A sodium niobate-based energy storage ceramic material and a preparation method thereof

Abstract

This invention proposes a sodium niobate-based energy storage ceramic material and its preparation method. The general chemical formula of this ceramic material is: (1-x)(0.6NaNbO3-0.4Sr 0.7 Bi 0.2 Mg 1 / 3 Nb 2 / 3 O3)-xBaTiO3(Ⅰ); In formula (Ⅰ), x is the mole fraction, with a value range of 0.05≤x≤0.20. It is derived from NaNbO3-Sr 0.7 Bi 0.2 Mg 1 / 3 Nb 2 / The 3O3 substrate material and BaTiO3 material were prepared by solid-state reaction sintering. The (1-x)(0.6NaNbO3-0.4Sr) material prepared in this invention... 0.7 Bi 0.2 Mg 1 / 3 Nb 2 / 3 O3-xBaTiO3 ceramic material not only possesses high polarization strength and high breakdown strength, but also extremely high energy storage density. This ceramic material is a lead-free and environmentally friendly high-quality energy storage ceramic, with performance significantly superior to other ceramic systems, meeting the requirements for applications such as pulse dielectric capacitors.

Description

Technical Field

[0001] This invention relates to the field of ceramic material preparation technology, and in particular to a sodium niobate-based energy storage ceramic material and its preparation method. Background Technology

[0002] Dielectric capacitors are characterized by their relatively high power density (approximately 10). 8 With its advantages such as high energy density (W / kg), ultrafast charge / discharge speed (on the order of microseconds or nanoseconds), and low cost, dielectric capacitors have become ideal materials for pulsed power systems. However, compared to other energy storage devices, the low energy density of dielectric capacitors limits their development into miniaturized and lightweight electronic components, failing to adequately meet practical application requirements. Therefore, the research on dielectric capacitors with high energy density has attracted much attention and has become a current research hotspot.

[0003] Sodium niobate (NaNbO3, abbreviated as NN) is an environmentally friendly energy storage ceramic material, which benefits from its unique wide bandgap (greater than 3.25 eV) and high polarization (reaching 38 μC / cm at 125 kV / cm). 2 The advantages of this technology provide the necessary conditions for dielectric energy storage. However, due to the similarity of free energy between the antiferroelectric P phase and the metastable ferroelectric Q phase in NaNbO3, an irreversible phase transition from the antiferroelectric P phase to the ferroelectric Q phase will occur under an applied electric field or increased temperature, resulting in poor energy storage performance and exhibiting a square hysteresis loop.

[0004] To improve the energy storage performance of NN ceramics, methods generally include optimizing the preparation process, chemical modification, introducing other perovskite oxides with low tolerance factors to form a stable antiferroelectric phase in a solid solution, or introducing cations with different ionic radii and valence states to break long-range ferroelectric domains and form short-range nanodomains, thereby enhancing relaxation performance and reducing polarization hysteresis. For example, improvements can be made to the preparation process, such as modifying the sintering method or using rolling processes. In terms of chemical modification, perovskite oxides with low tolerance factors, such as calcium zirconate (CaZrO3) and strontium zirconate (SrZrO3), can be introduced, or bismuth ions (Bi) can be introduced. 3+ ), iron ions (Fe) 3+ ), niobium ions (Nb) 5 + ), magnesium ions (Mg 2+ The presence of cations such as Bi, Sr, and Mg enhances the relaxation and insulation properties of NNN-based ceramics to some extent, effectively reducing polarization intensity and improving energy storage efficiency. However, the low maximum polarization intensity limits further increases in energy storage density.

[0005] Furthermore, existing NN-based energy storage ceramics have struggled to achieve significant breakthroughs in breakdown field strength and energy storage density; specifically, the breakdown field strength is below 1000 kV / cm, and the energy storage density is below 20 J / cm². 3 Generally speaking, while the ferroelectric Q phase in NN ceramics can improve polarization strength, it conversely worsens dielectric breakdown strength; conversely, while a high content of the paraelectric phase is beneficial for improving dielectric breakdown strength, it reduces the polarization strength of the dielectric ceramic. Therefore, there is an urgent need to develop a novel NN-based ceramic material to balance the existence of these two phases and simultaneously achieve a dual improvement in both high breakdown strength and high energy storage performance of NN-based ceramics. Summary of the Invention

[0006] In view of this, the present invention proposes a sodium niobate-based energy storage ceramic material with ultra-high breakdown strength and energy storage density and its preparation method.

[0007] On one hand, the present invention provides a sodium niobate-based energy storage ceramic material, the general chemical formula of which is:

[0008] (1-x)(0.6NaNbO3-0.4Sr 0.7 Bi 0.2 Mg 1 / 3 Nb 2 / 3 O3)-xBaTiO3 (Ⅰ);

[0009] In equation (Ⅰ), x is the mole fraction, and its value ranges from 0.05 to x ≤ 0.20.

[0010] Based on the above technical solutions, preferably, the value of x is one of 0.05, 0.10, 0.15 or 0.20.

[0011] By adopting the above technical solution and adjusting the value of x within a suitable range, the material properties can be optimized, thereby improving the energy storage density, dielectric breakdown strength and dielectric properties, and meeting the requirements of high energy storage density and high breakdown strength.

[0012] Furthermore, the breakdown field strength of the ceramic material is not less than 1140 kV / cm, and the total energy storage density is not less than 25.86 J / cm³. 2 .

[0013] By adopting the above technical solution, it is shown that the ceramic material of the present invention can not only store more energy per unit volume, but also work safely at higher voltages without easily breaking down, thereby ensuring the reliability of the system and providing a favorable guarantee for the long-term operation of the system, making the material have great application potential in the field of high-performance electronic devices.

[0014] On the other hand, the present invention provides a method for preparing the above-mentioned sodium niobate-based energy storage ceramic material, wherein the ceramic material is composed of NaNbO3-Sr 0.7 Bi 0.2 Mg 1 / 3 Nb 2 / 3 O3 substrate material and BaTiO3 material were sintered by solid-state reaction method.

[0015] By adopting the above technical solution, Sr is introduced into NaNbO3. 0.7 Bi 0.2 Mg 1 / 3 Nb 2 / 3 Following the introduction of O3, the coexistence of the relaxor phase and the paraelectric phase (weakly polar phase) is achieved, thus contributing to the ceramic's advantages of high breakdown strength and low polarization hysteresis. Building upon this, further introduction of BaTiO3, which possesses high polarization intensity, can enhance the polarization intensity of the NN-SBMN ceramic. Simultaneously, utilizing Ba... 2+ A larger ionic radius increases the lattice strain energy of the ceramic matrix, inhibits grain boundary migration, and prevents grain growth, thereby further improving the breakdown strength to achieve a high-performance sodium niobate-based energy storage ceramic material with both high breakdown strength and high energy storage density.

[0016] Meanwhile, solid-state sintering is relatively simple to operate and typically does not require complex equipment or reaction conditions. It also yields more uniform reaction precursors, contributing to a more uniform final product. Other sintering methods are more expensive. For example, vapor-phase sintering better guarantees material purity but requires specialized equipment and a vacuum environment; while cold sintering reduces complex steps and improves production efficiency, it requires specialized equipment, thus increasing costs.

[0017] The method specifically includes the following steps:

[0018] S1. Determine the stoichiometric ratio according to the stated chemical formula, prepare the raw materials according to the stoichiometric ratio, and prepare NaNbO3-Sr. 0.7 Bi 0.2 Mg 1 / 3 Nb 2 / 3 O3 substrate material;

[0019] S2, the NaNbO3-Sr from step S1 0.7 Bi 0.2 Mg 1 / 3 Nb 2 / 3 After mixing the O3 substrate material and BaTiO3 material with the solvent, they are subjected to a single ball milling process.

[0020] S3. Drying step S2: After the solution has been ball-milled once, it is ground to obtain powder.

[0021] S4. The powder from the pre-sintering step S3 is kept at a certain temperature and then cooled down, and then naturally cooled to room temperature.

[0022] S5. After grinding the powder from step S4, mix it with solvent and perform a second ball milling.

[0023] S6. After the solution from the second ball milling in step S5 is dried, it is mixed with a polyvinyl alcohol solution and ground to obtain powder particles.

[0024] S7. The powdered particles from step S6 are compressed into a sheet to obtain a circular green body;

[0025] S8. The circular green body from step S7 is sintered into porcelain, cooled down, and then naturally cooled and ground to obtain ceramic material.

[0026] By employing the above-mentioned technical solutions, sodium niobate-based energy storage ceramic materials with precise chemical composition, uniform particle size, high density, and good crystal phase stability can be prepared. These measures not only ensure that the final material has high breakdown strength, high energy storage density, and low polarization hysteresis, but also make it suitable for applications in high-performance electronic devices, such as high-frequency electronic devices and pulsed power systems.

[0027] Furthermore, the NaNbO3-Sr 0.7 Bi 0.2 Mg 1 / 3 Nb 2 / 3 The preparation of O3 substrate materials all adopts the following steps:

[0028] A1. Prepare the raw materials according to the stoichiometric ratio, wherein the raw materials include Na2CO3, Nb2O5, Bi2O3, SrCO3, and MgO;

[0029] A2. After mixing the raw materials from step A1 with the solvent, perform ball milling once;

[0030] A3. Drying step A2: After the solution is ball-milled once, it is ground to obtain powder;

[0031] A4. The powder from the pre-sintering step A3 is kept at a certain temperature and then cooled down, and then naturally cooled to room temperature.

[0032] A5. After grinding the powder from step A4, mix it with the solvent and perform a second ball milling.

[0033] A6. After the solution from step A5 has been ball-milled twice, it is mixed with a polyvinyl alcohol solution and ground to obtain powdered particles.

[0034] A7. Press the powdered particles from step A6 into a sheet to obtain a circular green body;

[0035] A8. Sinter the circular green body from step A7 into porcelain, cool it down and then allow it to cool naturally, then grind it thin to obtain NaNbO3-Sr. 0.7 Bi 0.2 Mg 1 / 3 Nb 2 / 3 O3 substrate material.

[0036] By adopting the above technical solution, due to the similarity of free energy between the antiferroelectric P phase and the metastable ferroelectric Q phase in NaNbO3, an irreversible phase transition from the antiferroelectric P phase to the ferroelectric Q phase will occur under the influence of an applied electric field or increased temperature, resulting in large polarization hysteresis and exhibiting a square hysteresis loop, leading to poor energy storage performance. Introducing Sr into NaNbO3... 0.7 Bi 0.2 Mg 1 / 3 Nb 2 / 3 After O3 is applied, the relaxor phase and the paraelectric phase (weakly polar phase) can coexist, thereby enabling the substrate material to exert the advantages of high breakdown strength and low polarization hysteresis, and ultimately achieve higher energy storage efficiency and energy storage density.

[0037] Furthermore, the ball milling time is 8 hours, and the rotation speed is 350 r / min; the prerequisites for ball milling are: the total mass of the grinding balls is 284 g; the diameters of the grinding balls are 10 mm, 8 mm, and 5 mm, and the ratio of the grinding balls of the corresponding diameters is 2:3:5; the total volume of the grinding balls and the mixture is 1 / 2 of the volume of the ball milling device.

[0038] By adopting the above technical solutions, excessively long ball milling times can cause the surface zirconium powder of the grinding beads to detach and mix into the solution, while excessively short ball milling times will affect the fineness of the material. Appropriately increasing the rotation speed can increase the kinetic energy of the grinding media, thereby enhancing the collision and friction between particles and improving grinding efficiency. The number and weight of the grinding beads also directly affect the grinding effect; an appropriate ratio can ensure that the grinding beads move fully within the jar, increasing collision and friction, thereby improving the fineness of the material. By adopting the above technical solutions and rationally controlling the ball milling time, rotation speed, and the ratio of grinding beads, zirconium powder contamination can be effectively avoided, while ensuring sufficient material fineness and improving grinding efficiency.

[0039] Based on the above technical solutions, preferably, the grinding beads are zirconium balls.

[0040] First, a longer ball milling time ensures thorough mixing of the raw materials, which helps reduce particle size differences and improves the uniformity of the final material. A moderate rotation speed ensures the efficiency of the ball mill while avoiding heat accumulation caused by excessively high rotation speeds, which could affect the quality of the material and increase energy consumption.

[0041] Secondly, a reasonable total mass of grinding balls can ensure sufficient impact and grinding force, which helps to improve the fineness of the mixture. The effective cooperation of grinding balls of different sizes ensures the effective crushing of large particles while avoiding over-grinding of excessively fine particles.

[0042] Finally, an appropriate filling amount can ensure that the grinding beads move more freely within the grinding device, thereby improving grinding efficiency.

[0043] By adopting the above technical solution, a more efficient and precise ball milling process can be achieved, laying the foundation for the subsequent preparation of uniform, fine, and well-dispersed powders. Furthermore, this process also helps improve the uniformity, density, and performance of the final sodium niobate-based energy storage ceramic material, ensuring its excellent performance in practical applications.

[0044] Furthermore, in step S4, the pre-sintering temperature is 850℃; the holding time is 3h; the cooling rate is 5℃ / min, and the temperature drops to 450℃.

[0045] By adopting the above technical solution, the initial reaction between powders can be promoted, a stable crystalline phase can be formed, some impurities can be removed, and the purity and stability of the material can be improved.

[0046] Furthermore, the concentration of the polyvinyl alcohol solution is 3 wt%.

[0047] By employing the above technical solution, the powder can be effectively bound together, ensuring that every part of the powder is coated with PVA solution, thereby forming uniform particles during granulation while maintaining good flowability. Furthermore, the 3wt% polyvinyl alcohol solution helps form particles with good flowability and compressibility, which is beneficial for subsequent tableting. It can improve molding stability, reduce cracks and defects during molding, and leaves no obvious residue after decomposition at high temperatures, contributing to the uniform sintering of ceramic materials and reducing porosity and other defects.

[0048] Furthermore, in step S7, the tableting pressure is 20 MPa; the circular green blank also needs to be held under a pressure of 200 MPa for 5 minutes.

[0049] By adopting the above technical solutions, the density and molding stability of the green body can be improved, while defects are reduced, its electrical properties are optimized, and further cold isostatic pressing is facilitated. Holding pressure at a higher pressure helps to expel pores and improve density, which is key to ensuring good dielectric properties. A holding time of 5 minutes can enhance the tightness of interparticle contact, reduce internal defects, and improve the uniformity and consistency of the material.

[0050] Furthermore, in step S8, the process of sintering the circular green body from step S7 into ceramic, cooling it down, and then allowing it to cool naturally to obtain ceramic material specifically includes:

[0051] The circular green body from step S7 is heated to 600℃ at 2℃ / min and held for 6 hours, then heated to the sintering temperature at 5℃ / min and held for 3 hours, and then cooled to 450℃ at 5℃ / min. After natural cooling, it is ground thin to obtain the ceramic material; the sintering temperature is 1170~1220℃.

[0052] By employing the above-mentioned technical solutions, the gradual heating and cooling method helps reduce internal thermal stress in the material, preventing the formation of cracks and defects, thereby improving the material's density and uniformity. Furthermore, appropriate holding time ensures the full progress of the chemical reaction, optimizes the material's microstructure, and improves the final ceramic material's mechanical strength and electrical properties, ensuring its excellent performance in practical applications.

[0053] Furthermore, the thickness of the ceramic material is 50–60 μm.

[0054] By adopting the above technical solutions, the energy storage density and dielectric properties of the material can be significantly improved. This thin-layer design not only helps to improve the breakdown strength of the material and reduce internal defects, but also optimizes its performance in high-frequency applications, enabling it to exhibit excellent performance in applications requiring high energy output and fast charging and discharging, such as pulsed power systems, while simultaneously achieving miniaturization and weight reduction of electronic components.

[0055] The sodium niobate-based energy storage ceramic material provided by this invention has the following advantages over the prior art:

[0056] 1. The preparation method of the NN-based ceramic material prepared by this invention is simple, the raw materials are readily available, and the production efficiency is high, making it suitable for large-scale practical production applications.

[0057] 2. The (1-x)(0.6NaNbO3-0.4Sr) prepared by this invention 0.7 Bi 0.2 Mg 1 / 3 Nb 2 / 3 O3)-xBaTiO3 ceramic material not only possesses high polarization strength and high breakdown strength, but also extremely high energy storage density. This ceramic material is a lead-free and environmentally friendly high-quality energy storage ceramic, with performance significantly superior to other ceramic systems, meeting the requirements for its application in pulse dielectric capacitors and other fields.

[0058] 3. In preparing sodium niobate-based ceramic materials, this invention employs a stepped heating and cooling sintering method, which avoids phase transformations that may be induced by excessively rapid heating and cooling, as well as grain size growth caused by excessively slow cooling, thereby improving the phase stability and energy storage performance of the ceramic.

[0059] 4. This invention uses 0.6NaNbO3-0.4Sr 0.7 Bi 0.2 Mg 1 / 3 Nb 2 / 3 Using O3 ceramic material as the matrix, the energy storage performance of the matrix is ​​regulated by doping with the ferroelectric material BaTiO3. This is achieved by modifying 0.6NaNbO3-0.4Sr with BaTiO3. 0.7 Bi 0.2 Mg 1 / 3 Nb 2 / 3 O3 energy storage ceramic materials exhibit increased polarization and breakdown strength with increasing doping concentration, achieving two key energy storage advantages:

[0060] (1) It further improved the polarization intensity of ceramics;

[0061] (2) The breakdown strength has been further improved.

[0062] 5. The ceramic material prepared by this invention has a breakdown field strength of not less than 1140 kV / cm and a storage density of not less than 25.86 J / cm³. 2 Its performance is significantly better than that of other ceramic materials. Attached Figure Description

[0063] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0064] Figure 1 The image shows the XRD pattern of the sodium niobate-based energy storage ceramic material prepared in Example 1 of this invention.

[0065] Figure 2 This is the breakdown field strength diagram of the sodium niobate-based energy storage ceramic material prepared in Example 1 of the present invention;

[0066] Figure 3 The image shows an electron microscope image of the sodium niobate-based energy storage ceramic sample prepared in Example 1 of this invention. In the image, a represents 0.6NaNbO3-0.4Sr. 0.7 Bi 0.2 Mg 1 / 3 Nb 2 / 3 O3 ceramic sample, b is the ceramic sample prepared in Example 1;

[0067] Figure 4The image shows the UV-Vis absorption spectrum and a magnified view of the sodium niobate-based energy storage ceramic sample prepared in Example 1 of this invention; in the image, a is the absorption spectrum; b is the UV-Vis absorption spectrum; and c is a magnified view of the UV-Vis absorption spectrum.

[0068] Figure 5 The hysteresis loop of the sodium niobate-based energy storage ceramic prepared in Example 1 of this invention under the breakdown electric field;

[0069] Figure 6 This is a graph showing the relationship between the effective energy storage density and energy storage efficiency of the sodium niobate-based energy storage ceramic prepared in Example 1 of the present invention and the electric field strength. Detailed Implementation

[0070] Xie et al. (DOI:10.1016 / j.jmat.2021.11.012) improved NaNbO3 by doping it with Bi. 0.5 K 0.5 ZrO3-induced relaxation phase transition improves relaxation performance, thereby increasing effective energy storage density. Although this ceramic exhibits a high energy density of 45 μC / cm³... 2 While the polarization intensity is high, relaxor ferroelectrics typically exhibit a significant hysteresis effect due to their polarization characteristics. Under high electric fields, energy losses during polarization and depolarization can lead to localized heating, thereby reducing the overall breakdown strength of the material. Consequently, the breakdown strength of this ceramic is less than 450 kV / cm, resulting in a final energy storage density of only 4.4 J / cm³. 3 Guo et al. (DOI:10.1016 / j.ceramint.2024.09.350) obtained the results using 0.8 (Na) 0.5 Li 0.5 NbO3)-0.2(Sr 0.5 Bi 0.5 (Fe) 0.5 Ti 0.25 Zr 0.25 The addition of MnO to O3 ceramics significantly improved the energy storage performance of high-entropy ceramics, achieving a value of 7.93 J / cm³. 3 The effective energy storage density is 90.6%, but the breakdown strength is only 500 kV / cm, which limits its further improvement in energy storage performance. Zhang et al. (DOI:10.1016 / j.jmat.2021.09.007) introduced (Bi) into NaNbO3. 0.8 Sr 0.2 (Fe) 0.9 Nb 0.1 O3 was used to construct a relaxor-antiferroelectric ceramic, which combined the advantages of antiferroelectricity and relaxor-ferroelectricity, exhibiting a stable antiferroelectric phase and enhanced dielectric relaxation behavior. Its breakdown strength reached 970 kV / cm, and a final dielectric strength of 16.5 J / cm was achieved. 3It boasts an ultra-high effective energy storage density and an energy storage efficiency of 83.3%.

[0071] Given that existing technologies do not meet the inventor's expectations, the inventor made this invention through further research.

[0072] This invention utilizes the pre-preparation of NaNbO3-Sr 0.7 Bi 0.2 Mg 1 / 3 Nb 2 / 3 O3 substrate material provides ceramic materials with advantages such as high breakdown strength and low polarization hysteresis. Building upon this, the polarization strength of NN-SBMN ceramics is further enhanced by directly sintering the substrate material with BaTiO3 material using a solid-state sintering method. Simultaneously, Ba... 2+ A larger ionic radius increases the lattice strain energy of the ceramic matrix, inhibits grain boundary migration, and prevents grain growth, thereby further improving the breakdown strength to achieve a high-performance sodium niobate-based energy storage ceramic material with both high breakdown strength and high energy storage density.

[0073] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0074] The present invention will be further described below with reference to specific embodiments. The scope of protection of the present invention is not limited to the following embodiments. The main sources of materials involved in the embodiments are shown in Table 1 below. Other materials not specified are conventional commercially available products.

[0075] Table 1 Material Source Description

[0076]

[0077] The following are preparation examples of the present invention. Preparation Examples 1 to 3 each provide a substrate material, and Preparation Example 4 provides a BaTiO3 material.

[0078] Preparation Example 1

[0079] The preparation example provided is 0.7NaNbO3-0.3Sr 0.7 Bi 0.2 Mg 1 / 3 Nb 2 / 3 The O3 substrate material is prepared by the following steps:

[0080] S1. Prepare raw materials according to stoichiometric ratio, wherein the raw materials include Na2CO3, Nb2O5, Bi2O3, SrCO3, and MgO;

[0081] S2. After mixing the raw materials from step S1 with the solvent, perform ball milling once;

[0082] S3. Drying step S2: After the solution has been ball-milled once, it is ground to obtain powder.

[0083] S4. The powder from the pre-sintering step S3 is kept at a certain temperature and then cooled down, and then naturally cooled to room temperature.

[0084] S5. After grinding the powder from step S4, mix it with solvent and perform a second ball milling.

[0085] S6. After the solution from the second ball milling in step S5 is dried, it is mixed with a polyvinyl alcohol solution and ground to obtain powder particles.

[0086] Specifically: The polyvinyl alcohol solution concentration is 3wt%, which is mixed with the powder to form a slurry, and then ground into powder.

[0087] S7. The powdered particles from step S6 are compressed into a sheet to obtain a circular green body;

[0088] Specifically: the green preform for tableting needs to be placed in a cold isostatic press and held at a pressure of 200 MPa for 5 minutes.

[0089] S8. The circular green body from step S7 is sintered into porcelain, cooled down, and then naturally cooled and ground to obtain ceramic material.

[0090] Specifically: raise the temperature to 600℃ at a rate of 2℃ / min and hold for 6 hours, then raise the temperature to 1150℃ at a rate of 5℃ / min and hold for 3 hours.

[0091] The substrate material prepared in this example has a dielectric constant of 160 kHz and a breakdown strength of 80 kV / cm.

[0092] Preparation Example 2

[0093] The preparation example provided is 0.6NaNbO3-0.4Sr 0.7 Bi 0.2 Mg 1 / 3 Nb 2 / 3 The O3 substrate material is prepared by the following steps:

[0094] S1. Prepare raw materials according to stoichiometric ratio, wherein the raw materials include Na2CO3, Nb2O5, Bi2O3, SrCO3, and MgO;

[0095] S2. After mixing the raw materials from step S1 with the solvent, perform ball milling once;

[0096] S3. Drying step S2: After the solution has been ball-milled once, it is ground to obtain powder.

[0097] S4. The powder from the pre-sintering step S3 is kept at a certain temperature and then cooled down, and then naturally cooled to room temperature.

[0098] S5. After grinding the powder from step S4, mix it with solvent and perform a second ball milling.

[0099] S6. After the solution from the second ball milling in step S5 is dried, it is mixed with a polyvinyl alcohol solution and ground to obtain powder particles.

[0100] Specifically: The polyvinyl alcohol solution concentration is 3wt%, which is mixed with the powder to form a slurry, and then ground into powder.

[0101] S7. The powdered particles from step S6 are compressed into a sheet to obtain a circular green body;

[0102] Specifically: the green preform for tableting needs to be placed in a cold isostatic press and held at a pressure of 200 MPa for 5 minutes.

[0103] S8. The circular green body from step S7 is sintered into porcelain, cooled down, and then naturally cooled and ground to obtain ceramic material.

[0104] Specifically: raise the temperature to 600℃ at a rate of 2℃ / min and hold for 6 hours, then raise the temperature to 1150℃ at a rate of 5℃ / min and hold for 3 hours.

[0105] The substrate material obtained in this preparation example has a dielectric constant of 200 kHz and a breakdown strength of 120 kV / cm.

[0106] Preparation Example 3

[0107] The preparation example provided is 0.5NaNbO3-0.5Sr 0.7 Bi 0.2 Mg 1 / 3 Nb 2 / 3 The O3 substrate material is prepared by the following steps:

[0108] S1. Prepare raw materials according to stoichiometric ratio, wherein the raw materials include Na2CO3, Nb2O5, Bi2O3, SrCO3, and MgO;

[0109] S2. After mixing the raw materials from step S1 with the solvent, perform ball milling once;

[0110] S3. Drying step S2: After the solution has been ball-milled once, it is ground to obtain powder.

[0111] S4. The powder from the pre-sintering step S3 is kept at a certain temperature and then cooled down, and then naturally cooled to room temperature.

[0112] S5. After grinding the powder from step S4, mix it with solvent and perform a second ball milling.

[0113] S6. After the solution from the second ball milling in step S5 is dried, it is mixed with a polyvinyl alcohol solution and ground to obtain powder particles.

[0114] Specifically: The polyvinyl alcohol solution concentration is 3wt%, which is mixed with the powder to form a slurry, and then ground into powder.

[0115] S7. The powdered particles from step S6 are compressed into a sheet to obtain a circular green body;

[0116] Specifically: the green preform for tableting needs to be placed in a cold isostatic press and held at a pressure of 200 MPa for 5 minutes.

[0117] S8. The circular green body from step S7 is sintered into porcelain, cooled down, and then naturally cooled and ground to obtain ceramic material.

[0118] Specifically: raise the temperature to 600℃ at a rate of 2℃ / min and hold for 6 hours, then raise the temperature to 1150℃ at a rate of 5℃ / min and hold for 3 hours.

[0119] The substrate material prepared in this example has a dielectric constant of 180 kHz and a breakdown strength of 110 kV / cm.

[0120] Preparation Example 2 (0.6NaNbO3-0.4Sr) 0.7 Bi 0.2 Mg 1 / 3 Nb 2 / 3 Compared to Preparation Examples 1 and 3, Preparation Example 2 (O3) exhibits significant advantages in both dielectric constant and breakdown strength. Specifically, the dielectric constant of Preparation Example 2 reaches 200 kHz, higher than that of Preparation Example 1 (160 kHz) and Preparation Example 3 (180 kHz); simultaneously, its breakdown strength of 120 kV / cm is also significantly better than that of Preparation Example 1 (80 kV / cm) and Preparation Example 3 (110 kV / cm). This means that Preparation Example 2 has higher energy storage capacity and stronger high-voltage withstand characteristics in terms of electrical performance, making it more suitable for application in high-performance electronic components and high-frequency equipment.

[0121] In summary, the inventors prepared 0.6NaNbO3-0.4Sr in Example 2. 0.7 Bi 0.2 Mg 1 / 3 Nb 2 / 3 Taking O3 substrate material as an example, sodium niobate-based ceramic materials as shown in Examples 1 to 3 were prepared by solid-state sintering with BaTiO3 material, which has ferroelectric properties.

[0122] Example 1

[0123] The general chemical formula of the sodium niobate-based ceramic material in this embodiment is as follows: 0.85(0.6NaNbO3-0.4Sr 0.7 Bi 0.2 Mg1 / 3 Nb 2 / 3 The ceramic material, O3)-0.15BaTiO3, is prepared by the following steps:

[0124] Step S1: Referring to Preparation Example 2, prepare additional raw materials BaCO3 and TiO2 (molar ratio of 1:1);

[0125] Step S2: Place the powder from Step S1 into a nylon ball mill jar containing zirconium balls, and mix with anhydrous ethanol as a solvent. Set the rotation speed of the planetary ball mill to 350 r / min and mill for 8 hours. The total mass of the zirconium balls is 284 g. The diameters of the zirconium balls are 10 mm, 8 mm, and 5 mm, and the ratio of zirconium balls of the corresponding diameters is 2:3:5. The total volume of the zirconium balls and the mixture is 1 / 2 of the volume of the ball mill.

[0126] Step S3: Place the mixed solution obtained after ball milling in step S2 into a drying oven at 70°C for drying, and then grind the dried powder thoroughly in a mortar for 20 minutes.

[0127] Step S4: The powder ground in step S3 is placed into a crucible, then placed in a muffle furnace, sintered at 850°C and held for 3 hours, then cooled to 450°C at 5°C / min and allowed to cool naturally to room temperature.

[0128] Step S5: Place the pre-sintered powder from step S4 into a mortar and pre-grind for 20 minutes, then pour it into a ball mill containing zirconium beads. Mix with anhydrous ethanol as a solvent, set the ball mill speed to 350 r / min, and ball mill for 8 hours.

[0129] Step S6: After drying the mixed solution after ball milling in step S5 in a drying oven at a temperature of 70°C, add polyvinyl alcohol solution and mix, then grind thoroughly until dry powder is formed to complete granulation.

[0130] Step S7: Take an appropriate amount of the granulated powder from step S6, pour it into a mold, and apply a force of 20MPa on a tablet press to compress it into a round green body; then place the round green body into a cold isostatic press and hold it under a pressure of 200MPa for 5 minutes.

[0131] Step S8: Use the powder pre-fired in step S4 (the amount is enough to completely cover the green body. The powder is 0.6NaNbO3-0.4Sr). 0.7 Bi 0.2 Mg 1 / 3 Nb 2 / 3O3 (the same below) is used to bury the corresponding ceramic green body and place it in a crucible. The crucible is then placed in a muffle furnace and heated to 600°C at 2°C / min and held for 6 hours. The temperature is then increased to 1180°C at 5°C / min and sintered for 3 hours. The temperature is then decreased to 450°C at 5°C / min and allowed to cool naturally to room temperature. The material is then ground thin to obtain a sodium niobate-based energy storage ceramic material with a thickness of 50 μm.

[0132] The sodium niobate-based ceramic material prepared in this embodiment has a composition of 0.85 (0.6NaNbO3-0.4Sr). 0.7 Bi 0.2 Mg 1 / 3 Nb 2 / 3 XRD patterns related to O3)-0.15BaTiO3 are as follows: Figure 1 As shown, by Figure 1 It can be seen that the ceramic material in this embodiment exhibits a pure perovskite structure without obvious secondary phase formation, indicating that Ba 2+ and Ti 4+ It has successfully diffused into the NaNbO3 lattice and formed a solid solution.

[0133] Example 2

[0134] The general chemical formula of the sodium niobate-based ceramic material in this embodiment is as follows: 0.95(0.6NaNbO3-0.4Sr 0.7 Bi 0.2 Mg 1 / 3 Nb 2 / 3 The ceramic material, O3)-0.05BaTiO3, is prepared by the following steps:

[0135] Step S1: Referring to Preparation Example 2, prepare additional raw materials BaCO3 and TiO2 (molar ratio of 1:1);

[0136] Step S2: Place the powder from Step S1 into a nylon ball mill jar containing zirconium balls, and mix with anhydrous ethanol as a solvent. Set the rotation speed of the planetary ball mill to 350 r / min and mill for 8 hours. The total mass of the zirconium balls is 284 g. The diameters of the zirconium balls are 10 mm, 8 mm, and 5 mm, and the ratio of zirconium balls of the corresponding diameters is 2:3:5. The total volume of the zirconium balls and the mixture is 1 / 2 of the volume of the ball mill.

[0137] Step S3: Place the mixed solution obtained after ball milling in step S2 into a drying oven at 70°C for drying, and then grind the dried powder thoroughly in a mortar for 20 minutes.

[0138] Step S4: The powder ground in step S3 is placed into a crucible, then placed in a muffle furnace, sintered at 850°C and held for 3 hours, then cooled to 450°C at 5°C / min and allowed to cool naturally to room temperature.

[0139] Step S5: Place the pre-sintered powder from step S4 into a mortar and pre-grind for 20 minutes, then pour it into a ball mill containing zirconium beads. Mix with anhydrous ethanol as a solvent, set the ball mill speed to 350 r / min, and ball mill for 8 hours.

[0140] Step S6: After drying the mixed solution after ball milling in step S5 in a drying oven at a temperature of 70°C, add polyvinyl alcohol solution and mix, then grind thoroughly until dry powder is formed to complete granulation.

[0141] Step S7: Take an appropriate amount of the granulated powder from step S6, pour it into a mold, and apply a force of 20MPa on a tablet press to compress it into a round green body; then place the round green body into a cold isostatic press and hold it under a pressure of 200MPa for 5 minutes.

[0142] Step S8: The corresponding ceramic green body is buried with the powder pre-fired in step S4, placed in a crucible, and placed in a muffle furnace. The temperature is increased to 600℃ at 5℃ / min and held for 6 hours. Then, the temperature is increased to 1200℃ at 8℃ / min and sintered for 3 hours. The temperature is then decreased to 450℃ at 10℃ / min and naturally cooled to room temperature. The material is then ground thin to obtain a sodium niobate-based energy storage ceramic material with a thickness of 50μm.

[0143] Example 3

[0144] The general chemical formula of the sodium niobate-based ceramic material in this embodiment is as follows: 0.8(0.6NaNbO3-0.4Sr 0.7 Bi 0.2 Mg 1 / 3 Nb 2 / 3 The ceramic material, O3)-0.2BaTiO3, is prepared by the following steps:

[0145] Step S1: Referring to Preparation Example 2, prepare additional raw materials BaCO3 and TiO2 (molar ratio of 1:1);

[0146] Step S2: Place the powder from Step S1 into a nylon ball mill jar containing zirconium balls, and mix with anhydrous ethanol as a solvent. Set the rotation speed of the planetary ball mill to 350 r / min and mill for 8 hours. The total mass of the zirconium balls is 284 g. The diameters of the zirconium balls are 10 mm, 8 mm, and 5 mm, and the ratio of zirconium balls of the corresponding diameters is 2:3:5. The total volume of the zirconium balls and the mixture is 1 / 2 of the volume of the ball mill.

[0147] Step S3: Place the mixed solution obtained after ball milling in step S2 into a drying oven at 70°C for drying, and then grind the dried powder thoroughly in a mortar for 20 minutes.

[0148] Step S4: The powder ground in step S3 is placed into a crucible, then placed in a muffle furnace, sintered at 850°C and held for 3 hours, then cooled to 450°C at 5°C / min and allowed to cool naturally to room temperature.

[0149] Step S5: Place the pre-sintered powder from step S4 into a mortar and pre-grind for 20 minutes, then pour it into a ball mill containing zirconium beads. Mix with anhydrous ethanol as a solvent, set the ball mill speed to 350 r / min, and ball mill for 8 hours.

[0150] Step S6: After drying the mixed solution after ball milling in step S5 in a drying oven at a temperature of 70°C, add polyvinyl alcohol solution and mix, then grind thoroughly until dry powder is formed to complete granulation.

[0151] Step S7: Take an appropriate amount of the granulated powder from step S6, pour it into a mold, and apply a force of 20MPa on a tablet press to compress it into a round green body; then place the round green body into a cold isostatic press and hold it under a pressure of 200MPa for 5 minutes.

[0152] Step S8: The corresponding ceramic green body is buried with the powder pre-fired in step S4, placed in a crucible, and placed in a muffle furnace. The temperature is increased to 600℃ at 1℃ / min and held for 6 hours. Then, the temperature is increased to 1220℃ at 1℃ / min and sintered for 3 hours. The temperature is then decreased to 450℃ at 1℃ / min and naturally cooled to room temperature. The material is then ground thin to obtain a sodium niobate-based energy storage ceramic material with a thickness of 60μm.

[0153] In Example 1, the heating rate was 2°C / min to 600°C and held for 6 hours, followed by a rate of 5°C / min to 1180°C and a holding time of 3 hours. This heating rate ensured uniform release of internal stress while avoiding structural changes due to excessively rapid heating, thus maintaining the stability of the material's microstructure. During the cooling phase, the temperature was reduced to 450°C at a rate of 5°C / min. This cooling rate effectively controlled grain growth, preventing excessively coarse grains that could negatively impact the material's mechanical and electrical properties. In contrast, Example 2 had a faster heating rate (5°C / min to 600°C) and a higher final sintering temperature (1200°C), which could lead to faster grain growth during sintering, affecting the material's microstructure and properties. Furthermore, Example 2 also had a faster cooling rate (10°C / min), which could result in greater residual stress within the material, affecting its mechanical strength and electrical properties. The heating and cooling rates in Example 3 were very slow (both 1°C / min). Although this slow heating and cooling process helps reduce the internal stress of the material, it may also lead to excessively rapid grain growth. This is because the longer holding time provides more opportunities for grain growth, which may eventually lead to excessively large grain size and thus reduce the overall performance of the material.

[0154] In summary, the heating and cooling rates used in Example 1 were moderate, which avoided phase transformation and abnormal grain growth that might be caused by rapid heating and cooling, while ensuring the uniform release of internal stress in the material. As a result, the prepared sodium niobate-based ceramic material has better phase stability and energy storage performance.

[0155] Taking Example 1 above as an example, the inventors tested the total energy storage density, effective density, and energy storage efficiency of the sodium niobate-based ceramic material prepared in Example 1. The test results are shown in Table 2 below. All the above performance tests were performed using hysteresis loops measured by a Polyk ferroelectric analyzer. The calculation method is as follows:

[0156]

[0157]

[0158]

[0159] In equations (II) to (IV) above, W, W rec η and E represent the total energy storage density, effective energy storage density, and energy storage efficiency of the dielectric ceramic, respectively; P and E represent the total energy storage density, effective energy storage density, and energy storage efficiency of the dielectric ceramic, respectively. max P rThese represent the external electric field experienced by the dielectric ceramic, the maximum polarization intensity under the external electric field, and the residual polarization intensity after the electric field is removed, respectively. The effective energy storage density and energy storage efficiency are related to the electric field strength as follows: Figure 5 As shown.

[0160] Table 2 Performance Test Results

[0161]

[0162] Based on the performance test results in Table 2, Figure 2 It can be seen that the data distribution is relatively concentrated, that is, the breakdown strength of most samples is close to 1140kV / cm.

[0163] Based on the performance test results in Table 2, Figure 3 It can be determined that a is 0.6NaNbO3-0.4Sr 0.7 Bi 0.2 Mg 1 / 3 Nb 2 / 3 SEM images of O3 matrix ceramics, b is the SEM image of the ceramic sample prepared in Example 1. It can be clearly seen that the grain size in image b is smaller. The finer the grains, the more grain boundaries there are, which improves the electric field distribution and enhances the breakdown resistance.

[0164] Based on the performance test results in Table 2, Figure 4 As can be seen, Figure (a) shows the change in absorbance of the material at different wavelengths, revealing that the material has a strong absorption capacity for light in the visible light range, especially in the short wavelength region. Figure (b) shows the optical bandgap energy of the material obtained by the Tauc plotting method, which is about 3.75 eV. This value indicates that the material belongs to a wide bandgap semiconductor and is suitable for optoelectronic applications in the ultraviolet and visible light regions.

[0165] Based on the performance test results in Table 2, Figure 5 As can be seen, the two curves in the figure clearly demonstrate that the polarization intensity increases with the increase of the electric field strength, exhibiting a linear growth trend. This phenomenon indicates that the material can effectively generate a polarization effect when subjected to an applied electric field, thereby achieving charge separation and accumulation. Furthermore, the figure also mentions that the material exhibits good nonlinear optical properties in the weak electric field range, meaning that a significant polarization enhancement effect can be observed even under relatively small electric field strengths.

[0166] Based on the performance test results in Table 2, Figure 6 It can be seen that as the electric field strength increases, the effective energy storage density gradually increases, while the energy storage efficiency initially decreases slightly and then tends to stabilize. This indicates that within a certain range of electric field strength, the energy storage performance of the material will improve, but at higher electric field strengths, the energy storage efficiency may be affected. Therefore, rationally controlling the electric field strength is crucial for optimizing the energy storage performance of the material.

[0167] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A sodium niobate-based energy storage ceramic material, characterized in that, The general chemical formula of the ceramic material is: (1-x)(0.6NaNbO3-0.4Sr 0.7 Bi 0.2 Mg 1 / 3 Nb 2 / 3 O3)- x BaTiO3(I); In equation (I), x is the mole fraction, and its value ranges from 0.05 to 1. x ≤ 0.20; The breakdown field strength of the ceramic material is not less than 1140 kV / cm, and the total energy storage density is not less than 25.86 J / cm³. 2 .

2. A method for preparing the sodium niobate-based energy storage ceramic material as described in claim 1, characterized in that, The ceramic material is composed of NaNbO3-Sr 0.7 Bi 0.2 Mg 1 / 3 Nb 2 / 3 O3 substrate material and BaTiO3 material were sintered by solid-state reaction method.

3. The method as described in claim 2, characterized in that, The method includes the following steps: S1. Determine the stoichiometric ratio according to the stated chemical formula, prepare the raw materials according to the stoichiometric ratio, and prepare NaNbO3-Sr. 0.7 Bi 0.2 Mg 1 / 3 Nb 2 / 3 O3 substrate material; S2, the NaNbO3-Sr from step S1 0.7 Bi 0.2 Mg 1 / 3 Nb 2 / 3 O3 substrate material and BaTiO3 material are mixed with solvent to obtain a mixture, and the mixture is ball-milled once; S3. Drying step S2: After the solution has been ball-milled once, it is ground to obtain powder. S4. The powder from the pre-sintering step S3 is kept at a certain temperature and then cooled down, and then naturally cooled to room temperature. S5. After grinding the powder from step S4, mix it with a solvent to obtain a mixture, and then perform a second ball milling on the mixture. S6. After the solution from the second ball milling in step S5 is dried, it is mixed with a polyvinyl alcohol solution and ground to obtain powder particles. S7. The powdered particles from step S6 are compressed into a sheet to obtain a circular green body; S8. The circular green body from step S7 is sintered into porcelain, cooled down, and then naturally cooled and ground to obtain ceramic material.

4. The method as described in claim 3, characterized in that, In step S1, the NaNbO3-Sr 0.7 Bi 0.2 Mg 1 / 3 Nb 2 / 3 The preparation of O3 substrate materials all adopts the following steps: A1. Prepare the raw materials according to the stoichiometric ratio, wherein the raw materials include Na2CO3, Nb2O5, Bi2O3, SrCO3, and MgO; A2. After mixing the raw materials from step A1 with the solvent to obtain a mixture, the mixture is ball-milled once. A3. Drying step A2: After the solution is ball-milled once, it is ground to obtain powder; A4. The powder from the pre-sintering step A3 is kept at a certain temperature and then cooled down, and then naturally cooled to room temperature. A5. After grinding the powder from step A4, mix it with a solvent to obtain a mixture, and then perform a second ball milling on the mixture; A6. After the solution from step A5 has been ball-milled twice, it is mixed with a polyvinyl alcohol solution and ground to obtain powdered particles. A7. Press the powdered particles from step A6 into a sheet to obtain a circular green body; A8. Sinter the circular green body from step A7 into porcelain, cool it down and then allow it to cool naturally, then grind it thin to obtain NaNbO3-Sr. 0.7 Bi 0.2 Mg 1 / 3 Nb 2 / 3 O3 substrate material.

5. The method as described in claim 3, characterized in that, The ball milling time was 8 hours, and the rotation speed was 350 r / min. The prerequisites for ball milling are: the total mass of the grinding balls is 284g; the diameters of the grinding balls are 10mm, 8mm and 5mm, and the ratio of the grinding balls of the corresponding diameters is 2:3:5; the total volume of the grinding balls and the mixture is 1 / 2 of the volume of the ball milling device.

6. The method as described in claim 3, characterized in that, In step S4, the pre-sintering temperature is 850℃; the holding time is 3h; the cooling rate is 5℃ / min, and the temperature drops to 450℃.

7. The method as described in claim 3, characterized in that, In step S6, the concentration of the polyvinyl alcohol solution is 3 wt%.

8. The method as described in claim 3, characterized in that, In step S8, the process of sintering the circular green body from step S7 into ceramic, cooling it down, and then allowing it to cool naturally to obtain ceramic material specifically includes: The circular green body from step S7 is heated to 600℃ at 2℃ / min and held for 6 hours, then heated to the sintering temperature at 5℃ / min and held for 3 hours, then cooled to 450℃ at 5℃ / min, and then naturally cooled and ground to obtain the ceramic material. The sintering temperature is 1170~1220℃.

9. The method as described in claim 8, characterized in that, The thickness of the ceramic material is 50~60 μm.

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