A sodium bismuth titanate-based lead-free ceramic material, a preparation method and applications thereof

Abstract

The application relates to the technical field of ceramic material preparation, in particular to a sodium bismuth titanate-based lead-free ceramic material, a preparation method and application. 0.5 Na 0.5 Ti03‑xSr 1 / 2 Nd 1 / 3 (Mg 1 / 3Nb 2 / 3 )O3, Sr 1 / 2 Nd 1 / 3 (Mg 1 / 3 Nb 2 / 3 )O3 is doped and substituted, or Nd 0.5 / (Mg 0.5 Nb 3+ ) 2 / 3 is doped and substituted in (1-x)(0.7Bi 1 / 3 Na 3+ Ti03-0.3SrTiO3), long-range ordered ferroelectricity is destroyed, the relaxation behavior of the ceramic is enhanced, and the dielectric temperature stability of the ceramic material is improved. Under the conditions of high dielectric constant and extremely low dielectric loss, the sodium bismuth titanate-based lead-free ceramic material with wide dielectric temperature region and high frequency stability is obtained, the prepared ceramic material has the characteristics of high breakdown voltage, high energy storage density and excellent dielectric temperature stability, can stably work in a harsh environment such as high temperature and high electric field, and is suitable for application in a high pulse power system. The problems of high dielectric loss, low energy storage density, low energy storage efficiency and narrow working temperature region of the sodium bismuth titanate-based ceramic material in the prior art are solved.

Description

Technical Field

[0001] The present invention relates to the technical field of ceramic material preparation, specifically to a sodium bismuth titanate-based lead-free ceramic material, a preparation method and applications, and especially to a high-serviceability sodium bismuth titanate-based lead-free high-entropy energy storage ceramic material, a preparation method and applications. Background Art

[0002] With the rapid development of human society, energy crises and environmental pollution are becoming increasingly severe. To reduce the waste of renewable energy, developing efficient, reliable, low-cost, and environmentally friendly energy storage devices is of great importance. Currently, widely used energy storage devices include batteries, electrochemical capacitors, and dielectric capacitors. Dielectric ceramics, as one type of dielectric capacitor, have attracted widespread attention and research due to their extremely long safe service life, excellent fatigue resistance, and ultra-high power density. Ceramic capacitors made from dielectric ceramics are widely used in electronic filters, pulsed power devices, renewable energy storage, hybrid vehicles, and other fields. With the rapid development of the electronics industry, the application of ceramic capacitors has expanded, and their operating environments have become increasingly complex, placing higher demands on their performance. For example, electronic equipment in automotive control systems, manned space flight, rockets and satellites, and oil exploration requires operating temperatures above 150°C. Therefore, these electronic devices require not only excellent dielectric properties but also excellent temperature stability over a wide temperature range to enhance their reliability in high-temperature applications. However, the extremely unstable dielectric constant and dielectric loss of ceramic capacitors used in filters and resonators at high frequencies can easily lead to distortion of transmitted signals, necessitating high frequency stability. However, current dielectric ceramics have problems such as low energy storage density and efficiency, poor temperature stability, and the presence of lead elements that are harmful to health and pollute the environment. They cannot meet the above requirements, limiting their further development and application.

[0003] Sodium bismuth titanate-based ceramics have high spontaneous polarization intensity (>40μC / cm 2 ) and a relatively high Curie temperature (~320°C) are considered to be a candidate material for capacitors with high energy storage performance. Researchers have used the bimodal characteristics of the dielectric temperature spectrum of sodium bismuth titanate-based ceramics to dope components to destroy the long-range order of the ferroelectric and enhance the relaxation behavior, thereby obtaining excellent wide-temperature stability, which is beneficial to improving the thermal stability of ceramic capacitors and extending their service life. However, due to the sharp increase in dielectric loss of ceramics under high temperature and high frequency, it is difficult to achieve a stable dielectric constant and low dielectric loss in a wide temperature range.

[0004] The Chinese invention with publication number CN117383930A discloses a sodium bismuth titanate-based lead-free energy storage ceramic material with high ferroelectric stability and temperature stability and its preparation method. The general structural formula of the ceramic material is (1-x)(0.85Bi0.5Na0.5TiO3-0.15NaNbO3)-xSrHfO3, where the value of x is 0.04~0.15. The ceramic material is prepared by batching, ball milling, pre-sintering, secondary ball milling, screening, tableting, and sintering. The preparation method is simple, low-cost, reproducible, and has a high yield. The obtained ceramic material has high ferroelectric stability (cycle stability and frequency stability), good temperature stability, and energy storage characteristics. When x=0.10, the dielectric constant at 100 kHz is εr150℃,100kHz=1065.39, the dielectric loss tanδ150℃,100kHz=0.01472, and within the temperature range of 68℃ to 371℃, the capacitance-temperature change rate satisfies TCC150℃≤±15%, the breakdown strength is 250 kV / cm, and the maximum polarization strength is 33 C / cm. 2 , the effective energy storage density is 3.05J / cm 3 , with an energy storage efficiency of up to 75.9%. A Chinese invention patent, publication number CN113387697A, discloses a sodium bismuth titanate-based ceramic material and preparation method that combines high ferroelectric stability with ultrafast charge and discharge speeds and high energy storage efficiency. The general formula of the ceramic material is (1-x)Na0.5Bi0.5TiO3-xCaTiO3, where x represents the molar ratio of CaTiO3 to the total mass, and the value of x ranges from 0.1 to 0.25. The ceramic material is prepared through batching, pre-sintering, ball milling, tableting, and pressureless sealed sintering. The preparation method is simple, reproducible, and has a high yield. The resulting ceramic material exhibits high ferroelectric stability (frequency stability and cycling stability), extremely low remanent polarization, and extremely high energy storage efficiency and charge-discharge performance. It is highly practical and easy to produce, making it a high-performance lead-free ferroelectric ceramic and a new candidate material in the field of pulsed power material systems. Although both of the above methods greatly improve the energy storage efficiency, the reduction in polarization intensity leads to limited energy storage density and poor breakdown resistance, which still cannot meet the current demand for ceramic capacitors.

[0005] It can be seen that although people have conducted a lot of research on sodium bismuth titanate-based ceramics and have made great progress in sodium bismuth titanate-based relaxation energy storage ceramic capacitors, the design and development of wide-temperature range dielectric materials suitable for cutting-edge technology is still extremely lacking. It is necessary to further explore and develop ceramic materials with high serviceability characteristics such as stable high dielectric constant, low dielectric loss and high energy storage density in an ultra-wide temperature range to meet the current development needs of ceramic capacitors. Summary of the Invention

[0006] In response to the problems of high dielectric loss, low energy storage density and low energy storage efficiency, and narrow operating temperature range of sodium bismuth titanate-based ceramic materials in the prior art, the present invention provides a sodium bismuth titanate-based lead-free ceramic material, a preparation method, and an application.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions:

[0008] The present invention provides a sodium bismuth titanate-based lead-free ceramic material, the general formula of which is: (1-x)Bi 0.5 Na 0.5 Ti03-xSr 1 / 2 Nd 1 / 3 (Mg 1 / 3 Nb 2 / 3 )O3 or (1-x)(0.7Bi 0.5 Na 0.5 Ti03-0.3SrTiO3)-xNd(Mg 2 / 3Nb 1 / 3 )O3, where x is Sr 1 / 2 Nd 1 / 3 (Mg 1 / 3 Nb 2 / 3 )O3 or Nd(Mg 2 / 3 Nb 1 / 3 )The molar ratio of O3 to the total mass is 0.06≤x≤0.21.

[0009] Optionally, the general formula of the ceramic material is: (1-x)Bi 0.5 Na 0.5 Ti03-xSr 1 / 2 Nd 1 / 3 (Mg 1 / 3 Nb 2 / 3 )O3, x is Sr 1 / 2 Nd 1 / 3 (Mg 1 / 3 Nb 2 / 3 )The molar ratio of O3 to the total mass is 0.12≤x≤0.21.

[0010] Optionally, the general formula of the ceramic material is: (1-x)(0.7Bi 0.5 Na 0.5 Ti03-0.3SrTiO3)-xNd(Mg 2 / 3Nb 1 / 3 )O3, x is Nd(Mg 2 / 3 Nb 1 / 3 )The molar ratio of O3 to the total mass is 0.06≤x≤0.12.

[0011] The present invention also provides a method for preparing the sodium bismuth titanate-based lead-free ceramic material as described above, comprising:

[0012] Mixing Bi2O3, Na2CO3, SrCO3, TiO2, Nd2O3, MgO and Nb2O5 in a proportion according to a general formula of ceramic materials to obtain a raw material mixture;

[0013] Pre-calcining and grinding the raw material mixture to obtain pre-calcined powder;

[0014] The pre-fired powder is ball-milled, sieved, tableted and sintered to obtain sodium bismuth titanate-based lead-free ceramic material.

[0015] Optionally, the method of mixing Bi2O3, Na2CO3, SrCO3, TiO2, Nd2O3, MgO and Nb2O5 in a proportion of the general formula of ceramic materials to obtain the raw material mixture is:

[0016] Bi2O3, Na2CO3, SrCO3, TiO2, Nd2O3, MgO and Nb2O5 with a purity of more than 99% are mixed according to the general proportion of ceramic materials, zirconium balls are used as grinding balls, anhydrous ethanol is used as ball milling medium, the mixture is ball milled for 22 to 24 hours, the zirconium balls are separated, and the mixture is dried at 60°C to 80°C to obtain a raw material mixture.

[0017] Optionally, the temperature for pre-firing the raw material mixture is 800° C. to 900° C., and the pre-firing time is 2 to 4 hours.

[0018] Optionally, during the process of ball milling, sieving, tableting and sintering the pre-calcined powder, tableting is performed by cold isostatic pressing at a pressure of 180 to 220 MPa, and the tableting time is 5 to 7 minutes.

[0019] Optionally, in the process of ball milling, screening, tableting and sintering the pre-calcined powder, the sintering is pressureless and closed sintering, the sintering temperature is 1100° C. to 1200° C., and the sintering time is 2 to 4 hours.

[0020] A sodium bismuth titanate-based lead-free ceramic material prepared by the above method is 2 ~10 6 In the Hz frequency range, the dielectric loss of the ceramic material is less than 0.05; at 10kHz and 150℃, the dielectric constant is 720.4-727.3, the dielectric loss is 0.0019-0.0126; and the energy storage density is 7.5-10.4J / cm 3 .

[0021] For example, the application of the sodium bismuth titanate-based lead-free ceramic material in the preparation of capacitors.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] The present invention discloses a sodium bismuth titanate-based lead-free ceramic material, the general formula of which is: (1-x)Bi 0.5 Na 0.5 Ti03-xSr 1 / 2 Nd 1 / 3 (Mg 1 / 3 Nb 2 / 3 )O3 or (1-x)(0.7Bi 0.5 Na 0.5 Ti03-0.3SrTiO3)-xNd(Mg 2 / 3Nb 1 / 3 )O3, where x is Sr 1 / 2 Nd 1 / 3 (Mg 1 / 3 Nb 2 / 3 )O3 or Nd(Mg 2 / 3 Nb 1 / 3 )O3 accounts for the molar ratio of the total mass, 0.06≤x≤0.21. 0.5 Na 0.5 Ti03-xSr 1 / 2 Nd 1 / 3 (Mg 1 / 3 Nb 2 / 3 )O3 in Sr 1 / 2 Nd 1 / 3 (Mg 1 / 3Nb 2 / 3 )O3 + Doping substitution, or in (1-x)(0.7Bi 0.5 Na 0.5 TiO3-0.3SrTiO3) in Nd 3+ / (Mg 2 / 3 Nb 1 / 3 ) 3+ Doping and substitution both disrupt the long-range ferroelectric order, enhance the ceramic's relaxation behavior, and improve the dielectric temperature stability of the ceramic material. By combining high dielectric constants with extremely low dielectric loss, lead-free sodium bismuth titanate-based ceramic materials with a wide dielectric temperature range and high frequency stability have been achieved. These ceramic materials exhibit high breakdown voltage, high energy storage density, and excellent dielectric temperature stability. They can operate stably in harsh environments such as high temperatures and high electric fields, making them suitable for applications in high-pulse power systems.

[0024] Furthermore, at 0.7Bi 0.5 Na 0.5 Nd in TiO3-0.3SrTiO3 system 3+ / (Mg 2 / 3 Nb 1 / 3 ) 3+Doping substitution enriches the types of polar nano-micro-regions with different polarities. The coexistence of rhombohedral and tetragonal phases is conducive to maintaining high dielectric constant and low dielectric loss, excellent dielectric temperature stability and high energy storage density while broadening the dielectric temperature stability range. It can work in extreme environments and is suitable for the preparation and application of multilayer ceramic capacitors.

[0025] Furthermore, in Bi 0.5 Na 0.5 Ti03-xSr 1 / 2 Nd 1 / 3 (Mg 1 / 3 Nb 2 / 3 )O3 system, high entropy components were introduced, and Sr 2+ and Nd 3+ Replace Bi 3+ and Na + , (Mg 1 / 3 Nb 2 / 3 ) 4+ Replace Ti 4+ By constructing a high entropy structure based on sodium bismuth titanate through multi-element substitution, the co-doping of multiple elements increases the local structural disorder and charge fluctuation, inducing the generation of a random electric field, and the existence of a random electric field is conducive to enhancing the relaxation behavior and reducing the residual polarization intensity. Therefore, it is beneficial to improve the dielectric stability and energy storage efficiency of ceramics. In addition, the large ion radius Mg 2+ and Nb 5+ The introduction of intensifies the lattice distortion, which is beneficial to the refinement of grains. The increase in density significantly improves the breakdown voltage of the ceramic. The prepared ceramic material also has the characteristics of high breakdown voltage, high energy storage density, and excellent dielectric temperature stability, and also meets the requirements of extreme working environments.

[0026] The present invention also provides a method for preparing the sodium bismuth titanate-based lead-free ceramic material as described above. The method comprises the following steps: mixing Bi2O3, Na2CO3, SrCO3, TiO2, Nd2O3, MgO and Nb2O5 in proportion according to the general formula of the ceramic material to obtain a raw material mixture; then pre-calcining and grinding the raw material mixture to obtain a pre-calcined powder; and finally, ball milling, sieving, tableting and sintering the pre-calcined powder to obtain the sodium bismuth titanate-based lead-free ceramic material. The preparation method is simple, low in cost, has good repeatability, a high yield and is easy to produce. The selected raw materials do not contain lead and are environmentally friendly. The advanced cold isostatic pressing technology is used to reduce the risk of cracking and delamination of the green body, and the green body obtained has high density and uniform quality.

[0027] The present invention also provides a sodium bismuth titanate-based lead-free ceramic material prepared by the above method. 2 ~10 6In the Hz frequency range, the dielectric loss of the ceramic material is less than 0.05; at 10kHz and 150℃, the dielectric constant is 720.4-727.3, the dielectric loss is 0.0019-0.0126; and the energy storage density is 7.5-10.4J / cm 3 The material has the characteristics of high breakdown voltage, high energy storage density, and excellent dielectric temperature stability, and has broad application prospects in capacitors, energy storage components, electronic filters, piezoelectric sensors and other fields.

[0028] For example, the application of the aforementioned sodium bismuth titanate-based lead-free ceramic material in the preparation of capacitors. Capacitors made with this lead-free sodium bismuth titanate ceramic material have high energy conversion efficiency, good temperature resistance, durability, and stability, and have broad application prospects in various fields such as electric vehicles, smart grids, aerospace, and communications equipment. In particular, these capacitors can play an important role in applications requiring high energy density, high efficiency, long life, and environmental protection. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 The present invention is a schematic flow chart of a method for preparing a sodium bismuth titanate-based lead-free ceramic material.

[0030] Figure 2 This is a graph showing the relationship between the dielectric constant and dielectric loss of the ceramic materials prepared in Examples 1-4 of the present invention at room temperature and frequency.

[0031] Figure 3 This is a graph showing the relationship between the dielectric constant and dielectric loss of the ceramic material prepared in Example 1 and temperature at different test frequencies.

[0032] Figure 4 This is a graph showing the relationship between the dielectric constant and dielectric loss of the ceramic material prepared in Example 2 and temperature at different test frequencies.

[0033] Figure 5 This is a graph showing the relationship between the dielectric constant and dielectric loss of the ceramic material prepared in Example 3 and temperature at different test frequencies.

[0034] Figure 6 This is a graph showing the relationship between the dielectric constant and dielectric loss of the ceramic material prepared in Example 4 and temperature at different test frequencies.

[0035] Figure 7 This is a graph showing the relationship between the dielectric constant and dielectric loss of the ceramic materials prepared in Examples 1-4 of the present invention and the temperature at 10 kHz.

[0036] Figure 8 The Δε / ε of the ceramic materials prepared in Examples 1-4 of the present invention at 10kHz is 150℃ Curves that vary with temperature.

[0037] Figure 9 The graph shows the change of the unipolar hysteresis loop of the prepared pure BNT-based ceramics under different electric fields.

[0038] Figure 10 This is a diagram showing the change of the unipolar hysteresis loop of the ceramic material prepared in Example 3 of the present invention under different electric fields.

[0039] Figure 11 This is a graph showing changes in energy storage density and energy storage efficiency of the ceramic materials prepared in Examples 1-4 of the present invention.

[0040] Figure 12 The chart below is a comparison of the maximum polarization value, residual polarization value, and breakdown field strength of pure BNT ceramics and the ceramic materials prepared in Examples 1-4.

[0041] Figure 13 These are the XRD patterns of the ceramic materials prepared in Examples 5-8 of the present invention.

[0042] Figure 14 This is a scanning electron microscope image of the ceramic material prepared in Example 7 of the present invention.

[0043] Figure 15 This is a graph showing the relationship between the dielectric constant and dielectric loss of the ceramic materials prepared in Examples 5-8 of the present invention at room temperature and frequency.

[0044] Figure 16 This is a graph showing the relationship between the dielectric constant and dielectric loss of the ceramic material prepared in Example 5 of the present invention and the temperature at different test frequencies.

[0045] Figure 17 This is a graph showing the relationship between the dielectric constant and dielectric loss of the ceramic material prepared in Example 6 of the present invention and the temperature at different test frequencies.

[0046] Figure 18 This is a graph showing the relationship between the dielectric constant and dielectric loss of the ceramic material prepared in Example 7 of the present invention and the temperature at different test frequencies.

[0047] Figure 19 This is a graph showing the relationship between the dielectric constant and dielectric loss of the ceramic material prepared in Example 8 of the present invention and the temperature at different test frequencies.

[0048] Figure 20 This is a graph showing the relationship between the dielectric constant and dielectric loss of the ceramic materials prepared in Examples 5-8 of the present invention at 10 kHz and temperature.

[0049] Figure 21 The Δε / ε of the ceramic materials prepared in Examples 5-8 of the present invention at 10kHz is 150℃ Curves that vary with temperature.

[0050] Figure 22 The temperature change rate of the ceramic material prepared in Examples 5-8 of the present invention meets the TCC 150℃ ≤ ±15% temperature range curve.

[0051] Figure 23 This is a graph showing changes in the unipolar hysteresis loop of the ceramic materials prepared in Examples 5-8 of the present invention under an electric field of 250 kV / cm.

[0052] Figure 24 This is a graph showing changes in energy storage density and energy storage efficiency of the ceramic materials prepared in Examples 5-8 of the present invention. DETAILED DESCRIPTION

[0053] To facilitate understanding of the features and effects of the present invention by those skilled in the art, the following provides a general description and definition of the terms and expressions used in the specification and claims. Unless otherwise indicated, all technical and scientific terms used herein have the ordinary meanings as understood by those skilled in the art regarding the present invention. In the event of conflict, the definitions in this specification shall prevail.

[0054] The theories or mechanisms described and disclosed herein, whether correct or incorrect, should not limit the scope of the present invention in any way, that is, the present invention can be implemented without being limited by any specific theory or mechanism.

[0055] All features, such as values, amounts, contents, and concentrations, described herein as numerical ranges or percentage ranges are provided for simplicity and convenience only. Accordingly, the description of numerical ranges or percentage ranges should be considered to include and specifically disclose all possible subranges and individual values ​​within the range (including integers and fractions).

[0056] In this document, unless otherwise specified, “include,” “including,” “contains,” “has” or similar terms cover the meanings of “consisting of” and “mainly consisting of,” for example, “A includes a” covers the meanings of “A includes a and other” and “A only includes a.”

[0057] In this document, for the sake of brevity, not all possible combinations of the various technical features in each embodiment or example are described. Therefore, as long as there are no contradictions in the combination of these technical features, the various technical features in each embodiment or example can be combined in any way, and all possible combinations should be considered to be within the scope of this specification.

[0058] Below in conjunction with specific embodiment, further set forth the present invention.Should be understood that these embodiments are only used to illustrate the present invention and are not used in limiting the scope of the present invention.In addition, should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall equally within the scope limited by the appended claims of the application.

[0059] The following examples were prepared using conventional instruments and equipment in the art. Experimental methods in the following examples, where specific conditions are not specified, were generally performed under conventional conditions or according to the conditions recommended by the manufacturer. The various raw materials used in the following examples, unless otherwise specified, were conventional commercially available products, with specifications conventional in the art. In the present specification and the following examples, unless otherwise specified, "%" indicates percentage by weight, "part" indicates parts by weight, and "ratio" indicates weight ratio.

[0060] The present invention will be further described in detail below with reference to specific embodiments, which are intended to explain the present invention rather than to limit it.

[0061] The present invention discloses a sodium bismuth titanate-based lead-free ceramic material, the general formula of which is: (1-x)Bi 0.5 Na 0.5 Ti03-xSr 1 / 2 Nd 1 / 3 (Mg 1 / 3 Nb 2 / 3 )O3 or (1-x)(0.7Bi 0.5 Na 0.5 Ti03-0.3SrTiO3)-xNd(Mg 2 / 3Nb 1 / 3 )O3, where x is Sr 1 / 2 Nd 1 / 3 (Mg 1 / 3 Nb 2 / 3 )O3 or Nd(Mg 2 / 3 Nb 1 / 3 )The molar ratio of O3 to the total mass is 0.06≤x≤0.21.

[0062] Furthermore, the general formula of the ceramic material is: (1-x)Bi 0.5 Na 0.5 Ti03-xSr 1 / 2 Nd 1 / 3 (Mg 1 / 3 Nb 2 / 3 )O3, x is Sr 1 / 2 Nd 1 / 3 (Mg 1 / 3 Nb 2 / 3)The molar ratio of O3 to the total mass is 0.12≤x≤0.21, preferably, 0.15≤x≤0.21, and further, 0.18≤x≤0.21.

[0063] Furthermore, the general formula of the ceramic material is: (1-x)(0.7Bi 0.5 Na 0.5 Ti03-0.3SrTiO3)-xNd(Mg 2 / 3 Nb 1 / 3 )O3, x is Nd(Mg 2 / 3 Nb 1 / 3 )The molar ratio of O3 to the total mass is 0.06≤x≤0.12, preferably, 0.08≤x≤0.12, and further preferably, 0.1≤x≤0.12.

[0064] See also Figure 1 The present invention also provides a method for preparing the above-mentioned sodium bismuth titanate-based lead-free ceramic material, comprising:

[0065] S1: Bi2O3, Na2CO3, SrCO3, TiO2, Nd2O3, MgO and Nb2O5 are mixed in a proportion according to the general formula of ceramic materials to obtain a raw material mixture, specifically:

[0066] Bi2O3, Na2CO3, SrCO3, TiO2, Nd2O3, MgO and Nb2O5 with a purity of more than 99% are mixed according to the general proportion of ceramic materials, placed in a nylon jar, and milled for 22 to 24 hours using zirconium balls as grinding balls and anhydrous ethanol as ball milling medium. The zirconium balls are separated and dried at 60°C to 80°C to obtain a raw material mixture.

[0067] S2: Pre-calcining and grinding the raw material mixture to obtain pre-calcined powder, specifically:

[0068] The raw material mixture is placed in an alumina crucible, compacted with an agate rod, covered, pre-fired at 800°C to 900°C for 2 to 4 hours, cooled to room temperature, and ground with a mortar to obtain pre-fired powder.

[0069] S3: The pre-fired powder is ball-milled, sieved, tableted and sintered to obtain a sodium bismuth titanate-based lead-free ceramic material, specifically: the pre-fired powder is placed in a nylon jar, fully mixed and ball-milled for 20 to 24 hours, the zirconium balls are separated, and the powder is dried at 60°C to 80°C and ground. After grinding, the powder is sieved through a 120 to 180 mesh sieve, and cold isostatically pressed at a pressure of 180 to 220 MPa for 5 to 7 minutes to form a cylindrical green body. The cylindrical green body is placed on a zirconia plate, and the zirconia plate is placed in an alumina sealed sagger. The powder is sintered at a constant temperature of 1100°C to 1200°C for 2 to 4 hours, and naturally cooled to room temperature with the furnace to prepare a sodium bismuth titanate-based lead-free ceramic material.

[0070] The present invention also provides a sodium bismuth titanate-based lead-free ceramic material prepared by the above method. 2 ~10 6 In the Hz frequency range, the dielectric loss of the ceramic material is less than 0.05; at 10kHz and 150℃, the dielectric constant is 720.4-727.3, the dielectric loss is 0.0019-0.0126; and the energy storage density is 7.5-10.4J / cm 3 The material has the characteristics of high breakdown voltage, high energy storage density, and excellent dielectric temperature stability, and has broad application prospects in capacitors, energy storage components, electronic filters, piezoelectric sensors and other fields.

[0071] For example, the application of the aforementioned sodium bismuth titanate-based lead-free ceramic material in the preparation of capacitors. Capacitors made with this lead-free sodium bismuth titanate ceramic material have high energy conversion efficiency, good temperature resistance, durability, and stability, and have broad application prospects in various fields such as electric vehicles, smart grids, aerospace, and communications equipment. In particular, these capacitors can play an important role in applications requiring high energy density, high efficiency, long life, and environmental protection.

[0072] Example 1

[0073] According to 0.88Bi 0.5 Na 0.5 Ti03-0.12Sr 1 / 2 Nd 1 / 3 (Mg 1 / 3 Nb 2 / 3 )O3 stoichiometrically, 9.1444 g Bi2O3, 2.0634 g Na2CO3, 0.7826 g SrCO3, 6.3337 g TiO2, 0.9331 g Nb2O5, 0.1424 g MgO and 0.5944 g Nd2O3 with a purity of more than 99.00% were weighed respectively, mixed evenly, and then put into a nylon jar. Zirconium balls were used as grinding balls and anhydrous ethanol was used as ball milling medium. The mixture was fully mixed and ball milled for 24 h. The zirconium balls were separated, and the mixture was dried at 80°C for 24 h. The mixture was ground in a mortar to obtain a raw material mixture.

[0074] The raw material mixture was placed in an alumina crucible, compacted with an agate rod, covered, and heated to 850°C in a muffle furnace at a heating rate of 3°C / min for constant temperature pre-calcination for 3 h. The mixture was naturally cooled to room temperature and ground with a mortar to obtain pre-calcined powder.

[0075] The pre-calcined powder was put into a nylon jar, mixed thoroughly and ball-milled for 24 hours, the zirconium balls were separated, dried at 80°C for 24 hours, ground with a mortar, passed through a 120-mesh sieve, and pressed into a cylindrical body with a diameter of 11.5 mm and a thickness of 1 mm in a tablet press, and then cold isostatically pressed at a pressure of 200 MPa for 5 minutes.

[0076] The cylindrical green body after cold isostatic pressing was placed on a zirconia plate, and the zirconia plate was placed in an alumina closed sagger. The temperature was raised to 1130°C at a heating rate of 3°C / min, sintered at a constant temperature for 3 hours, and naturally cooled to room temperature in the furnace to prepare sodium bismuth titanate-based lead-free energy storage ceramic material.

[0077] Example 2

[0078] According to 0.85Bi 0.5 Na 0.5 Ti03-0.15Sr 1 / 2 Nd 1 / 3 (Mg 1 / 3 Nb 2 / 3 )O3 stoichiometrically, 8.8254 g Bi2O3, 1.9914 g Na2CO3, 0.9775 g SrCO3, 6.1128 g TiO2, 1.1729 g Nb2O5, 0.1778 g MgO and 0.7423 g Nd2O3 with a purity of more than 99.00% were weighed respectively, mixed evenly, and then put into a nylon jar. Zirconium balls were used as grinding balls and anhydrous ethanol was used as ball milling medium. The mixture was thoroughly mixed and ball milled for 24 h. The zirconium balls were separated, and the mixture was dried at 80°C for 24 h. The mixture was ground in a mortar to obtain a raw material mixture.

[0079] The raw material mixture was placed in an alumina crucible, compacted with an agate rod, covered, and heated to 850°C in a muffle furnace at a heating rate of 3°C / min for constant temperature pre-calcination for 3 h. The mixture was naturally cooled to room temperature and ground with a mortar to obtain pre-calcined powder.

[0080] The pre-calcined powder was put into a nylon jar, mixed thoroughly and ball-milled for 24 hours, the zirconium balls were separated, dried at 80°C for 24 hours, ground with a mortar, passed through a 120-mesh sieve, and pressed into a cylindrical body with a diameter of 11.5 mm and a thickness of 1 mm in a tablet press, and then cold isostatically pressed at a pressure of 200 MPa for 5 minutes.

[0081] The cylindrical green body after cold isostatic pressing was placed on a zirconia plate, and the zirconia plate was placed in an alumina closed sagger. The temperature was raised to 1130°C at a heating rate of 3°C / min, sintered at a constant temperature for 3 hours, and naturally cooled to room temperature in the furnace to prepare sodium bismuth titanate-based lead-free energy storage ceramic material.

[0082] Example 3

[0083] According to 0.82Bi0.5 Na 0.5 Ti03-0.18Sr 1 / 2 Nd 1 / 3 (Mg 1 / 3 Nb 2 / 3 )O3 stoichiometrically, 8.5068g Bi2O3, 1.9195g Na2CO3, 1.1720g SrCO3, 5.8921g TiO2, 1.4031g Nb2O5, 0.2132g MgO and 0.8901g Nd2O3 with a purity of more than 99.00% were weighed respectively, mixed evenly, and put into a nylon jar. Zirconium balls were used as grinding balls and anhydrous ethanol was used as ball milling medium. The mixture was fully mixed and ball milled for 24 hours. The zirconium balls were separated, and the mixture was dried at 80°C for 24 hours. The mixture was ground in a mortar to obtain a raw material mixture.

[0084] The raw material mixture was placed in an alumina crucible, compacted with an agate rod, covered, and heated to 850°C in a muffle furnace at a heating rate of 3°C / min for constant temperature pre-calcination for 3 h. The mixture was naturally cooled to room temperature and ground with a mortar to obtain pre-calcined powder.

[0085] The pre-calcined powder was put into a nylon jar, mixed thoroughly and ball-milled for 24 hours, the zirconium balls were separated, dried at 80°C for 24 hours, ground with a mortar, passed through a 120-mesh sieve, and pressed into a cylindrical body with a diameter of 11.5 mm and a thickness of 1 mm in a tablet press, and then cold isostatically pressed at a pressure of 200 MPa for 5 minutes.

[0086] The cylindrical green body after cold isostatic pressing was placed on a zirconia plate, and the zirconia plate was placed in an alumina closed sagger. The temperature was raised to 1130°C at a heating rate of 3°C / min, sintered at a constant temperature for 3 hours, and naturally cooled to room temperature in the furnace to prepare sodium bismuth titanate-based lead-free energy storage ceramic material.

[0087] Example 4

[0088] According to 0.79Bi 0.5 Na 0.5 Ti03-0.21Sr 1 / 2 Nd 1 / 3 (Mg 1 / 3 Nb 2 / 3 )O3 stoichiometrically, 8.1888g Bi2O3, 1.8477g Na2CO3, 1.3662g SrCO3, 5.6719g TiO2, 1.6393g Nb2O5, 0.2485g MgO and 1.0376g Nd2O3 with a purity of more than 99.00% were weighed respectively, mixed evenly, and put into a nylon jar. Zirconium balls were used as grinding balls and anhydrous ethanol was used as ball milling medium. The mixture was fully mixed and ball milled for 24 hours. The zirconium balls were separated, and the mixture was dried at 80°C for 24 hours. The mixture was ground in a mortar to obtain a raw material mixture.

[0089] The raw material mixture was placed in an alumina crucible, compacted with an agate rod, covered, and heated to 850°C in a muffle furnace at a heating rate of 3°C / min for constant temperature pre-calcination for 3 h. The mixture was naturally cooled to room temperature and ground with a mortar to obtain pre-calcined powder.

[0090] The pre-calcined powder was put into a nylon jar, mixed thoroughly and ball-milled for 24 hours, the zirconium balls were separated, dried at 80°C for 24 hours, ground with a mortar, passed through a 120-mesh sieve, and pressed into a cylindrical body with a diameter of 11.5 mm and a thickness of 1 mm in a tablet press, and then cold isostatically pressed at a pressure of 200 MPa for 5 minutes.

[0091] The cylindrical green body after cold isostatic pressing was placed on a zirconia plate, and the zirconia plate was placed in an alumina closed sagger. The temperature was raised to 1130°C at a heating rate of 3°C / min, sintered at a constant temperature for 3 hours, and naturally cooled to room temperature in the furnace to prepare sodium bismuth titanate-based lead-free energy storage ceramic material.

[0092] Example 5

[0093] According to 0.94 (0.7Bi 0.5 Na 0.5 TiO3-0.3SrTiO3)-0.06Nd(Mg 2 / 3 Nb 1 / 3 )O3 stoichiometrically, 6.8059 g Bi2O3, 1.5357 g Na2CO3, 3.6614 g SrCO3, 6.7343 g TiO2, 0.2337 g Nb2O5, 0.1417 g MgO and 0.8874 g Nd2O3 with a purity of more than 99.00% were weighed respectively, mixed evenly, and put into a nylon jar. Zirconium balls were used as grinding balls and anhydrous ethanol was used as ball milling medium. The mixture was thoroughly mixed and ball milled for 24 h. The zirconium balls were separated, and the mixture was dried at 80°C for 24 h. The mixture was ground in a mortar to obtain a raw material mixture.

[0094] The raw material mixture was placed in an alumina crucible, compacted with an agate rod, covered, and heated to 850°C in a muffle furnace at a heating rate of 3°C / min for constant temperature pre-calcination for 3 h. The mixture was naturally cooled to room temperature and ground with a mortar to obtain pre-calcined powder.

[0095] The pre-calcined powder was put into a nylon jar, mixed thoroughly and ball-milled for 24 hours, the zirconium balls were separated, dried at 80°C for 24 hours, ground with a mortar, passed through a 120-mesh sieve, and pressed into a cylindrical body with a diameter of 11.5 mm and a thickness of 1 mm in a tablet press, and then cold isostatically pressed at a pressure of 200 MPa for 5 minutes.

[0096] The cylindrical green body after cold isostatic pressing was placed on a zirconia plate, and the zirconia plate was placed in an alumina closed sagger. The temperature was raised to 1130°C at a heating rate of 3°C / min, sintered at a constant temperature for 3 hours, and naturally cooled to room temperature in the furnace to prepare sodium bismuth titanate-based lead-free energy storage ceramic material.

[0097] Example 6

[0098] 0.92(0.7Bi 0.5 Na 0.5 TiO3-0.3SrTiO3)-0.08Nd(Mg 2 / 3 Nb 1 / 3 )O3 stoichiometrically, 6.6536 g Bi2O3, 1.5013 g Na2CO3, 3.5795 g SrCO3, 6.5836 g TiO2, 0.3112 g Nb2O5, 0.1887 g MgO and 1.1819 g Nd2O3 with a purity of more than 99.00% were weighed respectively, mixed evenly, and put into a nylon jar. Zirconium balls were used as grinding balls and anhydrous ethanol was used as ball milling medium. The mixture was thoroughly mixed and ball milled for 24 h. The zirconium balls were separated, and the mixture was dried at 80°C for 24 h. The mixture was ground in a mortar to obtain a raw material mixture.

[0099] The raw material mixture was placed in an alumina crucible, compacted with an agate rod, covered, and heated to 850°C in a muffle furnace at a heating rate of 3°C / min for constant temperature pre-calcination for 3 h. The mixture was naturally cooled to room temperature and ground with a mortar to obtain pre-calcined powder.

[0100] The pre-calcined powder was put into a nylon jar, mixed thoroughly and ball-milled for 24 hours, the zirconium balls were separated, dried at 80°C for 24 hours, ground with a mortar, passed through a 120-mesh sieve, and pressed into a cylindrical body with a diameter of 11.5 mm and a thickness of 1 mm in a tablet press, and then cold isostatically pressed at a pressure of 200 MPa for 5 minutes.

[0101] The cylindrical green body after cold isostatic pressing was placed on a zirconia plate, and the zirconia plate was placed in an alumina closed sagger. The temperature was raised to 1130°C at a heating rate of 3°C / min, sintered at a constant temperature for 3 hours, and naturally cooled to room temperature in the furnace to prepare sodium bismuth titanate-based lead-free energy storage ceramic material.

[0102] Example 7

[0103] According to 0.90(0.7Bi 0.5 Na 0.5 Ti03-0.3SrTiO3)-0.10Nd(Mg 2 / 3 Nb 1 / 3)O3 stoichiometrically, 6.5018 g Bi2O3, 1.4671 g Na2CO3, 3.4978 g SrCO3, 6.4334 g TiO2, 0.3886 g Nb2O5, 0.2357 g MgO and 1.4757 g Nd2O3 with a purity of more than 99.00% were weighed respectively, mixed evenly, and put into a nylon jar. Zirconium balls were used as grinding balls and anhydrous ethanol was used as ball milling medium. The mixture was thoroughly mixed and ball milled for 24 h. The zirconium balls were separated, and the mixture was dried at 80°C for 24 h. The mixture was ground in a mortar to obtain a raw material mixture.

[0104] The raw material mixture was placed in an alumina crucible, compacted with an agate rod, covered, and heated to 850°C in a muffle furnace at a heating rate of 3°C / min for constant temperature pre-calcination for 3 h. The mixture was naturally cooled to room temperature and ground with a mortar to obtain pre-calcined powder.

[0105] The pre-calcined powder was put into a nylon jar, mixed thoroughly and ball-milled for 24 hours, the zirconium balls were separated, dried at 80°C for 24 hours, ground with a mortar, passed through a 120-mesh sieve, and pressed into a cylindrical body with a diameter of 11.5 mm and a thickness of 1 mm in a tablet press, and then cold isostatically pressed at a pressure of 200 MPa for 5 minutes.

[0106] The cylindrical green body after cold isostatic pressing was placed on a zirconia plate, and the zirconia plate was placed in an alumina closed sagger. The temperature was raised to 1130°C at a heating rate of 3°C / min, sintered at a constant temperature for 3 hours, and naturally cooled to room temperature in the furnace to prepare sodium bismuth titanate-based lead-free energy storage ceramic material.

[0107] Example 8

[0108] According to 0.88 (0.7Bi 0.5 Na 0.5 TiO3-0.3SrTiO3)-0.12Nd(Mg 2 / 3 Nb 1 / 3 )O3 stoichiometrically, 6.3502g Bi2O3, 1.4329g Na2CO3, 3.4163g SrCO3, 6.2834g TiO2, 0.4658g Nb2O5, 0.2825g MgO and 1.7689g Nd2O3 with a purity of more than 99.00% were weighed respectively, mixed evenly, and put into a nylon jar. Zirconium balls were used as grinding balls and anhydrous ethanol was used as ball milling medium. The mixture was thoroughly mixed and ball milled for 24 hours. The zirconium balls were separated, and the mixture was dried at 80°C for 24 hours. The mixture was ground in a mortar to obtain a raw material mixture.

[0109] The raw material mixture was placed in an alumina crucible, compacted with an agate rod, covered, and heated to 850°C in a muffle furnace at a heating rate of 3°C / min for constant temperature pre-calcination for 3 h. The mixture was naturally cooled to room temperature and ground with a mortar to obtain pre-calcined powder.

[0110] The pre-calcined powder was put into a nylon jar, mixed thoroughly and ball-milled for 24 hours, the zirconium balls were separated, dried at 80°C for 24 hours, ground with a mortar, passed through a 120-mesh sieve, and pressed into a cylindrical body with a diameter of 11.5 mm and a thickness of 1 mm in a tablet press, and then cold isostatically pressed at a pressure of 200 MPa for 5 minutes.

[0111] The cylindrical green body after cold isostatic pressing was placed on a zirconia plate, and the zirconia plate was placed in an alumina closed sagger. The temperature was raised to 1130°C at a heating rate of 3°C / min, sintered at a constant temperature for 3 hours, and naturally cooled to room temperature in the furnace to prepare sodium bismuth titanate-based lead-free energy storage ceramic material.

[0112] To further test the performance of the sodium bismuth titanate-based lead-free energy storage ceramic material prepared by the present invention, the sodium bismuth titanate-based lead-free energy storage ceramic material prepared in Examples 1-8 was selected respectively, and its surface was polished with 320-mesh sandpaper, and then polished to 0.5 mm thick with 1500-mesh sandpaper and corundum. After being ultrasonically wiped with alcohol, it was ground into powder and XRD tested using a MiniFlex600 diffractometer produced by Rigaku Corporation of Japan. One of the ceramic materials prepared in Examples 1-8 above was selected for grinding, polishing, ultrasonication, and wiping clean. Silver paste was coated on the upper and lower surfaces of the ceramic sample, respectively, and placed in a muffle furnace at 840°C for 30 min. It was naturally cooled to room temperature and the dielectric properties of the material were tested using a DMS-2000 high-temperature dielectric impedance spectrometer produced by Bailibo Technology Co., Ltd. One of the ceramic materials prepared in Examples 1-8 above was selected for grinding, polishing, ultrasonication, and wiping clean. The upper and lower surfaces of the ceramic sample were respectively coated with silver paste, placed in a muffle furnace at 840°C for 30 min, and naturally cooled to room temperature. The dielectric properties of the material were tested using a DMS-2000 high-temperature dielectric impedance spectrometer produced by Bailibo Technology Co., Ltd.

[0113] See also Figure 2 The relationship between the dielectric constant and dielectric loss of the ceramic materials prepared by Examples 1-4 at room temperature and the frequency is shown. It can be seen that the dielectric constant of the ceramic materials has a platform that is independent of the dielectric frequency and has excellent frequency stability. 2 ~10 6 The dielectric loss of ceramic materials in the Hz frequency range is less than 0.04, and as Sr 1 / 2 Nd 1 / 3 (Mg 1 / 3 Nb 2 / 3 ) With the increase of O3 doping amount, the dielectric constant and dielectric loss decrease, and the frequency stability of ceramic materials gradually improves. Figures 3 to 6 From the relationship diagram of the dielectric constant and dielectric loss of the ceramic materials prepared in Examples 1 to 4 at different test frequencies, it can be seen that under the test temperature range of -150℃ to 450℃, the dielectric constant ε of the ceramic material prepared in Example 4 at 10kHz and 150℃ is150℃,10 kHz =720.4, dielectric loss tanδ 150℃,10 kHz = 0.0019, achieving a large dielectric constant and extremely low dielectric loss. Figure 7 , the relationship between the dielectric constant and dielectric loss of the ceramic materials prepared in Examples 1-4 at 10kHz and temperature, it can be seen that Sr 1 / 2 Nd 1 / 3 (Mg 1 / 3 Nb 2 / 3 )O3 doping makes the dielectric curve appear a dielectric platform in a wide temperature range and gradually broadens with the increase of doping amount, indicating that the long-range ordered ferroelectricity of the ceramic is destroyed and the relaxation behavior is gradually enhanced, which is conducive to improving the dielectric temperature stability of the ceramic material. 1 / 2 Nd 1 / 3 (Mg 1 / 3 Nb 2 / 3 ) As the doping of O3 increases, the dielectric loss gradually decreases. The dielectric loss of the ceramic material prepared in Example 3 is less than 0.02 in an ultra-wide temperature range of 48°C to 404°C. Figure 8 , the ceramic materials prepared by Examples 1-4 have a Δε / ε ratio at 10 kHz. 150℃ As shown in the temperature-dependent relationship diagram, it is generally believed that the rate of change of the dielectric constant (Δ ε / ε 150℃ ) does not exceed 15%, which means that the dielectric constant of the ceramic material has good temperature stability. The results show that as Sr 1 / 2 Nd 1 / 3 (Mg 1 / 3 Nb 2 / 3 )O3 doping broadens the dielectric temperature stability temperature range of ceramic materials. In the temperature range of -17℃~450℃, the dielectric temperature change rate TCC of the ceramic material in Example 3 is 150℃ ≤±15%, by Figure 8 It can be seen that the unipolar hysteresis loop of the ceramic material gradually becomes thinner and the residual polarization intensity gradually decreases, indicating that the energy storage efficiency of the ceramic material gradually increases. Figure 9 and Figure 10 It can be seen that pure BNT ceramics are pure Bi 0.5 Na 0.5 The residual polarization value of TiO3 ceramics is large and the breakdown field strength is low. Compared with the ceramic material prepared in Example 3, the ceramic material prepared in Example 3 has a higher breakdown voltage, which can reach 480kV / cm. Figure 11 It can be seen that in the figure, P max is the maximum polarization value, P r is the residual polarization value, E b The effective energy storage density of the prepared pure BNT ceramic is only 1.8 J / cm 3, the energy storage efficiency is only 58.6%, and the breakdown field strength is relatively low, which is 160 kV / cm. However, the ceramic material prepared in Example 3 has excellent energy storage performance, and its effective energy storage density is 7.5 J / cm 3 , the energy storage efficiency is 82.6%. Compared with the prepared pure BNT ceramics, the effective energy storage density is increased by 416%, the energy storage efficiency is increased by 141%, and the breakdown field strength is increased by 300%. Figure 12 From the changes in the maximum polarization value, residual polarization value, and breakdown field strength of pure BNT ceramics and the ceramic materials prepared in Examples 1-4, it can be seen that due to the effective reduction of the residual polarization value and the substantial increase in the breakdown field strength, the effective energy storage density and energy storage efficiency of the ceramic material prepared in Example 3 are significantly improved.

[0114] See also Figure 13 From the XRD patterns of the ceramic materials prepared in Examples 5-8, it can be seen that all the ceramics prepared are perovskite structures, and no second phase is observed, indicating that the third component Nd (Mg 2 / 3 Nb 1 / 3 )O3 has completely dissolved into 0.7Bi 0.5 Na 0.5 In the lattice of Ti03-0.3SrTiO3. Figure 14 This is a surface scanning electron microscope image of the ceramic material prepared in Example 8 of the present invention. The average grain size is 0.86 μm, which is similar to the 0.7Bi prepared by Zhang Ying et al. in 2024. 0.5 Na 0.5 Compared with the average grain size of 1.31 μm of Ti03-0.3SrTiO3 ceramics (https: / / doi.org / 10.1016 / j.actamat.2024.120109), the grain size has been significantly refined. Therefore, the ceramic material prepared in Example 7 of the present invention has a dense structure and lower dielectric loss. Figure 15 It can be seen that the dielectric constant of ceramic materials has a platform that is independent of the dielectric frequency and has excellent frequency stability. 2 ~10 6 The dielectric loss of ceramic materials in the Hz frequency range is less than 0.05, and as Nd(Mg 2 / 3 Nb 1 / 3 ) With the increase of O3 doping amount, the dielectric constant and dielectric loss decrease, and the frequency stability of ceramic materials gradually improves. Figures 16 to 19 , are the dielectric temperature spectra of the ceramic materials prepared in Examples 5 to 8, respectively. The test temperature range is -150℃~450℃. Among them, the dielectric constant ε of the ceramic material prepared in Example 8 at 10kHz and 150℃ is 150℃,10 kHz =727.3, dielectric loss tanδ 150℃,10 kHz=0.0126, with a larger dielectric constant and lower dielectric loss. Figure 20 It can be seen that Nd(Mg 2 / 3 Nb 1 / 3 )O3 doping causes a dielectric platform to appear in the dielectric curve within a wide temperature range and gradually widens with the increase of doping amount, indicating that the long-range ordered ferroelectricity of the ceramic is destroyed and the relaxation phase gradually increases, which is beneficial to improving the dielectric temperature stability of the ceramic material. Figure 21 The Δε / ε of the ceramic materials prepared in Examples 5-8 at 10 kHz 150℃ Temperature dependence and Figure 22 The temperature change rate of the ceramic materials prepared in Examples 5-8 meets the TCC 150℃ ≤ ±15% of the temperature range, it can be seen that as Nd(Mg 2 / 3 Nb 1 / 3 )O3 doping, the dielectric temperature stable temperature range of the ceramic material gradually widens. The ceramic material prepared in Example 7 has a capacitance temperature change rate TCC within the temperature range of -20℃~407℃. 150℃ ≤ ±15%. Figure 23 The unipolar hysteresis loops of the ceramic materials prepared in Examples 5-8 under an electric field of 250 kV / cm show that as Nd(Mg 2 / 3 Nb 1 / 3 ) With the increase of O3 doping amount, the hysteresis loop of ceramic material gradually becomes finer, indicating that the energy storage efficiency gradually improves. Figure 24 From the energy storage density and energy storage efficiency of the ceramic materials prepared in Examples 5-8, it can be seen that the energy storage performance of the ceramic material prepared in Example 7 is significantly improved, and its energy storage density is 10.4 J / cm 3 , the energy storage efficiency is 83.6%.

[0115] Based on the above results, it can be seen that the sodium bismuth titanate-based lead-free energy storage ceramics of the present invention have an ultra-wide dielectric stable temperature range, a high dielectric constant, extremely low dielectric loss, high frequency stability, extremely high breakdown voltage and high energy storage density, and are expected to be used in ceramic energy storage capacitors with high serviceability characteristics under high electric fields and high temperatures.

[0116] In summary, the present invention provides a sodium bismuth titanate-based lead-free ceramic material, a preparation method and an application thereof, by 0.5 Na 0.5 Ti03-xSr 1 / 2 Nd 1 / 3 (Mg 1 / 3 Nb 2 / 3 )O3 in Sr 1 / 2 Nd 1 / 3 (Mg 1 / 3 Nb 2 / 3)O3 + Doping substitution, or in (1-x)(0.7Bi 0.5 Na 0.5 TiO3-0.3SrTiO3) in Nd 3+ / (Mg 2 / 3 Nb 1 / 3 ) 3+ Doping substitution disrupts the long-range ferroelectric order, enhances the ceramic's relaxation behavior, and improves the dielectric temperature stability of the ceramic material. With a high dielectric constant and extremely low dielectric loss, lead-free sodium bismuth titanate-based ceramic materials with a wide dielectric temperature range and high frequency stability have been obtained. The prepared ceramic materials all exhibit high breakdown voltage, high energy storage density, and excellent dielectric temperature stability. They can operate stably in harsh environments such as high temperatures and high electric fields, making them suitable for applications in high-pulse power systems.

[0117] The above description is merely a preferred embodiment of the present invention and is not intended to impose any limitation on the technical solution of the present invention. Those skilled in the art should understand that, without departing from the spirit and principles of the present invention, the technical solution can also be subjected to several simple modifications and replacements, and these modifications and replacements are also within the scope of protection covered by the claims.

Claims

1. A sodium bismuth titanate-based lead-free ceramic material, characterized in that: The general formula of the ceramic material is: (1-x)Bi 0.5 Na 0.5 TiO3-xSr 1 / 2 Nd 1 / 3 (Mg 1 / 3 Nb 2 / 3 )O3, x is Sr 1 / 2 Nd 1 / 3 (Mg 1 / 3 Nb 2 / 3 )The molar ratio of O3 to the total mass is 0.12≤x≤0.

21.

2. The method for preparing sodium bismuth titanate-based lead-free ceramic material according to claim 1, wherein: include: Mixing Bi2O3, Na2CO3, SrCO3, TiO2, Nd2O3, MgO and Nb2O5 in a proportion according to a general formula of ceramic materials to obtain a raw material mixture; Pre-calcining and grinding the raw material mixture to obtain pre-calcined powder; The pre-fired powder is ball-milled, sieved, tableted and sintered to obtain sodium bismuth titanate-based lead-free ceramic material.

3. The method for preparing sodium bismuth titanate-based lead-free ceramic material according to claim 2, characterized in that: The method of mixing Bi2O3, Na2CO3, SrCO3, TiO2, Nd2O3, MgO and Nb2O5 in a proportion according to the general formula of ceramic materials to obtain the raw material mixture is as follows: Bi2O3, Na2CO3, SrCO3, TiO2, Nd2O3, MgO and Nb2O5 with a purity of more than 99% are mixed according to the general proportion of ceramic materials, zirconium balls are used as grinding balls, anhydrous ethanol is used as ball milling medium, the mixture is ball milled for 22 to 24 hours, the zirconium balls are separated, and the mixture is dried at 60°C to 80°C to obtain a raw material mixture.

4. The method for preparing sodium bismuth titanate-based lead-free ceramic material according to claim 2, characterized in that: The temperature for pre-firing the raw material mixture is 800° C. to 900° C., and the pre-firing time is 2 to 4 hours.

5. The method for preparing sodium bismuth titanate-based lead-free ceramic material according to claim 2, characterized in that: In the process of ball milling, screening, tableting and sintering the pre-burned powder, the tableting adopts cold isostatic pressing with a pressure of 180 to 220 MPa and the tableting time is 5 to 7 minutes.

6. The method for preparing sodium bismuth titanate-based lead-free ceramic material according to claim 2, characterized in that: In the process of ball milling, screening, tableting and sintering the pre-burned powder, the sintering is pressureless and closed sintering, the sintering temperature is 1100° C. to 1200° C., and the sintering time is 2 to 4 hours.

7. A sodium bismuth titanate-based lead-free ceramic material prepared by the method according to any one of claims 2 to 6, characterized in that: In 10 2 ~10 6 In the Hz frequency range, the dielectric loss of this ceramic material is less than 0.

05.

8. A sodium bismuth titanate-based lead-free ceramic material according to claim 7, characterized in that: At 10kHz and 150℃, the dielectric constant is 720.4~727.3, the dielectric loss is 0.0019~0.0126, and the energy storage density is 7.5~10.4J / cm 3 .

9. Use of the sodium bismuth titanate-based lead-free ceramic material according to claim 1 in the preparation of capacitors.

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