Wide-temperature-range stable energy storage ceramic capacitor dielectric material and preparation method thereof

Abstract

The invention discloses a wide-temperature-range stable energy storage ceramic capacitor dielectric material and a preparation method thereof. The material comprises a tetragonal sodium bismuth titanate-strontium titanate matrix phase and an orthorhombic calcium iron tantalate solid solution phase, the molar ratio of the matrix phase to the solid solution phase is 1: a, and a is greater than 0 and less than or equal to 0.33. The preparation method of the material comprises the following steps: weighing the raw materials according to the stoichiometric ratio, and carrying out primary ball milling, pre-sintering, secondary ball milling, granulation, blank making and sintering to obtain the material. According to the dielectric material, A-site and B-site multi-element co-doping is carried out in a perovskite structure, so that long-range ferroelectric order is destroyed into a polar nanometer micro-region; and Ca < 2 + > with small ion radius induces the oxygen octahedron to incline orderly to form a ferroelastic micro-domain structure. The ferroelastic-ferroelectric hybrid structure plays an important role in reducing hysteresis loss, improving a breakdown electric field and ensuring structural stability. The dielectric ceramic solves the technical problems that sodium bismuth titanate-based energy storage ceramic is low in energy storage density and difficult to stably work in a wide temperature range.

Description

Technical Field

[0001] This invention relates to a capacitor dielectric material, specifically to a wide-temperature-range stable energy storage ceramic capacitor dielectric material and its preparation method, belonging to the field of ceramic dielectric energy storage. Background Technology

[0002] Dielectric capacitors are widely used in pulse power systems and energy storage due to their fast charge / discharge rates, high power density, and excellent service life. With the development of electronic information technology, higher demands are being placed on the integration and miniaturization of next-generation dielectric capacitors. However, the relatively low energy storage density and efficiency of capacitors are major factors restricting their development and large-scale application. In recent years, various types of dielectric capacitor materials, such as ferroelectrics, relaxor ferroelectrics, antiferroelectrics, and superparaelectrics, have seen rapid development. Ferroelectric ceramics, due to their spontaneous polarization characteristics, easily reach polarization saturation and exhibit a large polarization response under an applied electric field, but still retain high residual polarization after the applied electric field is removed, exhibiting significant hysteresis losses. Furthermore, ferroelectric ceramics typically reach saturation at relatively low electric fields, exhibiting low Wrec and η. Antiferroelectrics, due to the ferroelectric-antiferroelectric phase transition, exhibit characteristics similar to paraelectrics at low electric fields, possessing a near-linear hysteresis loop; above the critical electric field, they exhibit significant hysteresis, displaying ferroelectricity. Relaxor ferroelectrics are a current research hotspot in energy storage and dielectric materials. These materials contain dynamic, polar nanoregions of varying sizes that are interconnected and interact with each other. Under an applied electric field, these nanoregions rotate in the direction of the field, exhibiting a high polarization response. However, the interaction between different nanoregions creates resistance, resulting in a slight hysteresis. Therefore, relaxor ferroelectric ceramics macroscopically exhibit high polarization intensity and inherent slight hysteresis. Unlike conventional relaxor ferroelectrics, the polar nanoregions in superparaelectrics are isolated and dispersed, capable of free rotation at room temperature. Under an applied electric field, they exhibit moderate to high maximum polarization intensity, with almost zero residual polarization intensity after the electric field is removed. Therefore, superparaelectric materials show great potential for achieving high energy density and high storage characteristics.

[0003] Among many dielectric materials, Bi 0.5 Na 0.5 TiO3(BNT) due to Bi 3+ 6 S 2 It exhibits high spontaneous polarization (approximately 45 μC / cm²) due to the lone pair electron effect, and two dielectric anomalous peaks (T0, T ...) are present in the dielectric temperature spectrum. s 200 °C and T m At 320 °C, it is expected that chemical modification can enhance its relaxation characteristics, enabling excellent energy storage performance over a wide temperature range. However, the strong ferroelectricity of sodium bismuth titanate leads to high remanent polarization and coercive field, and it is prone to saturation under low applied electric fields, which seriously affects its overall energy storage performance and restricts its industrial application in the energy storage field. In addition, near the low-temperature anomalous peak (T... s The polarization intensity and dielectric loss of the material are extremely sensitive to temperature changes. Temperatures approaching this region lead to a significant increase in dielectric loss, severely impairing energy storage performance. Furthermore, near the high-temperature anomalous peak (T... m In sodium bismuth titanate, a fundamental transformation from a polar to a nonpolar phase occurs, and the sharp decrease in polarization intensity leads to a precipitous drop in the material's energy storage density. The presence of these two dielectric anomaly peaks prevents sodium bismuth titanate from maintaining effective operation over a wide temperature range, exhibiting significant performance fluctuations. There is an urgent need to find a new system of sodium bismuth titanate-based energy storage ceramics that can suppress the two dielectric anomaly peaks and achieve a transition from a sharp phase transition to a highly dispersed phase transition, thus enabling stable operation over a wide temperature range. Summary of the Invention

[0004] To address the problems existing in the prior art, the first objective of this invention is to provide a wide-temperature-range stable dielectric material for energy storage ceramic capacitors. This dielectric material first introduces ST (stable dielectric peak) into the matrix phase to eliminate low-temperature dielectric anomaly peaks. Then, through a perovskite solid solution phase, it enhances the relaxation characteristics of the matrix phase while significantly suppressing the dielectric anomaly peaks, inhibiting dielectric loss, and improving the temperature stability of dielectric performance. Furthermore, the introduction of the solid solution phase also... m By moving the material below room temperature, superparaelectric ceramics with OTC multiphase coexistence at room temperature were constructed.

[0005] The second objective of this invention is to provide a method for preparing a wide-temperature-range stable energy storage ceramic capacitor dielectric material.

[0006] To achieve the above technical objectives, the present invention provides a wide-temperature-range stable energy storage ceramic capacitor dielectric material, the dielectric material comprising a tetragonal sodium bismuth titanate-strontium titanate (BNST) matrix phase and a calcium orthogonal iron tantalate (CFT) solid solution phase; the molar ratio of the matrix phase to the solid solution phase is 1:a, 0 < a ≤ 0.33.

[0007] In the technical solution provided by this invention, strontium titanate (ST) is introduced into sodium bismuth titanate (BNT) for doping. This pre-disrupts the long-range order of the trigonal phase at room temperature, preventing the material from undergoing a thermotropic phase transition from trigonal to tetragonal on a macroscopic scale. Therefore, in the dielectric temperature spectrum of the matrix phase, the low-temperature dielectric anomaly peak corresponding to this phase transition naturally disappears, leaving only a single diffuse peak representing the relaxation state to the paraelectric phase. Furthermore, by doping the perovskite solid solution phase, various cations with different radii, valence states, and electronegativity are introduced, inducing a strong random electric field and random strain field at the lattice scale. This transforms the long-range ordered ferroelectric domains into nanodomains or polar nanoregions (PNRs), significantly enhancing relaxation characteristics through the reduction in domain size and coupling. This is manifested in the dielectric temperature spectrum as a suppression and broadening of the dielectric peak, and T... m When moved below room temperature, it exhibits a superparaelectric state. Furthermore, through Ca... 2+ The small ionic radius reduces the perovskite tolerance factor, inducing an ordered tilting of oxygen octahedrons and forming a ferroelastic domain structure. The reason why the existence of this ferroelastic-ferroelectric hybrid domain optimizes temperature stability and energy storage performance is mainly reflected in the following aspects:

[0008] (1) Temperature stability optimization: Ferroelastic microdomains form a thermally stable rigid framework, which inhibits the agglomeration and growth of PNRs. Combined with the temperature insensitivity of multiphase coexistence, the temperature stability is optimized.

[0009] (2) Energy storage performance optimization: Polarization hysteresis is reduced by atomic-scale polar heterogeneity, ferroelastic distortion delays polarization saturation, and highly active, weakly coupled polar nano-micro-regions respond rapidly to changes in the applied electric field to synergistically improve breakdown strength and optimize energy storage performance.

[0010] As a preferred embodiment, the stoichiometric ratio of sodium bismuth titanate to strontium titanate in the sodium bismuth titanate matrix phase is 6~7:3~4.

[0011] As a preferred embodiment, the chemical formula of the perovskite solid solution phase is Ca(Fe). 0.5 Ta 0.5 O3. Among them, A-position Bi 3+ Na + 、Sr 2+ Ca 2+ Coexistence, B-position Ti 4+ Fe 3+ and Ta 5+ Coexistence, specifically the coexistence of multiple different cations, significantly enhances relaxation properties by reducing domain size and coupling degree.

[0012] As a preferred embodiment, the chemical formula of the medium material is (1-x)(0.70Bi). 0.5 Na 0.5TiO3-0.30BaTiO3)-xCa(Fe 0.5 Ta 0.5 O3, where x ranges from 0.15 to 0.20. Further preferred, x is 0.20.

[0013] It is important to note that the amount of solid solution added has a significant impact on the dielectric constant, dielectric loss, energy storage performance, and temperature stability of the material. If the amount of solid solution added is too low, the dielectric anomaly peak T will appear. m While the dielectric loss remains high, the dielectric performance stability is also poor; if the amount of solid solution added is too high, the dielectric abnormal peak T will appear. m The strong suppression results in a small dielectric constant, which is not conducive to the preparation of high-energy-storage-performance ceramic capacitor dielectric materials.

[0014] This invention also provides a method for preparing a wide-temperature-range stable energy storage ceramic capacitor dielectric material, comprising: weighing and mixing the dielectric material raw materials according to the stoichiometric ratio, subjecting them to ball milling and drying in sequence, and pre-sintering to obtain pre-sintered powder; subjecting the pre-sintered powder to ball milling and drying in sequence, adding a binder and mixing thoroughly to obtain granulated powder, and subjecting it to blanking and sintering in sequence to obtain the final product.

[0015] As a preferred embodiment, the raw materials for the dielectric material include Na2CO3, TiO2, Bi2O3, CaCO3, SrCO3, Fe2O3, and Ta2O5.

[0016] As a preferred embodiment, the ball milling method is wet ball milling, with the following conditions: the mass ratio of the media material, anhydrous ethanol and zirconium balls is 1:1~1.5:2.5~3, the rotation speed is 200~300 rpm, and the time is 20~48 h.

[0017] As a preferred embodiment, the drying conditions are: a temperature of 60~80℃ and a time of 20~24h.

[0018] As a preferred embodiment, the pre-sintering conditions are as follows: heating to 800-900°C at a heating rate of 3-8°C / min in an air atmosphere, holding at that temperature for 2-5 hours, and then cooling to room temperature in the furnace to obtain the desired result.

[0019] As a preferred embodiment, the secondary ball milling method is wet ball milling, with the following conditions: the mass ratio of pre-calcined powder, anhydrous ethanol and zirconium balls is 10~15:15~20:40~50, the rotation speed is 350~450 rpm, and the time is 12~24h.

[0020] As a preferred embodiment, the adhesive is polyvinyl butyral, and its addition amount is 1-3%.

[0021] As a preferred embodiment, the thorough mixing process is as follows: ethanol is added as a dispersant, and the mixture is stirred evenly at 200-300 rpm under conditions of 70-90°C, followed by drying, grinding, and sieving to obtain the final product.

[0022] As a preferred embodiment, the blanking process is cold pressing, which involves holding the granulated powder under pressure at 15-25 MPa for 3-10 minutes to obtain a cylindrical green blank with a diameter of 8-12 mm.

[0023] As a preferred embodiment, the sintering process is as follows: under an air atmosphere, the temperature is raised to 500-600°C at a heating rate of 3-8°C / min, held for 0.5-1.5 hours, and then raised to 1100-1200°C at a heating rate of 3-8°C / min, held for 2-5 hours, and the product is obtained.

[0024] Compared with the prior art, the beneficial technical effects of the technical solution provided by the present invention are as follows:

[0025] 1) The dielectric material provided by this invention first introduces ST into the matrix phase to eliminate the low-temperature dielectric anomalous peak. Then, through the perovskite solid solution phase, it not only enhances the relaxation characteristics of the matrix phase but also significantly suppresses the dielectric anomalous peak, inhibiting dielectric loss and improving the temperature stability of dielectric properties. Furthermore, the introduction of the solid solution phase also increases T... m By moving the material below room temperature, superparaelectric ceramics with OTC multiphase coexistence at room temperature were constructed.

[0026] 2) In the preparation method provided by this invention, orthorhombic CFT is doped into nonpolar tetragonal BNST, utilizing Ca 2+ Smaller ionic radii reduce the perovskite tolerance factor and induce the oxygen octahedrons to tilt in an orderly manner, thereby forming a rigid ferroelastic microdomain framework in the grain, which macroscopically manifests as a unique ferroelastic-ferroelectric hybrid domain structure.

[0027] 3) The technical solution provided by this invention, based on the structural and organizational characteristics of the aforementioned dielectric material, exhibits low loss, high energy density, and wide-temperature stability, solving the technical problem that sodium bismuth titanate-based energy storage ceramics are difficult to operate stably over a wide temperature range in the prior art. Testing shows that its relative permittivity remains between 410 and 540 within a temperature range of -150℃ to 400℃, with a TCC less than 15%, and its dielectric loss is less than 0.02 within a temperature range of -114℃ to 328℃. Furthermore, under an applied electric field of 60 kV / mm, W... rec Reaching 11.02 J / cm 3 η reaches 92.1%. Furthermore, within a temperature range of 25℃ to 160℃, under an applied electric field of 40 kV / mm, W rec Reaching 5.74 J / cm 3η reached 89.50%, W rec The fluctuation of η does not exceed 8%, and the fluctuation of η does not exceed 7%. Attached Figure Description

[0028] Figure 1 The XRD pattern of the dielectric material provided in Embodiment 1 of the present invention;

[0029] Figure 2 This is a SEM image of the dielectric material provided in Embodiment 1 of the present invention;

[0030] Figure 3 This is a domain structure diagram of the dielectric material provided in Embodiment 1 and Comparative Example 1 of the present invention;

[0031] in Figure 3 (a) is the domain structure of Comparative Example 1. Figure 3 (b) shows the ferroelastic domain structure of Example 1. Figure 3 (c) is the ferroelastic-ferroelectric hybrid domain structure of Example 1;

[0032] Figure 4 These are characterization diagrams of the dielectric properties of the dielectric materials provided in Embodiment 1 and Comparative Examples 1 and 2 of the present invention.

[0033] in, Figure 4 (a) is the dielectric temperature spectrum of Comparative Example 1. Figure 4 (b) Dielectric temperature spectra of Comparative Example 2 and Example 1, Figure 4 (c) is 1 / ε of Comparative Example 1 r -T diagram, Figure 4 (d) is 1 / ε of Example 1 r -T diagram;

[0034] Figure 5 These are characterization diagrams of the energy storage performance of the dielectric materials provided in Embodiment 1 and Comparative Examples 1-3 of the present invention;

[0035] in, Figure 5 (a) is the TCC curve of the dielectric materials obtained in Example 1, Comparative Example 1, and Comparative Example 2. Figure 5 (b) is a schematic diagram of the temperature range where tanδ < 0.02 for the dielectric materials obtained in Example 1, Comparative Example 1, and Comparative Example 2. Figure 5 (c) is a unipolar hysteresis loop diagram of the dielectric materials obtained in Example 1 and Comparative Examples 1 to 3. Detailed Implementation

[0036] To make the objectives, technical solutions, and advantages of the present invention more apparent, exemplary embodiments according to the present invention will be described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are merely a part of the embodiments of the present invention, and not all of the embodiments of the present invention. It should be understood that the present invention is not limited to the exemplary embodiments described herein. Based on the embodiments of the present invention described herein, all other embodiments obtained by those skilled in the art without inventive effort should fall within the protection scope of the present invention.

[0037] Example 1

[0038] This embodiment provides a wide-temperature-range stable energy storage ceramic capacitor dielectric material with the chemical formula 0.80(0.70Bi). 0.5 Na 0.5 TiO3-0.30BaTiO3)-0.20Ca(Fe 0.5 Ta 0.5 O3, the specific preparation process is as follows:

[0039] 1. Weigh out a certain amount of Na2CO3, TiO2, Bi2O3, CaCO3, SrCO3, Fe2O3, and Ta2O5 according to the stoichiometric ratio and place them in a ball mill jar. Use zirconia balls and anhydrous ethanol as the medium, with a mass ratio of raw materials, anhydrous ethanol, and zirconia balls of 1:1:3. Place the ball mill jar in a ball mill and ball mill at 250 rpm for 24 hours. After ball milling, dry at 70℃ for 24 hours to obtain mixed powder A. Place mixed powder A in a corundum crucible and heat it to 850℃ in air at a heating rate of 5℃ / min. Hold at this temperature for 3 hours and then cool it with the furnace to obtain pre-calcined powder.

[0040] 2. Pre-calcined powder, anhydrous ethanol, and zirconium balls were placed in a ball mill jar at a ratio of 15:20:45 and ball-milled at 400 rpm for 16 hours. After ball milling, the mixture was dried at 70°C for 24 hours to obtain homogeneous material B. 3% polyvinyl butyral and an appropriate amount of anhydrous ethanol were added to homogeneous material B, and the mixture was stirred on a magnetic stirrer at 80°C and 250 rpm. After drying, the mixture was thoroughly ground and passed through a 150-mesh sieve to obtain uniformly granulated powder.

[0041] 3. Weigh 0.18g of granulation powder and press it into a cylindrical green body with a diameter of about 10mm under a pressure of 20MPa for 5min. Place the green body in a corundum crucible and sinter it using the buried firing method. First, in an air atmosphere, raise the temperature to 550℃ at 5℃ / min and hold for 1h to remove the binder. Then, raise the temperature to 1180℃ at 5℃ / min and hold for 3h to sinter. Cool it in the furnace to obtain the final product.

[0042] Comparative Example 1

[0043] This comparative example is exactly the same as Example 1, except that no solid solution phase was added, and its chemical formula is 0.70Bi. 0.5 Na 0.5 TiO3-0.30BaTiO3.

[0044] Comparative Example 2

[0045] This comparative example is exactly the same as Example 1, except that the amount of solid solution added is different, and its chemical formula is 0.90(0.70Bi). 0.5 Na 0.5 TiO3-0.30BaTiO3)-0.10Ca(Fe 0.5 Ta 0.5 )O3.

[0046] Comparative Example 3

[0047] This comparative example is exactly the same as Example 1, except that the amount of solid solution added is different, and its chemical formula is 0.75 (0.70 Bi). 0.5 Na 0.5 TiO3-0.30BaTiO3)-0.25Ca(Fe 0.5 Ta 0.5 )O3.

[0048] The present invention has conducted a series of tests and characterizations on the above embodiments and comparative examples. The phase structure of the dielectric material obtained in Example 1 is as follows: Figure 1 As shown, through Figure 1 It can be seen that the material has a pure perovskite structure and no impurity phases. SEM images show that the material obtained in Example 1 has no obvious defects and good crystallinity. TEM testing of the material after FIB sample preparation yielded the following results: Figure 3 As shown, in Example 1, polar nanodomains are nested within striped ferroelastic domains, forming a unique ferroelastic-ferroelectric hybrid domain structure. The existence of ferroelastic domains is attributed to the doping of the orthorhombic phase CFT, which lowers the perovskite tolerance factor and induces ordered tilting of oxygen octahedra. To minimize elastic strain energy, this manifests macroscopically as ferroelastic domain walls. Furthermore, the co-doping of multiple heterovalent A and B-site cations in the perovskite structure disrupts long-range ferroelectric order, forming highly active, weakly coupled polar nanodomains. Within the ferroelastic domains, heterovalent ion doping reduces cell symmetry, forming a more stable, low-symmetry phase. This reduction in symmetry hinders field-induced cation displacement and oxygen octahedral rotation, thus delaying polarization saturation. The highly active, weakly coupled polar nanodomains can rapidly respond to changes in the applied electric field, reducing hysteresis losses. In addition, the ferroelastic strain hinders the aggregation of polar nanodomains caused by temperature increases, maintaining their highly active, weakly coupled state. Therefore, this unique ferroelectric hybrid domain structure plays an important role in optimizing dielectric energy storage performance.

[0049] The dielectric material obtained in Example 1 was polished to 0.3 mm, coated with medium-temperature silver paste on both sides, and fired at 550°C for 30 min to form a silver electrode. The dielectric constant ε was measured using a high-temperature impedance analyzer. r The dielectric loss tanδ is plotted as a function of temperature T and frequency f, with a test temperature range of -100 to 400℃ and test frequencies including 100Hz, 1kHz, 10kHz, and 100kHz. Based on ε at 1kHz... r -T curve plotting 1 / ε r -T curve, such as Figure 4 As shown in (b), T m The temperature dropped to -71°C, indicating that the material is in a superparaelectric state at room temperature. Figure 4 (d) shows the dielectric temperature spectrum of the material. The ceramic exhibits significant frequency dispersion and dielectric peak broadening. To evaluate the stability of the ceramic's dielectric properties, Δε at 1 kHz was calculated using the measured dielectric temperature spectrum. r / ε r150°C The change of dielectric constant with temperature / dielectric constant at 150℃ and the temperature range where tanδ < 0.02, such as Figure 5 As shown in (a) and (b), the dielectric constant of this material reaches 481.3 at 1 kHz and 150 °C, with a dielectric loss as low as 0.0066. The relative dielectric constant change rate is less than 15% in the temperature range of -150 °C to 400 °C, and the dielectric loss is less than 0.02 in the temperature range of -114 °C to 328 °C. Further, the dielectric material was polished to 0.07~0.10 mm, and a 1 mm diameter mask was applied to the ceramic sheet. A 1 mm diameter gold electrode was then fabricated using a magnetron sputtering apparatus. The hysteresis loop of the ceramic at 10 Hz was tested using an impedance analyzer, and the results are as follows... Figure 5 As shown in (c), as the applied electric field increases, the hysteresis loop gradually approaches saturation. Under an applied electric field of 60 kV / mm, Wrec reaches 11.02 J / cm3 and η reaches 92.1%.

[0050] The dielectric material obtained in Comparative Example 1, lacking a solid solution phase, only exhibits a tetragonal phase structure, based on ε at 1 kHz. r -T curve plotting 1 / ε r -T curve, T mAt 155℃, the material is in an ergodic relaxation state at room temperature. The dielectric temperature spectrum of the material shows a distinct dielectric anomalous peak. At 1kHz and 150℃, the relative permittivity is 4862, and the dielectric loss is as high as 0.015. The temperature stability of the dielectric constant is poor; the temperature range where the dielectric constant change rate is less than 15% is only 106~234℃, and the temperature range where the dielectric loss is less than 0.02 is 135~253℃. The hysteresis loop of the material at 10Hz was measured using an impedance analyzer, and the results are as follows... Figure 5 As shown, under an applied electric field of 18 kV / mm, W rec It reaches 1.63 J / cm3, and η reaches 75.73%.

[0051] The dielectric material obtained in Comparative Example 2, due to its low solid solution phase content, exhibits a higher tetragonal phase content despite the coexistence of tetragonal and orthorhombic phases in its structure. A significant dielectric anomalous peak still exists in the material's dielectric temperature spectrum, and the frequency dispersion phase is weaker than in Example 1. At 1 kHz and 150 °C, the relative permittivity is 10¹⁰.12, and the dielectric loss reaches 0.0078. The temperature stability of the dielectric constant is poor; the temperature range where the dielectric constant change rate is less than 15% is 24–323 °C, and the temperature range where the dielectric loss is less than 0.02 is -45–272 °C. Impedance analysis of the material at 10 Hz shows that under an applied electric field of 20 kV / mm, W… rec Reaching 2.28 J / cm 3 η reached 83.96%.

[0052] The dielectric material obtained in Comparative Example 3 had an excessively high content of solid solution phase, resulting in an excessively high content of orthorhombic phase in the structure. The hysteresis loop of the material at 10 Hz was measured using an impedance analyzer, and the results were as follows... Figure 5 As shown, under an applied electric field of 40 kV / mm, W rec Only 3.97 J / cm 3 η reached 89.9%.

Claims

1. A wide-temperature-range stable energy storage ceramic capacitor dielectric material, characterized in that: The medium material comprises a tetragonal sodium bismuth titanate-strontium titanate matrix phase and an orthogonalized calcium iron tantalate solid solution phase; the molar ratio of the matrix phase to the solid solution phase is 1:a, 0 < a ≤ 0.

33.

2. The wide-temperature-range stable energy storage ceramic capacitor dielectric material according to claim 1, characterized in that: The stoichiometric ratio of sodium bismuth titanate to strontium titanate in the sodium bismuth titanate matrix phase is 6-7:3-4; the chemical formula of the perovskite solid solution phase is Ca(Fe) 0.5 Ta 0.5 )O3.

3. The wide-temperature-range stable energy storage ceramic capacitor dielectric material according to claim 2, characterized in that: The chemical formula of the medium material is (1-x)(0.70Bi). 0.5 Na 0.5 TiO3-0.30BaTiO3)-xCa(Fe 0.5 Ta 0.5 )O3, where x ranges from 0.15 to 0.

20.

4. A method for preparing a wide-temperature-range stable energy storage ceramic capacitor dielectric material according to any one of claims 1 to 3, characterized in that: The raw materials for the medium are weighed and mixed according to the stoichiometric ratio, and then subjected to ball milling and drying in sequence, followed by pre-sintering to obtain pre-sintered powder. After ball milling and drying the pre-sintered powder a second time, a binder is added and mixed thoroughly to obtain granulated powder, which is then subjected to blanking and sintering in sequence to obtain the final product.

5. The method for preparing a wide-temperature-range stable energy storage ceramic capacitor dielectric material according to claim 4, characterized in that: The media material raw materials include Na2CO3, TiO2, Bi2O3, CaCO3, SrCO3, Fe2O3 and Ta2O5; the primary ball milling method is wet ball milling, with the following conditions: the mass ratio of media material raw materials, anhydrous ethanol and zirconium balls is 1:1~1.5:2.5~3, the rotation speed is 200~300 rpm, and the time is 20~48 h.

6. The method for preparing a wide-temperature-range stable energy storage ceramic capacitor dielectric material according to claim 4, characterized in that: The drying conditions are: temperature of 60~80℃ and time of 20~24h; the pre-sintering conditions are: heating to 800~900℃ at a heating rate of 3~8℃ / min in air atmosphere, holding at that temperature for 2~5h, and then cooling to room temperature in the furnace to obtain the product.

7. The method for preparing a wide-temperature-range stable energy storage ceramic capacitor dielectric material according to claim 4, characterized in that: The secondary ball milling method is wet ball milling, with the following conditions: the mass ratio of pre-calcined powder, anhydrous ethanol and zirconium balls is 10~15:15~20:40~50, the rotation speed is 350~450 rpm, and the time is 12~24h.

8. The method for preparing a wide-temperature-range stable energy storage ceramic capacitor dielectric material according to claim 4, characterized in that: The binder is polyvinyl butyral, and its addition amount is 1~3%; the process of thorough mixing is as follows: ethanol is added as a dispersant, and the mixture is stirred evenly at 200~300 rpm under 70~90℃ conditions, and then dried, ground and sieved in sequence to obtain the final product.

9. The method for preparing a wide-temperature-range stable energy storage ceramic capacitor dielectric material according to claim 4, characterized in that: The blanking process is cold pressing, which involves pressing the granulated powder at 15-25 MPa for 3-10 minutes to obtain a cylindrical green blank with a diameter of 8-12 mm.

10. The method for preparing a wide-temperature-range stable energy storage ceramic capacitor dielectric material according to claim 4, characterized in that: The sintering process is as follows: under an air atmosphere, heat to 500-600℃ at a heating rate of 3-8℃ / min, hold for 0.5-1.5h, then heat to 1100-1200℃ at a heating rate of 3-8℃ / min, hold for 2-5h, and the product is obtained.

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