Dielectric near-zero ceramic material with adjustable filtering characteristic and preparation method and application thereof

Abstract

The invention relates to a dielectric near-zero ceramic material with an adjustable filtering characteristic and a preparation method and application of the dielectric near-zero ceramic material, the dielectric near-zero ceramic material is silver-zinc oxide ceramic, metal silver elementary substances are uniformly distributed in a zinc oxide matrix, and the dielectric near-zero ceramic material comprises the following chemical components in percentage by mass: 10-40% of silver elementary substances, 57.7-87.7% of zinc oxide, 1.5-2.5% of bismuth oxide and 0.2-0.4% of silicon oxide. Wherein the metallic silver elementary substance in the ceramic material is uniformly distributed in a zinc oxide matrix, the metallic silver elementary substance is generated by in-situ reduction of silver oxide in a sintering process, and bismuth oxide and silicon oxide are used as sintering aids. Compared with the prior art, the tunable dielectric near-zero characteristic is realized by regulating and controlling the distribution state of the silver metal phase in the ceramic material, the material shows a transmission characteristic for electromagnetic waves at a high-frequency position and shows a shielding electromagnetic wave at a low-frequency dielectric near-zero position, and the problem of low-frequency interference faced by a traditional high-pass filter is solved; the method has important application value in the field of filters.

Description

Technical Field

[0001] This invention relates to the field of ceramic materials technology, and in particular to a near-zero dielectric ceramic material with adjustable filtering characteristics, its preparation method, and its application. Background Technology

[0002] In 5G / 6G communication systems, high-performance high-pass filters play a crucial role: they must suppress low-frequency interference signals while preserving the integrity of useful high-frequency signals, which directly affects communication speed, signal coverage, and transmission reliability. However, traditional LC filters and microstrip line filters struggle to meet this core requirement. The former suffers from high insertion loss and limited quality factor, while the latter is generally too large due to structural design limitations. Both of these factors jointly restrict the application of high-performance filters in miniaturized and highly integrated 5G / 6G base stations.

[0003] To overcome the bottlenecks of traditional solutions, current signal base station filters have upgraded from metal cavity structures to dielectric ceramic structures, i.e., ceramic filters. From the perspective of electromagnetic principles, the characteristic size of a dielectric resonator is inversely proportional to the square root of the material's relative permittivity: the higher the permittivity, the easier it is to confine the electromagnetic field within the material, achieving resonance in the target frequency band without requiring a larger size. Therefore, high-permeability ceramics have become the core carrier for filter miniaturization and integration. Currently, the industry commonly improves the material's permittivity through doping modification and composite processes, as seen in patents CN114988866A and CN114956798A. However, this technical approach still has significant limitations: on the one hand, in specific frequency bands, the material's permittivity is limited by the intrinsic polarization mechanism, making further improvement difficult and limiting miniaturization potential; on the other hand, achieving wide-range filtering often requires relying on switched filter banks, using several switched filters to achieve a wider bandwidth, but this approach significantly increases device size and structural complexity, contradicting the "lightweight and highly integrated" requirements of 5G / 6G base stations.

[0004] Technological exploration in the field of filters has long focused on positive permittivity materials, and the aforementioned bottlenecks in size and bandwidth stem precisely from the inherent limitations of this traditional system. In recent years, with the rapid development of metamaterials technology, near-zero dielectric materials (ENZ materials, whose real part of relative permittivity approaches zero) have provided a completely new path for filter innovation: they break away from the traditional logic of "reducing size by increasing permittivity" and instead utilize the special electromagnetic field characteristics of the near-zero dielectric state to significantly simplify filter structure design, achieving steep cutoff slopes and low passband losses; at the same time, the strong localization effect of the electromagnetic field can break through the diffraction limit of traditional filters, achieving efficient filtering at the subwavelength scale, fundamentally solving the size problem.

[0005] In summary, near-zero dielectric materials offer a breakthrough solution to the wide frequency range coverage and high performance requirements of 5G / 6G high-pass filters, and are of great pioneering significance for promoting the technological upgrading and industrial application of high-performance high-pass filters. Summary of the Invention

[0006] The purpose of this invention is to provide a near-zero dielectric ceramic material with tunable filtering characteristics, its preparation method and application, achieving tunable near-zero dielectric characteristics. The ceramic material has high electromagnetic wave transmittance at high frequencies and electromagnetic wave shielding characteristics at near-zero dielectric at low frequencies.

[0007] The objective of this invention can be achieved through the following technical solutions: In a first aspect, the present invention provides a near-zero dielectric ceramic material with adjustable filtering characteristics. The near-zero dielectric ceramic material is a silver-zinc oxide ceramic (Ag-ZnO ceramic), in which elemental silver is uniformly distributed in a zinc oxide matrix. Its chemical composition by mass percentage is: elemental silver 10-40%, zinc oxide 57.7-87.7%, bismuth oxide 1.5-2.5%, and silicon oxide 0.2-0.4%.

[0008] Preferably, the metallic silver is generated by in-situ reduction of silver oxide during sintering, and the bismuth oxide and silicon oxide are used as sintering aids.

[0009] More preferably, the purity of the silver oxide (Ag2O), zinc oxide (ZnO), bismuth oxide (Bi2O3), and silicon oxide (SiO2) is above 99%.

[0010] Preferably, when the silver content in the near-zero dielectric ceramic material is between 10-20%, the near-zero dielectric ceramic material exhibits dielectric resonance, and its dielectric constant is adjustable between -600 and 800; when the silver content in the near-zero dielectric ceramic material is between 25-40%, the near-zero dielectric ceramic material exhibits plasmon resonance, and its dielectric constant is adjustable between -1800 and 0.

[0011] Preferably, in electromagnetic simulation, the near-zero dielectric ceramic material, with a thickness of 0.6-1.6 mm, has a transmittance of more than 90% for electromagnetic waves in the high-frequency band and less than 20% for electromagnetic waves in the low-frequency band.

[0012] More preferably, the high-frequency band refers to 0.6-1 GHz.

[0013] More preferably, the low-frequency band refers to the near-zero dielectric frequency.

[0014] Secondly, the present invention provides a method for preparing the near-zero dielectric ceramic material with tunable filtering characteristics, comprising the following steps: S1: Weigh out silver oxide, zinc oxide, bismuth oxide, and silicon oxide as raw materials according to the mass percentage of each chemical component; S2: The raw materials weighed in step S1 are ball-milled to obtain a raw material slurry; then dried and sieved to obtain raw material powder; S3: The raw material powder obtained in step S2 is pre-fired, and after pre-firing, it is cooled with the furnace to obtain pre-fired ceramic powder. S4: The pre-fired ceramic powder obtained in step S3 is subjected to a second ball milling process, and then dried and sieved to obtain ceramic powder. S5: Using polyvinyl alcohol aqueous solution as a binder, the ceramic powder obtained in step S4 is granulated to obtain ceramic particles, which are then pressed into shape under a certain pressure to obtain a green body. S6: The green body obtained in step S5 is sintered, and after sintering, it is cooled in the furnace to obtain the near-zero dielectric ceramic material.

[0015] Preferably, in steps S2 and S4, anhydrous ethanol is used as the ball milling medium, the ball milling speed is 300-500 rpm, and the ball milling time is 3-5 h.

[0016] More preferably, in steps S2 and S4, the ball milling speed is 400 rpm and the ball milling time is 4 h.

[0017] Preferably, in steps S2 and S4, the ball milling process uses a combination of large and small zirconium balls.

[0018] More preferably, in steps S2 and S4, the diameter of the large zirconium ball is 8-10 mm, and the diameter of the small zirconium ball is 4-6 mm.

[0019] More preferably, in steps S2 and S4, the mass ratio of the large zirconium ball to the small zirconium ball is 1:1.5-1:2.5.

[0020] More preferably, in steps S2 and S4, the mass ratio of the large zirconium ball to the small zirconium ball is 1:2, and the total weight of the large zirconium ball and the small zirconium ball is 30g.

[0021] Preferably, in steps S2 and S4, the drying temperature is 70-100℃.

[0022] Preferably, in steps S2 and S4, the mesh size of the sieve used for the sieving process is 300-500 mesh.

[0023] Preferably, in step S3, the pre-firing treatment refers to heating to 700-950 ℃ at a heating rate of 3-4 ℃ / min and holding at that temperature for 1.5-2.5 h.

[0024] More preferably, in step S3, the pre-firing treatment refers to heating to 950°C at a heating rate of 3.5°C / min and holding at that temperature for 2 hours.

[0025] Preferably, in step S5, the concentration of the polyvinyl alcohol aqueous solution is 8-12 wt%. More preferably, in step S5, the concentration of the polyvinyl alcohol aqueous solution is 10 wt%.

[0026] Preferably, in step S5, the particle size of the ceramic particles is 0.2-1.0 μm.

[0027] Preferably, in step S5, the pressing pressure is 15-20 MPa.

[0028] Preferably, in step S5, the green blank is in the shape of a disc with a diameter of 1.5-2.5 cm and a thickness of 1-3 mm.

[0029] More preferably, in step S5, the diameter of the green blank is 2 cm and the thickness is 2 mm.

[0030] Preferably, in step S6, the sintering treatment refers to heating to 450-650 ℃ at a heating rate of 3-4 ℃ / min and holding at that temperature for 1.5-2.5 h; then continuing to heat to 950-1150 ℃ at a heating rate of 2.5-3.5 ℃ / min and holding at that temperature for 1.5-2.5 h.

[0031] More preferably, in step S6, the sintering treatment refers to heating to 550°C at a heating rate of 3.5°C / min and holding at that temperature for 2 hours; then continuing to heat to 1050°C at a heating rate of 3°C / min and holding at that temperature for 2 hours.

[0032] Thirdly, the present invention provides an application of the near-zero dielectric ceramic material with adjustable filtering characteristics as a filtering device in a communication equipment system.

[0033] In this invention, a conductive percolation network based on silver is constructed by controlling the distribution of elemental silver in a zinc oxide matrix. When the silver content exceeds the percolation threshold, the dielectric properties change from resonant to plasmonic, exhibiting a negative dielectric constant across the entire frequency range. From a microscopic electronic mechanism perspective, increasing the mass fraction of silver effectively increases the free electron concentration, resulting in a negative dielectric constant when the external testing frequency is lower than the plasmonic frequency. Therefore, by controlling the free electron concentration of Ag-ZnO ceramic materials, the near-zero dielectric frequency can be controlled.

[0034] Compared with the prior art, the present invention has the following beneficial effects: (1) The present invention provides a ceramic material for a high-pass filter with near-zero dielectric properties. The ceramic material is silver-zinc oxide (Ag-ZnO) ceramic, and bismuth oxide and silicon oxide are used as sintering aids. By controlling the distribution content of silver metal phase in the ceramic material, tunable near-zero dielectric properties are achieved. The ceramic material exhibits electromagnetic wave transmission characteristics at high frequencies and electromagnetic wave shielding characteristics at low-frequency near-zero dielectric properties.

[0035] (2) In this invention, the dielectric constant of the Ag-ZnO ceramic material is adjustable from -600 to 800 when dielectric resonance occurs, and the dielectric constant is adjustable from -1800 to 0 when plasma oscillation occurs.

[0036] (3) In electromagnetic simulation, when the thickness of the Ag-ZnO ceramic material of the present invention is 0.6-1.6 mm, its transmittance to electromagnetic waves is greater than 90% in the high frequency band and less than 20% in the low frequency band, especially at the near-zero dielectric frequency, thus solving the problem of low frequency interference faced by traditional high-pass filters.

[0037] (4) By designing and constructing Ag-ZnO ceramics with near-zero dielectric properties, this invention greatly simplifies the filter structure design and achieves a steep cutoff slope and low passband loss; it also breaks through the diffraction limit of traditional filters and realizes efficient filtering function at the subwavelength scale. Attached Figure Description

[0038] Figure 1 The figures show the microstructure of silver-zinc oxide ceramic materials with different silver contents (a1-a3 in the figures refer to a silver mass fraction of 10%, where a1 is a scanning electron microscope image, a2 is an EDS surface scan image, and a3 is a distribution map of elemental silver; b1-b3 refer to a silver mass fraction of 25%, where b1 is a scanning electron microscope image, b2 is an EDS surface scan image, and b3 is a distribution map of elemental silver; c1-c3 refer to a silver mass fraction of 40%, where c1 is a scanning electron microscope image, c2 is an EDS surface scan image, and c3 is a distribution map of elemental silver).

[0039] Figure 2 The dielectric spectrum of silver-zinc oxide ceramic materials with different silver contents is shown (in the figure, ab is the real part of the dielectric constant, c is the imaginary part of the dielectric constant, and d is the dielectric loss).

[0040] Figure 3 Silver-zinc oxide ceramic materials with different silver contents at different thicknesses S Parameters (ac) and transmission phase angle spectrum (df) (in the figure, a and d indicate a silver mass fraction of 10%, b and e indicate a silver mass fraction of 20%, and c and f indicate a silver mass fraction of 25%).

[0041] Figure 4The spectra of reflectance (ac), transmittance (df), and absorptivity (ac) of silver-zinc oxide ceramic materials with different silver contents at different thicknesses are shown in the figure (a and d indicate a silver mass fraction of 10%, b and e indicate a silver mass fraction of 20%, and c and f indicate a silver mass fraction of 25%).

[0042] Figure 5 Crystal structure diagrams of silver-zinc oxide ceramic materials with different silver contents. Detailed Implementation

[0043] This embodiment is implemented based on the technical solution of the present invention, and provides detailed implementation methods and specific operation processes. However, the scope of protection of the present invention is not limited to the following embodiment.

[0044] Unless otherwise specified, the reagents, methods, instruments, and equipment used in this invention are conventional in the art. Unless otherwise specified, the reagents and materials used in the following examples are all commercially available.

[0045] A near-zero dielectric ceramic material with adjustable filtering characteristics is disclosed. This near-zero dielectric ceramic material is a silver-zinc oxide ceramic, in which elemental silver is uniformly distributed within a zinc oxide matrix. Its chemical composition by mass percentage is: silver 10-40%, zinc oxide 57.7-87.7%, bismuth oxide 1.5-2.5%, and silicon oxide 0.2-0.4%. The elemental silver is generated by in-situ reduction of silver oxide during sintering, with bismuth oxide and silicon oxide acting as sintering aids. When the silver content in the near-zero dielectric ceramic material is between 10-20%, the material exhibits dielectric resonance, and its dielectric constant is adjustable from -600 to 800. When the silver content is between 25-40%, the material exhibits plasmon resonance, and its dielectric constant is adjustable from -1800 to 0.

[0046] Its preparation method is as follows: S1: Weigh out silver oxide, zinc oxide, bismuth oxide, and silicon oxide as raw materials according to the mass percentage of each chemical component; S2: The raw materials weighed in step S1 are ball-milled to obtain a raw material slurry; then dried and sieved to obtain raw material powder; S3: The raw material powder obtained in step S2 is pre-fired, and after pre-firing, it is cooled with the furnace to obtain pre-fired ceramic powder. S4: The pre-fired ceramic powder obtained in step S3 is subjected to a second ball milling process, and then dried and sieved to obtain ceramic powder. S5: Using polyvinyl alcohol aqueous solution as a binder, the ceramic powder obtained in step S4 is granulated to obtain ceramic particles, which are then pressed into shape under a certain pressure to obtain a green body. S6: The green body obtained in step S5 is sintered, and after sintering, it is cooled in the furnace to obtain the ceramic material.

[0047] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0048] In the following examples, the materials used, namely zinc oxide (ZnO), silver oxide (Ag2O), bismuth oxide (Bi2O3), and silicon oxide (SiO2), preferably have a purity of 99% or higher.

[0049] Example 1 A near-zero dielectric ceramic material with tunable filtering characteristics is provided. The ceramic material comprises 10% silver (by mass), 2% bismuth oxide (by mass), 0.3% silicon oxide (by mass), and 87.7% zinc oxide (by mass). The resulting ceramic material is designated as 10 wt% Ag-ZnO. The specific steps for preparing the ceramic material are as follows: (1) Ingredients: Weigh 10.74 g silver oxide, 2 g bismuth oxide, 0.3 g silicon oxide and 87.7 g zinc oxide according to the mass ratio of each component of the ceramic.

[0050] (2) Ball milling: Weigh different ceramic raw materials and put them into a ball milling jar containing zircon balls of different diameters, with the zircon balls having diameters of 4 mm and 8 mm. Then add anhydrous ethanol as the ball milling medium. The amount of ethanol added is just enough to cover the powder and zircon balls. The ball milling is carried out on a planetary ball mill for 4 hours at a speed of 400 rpm.

[0051] (3) Drying and sieving: The ball-milled raw slurry is separated into a drying dish using a sieve, and then the drying dish is placed in an oven at 70 ℃ until the alcohol in the powder evaporates and the powder is dried. After drying, it is sieved through a 400-mesh sieve.

[0052] (4) Pre-calcination: The dried and sieved raw material powder is placed in a crucible and heated to 950 ℃ at a heating rate of 3.5℃ / min. The temperature is held for 2 h and then cooled with the furnace to obtain pre-calcined powder.

[0053] (5) Secondary ball milling and sieving: ceramic powder is obtained by following steps 2 and 3.

[0054] (6) Granulation: Add 10 wt% polyvinyl alcohol binder to obtain ceramic particles with uniform particle size.

[0055] (7) Press molding: Press molding is performed under a pressure of 15 MPa or higher to obtain a round green blank with a diameter of 2 cm and a thickness of 2 mm.

[0056] (8) Sintering: The dried and sieved raw material powder is placed in a crucible and heated to 550 ℃ at a heating rate of 3.5 ℃ / min and held for 2 hours; then the temperature is increased to 1050 ℃ at a heating rate of 3 ℃ / min and held for 2 hours; finally, the ceramic material is obtained by cooling in the furnace.

[0057] (9) Performance testing: The dielectric properties of the ceramic material are tested using an impedance analyzer, including the real part, imaginary part and loss tangent of the dielectric constant.

[0058] (10) Simulation calculation: Substitute the measured dielectric parameters of the material and design the filter material in the CST electromagnetic simulation software. The thickness is 0.6-1.6 mm. Obtain the S-parameters, reflectivity, transmittance, absorptivity and transmittance phase angle of the filter material.

[0059] Example 2 A near-zero dielectric ceramic material with tunable filtering characteristics is disclosed. The ceramic material comprises 20% by mass of elemental silver, 2% by mass of bismuth oxide, 0.3% by mass of silicon oxide, and 77.7% by mass of zinc oxide. The resulting ceramic material is designated as 20 wt% Ag-ZnO. The specific preparation steps are the same as in Example 1.

[0060] Example 3 A near-zero dielectric ceramic material with tunable filtering properties is disclosed. The ceramic material comprises 25% by mass of elemental silver, 2% by mass of bismuth oxide, 0.3% by mass of silicon oxide, and 72.7% by mass of zinc oxide. The ceramic material is labeled as 25 wt% Ag-ZnO. The specific preparation steps are the same as in Example 1.

[0061] Example 4 A near-zero dielectric ceramic material with tunable filtering characteristics is disclosed. The ceramic material comprises 30% by mass of elemental silver, 2% by mass of bismuth oxide, 0.3% by mass of silicon oxide, and 67.7% by mass of zinc oxide. The ceramic material is labeled as 35 wt% Ag-ZnO. The specific steps for preparing the ceramic filter material are the same as in Example 1.

[0062] Example 5 A near-zero dielectric ceramic material with tunable filtering properties is disclosed. The ceramic material comprises 40% by mass of elemental silver, 2% by mass of bismuth oxide, 0.3% by mass of silicon oxide, and 57.7% by mass of zinc oxide. The ceramic material is labeled as 40 wt% Ag-ZnO. The preparation method is the same as in Example 1.

[0063] Depend on Figure 1It can be seen that by increasing the content of elemental silver in the zinc oxide matrix, a complete elemental silver network is gradually formed, which is also known as a silver percolation network. After the percolation network is formed, the free electrons inside the ceramic material generate collective oscillation behavior under the action of an external electric field, resulting in the material's macroscopic dielectric properties exhibiting resonant and plasmonic dielectric characteristics.

[0064] like Figure 2 As shown in a-2b, when the mass fraction of silver is 10-20%, the dielectric constant changes from positive to negative with increasing frequency, exhibiting typical resonant near-zero dielectric characteristics. Furthermore, when the mass fraction of silver increases to 25%, the dielectric constant becomes negative, exhibiting typical plasmonic near-zero dielectric characteristics with significant dispersion. The imaginary part of the dielectric constant and the tangent spectrum of the loss value of Ag-ZnO ceramic materials are shown in the figure. Figure 2 As shown in cd, when the dielectric constant changes from a positive value to a negative value, the loss tangent exhibits a large absorption peak, which helps to absorb electromagnetic waves; conversely, the loss value decreases with increasing frequency, and it exhibits high transmittance characteristics for electromagnetic waves.

[0065] Figure 3 Ag-ZnO ceramic materials with varying amounts of elemental silver S The relationship between parameters and transmittance phase angle clearly shows that at the resonant frequency, the reflection coefficient... S 11 A smaller value indicates a stronger ability to absorb electromagnetic waves. This is based on the characteristics of Ag-ZnO ceramic materials. S The parameters can be used to calculate its reflectance (R), transmittance (T), and absorptivity (A), such as... Figure 4 As shown, at near-zero dielectric frequency, the material's interaction mechanism with electromagnetic waves is mainly reflection and absorption, and electromagnetic waves hardly pass through. Conversely, when the test frequency is far from near-zero dielectric frequency, electromagnetic waves mainly pass through. At this time, the composite material can be regarded as having high-pass and low-impedance filtering characteristics.

[0066] Figure 5 This is a crystal structure diagram of silver and its composite ceramic materials. By comparing it with the standard card, it can be seen that elemental silver corresponds to five typical characteristic peaks, while zinc oxide corresponds to nine typical characteristic peaks, proving that silver exists in the composite material in the form of an element.

[0067] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A near-zero dielectric ceramic material with tunable filtering characteristics, characterized in that, The near-zero dielectric ceramic material is a silver-zinc oxide ceramic, in which elemental silver is uniformly distributed in the zinc oxide matrix. Its chemical composition by mass percentage is: elemental silver 10-40%, zinc oxide 57.7-87.7%, bismuth oxide 1.5-2.5%, and silicon oxide 0.2-0.4%.

2. The near-zero dielectric ceramic material with adjustable filtering characteristics according to claim 1, characterized in that, The metallic silver is generated by in-situ reduction of silver oxide during sintering, and the bismuth oxide and silicon oxide are used as sintering aids.

3. The near-zero dielectric ceramic material with adjustable filtering characteristics according to claim 1, characterized in that, When the silver content in the near-zero dielectric ceramic material is between 10-20%, the near-zero dielectric ceramic material undergoes dielectric resonance, and its dielectric constant is adjustable from -600 to 800. When the silver content in the near-zero dielectric ceramic material is between 25-40%, the near-zero dielectric ceramic material undergoes plasmonic oscillation, and its dielectric constant is adjustable from -1800 to 0.

4. A method for preparing a near-zero dielectric ceramic material with tunable filtering characteristics according to any one of claims 1-3, characterized in that, Includes the following steps: S1: Weigh out silver oxide, zinc oxide, bismuth oxide, and silicon oxide as raw materials according to the mass percentage of each chemical component; S2: The raw materials weighed in step S1 are ball-milled to obtain a raw material slurry; then dried and sieved to obtain raw material powder; S3: The raw material powder obtained in step S2 is pre-fired, and after pre-firing, it is cooled with the furnace to obtain pre-fired ceramic powder. S4: The pre-fired ceramic powder obtained in step S3 is subjected to a second ball milling process, and then dried and sieved to obtain ceramic powder. S5: Using polyvinyl alcohol aqueous solution as a binder, the ceramic powder obtained in step S4 is granulated to obtain ceramic particles, which are then pressed into shape under a certain pressure to obtain a green body. S6: The green body obtained in step S5 is sintered, and after sintering, it is cooled in the furnace to obtain the near-zero dielectric ceramic material.

5. The method for preparing a near-zero dielectric ceramic material with tunable filtering characteristics according to claim 4, characterized in that, In steps S2 and S4, All ball milling processes used anhydrous ethanol as the milling medium, with a milling speed of 300-500 rpm and a milling time of 3-5 h. The ball milling process employed a combination of large and small zirconium balls, wherein the diameter of the large zirconium balls was 8-10 mm, the diameter of the small zirconium balls was 4-6 mm, and the mass ratio of the large to small zirconium balls was 1:1.5-1:2.

5. The drying temperature is 70-100℃, and the sieve mesh size used for sieving is 300-500 mesh.

6. The method for preparing a near-zero dielectric ceramic material with tunable filtering characteristics according to claim 4, characterized in that, In step S3, the pre-firing treatment refers to heating to 700-950 ℃ at a heating rate of 3-4 ℃ / min and holding at that temperature for 1.5-2.5 h.

7. The method for preparing a near-zero dielectric ceramic material with tunable filtering characteristics according to claim 4, characterized in that, In step S5, the concentration of the polyvinyl alcohol aqueous solution is 8-12 wt%, and the particle size of the ceramic particles is 0.2-1.0 μm.

8. The method for preparing a near-zero dielectric ceramic material with tunable filtering characteristics according to claim 4, characterized in that, In step S5, the pressing pressure is 15-20 MPa, and the green blank is in the shape of a disc with a diameter of 1.5-2.5 cm and a thickness of 1-3 mm.

9. The method for preparing a near-zero dielectric ceramic material with tunable filtering characteristics according to claim 4, characterized in that, In step S6, the sintering treatment refers to heating to 450-650 ℃ at a heating rate of 3-4 ℃ / min and holding at that temperature for 1.5-2.5 h; then continuing to heat to 950-1150 ℃ at a heating rate of 2.5-3.5 ℃ / min and holding at that temperature for 1.5-2.5 h.

10. The application of a near-zero dielectric ceramic material with adjustable filtering characteristics as described in any one of claims 1-3 as a filtering device in a communication equipment system.

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