NBT-BSMT), pressurization, binder removal, and sintering, a sandwich-structured lead-free high-energy-density ceramic material can be obtained. Among these, NBT-BSMT has a relatively large grain size, with an average grain size of 2.2~2.8μm, and exhibits high energy density. P max However, its E b The grain size is relatively small; while NBST-CAT has a smaller grain size, with an average grain size of 0.6~1.2μm, making it more... E b However, its P maxThe difference in sintering temperature and thermal expansion coefficient between NBT-BSMT and NBST-CAT is relatively small, which is beneficial for obtaining dense ceramics. Such ceramics can enhance the high-density properties of NBT-BSMT. P max Advantages and NBST-CAT high E b The combination of these advantages allows it to simultaneously possess the high performance of NBT-BSMT. P max and NBST-CAT's high E b This invention yields a high-energy-density sandwich-structured ceramic. The lead-free, high-energy-density sandwich-structured ceramic material of this invention exhibits excellent energy density, simple preparation process, good stability, and excellent sintering performance, meeting the needs of various applications. Furthermore, it is lead-free and pollution-free, inexpensive, and technologically mature, making it suitable for industrial production.

[0016] Furthermore, in step S2, the organic solvent is a mixture of anhydrous ethanol and methyl ethyl ketone (MEK). Since anhydrous ethanol and MEK have different evaporation rates, selecting a specific ratio of anhydrous ethanol and MEK ensures that some solvent remains while evaporating, effectively preventing surface cracking caused by excessively rapid evaporation. Simultaneously, the casting slurry obtained by this invention exhibits good stability and rheological properties, high solids content, and can be dried quickly and efficiently, shortening drying time and facilitating large-scale industrial production.

[0017] Furthermore, in step S2, the amounts of anhydrous ethanol and butanone added to the NBST-CAT casting slurry are 0.8Na and 0.8Na, respectively. 0.35 Bi 0.35 Sr 0.3 TiO3-0.2CaAl 0.5 Ta 0.5 The O3 powder content is 45%~55% and 95%~105% by mass; the anhydrous ethanol and butanone content in the NBT-BSMT casting slurry are 0.8 (Na) 0.5 Bi 0.5 TiO3-0.2(Ba 0.7 Sr 0.3 (Mg) 1 / 3 Ta 2 / 3 Including 45%~55% and 95%~105% of O3 powder by mass can make the cast film tape more uniform.

[0018] Furthermore, in step S3, when the NBST-CAT and NBT-BSMT cast layers are alternately stacked, a total of eight layers are set, wherein the two sides are NBT-BSMT cast layers and the middle is an NBST-CAT cast layer. The two sides are each set with 1 to 3 NBT-BSMT cast layers and the middle is set with 2 to 6 NBST-CAT cast layers. Preferably, the two sides are each set with 2 NBT-BSMT cast layers and the middle is set with 4 NBST-CAT cast layers. This makes the number of NBST-CAT cast layers and NBT-BSMT cast layers the same, which will have both high breakdown strength and high polarization strength, thereby obtaining high energy storage density.

[0019] Furthermore, in step S3, the NBST-CAT cast layer and the NBT-BSMT cast layer are alternately stacked, and after pressing and heat treatment, a ceramic material green body is obtained. Specifically, the ceramic material green body is obtained by pressing under a first pressure and then performing a heat treatment, and then pressing under a second pressure and then performing a second heat treatment. The first pressure is less than the second pressure, which can prevent microcracks from appearing in the ceramic material green body, and it will be more dense in the subsequent sintering process.

[0020] Furthermore, in step S4, the debinding temperature is 500~600℃ and the debinding time is 1~3h, which can completely remove the colloid in the ceramic material and prevent pores from being left due to incomplete removal of colloid during subsequent sintering.

[0021] Furthermore, in step S4, the sintering temperature is 1170~1180℃ and the holding time is 1~3h, which can make the ceramic material more dense and have higher breakdown strength and energy storage efficiency.

[0022] Furthermore, this invention also discloses a sandwich-structured lead-free high energy density ceramic material prepared by the above method. The sandwich-structured lead-free high energy density ceramic material prepared by this invention has an alternating layered structure. This ceramic material has a high breakdown electric field strength, excellent energy storage characteristics, and an energy storage density of 5 J / cm². 3 The electric field strengths of all the above are above 300kV / cm, and the casting technology used in the preparation process is mature, inexpensive, environmentally friendly, and practical. Attached Figure Description

[0023] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 This is a schematic diagram of the stacking method of the lead-free multilayer ceramic material in Comparative Example 1; Figure 2 The X-ray diffraction (XRD) test results are for the sandwich-structured lead-free high energy density ceramic materials prepared in Comparative Examples 1, 2 and 2 of this invention. Figure 3 This is a SEM image of the lead-free multilayer ceramic material prepared in Comparative Example 1 of the present invention. Figure 4 The hysteresis loop of the lead-free multilayer ceramic material prepared in Comparative Example 1 of the present invention at room temperature (test frequency is 10 Hz). Figure 5 The dielectric temperature spectrum of the lead-free multilayer ceramic material prepared in Comparative Example 1 of this invention at different test frequencies; Figure 6 This is a schematic diagram of the stacking method of the lead-free multilayer ceramic material in Example 1; Figure 7 The hysteresis loop of the sandwich-structured lead-free high energy density ceramic material prepared in Example 1 at room temperature (test frequency 10 Hz). Figure 8 The dielectric temperature spectra of the sandwich-structured lead-free high energy density ceramic material prepared in Example 1 of this invention at different test frequencies are shown. Figure 9 This is a schematic diagram of the stacking method of the lead-free multilayer ceramic material in Example 2; Figure 10 This is a cross-sectional SEM image of the sandwich-structured lead-free high energy density ceramic material prepared in Example 2 of the present invention; Figure 11 for Figure 10 A magnified view of a local area; Figure 12 The hysteresis loop of the sandwich-structured lead-free high energy density ceramic material prepared in Example 2 of the present invention at room temperature (test frequency is 10Hz). Figure 13 The dielectric temperature spectra of the sandwich-structured lead-free high energy density ceramic material prepared in Example 2 of this invention at different test frequencies are shown. Figure 14 Hysteresis loops of the lead-free high energy density ceramic material with alternating layered structure prepared in Example 2 of the present invention at 1Hz, 2Hz, 5Hz, 10Hz, 20Hz, 50Hz and 100Hz under an electric field strength of 200kV / cm (test temperature is room temperature). Figure 15Hysteresis loops of the lead-free high energy density ceramic material with alternating layered structure prepared in Example 2 of the present invention at 200 kV / cm electric field strength, at 20°C, 40°C, 60°C, 80°C, 100°C, 120°C and 140°C (test frequency 10 Hz). Figure 16 Hysteresis loops of the alternating layered lead-free high energy density ceramic material prepared in Example 2 of the present invention at room temperature and an electric field strength of 200 kV / cm at 1, 10, 100, 1000, 5000, 10000, 50000 and 100000 cycles respectively (test frequency 10 Hz). Figure 17 The image shows the overdamped discharge curves of the sandwich-structured lead-free high energy density ceramic material prepared in Example 2 of this invention at room temperature (20°C) and an electric field strength of 250 kV / cm. Figure 18 The graph shows the change in discharge energy density over time of the sandwich-structured lead-free high energy density ceramic material prepared in Example 2 of this invention at room temperature (20°C) and an electric field strength of 250 kV / cm. Figure 19 The image shows the overdamped discharge curves of the sandwich-structured lead-free high energy density ceramic material prepared in Example 2 of this invention at 140°C and 250 kV / cm electric field strength. Figure 20 The graph shows the discharge energy density of the sandwich-structured lead-free high energy density ceramic material prepared in Example 2 of the present invention as a function of time under an electric field strength of 250 kV / cm and at 140°C. Figure 21 The figure shows the underdamped discharge curves of the sandwich-structured lead-free high energy density ceramic material prepared in Example 2 of this invention at room temperature and an electric field strength of 250 kV / cm. Figure 22 This is an underdamped discharge curve of the sandwich-structured lead-free high energy density ceramic material prepared in Example 2 of the present invention at 140°C and 250kV / cm electric field strength. Figure 23 This is a schematic diagram of the stacking method of the lead-free multilayer ceramic material in Example 3; Figure 24 The hysteresis loop of the sandwich-structured lead-free high energy density ceramic material prepared in Example 3 of the present invention at room temperature (test frequency is 10Hz). Figure 25 The dielectric temperature spectra of the sandwich-structured lead-free high energy density ceramic material prepared in Example 3 of this invention at different test frequencies are shown. Figure 26This is a schematic diagram of the stacking method of the lead-free multilayer ceramic material in Comparative Example 2; Figure 27 This is a SEM image of the lead-free multilayer ceramic material prepared in Comparative Example 2 of this invention. Figure 28 The hysteresis loop of the lead-free multilayer ceramic material prepared in Comparative Example 2 of the present invention at room temperature (test frequency is 10Hz). Figure 29 The dielectric temperature spectrum of the lead-free multilayer ceramic material prepared in Comparative Example 2 of this invention at different test frequencies is shown. Detailed Implementation

[0025] To enable those skilled in the art to understand the features and effects of the present invention, the terms and expressions used in the specification and claims are explained and defined in general below. Unless otherwise specified, all technical and scientific terms used herein have the ordinary meaning understood by those skilled in the art regarding the present invention, and in case of conflict, the definitions in this specification shall prevail.

[0026] The theories or mechanisms described and disclosed herein, whether right or wrong, should not in any way limit the scope of the invention, that is, the contents of the invention can be implemented without being limited by any particular theory or mechanism.

[0027] In this document, all features defined by numerical ranges or percentage ranges, such as numerical values, quantities, contents, and concentrations, are for the sake of brevity and convenience only. Accordingly, descriptions of numerical ranges or percentage ranges should be considered as covering and specifically disclosing all possible sub-ranges and individual numerical values ​​(including integers and fractions) within those ranges.

[0028] In this article, unless otherwise specified, “contains,” “includes,” “containing,” “has,” or similar terms cover the meanings of “composed of” and “mainly composed of,” for example, “A contains a” covers the meanings of “A contains a and others” and “A contains only a.”

[0029] For the sake of brevity, not all possible combinations of the technical features in each implementation scheme or embodiment are described herein. Therefore, as long as there is no contradiction in the combination of these technical features, the technical features in each implementation scheme or embodiment can be combined arbitrarily, and all possible combinations should be considered within the scope of this specification.

[0030] This invention provides a lead-free high energy density ceramic material with a sandwich structure, which is prepared by stacking NBST-CAT and NBT-BSMT, pressurizing, debinding, and sintering.

[0031] Among them, NBST-CAT is 0.8Na. 0.35 Bi0.35 Sr 0.3 TiO3-0.2CaAl 0.5 Ta 0.5 O3; NBT-BSMT is 0.8 (Na) 0.5 Bi 0.5 TiO3-0.2(Ba 0.7 Sr 0.3 (Mg) 1 / 3 Ta 2 / 3 )O3.

[0032] Specifically, the preparation method of a sandwich-structured lead-free high energy density ceramic material of the present invention includes the following steps: (1) According to the chemical formula 0.8Na 0.35 Bi 0.35 Sr 0.3 TiO3-0.2CaAl 0.5 Ta 0.5 O3 was prepared by mixing analytically pure Na2CO3, Bi2O3, TiO2, CaCO3, SrCO3, Al2O3, and Ta2O5, drying the mixture, sieving it, and then pre-calcining it at 850°C for 2-4 hours to obtain a solid powder. The lumpy powder was then sieved through a 120-mesh sieve to obtain NBST-CAT powder. The homogenization process was carried out using anhydrous ethanol as the medium via ball milling for 20-28 hours, and all powders were dried at 100°C after ball milling.

[0033] (2) According to the chemical formula 0.8 (Na 0.5 Bi 0.5 TiO3-0.2(Ba 0.7 Sr 0.3 (Mg) 1 / 3 Ta 2 / 3 Na2CO3, Bi2O3, TiO2, SrCO3, BaCO3, MgO2 and Ta2O5 are formulated and mixed evenly, dried and sieved, and then pre-calcined at 830°C for 1-3 hours to obtain block powder. The block powder is then passed through a 120-mesh sieve to obtain NBT-BSMT powder. The mixing process is carried out by ball milling with anhydrous ethanol as the medium for 20-28 hours, and all powders are dried at 100°C after ball milling.

[0034] (3) Preparation of casting paste: ① Weigh the organic solvent, binder and emulsifier according to the ratio, and ball mill for 4~6 hours to mix them evenly; ② Add the NBST-CAT powder, dispersant and plasticizer obtained in step (1) to the slurry after mixing evenly in step ①, and ball mill for 4~6 hours to mix evenly to obtain NBST-CAT casting slurry.

[0035] Add the NBT-BSMT powder, dispersant and plasticizer obtained in step (2) to the slurry after mixing evenly in step ①, and ball mill for 4~6 hours to mix evenly to obtain NBT-BSMT casting slurry.

[0036] The organic solvent mentioned above is a mixture of anhydrous ethanol and butanone. The adhesive is polyvinyl butyral; The emulsifier is trioleic acid glyceride; The dispersant is polyethylene glycol; The plasticizer is dibutyl phthalate; The proportions of anhydrous ethanol added are 45%–55% of the powder mass; methyl ethyl ketone (MEK) added is 95%–105% of the powder mass; trioleic acid glyceride added is 2%–4% of the powder mass; polyvinyl butyral added is 8%–12% of the powder mass; polyethylene glycol added is 8%–12% of the powder mass; and dibutyl phthalate added is 2%–4% of the powder mass. The powder in this case is 0.8Na. 0.35 Bi 0.35 Sr 0.3 TiO3-0.2CaAl 0.5 Ta 0.5 O3 powder or 0.8 (Na) 0.5 Bi 0.5 TiO3-0.2(Ba 0.7 Sr 0.3 (Mg) 1 / 3 Ta 2 / 3 )O3 powder.

[0037] (4) The NBST-CAT casting slurry and NBT-BSMT casting slurry obtained in step (3) are cast using a casting molding method to obtain NBST-CAT casting layer and NBT-BSMT casting layer respectively. Then, they are cut as needed and stacked alternately. Then, they are pressed for 10 minutes each at 4MPa and 6MPa pressure. After each pressing, they are immediately heat-treated at 80°C for 10 minutes. Then, they are pressed into thin sheets of 55~75μm to obtain a sandwich structure lead-free high energy density ceramic material green body. The cutting can be carried out according to the actual required size. Stacking refers to stacking the NBST-CAT casting layer and the NBT-BSMT casting layer. Specifically, the NBST-CAT casting layer is placed in the middle of the NBT-BSMT casting layer to obtain a sandwich structure lead-free high energy density ceramic material green body.

[0038] When NBST-CAT and NBT-BSMT casting layers are alternately stacked, a total of eight layers are set. The two sides consist of NBT-BSMT casting layers, and the middle layer is an NBST-CAT casting layer. The two sides each have 1 to 3 NBT-BSMT casting layers, and the middle layer has 2 to 6 NBST-CAT casting layers. In a preferred embodiment, the two sides each have 2 NBT-BSMT casting layers, and the middle layer has 4 NBST-CAT casting layers.

[0039] (5) The green body of the lead-free high energy density ceramic material with alternating layered structure obtained in step (4) is heat-treated at 500~600℃ for 1~3h to remove the binder, and then heat-treated at 1170~1180℃ for 1~3h to sinter into ceramic, thereby obtaining the lead-free high energy density ceramic material with sandwich structure. The present invention uses X-ray diffraction and field emission scanning electron microscopy to test the physical structural characteristics of the obtained sandwich-structured lead-free high energy density ceramic material. In addition, a gold film was deposited on the surface of the sintered sample, i.e., the obtained sandwich-structured lead-free high energy density ceramic material, to obtain a gold-plated electrode. Then, its ferroelectric properties were tested at a frequency of 10 Hz at room temperature, and its energy storage characteristics were calculated to obtain the recoverable energy density. W rec Total energy storage density ( W total ) and energy storage efficiency ( η The charge-discharge performance of the gold-plated electrode was tested at room temperature and an electric field strength of 250 kV / cm, and the discharge energy storage density was also measured. W dis ), current density ( C D ) and power density ( P D The calculation formula is as follows:

[0040] in, Represents current. Indicates the load resistance. Indicates the sample volume. Indicates the electrode area. Indicates the maximum current intensity. This indicates the intensity of the applied electric field.

[0041] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0042] The following examples use instruments and equipment conventional in the art. Experimental methods in the following examples, unless otherwise specified, are generally performed under conventional conditions or as recommended by the manufacturer. All raw materials used in the following examples are conventional commercially available products with specifications conventional in the art. In this specification and the following examples, unless otherwise specified, "%" refers to weight percentage, "parts" refers to parts by weight, and "ratio" refers to weight proportion.

[0043] Comparative Example 1 A lead-free multilayer ceramic material with the chemical formula: 0.8(Na) 0.5 Bi 0.5 TiO3-0.2(Ba 0.7 Sr 0.3 (Mg) 1 / 3Ta 2 / 3 O3 (NBT-BSMT). Figure 1 This is a schematic diagram of the stacking method of the lead-free multilayer ceramic material in Comparative Example 1.

[0044] (1) The preparation method of the above-mentioned lead-free multilayer high energy density ceramic material includes the following steps: according to the chemical formula 0.8(Na 0.5 Bi 0.5 TiO3-0.2(Ba 0.7 Sr 0.3 (Mg) 1 / 3 Ta 2 / 3 )O3, analytical grade Na2CO3, Bi2O3, TiO2, SrCO3, BaCO3, MgO2 and Ta2O5 were mixed by ball milling for 24 hours with anhydrous ethanol as the medium, dried at 100℃, passed through a 120-mesh sieve, and then pre-calcined at 830℃ for 2 hours to obtain a block solid. The block solid was then pulverized and ball milled again with anhydrous ethanol as the medium for 24 hours to obtain a uniform mixture. Then it was dried at 100℃ and passed through a 120-mesh sieve to obtain NBT-BSMT powder. (2) Preparation of casting paste: ① Weigh the organic solvent (anhydrous ethanol and methyl ethyl ketone), binder (polyvinyl butyral) and emulsifier (trioleyl glycerol) according to the ratio, and ball mill for 4 hours to mix them evenly; ② Add the powder, dispersant (polyethylene glycol) and plasticizer (dibutyl phthalate) obtained in step (1) to the slurry after mixing evenly in step ①, and ball mill for 4 hours to mix evenly to obtain NBT-BSMT casting slurry.

[0045] The amount of anhydrous ethanol added is 45% of the powder mass; the amount of butanone added is 95% of the powder mass; the amount of trioleic acid glyceride added is 2% of the powder mass; the amount of polyvinyl butyral added is 8% of the powder mass; the amount of polyethylene glycol added is 8% of the powder mass; and the amount of dibutyl phthalate added is 2% of the powder mass.

[0046] (4) The NBT-BSMT casting slurry obtained in step (3) is cast into an NBT-BSMT casting layer by casting molding. Then, it is cut and stacked as needed. For specific stacking methods, see [link to relevant documentation]. Figure 25 Then, it is pressed for 10 minutes each at 4MPa and 6MPa, and immediately after each pressing, it is heat-treated at 80°C for 10 minutes. Then it is pressed into thin sheets of 55~75μm to obtain lead-free multilayer ceramic material green bodies. (5) The lead-free multilayer ceramic material green body obtained in step (4) is subjected to debinding treatment at 600℃ for 2 hours, and then sintered at 1170℃ for 2 hours to obtain 0.8 (Na) 0.5 Bi 0.5 TiO3-0.2(Ba 0.7 Sr 0.3 (Mg) 1 / 3 Ta 2 / 3 O3 lead-free multilayer ceramic material, product marked as A1.

[0047] Figure 2 The X-ray diffraction (XRD) test results are shown for the sandwich-structured lead-free high energy density ceramic materials prepared in Comparative Examples 1, 2 and 2 of this invention. The XRD patterns show that the ceramic materials obtained in this example have a pure perovskite structure.

[0048] The surface grain growth of the sintered ceramic samples was tested using field emission scanning electron microscopy. Figure 3 The image shows a SEM image of the lead-free multilayer ceramic material prepared in Comparative Example 1 of this invention. As can be seen from the image, the lead-free multilayer ceramic material prepared in Comparative Example 1 has a large grain size and is very dense.

[0049] Gold-plated electrodes were prepared by depositing gold onto the surface of the sintered sample of Comparative Example 1 of this invention, and their ferroelectric properties were then tested at room temperature and a frequency of 10 Hz. Figure 4The image shows the hysteresis loop (test frequency 10Hz) of the lead-free multilayer ceramic material prepared in Comparative Example 1 of this invention at room temperature. Energy storage characteristics calculations based on the hysteresis loop show that the energy storage ceramic in this embodiment can achieve an energy storage density of 5.1 J / cm³ at room temperature. 3 The energy storage efficiency reaches 89%. The energy storage characteristics of this comparative energy storage ceramic material at room temperature are shown in Table 1.

[0050] Figure 5 The figure shows the dielectric temperature spectrum of the lead-free multilayer ceramic material prepared in Comparative Example 1 of this invention at different test frequencies. As can be seen from the figure, the Curie temperature at 1MHz is 133°C and the maximum dielectric constant is 1948.7.

[0051] Example 1 A lead-free high-energy-density ceramic material with an alternating layered structure was prepared by laminating NBST-CAT and NBT-BSMT, applying pressure, debinding, and sintering. NBST-CAT is composed of 0.8Na. 0.35 Bi 0.35 Sr 0.3 TiO3-0.2CaAl 0.5 Ta 0.5 O3; NBT-BSMT is 0.8 (Na) 0.5 Bi 0.5 TiO3-0.2(Ba 0.7 Sr 0.3 (Mg) 1 / 3 Ta 2 / 3 )O3. Figure 6 This refers to the specific layering method.

[0052] Specifically, the preparation method of the aforementioned lead-free high energy density ceramic material with alternating layered structures includes the following steps: (1) According to the chemical formula 0.8Na 0.35 Bi 0.35 Sr 0.3 TiO3-0.2CaAl 0.5 Ta 0.5 O3 was prepared by mixing analytically pure Na2CO3, Bi2O3, TiO2, CaCO3, SrCO3, Al2O3 and Ta2O5, and then ball-milling the mixture for 24 hours with anhydrous ethanol as the medium. The mixture was then dried at 100°C, passed through a 120-mesh sieve, and pre-calcined at 850°C for 3 hours to obtain a blocky solid. The blocky solid was then pulverized and ball-milled again for 24 hours with anhydrous ethanol as the medium to obtain a uniform mixture. Finally, it was dried at 100°C and passed through a 120-mesh sieve to obtain NBST-CAT powder. (2) According to the chemical formula 0.8 (Na 0.5 Bi 0.5 TiO3-0.2(Ba0.7 Sr 0.3 (Mg) 1 / 3 Ta 2 / 3 Na2CO3, Bi2O3, TiO2, SrCO3, BaCO3, MgO2 and Ta2O5 are mixed evenly, dried and sieved, and then pre-calcined at 830°C for 2 hours to obtain block powder. The block powder is then sieved through a 120-mesh sieve to obtain NBT-BSMT powder. (3) Preparation of casting paste: ① Weigh the organic solvent (anhydrous ethanol and methyl ethyl ketone), binder (polyvinyl butyral) and emulsifier (trioleyl glycerol) according to the ratio, and ball mill for 4 hours to mix them evenly; ② Add the powder, dispersant (polyethylene glycol) and plasticizer (dibutyl phthalate) obtained in step (1) to the slurry after mixing evenly in step ①, and ball mill for 4 hours to mix evenly to obtain NBST-CAT casting slurry.

[0053] Add the powder, dispersant (polyethylene glycol) and plasticizer (dibutyl phthalate) obtained in step (2) to the slurry after mixing evenly in step ①, and ball mill for 4 hours to mix evenly to obtain NBT-BSMT casting slurry.

[0054] The amount of anhydrous ethanol added is 48% of the powder mass; the amount of butanone added is 98% of the powder mass; the amount of trioleic acid glyceride added is 2.5% of the powder mass; the amount of polyvinyl butyral added is 9% of the powder mass; the amount of polyethylene glycol added is 9% of the powder mass; and the amount of dibutyl phthalate added is 2.5% of the powder mass.

[0055] (4) The NBST-CAT casting paste and NBT-BSMT casting paste obtained in step (3) are cast together by casting to obtain NBST-CAT casting layer and NBT-BSMT casting layer respectively; then they are cut as needed, and then the NBST-CAT casting layer is placed in the middle of the NBT-BSMT casting layer. For the specific stacking method, see Figure 24 The material was pressed for 10 minutes at 4 MPa and 6 MPa, and immediately after each pressing, it was heat-treated at 80°C for 10 minutes. Then it was pressed into thin sheets of 55-75 μm to obtain a sandwich-structured lead-free high energy density ceramic material green body. (5) The green body of the lead-free high energy density ceramic material with alternating layered structure obtained in step (4) is heat-treated at 600℃ for 2 hours to remove the glue, and then sintered at 1175℃ for 2 hours to obtain the lead-free high energy density ceramic material with alternating layered structure.

[0056] The sintered sample was plated with gold electrodes, and its ferroelectric properties were then tested at room temperature and 10 Hz. Figure 7 The image shows the hysteresis loop (test frequency 10 Hz) of the sandwich-structured lead-free high energy density ceramic material prepared in Example 1 at room temperature. Energy storage characteristics calculations based on the hysteresis loop show that the energy storage ceramic of this example can achieve an energy density of 6.35 J / cm³ at room temperature. 3 The energy storage efficiency can reach 93%. The energy storage characteristics of the energy storage ceramic material in this embodiment at room temperature are shown in Table 1.

[0057] Figure 8 The figure shows the dielectric temperature spectrum of the sandwich-structured lead-free high energy density ceramic material prepared in Example 1 of the present invention at different test frequencies. As can be seen from the figure, the Curie temperature at 1MHz is 119°C and the maximum dielectric constant is 1898.6.

[0058] Example 2 A lead-free high-energy-density ceramic material with an alternating layered structure was prepared by laminating NBST-CAT and NBT-BSMT, applying pressure, debinding, and sintering. NBST-CAT is composed of 0.8Na. 0.35 Bi 0.35 Sr 0.3 TiO3-0.2CaAl 0.5 Ta 0.5 O3; NBT-BSMT is 0.8 (Na) 0.5 Bi 0.5 TiO3-0.2(Ba 0.7 Sr 0.3 (Mg) 1 / 3 Ta 2 / 3 )O3. Figure 9 This refers to the specific layering method.

[0059] Specifically, the preparation method of the aforementioned lead-free high energy density ceramic material with alternating layered structures includes the following steps: (1) According to the chemical formula 0.8Na 0.35 Bi 0.35 Sr 0.3 TiO3-0.2CaAl 0.5 Ta 0.5 O3 was prepared by mixing analytically pure Na2CO3, Bi2O3, TiO2, CaCO3, SrCO3, Al2O3 and Ta2O5, and then ball-milling the mixture for 24 hours with anhydrous ethanol as the medium. The mixture was then dried at 100°C, passed through a 120-mesh sieve, and pre-calcined at 850°C for 3 hours to obtain a blocky solid. The blocky solid was then pulverized and ball-milled again for 24 hours with anhydrous ethanol as the medium to obtain a uniform mixture. Finally, it was dried at 100°C and passed through a 120-mesh sieve to obtain NBST-CAT powder. (2) According to the chemical formula 0.8 (Na 0.5 Bi0.5 TiO3-0.2(Ba 0.7 Sr 0.3 (Mg) 1 / 3 Ta 2 / 3 Na2CO3, Bi2O3, TiO2, SrCO3, BaCO3, MgO2 and Ta2O5 are mixed evenly, dried and sieved, and then pre-calcined at 830°C for 2 hours to obtain block powder. The block powder is then sieved through a 120-mesh sieve to obtain NBT-BSMT powder. (3) Preparation of casting paste: ① Weigh the organic solvent (anhydrous ethanol and methyl ethyl ketone), binder (polyvinyl butyral) and emulsifier (trioleyl glycerol) according to the ratio, and ball mill for 4 hours to mix them evenly; ② Add the powder, dispersant (polyethylene glycol) and plasticizer (dibutyl phthalate) obtained in step (1) to the slurry after mixing evenly in step ①, and ball mill for 4 hours to mix evenly to obtain NBST-CAT casting slurry.

[0060] Add the powder, dispersant (polyethylene glycol) and plasticizer (dibutyl phthalate) obtained in step (2) to the slurry after mixing evenly in step ①, and ball mill for 4 hours to mix evenly to obtain NBT-BSMT casting slurry.

[0061] The amount of anhydrous ethanol added is 50% of the powder mass; the amount of butanone added is 100% of the powder mass; the amount of trioleic acid glyceride added is 3% of the powder mass; the amount of polyvinyl butyral added is 10% of the powder mass; the amount of polyethylene glycol added is 10% of the powder mass; and the amount of dibutyl phthalate added is 3% of the powder mass.

[0062] (4) The NBST-CAT casting paste and NBT-BSMT casting paste obtained in step (3) are cast together by casting to obtain NBST-CAT casting layer and NBT-BSMT casting layer respectively; then they are cut as needed, and then the NBST-CAT casting layer is placed in the middle of the NBT-BSMT casting layer. For the specific stacking method, see Figure 25 Then, it is pressed for 10 minutes each at 4MPa and 6MPa, and immediately after each pressing, it is heat-treated at 80°C for 10 minutes. Then it is pressed into thin sheets of 55~75μm to obtain a sandwich structure lead-free high energy density ceramic material green body. (5) The green body of the lead-free high energy density ceramic material with alternating layered structure obtained in step (4) is subjected to debinding treatment at 600℃ for 2h, and then sintered at 1175℃ for 2h to obtain the lead-free high energy density ceramic material with sandwich structure, and the product is marked as A3.

[0063] The prepared sandwich-structured lead-free high-energy-density ceramic material was subjected to X-ray diffraction testing, such as... Figure 1 As can be seen from the XRD pattern, the ceramic material obtained in this embodiment has a pure perovskite structure.

[0064] The cross-section of the prepared lead-free high energy density ceramic material with alternating layered structure was tested. Figure 10 The image shows a cross-sectional SEM image of the lead-free high energy density ceramic material with sandwich structure prepared in Example 2 of the present invention. It can be seen from the image that the layered structure of the lead-free high energy density ceramic material with sandwich structure of NBST-CAT / NBT-BSMT prepared in this example is quite obvious. Figure 11 for Figure 10 A magnified view of a local area, by Figure 11 The layered structure of the lead-free high energy density ceramic material with the NBST-CAT / NBT-BSMT sandwich structure prepared in this embodiment can be observed more clearly.

[0065] The sintered sample was plated with gold electrodes, and its ferroelectric properties were then tested at room temperature and 10 Hz. Figure 12 The image shows the hysteresis loop (test frequency 10Hz) of the sandwich-structured lead-free high energy density ceramic material prepared in Example 2 of this invention at room temperature. Energy storage characteristics calculations based on the hysteresis loop show that the energy storage ceramic of this example can achieve an energy storage density of 6.83 J / cm³ at room temperature. 3 The energy storage efficiency can reach 92%. The energy storage characteristics of the energy storage ceramic material in this embodiment at room temperature are shown in Table 1.

[0066] Figure 13 The figure shows the dielectric temperature spectrum of the sandwich-structured lead-free high energy density ceramic material prepared in Example 2 of the present invention at different test frequencies. As can be seen from the figure, the Curie temperature at 1MHz is 118°C and the maximum dielectric constant is 1074.57.

[0067] Figure 14 The alternating layered lead-free high energy density ceramic material prepared in Example 2 of this invention was subjected to hysteresis loops at 1Hz, 2Hz, 5Hz, 10Hz, 20Hz, 50Hz, and 100Hz (test temperature was room temperature) under an electric field strength of 200kV / cm. Energy storage characteristics were calculated from the hysteresis loops, showing that the energy storage ceramic material in this example maintained an energy density of 2.08~1.99 J / cm² under room temperature and a 200kV / cm electric field strength. 3 The energy storage efficiency remains between 93.26% and 95.96%.

[0068] Figure 15The alternating layered lead-free high energy density ceramic material prepared in Example 2 of this invention was subjected to hysteresis loops (test frequency 10 Hz) at 200 kV / cm electric field strength, at temperatures of 20°C, 40°C, 60°C, 80°C, 100°C, 120°C, and 140°C. Energy storage characteristics were calculated from the hysteresis loops. The energy storage ceramic of this example maintains an energy density of 2.05–1.87 J / cm² at 10 Hz within a temperature range of 20–140°C. 3 The energy storage efficiency remains between 95.04% and 97%.

[0069] Figure 16 The hysteresis loops (test frequency 10Hz) of the lead-free high energy density ceramic material with alternating layered structure prepared in Example 2 of this invention are shown below at room temperature and an electric field strength of 200 kV / cm for 1, 10, 100, 1000, 5000, 10000, 50000, and 100000 cycles. Energy storage characteristics are calculated from the hysteresis loops. It can be seen that the energy storage ceramic of this example maintains an energy density of 1.95~2.03 J / cm² at a frequency of 10Hz, an electric field strength of 200 kV / cm, and a temperature of 20°C, with a cycle count range of 1~100000. 3 The energy storage efficiency remained between 94.4% and 95%. This indicates that the energy storage ceramic material in this embodiment has high energy storage performance and exhibits good temperature stability, frequency stability, and fatigue resistance.

[0070] Figure 17 The figure shows the overdamped discharge curves of the sandwich-structured lead-free high energy density ceramic material prepared in Example 2 of this invention at room temperature (20°C) and an electric field strength of 250 kV / cm. As can be seen from the figure, the maximum discharge current of the energy storage ceramic in this example under the conditions of 250 kV / cm electric field strength and 20°C is 6.14 A.

[0071] Figure 18 The graph shows the discharge energy density of the sandwich-structured lead-free high energy density ceramic material prepared in Example 2 of this invention as a function of time under room temperature (20°C) and an electric field strength of 250 kV / cm. As can be seen from the graph, the discharge time of the energy storage ceramic in this example under the conditions of 250 kV / cm electric field strength and 20°C is as short as 118.3 ns, and the discharge energy density is 1.47 J / cm². 3 .

[0072] Figure 19The figure shows the overdamped discharge curves of the sandwich-structured lead-free high energy density ceramic material prepared in Example 2 of the present invention at 140°C and 250kV / cm electric field strength. As can be seen from the figure, the maximum discharge current of the energy storage ceramic in this example under the conditions of 250kV / cm electric field strength and 140°C is 7.6A.

[0073] Figure 20 The graph shows the discharge energy density of the sandwich-structured lead-free high energy density ceramic material prepared in Example 2 of this invention as a function of time under electric field strengths of 140°C and 250 kV / cm. As can be seen from the graph, the discharge time of the energy storage ceramic in this example under electric field strengths of 250 kV / cm and 140°C is as short as 123.6 ns, and the discharge energy density is 1.65 J / cm. 3 .

[0074] Figure 21 The figure shows the underdamped discharge curves of the sandwich-structured lead-free high energy density ceramic material prepared in Example 2 of this invention at room temperature and an electric field strength of 250 kV / cm. As can be seen from the figure, the current density of the energy storage ceramic in this example is 628.1 A / cm² under the conditions of 250 kV / cm electric field strength and 20°C. 2 The power density is 78.52 MW / cm². 3 .

[0075] Figure 22 The figure shows the underdamped discharge curves of the sandwich-structured lead-free high energy density ceramic material prepared in Example 2 of this invention at 140°C and 250 kV / cm electric field strength. As can be seen from the figure, the current density of the energy storage ceramic in this example under the conditions of 250 kV / cm electric field strength and 140°C is 679.5 A / cm. 2 The power density is 84.94 MW / cm². 3 .

[0076] The energy storage characteristics of the energy storage ceramic material prepared according to the embodiments of the present invention at room temperature are shown in Table 1. As can be seen from Table 1, with the increase of the NBST-CAT layer thickness ratio, the breakdown field strength of the lead-free high energy density ceramic material with the sandwich structure of the present invention shows an increasing trend. The highest energy storage density and energy storage efficiency can be obtained when the thickness ratio of the NBT-BSMT layer and the NBST-CAT layer is 1:2:1, and the energy storage density and energy storage efficiency can reach 6.83 J / cm² at room temperature. 3 and 92%; Table 2 shows the energy storage characteristics of the energy storage ceramic material prepared in Example 2 of this invention at temperatures of 20°C, 40°C, 60°C, 80°C, 100°C, 120°C, and 140°C under conditions of 10Hz frequency and 250kV / cm electric field strength. As shown in Table 2, the energy storage density of the energy storage ceramic material in Example 2 of this invention can be maintained at 2.05~1.87 J / cm² at temperatures of 20~140°C under conditions of 10Hz frequency and 200kV / cm electric field strength. 3 Furthermore, the energy storage efficiency fluctuates between 95.04% and 97%.

[0077] Table 3 shows the energy storage characteristics of the energy storage ceramic material in this embodiment at frequencies of 1Hz, 2Hz, 5Hz, 10Hz, 20Hz, 50Hz, and 100Hz under room temperature and an electric field strength of 250kV / cm. As shown in Table 3, the energy storage ceramic material in Example 1 of this invention maintains an energy storage density of 2.08~1.99J / cm² at frequencies of 1~100Hz under room temperature and an electric field strength of 200kV / cm. 3 The energy storage efficiency can be maintained at 93.26~95.96%.

[0078] Table 4 shows the energy storage characteristics of the energy storage ceramic material in this embodiment at 1, 10, 100, 1000, 5000, 10000, 50000, and 100000 cycles under room temperature, 250 kV / cm electric field strength, and 10 Hz conditions. As shown in Table 4, the energy storage ceramic material in Example 2 of this invention maintains an energy density of 1.95~2.03 J / cm² at 1~100000 cycles under room temperature, 10 Hz, and an electric field strength of 200 kV / cm conditions. 3 The energy storage efficiency can be maintained at 94.4-95%; the energy storage density and energy storage efficiency do not fluctuate significantly, showing good frequency stability, temperature stability and fatigue resistance.

[0079] Table 5 shows the charge-discharge characteristics of the energy storage ceramic material in this embodiment under room temperature and an electric field strength of 250 kV / cm. As shown in Table 5, the maximum discharge current of the energy storage ceramic material in Example 1 under room temperature and an electric field strength of 250 kV / cm is 6.14 A, the discharge time is as short as 118.3 ns, and the discharge energy density is 1.47 J / cm². 3 The current density is 628.1 A / cm². 2 The power density is 78.52 MW / cm². 3 .

[0080] Table 6 shows the charge-discharge characteristics of the energy storage ceramic material in this embodiment under an electric field strength of 140°C and 250 kV / cm. As shown in Table 6, the maximum discharge current of the energy storage ceramic material in Example 1 under an electric field strength of 140°C and 250 kV / cm is 7.6 A, the discharge time is as short as 123.6 ns, and the discharge energy density is 1.65 J / cm³. 3 The current density is 679.5 A / cm². 2 The power density is 84.94 MW / cm². 3 The discharge time and discharge energy density did not fluctuate significantly, demonstrating good stability.

[0081] The lead-free high energy density ceramic material with sandwich structure prepared in Example 2 has a polarization intensity similar to that of Comparative Example 1 and a breakdown electric field similar to that of Comparative Example 2, indicating that it combines the advantages of Comparative Example 1 and Comparative Example 2 and produces a synergistic beneficial effect.

[0082] Table 1. Energy storage characteristics of the sandwich-structured lead-free high-energy-density ceramic material in the examples at room temperature and 10 Hz.

[0083] Table 2. Energy storage characteristics of the sandwich-structured lead-free high-energy-density ceramic material at different temperatures at a frequency of 10 Hz in Example 2.

[0084] Table 3. Energy storage characteristics of the sandwich-structured lead-free high-energy-density ceramic material in Example 2 at different frequencies under room temperature conditions.

[0085] Table 4. Energy storage characteristics of the lead-free high energy density ceramic material with sandwich structure in Example 2 at different cycle numbers at 10 Hz and room temperature.

[0086] Table 5. Charge-discharge characteristics of the lead-free high energy density ceramic material with sandwich structure in Example 2 at room temperature and 250 kV / cm electric field strength.

[0087] Table 6. Charge-discharge characteristics of the lead-free high energy density ceramic material with sandwich structure in Example 2 at 140°C and 250 kV / cm electric field strength.

[0088] The above examples demonstrate that when the ratio between the two dielectric layers reaches a specific value, the resulting sandwich-structured ceramic material possesses both the high performance of NBT-BSMT and... P maxand NBST-CAT's high E b This allows for the achievement of high energy storage density. Therefore, the prepared sodium bismuth titanate-based sandwich-structured high-energy-density ceramic material exhibits excellent energy storage performance, good temperature and frequency stability, fatigue resistance, and an ultrafast discharge rate, making it a promising candidate for advanced energy storage systems.

[0089] Example 3 A lead-free high-energy-density ceramic material with an alternating layered structure was prepared by laminating NBST-CAT and NBT-BSMT, applying pressure, debinding, and sintering. NBST-CAT is composed of 0.8Na. 0.35 Bi 0.35 Sr 0.3 TiO3-0.2CaAl 0.5 Ta 0.5 O3; NBT-BSMT is 0.8 (Na) 0.5 Bi 0.5 TiO3-0.2(Ba 0.7 Sr 0.3 (Mg) 1 / 3 Ta 2 / 3 )O3. Figure 23 This refers to the specific layering method.

[0090] Specifically, the preparation method of the aforementioned lead-free high energy density ceramic material with alternating layered structures includes the following steps: (1) According to the chemical formula 0.8Na 0.35 Bi 0.35 Sr 0.3 TiO3-0.2CaAl 0.5 Ta 0.5 O3 was prepared by mixing analytically pure Na2CO3, Bi2O3, TiO2, CaCO3, SrCO3, Al2O3 and Ta2O5, and then ball-milling the mixture for 24 hours with anhydrous ethanol as the medium. The mixture was then dried at 100°C, passed through a 120-mesh sieve, and pre-calcined at 850°C for 3 hours to obtain a blocky solid. The blocky solid was then pulverized and ball-milled again for 24 hours with anhydrous ethanol as the medium to obtain a uniform mixture. Finally, it was dried at 100°C and passed through a 120-mesh sieve to obtain NBST-CAT powder. (2) According to the chemical formula 0.8 (Na 0.5 Bi 0.5 TiO3-0.2(Ba 0.7 Sr 0.3 (Mg) 1 / 3 Ta 2 / 3Na2CO3, Bi2O3, TiO2, SrCO3, BaCO3, MgO2 and Ta2O5 are mixed evenly, dried and sieved, and then pre-calcined at 830°C for 2 hours to obtain block powder. The block powder is then sieved through a 120-mesh sieve to obtain NBT-BSMT powder. (3) Preparation of casting paste: ① Weigh the organic solvent (anhydrous ethanol and methyl ethyl ketone), binder (polyvinyl butyral) and emulsifier (trioleyl glycerol) according to the ratio, and ball mill for 4 hours to mix them evenly; ② Add the powder, dispersant (polyethylene glycol) and plasticizer (dibutyl phthalate) obtained in step (1) to the slurry after mixing evenly in step ①, and ball mill for 4 hours to mix evenly to obtain NBST-CAT casting slurry.

[0091] Add the powder, dispersant (polyethylene glycol) and plasticizer (dibutyl phthalate) obtained in step (2) to the slurry after mixing evenly in step ①, and ball mill for 4 hours to mix evenly to obtain NBT-BSMT casting slurry.

[0092] The amount of anhydrous ethanol added is 52% of the powder mass; the amount of butanone added is 102% of the powder mass; the amount of trioleic acid glyceride added is 3.5% of the powder mass; the amount of polyvinyl butyral added is 11% of the powder mass; the amount of polyethylene glycol added is 11% of the powder mass; and the amount of dibutyl phthalate added is 3.5% of the powder mass.

[0093] (4) The NBST-CAT casting paste and NBT-BSMT casting paste obtained in step (3) are cast together by casting to obtain NBST-CAT casting layer and NBT-BSMT casting layer respectively; then they are cut as needed, and then the NBST-CAT casting layer is placed in the middle of the NBT-BSMT casting layer. For the specific stacking method, see Figure 26 Then, it is pressed for 10 minutes each at 4MPa and 6MPa, and immediately after each pressing, it is heat-treated at 80°C for 10 minutes. Then it is pressed into thin sheets of 55~75μm to obtain a sandwich structure lead-free high energy density ceramic material green body. (5) The green body of the lead-free high energy density ceramic material with alternating layered structure obtained in step (4) is heat-treated at 600℃ for 2h for debinding, and then heat-treated at 1175℃ for 2h for sintering to obtain the lead-free high energy density ceramic material with sandwich structure of NBST-CAT / NBT-BSMT. The sintered sample was plated with gold electrodes, and its ferroelectric properties were then tested at room temperature and 10 Hz. Figure 24The image shows the hysteresis loop (test frequency 10Hz) of the sandwich-structured lead-free high energy density ceramic material prepared in Example 3 of this invention at room temperature. Energy storage characteristics calculations based on the hysteresis loop show that the energy storage ceramic of this example can achieve an energy density of 6.35 J / cm³ at room temperature. 3 The energy storage efficiency can reach 86.5%. The energy storage characteristics of the energy storage ceramic material in this embodiment at room temperature are shown in Table 1.

[0094] Figure 25 The figure shows the dielectric temperature spectrum of the sandwich-structured lead-free high energy density ceramic material prepared in Example 3 of the present invention at different test frequencies. As can be seen from the figure, the Curie temperature at 1MHz is 120°C and the maximum dielectric constant is 1007.8.

[0095] Comparative Example 2 A lead-free multilayer ceramic material with the chemical formula: 0.8Na 0.35 Bi 0.35 Sr 0.3 TiO3-0.2CaAl 0.5 Ta 0.5 O3 (NBST-CAT). Figure 26 This refers to the specific layering method.

[0096] (1) The above-mentioned preparation method of lead-free multilayer high energy density ceramic material includes the following steps: according to the chemical formula 0.8Na 0.35 Bi 0.35 Sr 0.3 TiO3-0.2CaAl 0.5 Ta 0.5 O3, Na2CO3, Bi2O3, TiO2, CaCO3, SrCO3, Al2O3 and Ta2O5 are prepared and mixed evenly, dried and sieved, and then pre-calcined at 850°C for 3 hours to obtain block powder. Then the block powder is passed through a 120-mesh sieve to obtain NBST-CAT powder. (2) Preparation of casting paste: ① Weigh the organic solvent (anhydrous ethanol and methyl ethyl ketone), binder (polyvinyl butyral) and emulsifier (trioleyl glycerol) according to the ratio, and ball mill for 4 hours to mix them evenly; ② Add the powder, dispersant (polyethylene glycol) and plasticizer (dibutyl phthalate) obtained in step (1) to the slurry after mixing evenly in step ①, and ball mill for 4 hours to mix evenly to obtain NBST-CAT casting slurry.

[0097] The amount of anhydrous ethanol added is 55% of the powder mass; the amount of butanone added is 105% of the powder mass; the amount of trioleic acid glyceride added is 4% of the powder mass; the amount of polyvinyl butyral added is 12% of the powder mass; the amount of polyethylene glycol added is 12% of the powder mass; and the amount of dibutyl phthalate added is 4% of the powder mass.

[0098] (4) The NBST-CAT casting slurry obtained in step (3) is cast into an NBST-CAT casting layer by casting molding. Then, it is cut and stacked as needed. For specific stacking methods, see [link to relevant documentation]. Figure 26 Then, it is pressed for 10 minutes each at 4MPa and 6MPa, and immediately after each pressing, it is heat-treated at 80°C for 10 minutes. Then it is pressed into thin sheets of 55-75μm to obtain lead-free multilayer ceramic material green bodies. (5) The lead-free multilayer ceramic material green body obtained in step (4) is kept at 600℃ for 2 hours for debinding treatment, and then sintered at 1170℃ for 2 hours to obtain NBST-CAT lead-free multilayer ceramic material, and the product is marked as A5.

[0099] The prepared lead-free multilayer ceramic material was subjected to X-ray diffraction testing, such as... Figure 1 As can be seen from the XRD pattern, the ceramic material obtained in this embodiment has a pure perovskite structure.

[0100] The surface grain growth of the sintered ceramic samples was tested using field emission scanning electron microscopy. Figure 27 The image shows a SEM image of the lead-free multilayer ceramic material prepared in Comparative Example 2 of this invention. As can be seen from the image, the grain size of the lead-free multilayer ceramic material prepared in Comparative Example 2 is small and very dense, which indicates that its breakdown strength is high (XXX).

[0101] The sintered sample was plated with gold electrodes, and its ferroelectric properties were then tested at room temperature and 10 Hz. Figure 28 The image shows the hysteresis loop (test frequency 10Hz) of the lead-free multilayer ceramic material prepared in Comparative Example 2 of this invention at room temperature. Energy storage characteristics are calculated from the hysteresis loop, showing that the energy storage ceramic in this embodiment can achieve an energy storage density of 5.4 J / cm³ at room temperature. 3 The energy storage efficiency can reach 90%. The energy storage characteristics of the energy storage ceramic material in this embodiment at room temperature are shown in Table 1.

[0102] Figure 29 The figure shows the dielectric temperature spectrum of the lead-free multilayer ceramic material prepared in Comparative Example 2 of this invention at different test frequencies. As can be seen from the figure, the Curie temperature at 1MHz is 98°C and the maximum dielectric constant is 826.2.

[0103] The ceramic material of this invention has a simple and mature preparation process, making it suitable for industrial production. It exhibits excellent energy storage characteristics and low dielectric loss. The energy storage density calculated based on the hysteresis loop can reach 6.83 J / cm³. 3 The electric field strength is above 300kV / cm.

[0104] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for preparing a lead-free high energy density ceramic material with a sandwich structure, characterized in that, Includes the following steps: S1: Preparation of 0.8Na 0.35 Bi 0.35 Sr 0.3 TiO3-0.2CaAl 0.5 Ta 0.5 O3 powder and 0.8 (Na) 0.5 Bi 0.5 TiO3-0.2(Ba 0.7 Sr 0.3 (Mg) 1 / 3 Ta 2 / 3 )O3 powder; S2: The 0.8Na 0.35 Bi 0.35 Sr 0.3 TiO3-0.2CaAl 0.5 Ta 0.5 O3 powder and 0.8 (Na) 0.5 Bi 0.5 TiO3-0.2(Ba 0.7 Sr 0.3 (Mg) 1 / 3 Ta 2 / 3 O3 powder was mixed with organic solvent, binder, emulsifier, dispersant and plasticizer to prepare NBST-CAT casting slurry and NBT-BSMT casting slurry; S3: After forming NBST-CAT casting slurry and NBT-BSMT casting slurry, NBST-CAT casting layer and NBT-BSMT casting layer are obtained respectively. The NBST-CAT casting layer and NBT-BSMT casting layer are alternately stacked, and after pressing and heat treatment, ceramic material green body is obtained. S4: After debinding and sintering the ceramic material green body, the lead-free high energy density ceramic material with sandwich structure is obtained.

2. The method for preparing a sandwich-structured lead-free high energy density ceramic material according to claim 1, characterized in that, In step S2, the organic solvent is a mixture of anhydrous ethanol and butanone.

3. The method for preparing a sandwich-structured lead-free high energy density ceramic material according to claim 2, characterized in that, In step S2, the amounts of anhydrous ethanol and butanone added to the NBST-CAT casting slurry are 0.8Na and 0.8Na, respectively. 0.35 Bi 0.35 Sr 0.3 TiO3-0.2CaAl 0.5 Ta 0.5 45%~55% and 95%~105% of the O3 powder mass; The amounts of anhydrous ethanol and butanone added to the NBT-BSMT casting slurry were 0.8 (Na) 0.5 Bi 0.5 TiO3-0.2(Ba 0.7 Sr 0.3 (Mg) 1 / 3 Ta 2 / 3 )45%~55% and 95%~105% of the O3 powder mass.

4. The method for preparing a sandwich-structured lead-free high energy density ceramic material according to claim 1, characterized in that, In step S3, when the NBST-CAT casting layer and the NBT-BSMT casting layer are alternately stacked, a total of eight layers are set. The two sides are NBT-BSMT casting layers and the middle is an NBST-CAT casting layer. The two sides are each set with 1 to 3 NBT-BSMT casting layers and the middle is set with 2 to 6 NBST-CAT casting layers.

5. The method for preparing a sandwich-structured lead-free high-energy-density ceramic material according to claim 4, characterized in that, In step S3, when the NBST-CAT casting layer and the NBT-BSMT casting layer are alternately stacked, a total of eight layers are set. The two sides are NBT-BSMT casting layers and the middle is an NBST-CAT casting layer. The two sides each have two NBT-BSMT casting layers and the middle has four NBST-CAT casting layers.

6. The method for preparing a sandwich-structured lead-free high energy density ceramic material according to claim 1, characterized in that, In step S3, the NBST-CAT cast layer and the NBT-BSMT cast layer are alternately stacked, and after pressing and heat treatment, a ceramic material green body is obtained. Specifically, the ceramic material green body is obtained by pressing under a first pressure and then heat treatment, and then pressing under a second pressure and then heat treatment. The first pressure is less than the second pressure.

7. The method for preparing a sandwich-structured lead-free high energy density ceramic material according to claim 1, characterized in that, In step S4, the glue discharge temperature is 500~600℃ and the glue discharge time is 1~3h.

8. The method for preparing a sandwich-structured lead-free high-energy-density ceramic material according to claim 1, characterized in that, In step S4, the sintering temperature is 1170~1180℃ and the holding time is 1~3h.

9. A lead-free, high-energy-density ceramic material with a sandwich structure, characterized in that, The ceramic material is prepared by the method according to any one of claims 1 to 8; the electric field strength of the ceramic material is greater than 300 kV / cm, and the energy storage density is greater than 5 J / cm². 3 .

10. The application of the sandwich-structured lead-free high energy density ceramic material as described in claim 9 in a dielectric capacitor.

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