Zinc borate microwave dielectric ceramic as well as preparation method and application thereof

Abstract

The invention discloses zinc borate microwave dielectric ceramic as well as a preparation method and application thereof, and relates to the technical field of microwave ceramic. The general chemical formula of the ceramic is Zn3BxO (3x + 6) / 2, wherein x is more than or equal to 6.5 and less than or equal to 8. The zinc borate ceramic is synthesized through a traditional solid phase sintering method, the sintering temperature ranges from 850 DEG C to 975 DEG C, the dielectric constant ranges from 3.6 to 7.6, and the highest quality factor can reach 78200 GHz. The preparation method can provide an alternative method for preparation of microwave communication component materials such as 6G communication resonators and filters, and has a wide application prospect.

Description

Technical Field

[0001] The present invention relates to the technical field of microwave ceramics, and in particular to a zinc borate microwave dielectric ceramic and a preparation method and application thereof. Background Art

[0002] The advancement of wireless communication technology, particularly 5G and the upcoming 6G, places higher demands on resonators and filters: lower dielectric loss, smaller size, higher temperature stability, and lower production costs. As the primary material for resonators and filters, microwave dielectric ceramics also require continuous optimization and upgrading to meet the demands of high-frequency, high-speed, and highly integrated communication equipment. Microwave dielectric ceramics with low dielectric constants, high quality factors, and near-zero resonant frequency coefficients are in high demand.

[0003] Low-temperature co-fired ceramic (LTCC) technology has attracted attention for its ability to achieve high-density integration and three-dimensional circuit structures. This requires the sintering temperature of microwave dielectric ceramics to be lower than the melting point of the metal electrodes (typically silver electrodes, melting at 961°C). Common methods for achieving low-temperature sintering of microwave dielectric ceramics include introducing low-melting-point glass phases or oxides, employing chemical synthesis or using ultrafine powders as raw materials to enhance sintering activity, and developing systems with inherently low sintering temperatures. The first two methods have limitations. Researching ceramic systems with inherently low sintering temperatures can address the sintering temperature issue while barely affecting the microwave dielectric properties of the ceramics. Zinc borate microwave dielectric ceramics, due to their unique crystal structure and chemical composition, are expected to offer lower sintering temperatures, lower dielectric constants, and lower dielectric losses, thus playing an important role in LTCC technology. However, the volatilization of boron during the preparation of borate ceramics leads to unstable phase composition during sintering, causing abnormal grain growth and localized component segregation, significantly degrading dielectric properties and limiting their application in the millimeter-wave frequency band. Summary of the Invention

[0004] To address the shortcomings of the aforementioned background technology, the present invention provides a zinc borate microwave dielectric ceramic, a preparation method, and applications thereof. This method utilizes a solid-phase sintering process to produce a zinc borate ceramic with a low dielectric constant and a high quality factor, meeting the basic requirements of LTCC technology.

[0005] The first object of the present invention is to provide a zinc borate microwave dielectric ceramic, wherein the zinc borate microwave dielectric ceramic has the chemical formula Zn3B x O (3x+6) / 2 , where 6.5≤x≤8.

[0006] Preferably, the zinc borate microwave dielectric ceramic includes a Zn3(BO3)2 phase and a Zn4O(BO2)6 phase, or a Zn3(BO3)2 phase and a ZnO phase.

[0007] Preferably, the chemical formula of the zinc borate microwave dielectric ceramic includes Zn3B 6.5 O 12.75 、Zn3B7O 13.5 、Zn3B 7.5 O 14.25 、Zn3B8O 15 .

[0008] Preferably, the zinc borate microwave dielectric ceramic has a dielectric constant of 3.6 to 7.6, a quality factor Q×f of 4500 GHz to 78200 GHz, and a resonant frequency temperature coefficient of -79 to -101 ppm / °C.

[0009] A second object of the present invention is to provide a method for preparing zinc borate microwave dielectric ceramics, comprising the following steps: According to the chemical formula Zn3B x O (3x+6) / 2 The ingredients are mixed in a stoichiometric ratio, wherein 6.5≤x≤8, to obtain a mixed powder; the mixed powder is ball-milled to obtain a first slurry; The first slurry is dried and passed through a 120-mesh sieve, and then pre-calcined at 700-850° C. to obtain a pre-calcined powder; The pre-calcined powder is ball-milled again to obtain a second slurry; The second slurry is dried and passed through a 120-mesh sieve, and then mixed with a binder to form granules and tablets to obtain a ceramic green body; the ceramic green body is debinded and sintered at 850° C. to 975° C. to obtain zinc borate microwave dielectric ceramics.

[0010] Preferably, the ball milling is wet ball milling, using a polytetrafluoroethylene ball milling jar, zirconium oxide grinding balls and a planetary ball mill, wherein the ball milling aid is anhydrous ethanol.

[0011] Preferably, during ball milling, the volume ratio of powder: zirconium oxide grinding balls: anhydrous ethanol is 1:1:1-1.5.

[0012] Preferably, during pre-firing and sintering, the heating rate is 3-5°C / min, and the cooling rate is 2°C / min; the holding time for pre-firing is 2-4 hours; the holding time for sintering is 2-4 hours; the debinding temperature is ≥500°C, and the holding time during debinding is 1-3 hours.

[0013] Preferably, the binder is polyvinyl alcohol, and the weight ratio of the powder of the second slurry after drying and passing through a 120-mesh sieve to the polyvinyl alcohol is 95-110:9; and the ceramic body is formed under a uniaxial pressure of 100 MPa.

[0014] The third object of the present invention is to provide an application of zinc borate microwave dielectric ceramics in microwave communication components.

[0015] Compared with the prior art, the present invention has the following beneficial effects: The present invention provides a zinc borate microwave dielectric ceramic, its preparation method, and application. The present invention utilizes a solid-phase sintering method to produce zinc borate ceramics with low dielectric constant and high quality factor. By varying the boron content to optimize the ceramic's chemical composition, the uniformly distributed nanoscale precipitates within the ceramic matrix positively impact the ceramic's dielectric loss. When the x=7 component is used, the quality factor of the ceramic increases by 33% (58,500 GHz to 78,200 GHz), improving the ceramic's microwave dielectric properties. This invention offers a promising alternative material for microwave communication components such as dielectric resonators and dielectric filters, as well as for LTCC high-frequency communication assemblies. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 The XRD patterns of the microwave dielectric ceramics prepared in Examples 1 to 4 are shown.

[0017] Figure 2 This is the SEM spectrum of the microwave dielectric ceramic at the preferred sintering temperature of 875°C in Example 2.

[0018] Figure 3 HAADF image and EDS spectrum of the microwave dielectric ceramic at the preferred sintering temperature of 875°C in Example 2.

[0019] Figure 4 Schematic diagram of the dielectric constants of the microwave dielectric ceramic samples prepared in Examples 1 to 4.

[0020] Figure 5 Schematic diagram of the quality factor of the microwave dielectric ceramic samples prepared in Examples 1 to 4. DETAILED DESCRIPTION

[0021] In order to enable those skilled in the art to better understand and implement the technical solution of the present invention, the present invention is further described below with reference to specific embodiments and drawings, but the embodiments are not intended to limit the present invention.

[0022] The present invention provides a zinc borate microwave dielectric ceramic, its preparation method, and applications. The ceramic is synthesized using a conventional solid-phase sintering method at a temperature of 850-975°C, resulting in a dielectric constant between 3.6 and 7.6, and a quality factor up to 78,200 GHz. This invention offers an alternative method for preparing materials for microwave communication components, such as resonators and filters for 6G communications, and has broad application prospects.

[0023] In order to achieve the above object, the first aspect of the present invention provides a zinc borate microwave dielectric ceramic, the chemical formula of the zinc borate microwave dielectric ceramic is Zn3B x O(3x+6) / 2 , where 6.5≤x≤8.

[0024] The zinc borate microwave dielectric ceramic includes a Zn3(BO3)2 phase and a Zn4O(BO2)6 phase, or a Zn3(BO3)2 phase and a ZnO phase.

[0025] The chemical formula of the zinc borate microwave dielectric ceramic includes Zn3B 6.5 O 12.75 、Zn3B7O 13.5 、Zn3B 7.5 O 14.25 、Zn3B8O 15 .

[0026] The zinc borate microwave dielectric ceramic has a dielectric constant of 3.6 to 7.6, a quality factor Q×f of 4500 GHz to 78200 GHz, and a resonant frequency temperature coefficient of -79 to -101 ppm / °C.

[0027] The ceramic provided by the present invention has the best microwave dielectric properties. Zn3B7O sintered at 875℃ 13.5 The ceramic has excellent dielectric properties, with a dielectric constant of 6.6 and a quality factor Q×f of 78200GHz.

[0028] The zinc borate microwave dielectric ceramic provided by the present invention obtains better dielectric properties through a non-stoichiometric method.

[0029] A second aspect of the present invention provides a method for preparing zinc borate microwave dielectric ceramics, comprising the following steps: According to the chemical formula Zn3B x O (3x+6) / 2 The ingredients are mixed in a stoichiometric ratio, wherein 6.5≤x≤8, to obtain a mixed powder; the mixed powder is ball-milled to obtain a first slurry; The first slurry is dried and passed through a 120-mesh sieve, and then pre-calcined at 700-850° C. to obtain a pre-calcined powder; The pre-calcined powder is ball-milled again to obtain a second slurry; The second slurry is dried and passed through a 120-mesh sieve, and then mixed with a binder to form granules and tablets to obtain a ceramic green body; the ceramic green body is debinded and sintered at 850° C. to 975° C. to obtain zinc borate microwave dielectric ceramics.

[0030] This invention synthesizes non-stoichiometric zinc borate ceramics through traditional solid-phase sintering at a temperature of 850-975°C, achieving a dielectric constant between 3.6 and 7.6, and a quality factor of up to 78,200 GHz. This invention offers an alternative method for preparing materials for microwave communication components, such as resonators and filters for 6G communications, and has broad application prospects.

[0031] The ball milling is wet ball milling, using polytetrafluoroethylene ball milling jars, zirconium oxide grinding balls and planetary ball mills, and the ball milling aid is anhydrous ethanol.

[0032] During ball milling, the volume ratio of powder: zirconia grinding balls: anhydrous ethanol is 1:1:1~1.5.

[0033] During pre-firing and sintering, the heating rate is 3-5°C / min, and the cooling rate is 2°C / min; the holding time for pre-firing is 2-4 hours; the holding time for sintering is 2-4 hours; the debinding temperature is ≥500°C, and the holding time for debinding is 1-3 hours.

[0034] The binder is polyvinyl alcohol, and the weight ratio of the powder to the polyvinyl alcohol is 95-110:9. The ceramic body is formed under a uniaxial pressure of 100 MPa. The powder is obtained by drying the second slurry and passing it through a 120-mesh sieve.

[0035] Exemplarily, a method for preparing zinc borate microwave dielectric ceramics comprises the following steps: (1) ZnO and B2O3 are mixed according to the chemical formula Zn3B x O (3x+6) / 2 The ingredients are prepared in a stoichiometric ratio, wherein 6.5≤x≤8, and the obtained mixture is ball-milled once to obtain a slurry, and the ball-milling time is 12 hours; (2) The slurry was dried at 80°C to constant weight and passed through a 120-mesh sieve. The resulting powder was pre-calcined at 700°C to 850°C to synthesize Zn3B2O6 and Zn4OB6O 12 Ceramic powder, or Zn3B2O6 and ZnO ceramic powder, holding time is 3h; (3) The pre-burned powder is subjected to secondary ball milling to obtain a slurry, and the secondary ball milling time is 6 hours; (4) The slurry is dried at 80°C to constant weight and passed through a 120-mesh sieve. The resulting powder is mixed with a binder and granulated and tableted to obtain a ceramic body; (5) The ceramic body is first heated to 500℃ for heat preservation and debinding, then heated to 850℃~975℃ for sintering to densify the structure, and then cooled to below 200℃ and cooled in the furnace.

[0036] The purity of ZnO and B2O3 is 99.99%.

[0037] In step (2) and step (5), the heating rate is 3°C / min to 5°C / min, and the cooling rate is 2°C / min.

[0038] The binder in step (4) is polyvinyl alcohol, and the weight ratio of the powder to the polyvinyl alcohol is 100:9; the ceramic body is formed under a uniaxial pressure of 100 MPa.

[0039] The holding time during debinding in step (5) is 2 h, and the sintering time is 3 h.

[0040] A third aspect of the present invention provides a zinc borate microwave dielectric ceramic for use in microwave communication components. This zinc borate microwave dielectric ceramic offers an alternative method for preparing materials for microwave communication components, such as resonators and filters for 6G communications, and has broad application prospects.

[0041] It should be noted that the experimental methods used in the present invention are all conventional methods unless otherwise specified; the reagents and materials used are all commercially available unless otherwise specified.

[0042] Example 1 Ingredients: ZnO (99.99%), B2O3 (99.99%) according to the chemical formula Zn3B 6.5 O 12.75 The stoichiometric ratio is used for batching, namely Zn3B x O (3x+6) / 2 x=6.5; Primary ball milling: The weighed raw materials were placed in a polytetrafluoroethylene ball mill, and milled in a planetary ball mill using anhydrous ethanol as a ball milling aid and zirconia grinding balls for 12 h. The volume ratio of powder: zirconia grinding balls: anhydrous ethanol was 1:1:1.5 to obtain a uniformly mixed slurry. Drying: Dry the milled slurry at 80°C to constant weight and pass it through a 120-mesh standard sieve to obtain a dispersed mixture; Pre-firing: The mixture is pre-fired in a muffle furnace at a temperature of 750°C for 3 hours to synthesize Zn3B2O6 ceramic powder; Secondary ball milling: The pre-calcined Zn3B2O6 powder is subjected to secondary ball milling to obtain Zn3B2O6 compound slurry. The secondary ball milling time is 6 hours, and the other parameters are the same as the primary ball milling; Drying: The ball-milled Zn3B2O6 compound slurry was dried at 80°C to a constant weight and passed through a 120-mesh standard sieve to obtain a dispersed Zn3B2O6 compound powder; Granulation: Add polyvinyl alcohol (PVA) binder to Zn3B2O6 compound powder at a weight ratio of 100:9. Grind the powder in an agate mortar to mix it evenly with the raw materials. Then pass it through a 40-mesh standard sieve to obtain the raw material for the next step of pressing and molding. Compression molding: Weigh a certain amount of powder and pour it into a mold. Then, press it into a ceramic green body with a diameter of 12 mm and a height of 7 mm under a pressure of 100 MPa for 3 minutes in a tablet press. Debinding and sintering: Place the pressed green body into a high-temperature furnace, set the furnace heating rate to 5℃ / min, heat to 600℃ and keep warm for 2h to debind, then increase the temperature to the corresponding sintering temperature at the same heating rate. The sintering temperatures are selected as 850℃, 875℃, 900℃, 925℃, 950℃, and 975℃ respectively. Keep warm for 3h at each sintering temperature, then cool to 200℃ at a cooling rate of 2℃ / min, stop the program, and let the furnace cool down naturally. Samples with sintering temperatures of 850℃, 875℃, 900℃, 925℃, 950℃, and 975℃ are obtained.

[0043] Sample post-processing and testing: The sintered samples were ground to 2000 mesh with sandpaper and surface polished, and then ultrasonically cleaned.

[0044] Example 2 Same as Example 1, except that, according to the chemical formula Zn3B7O 13.5 The stoichiometric ratio is used for batching, namely Zn3B x O (3x+6) / 2 Where x=7.

[0045] Example 3 Same as Example 1, except that, according to the chemical formula Zn3B 7.5 O 14.25 The stoichiometric ratio is used for batching, namely Zn3B x O (3x+6) / 2 x=7.5.

[0046] Example 4 Same as Example 1, except that, according to the chemical formula Zn3B8O 15 The stoichiometric ratio is used for batching, namely Zn3B x O (3x+6) / 2 Where x=8.

[0047] In order to illustrate the relevant properties of the microwave dielectric ceramic prepared by the present invention, the relevant properties are described with reference to the accompanying drawings.

[0048] from Figure 1 It can be seen from the XRD that when x=6.5, the phase structure of the zinc borate microwave dielectric ceramic material prepared at 925℃ is Zn3(BO3)2 phase and ZnO phase. When x=7, the phase structure of the zinc borate microwave dielectric ceramic material prepared at 875℃ is Zn3(BO3)2 single phase. When 7.5≤x≤8, the phase structure of the zinc borate microwave dielectric ceramic material prepared at 975℃ is Zn3(BO3)2 phase and Zn4O(BO2)6 phase. Figure 2 As shown, SEM analysis of the x=7 component revealed that unidentified grains precipitated at the grain boundaries of Zn3(BO3)2, see Figure 3 As shown in the figure, further TEM analysis revealed that nano-scale ZnO precipitates were evenly distributed in the Zn3(BO3)2 matrix. The evenly distributed nano-scale precipitates had a positive effect on the dielectric loss of the ceramic, increasing the quality factor of the x=7 component ceramic by 33% (58500 GHz to 78200 GHz). Figure 4 As shown, the dielectric constants of the samples prepared in the embodiments of the present invention are all less than 10 and are adjustable in the range of 3.6-7.6. Figure 5 As shown, the quality factor can reach up to 78200 GHz.

[0049] Taking the microwave dielectric ceramic provided in Example 2 as an example, the sintered ceramic was subjected to performance testing, and its best performance parameters were as follows: the microwave dielectric ceramic sintered at 875° C. had a dielectric constant of 6.6 and a quality factor Q×f of 78200 GHz.

[0050] The present invention describes preferred embodiments and their effects. However, those skilled in the art, once informed of the basic inventive concept, may make additional changes and modifications to these embodiments. Therefore, it is intended that the appended claims be interpreted to include the preferred embodiments as well as all changes and modifications that fall within the scope of the invention.

[0051] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A zinc borate microwave dielectric ceramic, characterized in that: The general chemical formula of the zinc borate microwave dielectric ceramic is Zn3B x O (3x+6) / 2 , where 6.5≤x≤8.

2. The zinc borate microwave dielectric ceramic according to claim 1, characterized in that: The zinc borate microwave dielectric ceramic includes a Zn3(BO3)2 phase and a Zn4O(BO2)6 phase, or a Zn3(BO3)2 phase and a ZnO phase.

3. The zinc borate microwave dielectric ceramic according to claim 1, characterized in that The chemical formula of the zinc borate microwave dielectric ceramic includes Zn3B 6.5 O 12.75 、Zn3B7O 13.5 、Zn3B 7.5 O 14.25 、Zn3B8O 15 .

4. The zinc borate microwave dielectric ceramic according to claim 1, characterized in that: The zinc borate microwave dielectric ceramic has a dielectric constant of 3.6 to 7.6, a quality factor Q×f of 4500 GHz to 78200 GHz, and a resonant frequency temperature coefficient of -79 to -101 ppm / °C.

5. A method for preparing the zinc borate microwave dielectric ceramic according to any one of claims 1 to 4, characterized in that: The following steps are involved: According to the chemical formula Zn3B x O (3x+6) / 2 The ingredients are mixed in a stoichiometric ratio, wherein 6.5≤x≤8, to obtain a mixed powder; the mixed powder is ball-milled to obtain a first slurry; The first slurry is dried and passed through a 120-mesh sieve, and then pre-calcined at 700-850° C. to obtain a pre-calcined powder; The pre-calcined powder is ball-milled again to obtain a second slurry; The second slurry is dried and passed through a 120-mesh sieve, and then mixed with a binder to form granules and tablets to obtain a ceramic green body; the ceramic green body is debinded and sintered at 850° C. to 975° C. to obtain zinc borate microwave dielectric ceramics.

6. The method for preparing zinc borate microwave dielectric ceramics according to claim 5, characterized in that: The ball milling is all wet ball milling, using a polytetrafluoroethylene ball milling jar, zirconium oxide grinding balls and a planetary ball mill, wherein the ball milling aid is anhydrous ethanol.

7. The method for preparing zinc borate microwave dielectric ceramics according to claim 6, characterized in that: During ball milling, the volume ratio of powder: zirconia grinding balls: anhydrous ethanol is 1:1:1~1.

5.

8. The method for preparing zinc borate microwave dielectric ceramics according to claim 5, characterized in that: During pre-firing and sintering, the heating rate is 3-5°C / min, and the cooling rate is 2°C / min; the holding time for pre-firing is 2-4 hours; the holding time for sintering is 2-4 hours; the debinding temperature is ≥500°C, and the holding time for debinding is 1-3 hours.

9. The method for preparing zinc borate microwave dielectric ceramics according to claim 5, characterized in that: The binder is polyvinyl alcohol, and the weight ratio of the powder of the second slurry after drying and passing through a 120-mesh sieve to the polyvinyl alcohol is 95-110:9; the ceramic body is formed under a uniaxial pressure of 100 MPa.

10. Use of the zinc borate microwave dielectric ceramic according to any one of claims 1 to 4 in microwave communication components.

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