Low dielectric constant olivine structure microwave dielectric ceramic material and preparation method thereof

Abstract

The invention discloses a low dielectric constant olivine structure microwave dielectric ceramic material and a preparation method thereof, the chemical general formula of the material is Mg2SiO4-xF2x, and the value range of x is 0 lt; x is less than 0.5. A solid-state reaction method is adopted, and the preparation method comprises the steps of burdening, ball milling, drying, pre-sintering, granulation, forming, sintering and the like. In an olivine structure, O < 2-> is replaced by F <->, a Mg2SiO4-xF2x solid solution is constructed, on the premise of ''-'' maintaining charge balance, F <-> stably enters crystal lattices, controllable micro-distortion is introduced to avoid violent structure instability, higher electronegativity is beneficial to improvement of bonding ionic property and inhibition of dielectric relaxation and scattering related to lattice vibration, and the performance of the material is improved. The dielectric loss is reduced, and the dielectric constant and the temperature coefficient are optimized. The crystal lattice vibration loss is reduced by high crystallinity and low defect density, the pore scattering loss is reduced by high density, and the dielectric relaxation loss is inhibited by proper F-optimized bonding strength.

Description

Technical Field

[0001] This invention relates to microwave dielectric ceramic materials and their preparation, and particularly to a low dielectric constant olivine structure microwave dielectric ceramic material and its preparation method. Background Technology

[0002] Microwave dielectric ceramics refer to ceramic materials used as dielectric materials in microwave frequency band (300 MHz to 300 GHz) circuits, capable of realizing one or more functions. They are widely used as dielectric layers in microwave circuits, becoming an indispensable key component in modern information and communication systems. Their applications include communication navigation, radar detection, satellite communication, and next-generation wireless technologies. With the rapid development of the Internet of Things and the continuous advancement of fifth-generation and sixth-generation mobile communication technologies (5G / 6G), the requirements for material performance in microwave devices are increasingly demanding, especially in terms of a wide range of dielectric constants, low dielectric loss, and excellent temperature stability. These continuously increasing performance requirements aim to meet the development trends of circuit miniaturization, integration, high reliability, and low cost.

[0003] With the advent of 5G and the future 6G era, wireless communication technology is gradually developing towards millimeter-wave transmission, which places higher demands on communication systems, including higher frequency, integration, high reliability, and low latency. Therefore, signal transmission delay and bandwidth have become key research areas. Based on the positive correlation between signal delay time and dielectric constant (t... d =lc / (c × √εr), where t d Indicates the signal delay time. l c For transmission distance, c At the speed of light, ε r The dielectric constant (dielectric constant) helps reduce the delay of electromagnetic waves propagating in a medium. Furthermore, a low dielectric constant means that the material has a lower degree of polarization under an electric field, effectively reducing microwave signal delay and energy loss during transmission, thus improving signal transmission quality and efficiency. In applications such as high-frequency communication, satellite communication, and radar, the use of microwave dielectric ceramic materials with low dielectric constants can significantly enhance the performance stability and reliability of the system. Simultaneously, to achieve low loss and good thermal stability in microwave devices, the material also needs to possess high dielectric constant. Q Value (quality factor) Q × f ) and the near-zero temperature coefficient of resonant frequency (τ) f Therefore, in applications such as high-frequency communication, satellite communication, and radar, there is a particularly urgent need for microwave dielectric ceramic materials with low dielectric constant, high quality factor, and good temperature stability.

[0004] Currently, several inorganic compounds with low dielectric constants have been reported in the literature, most of which are aluminate and silicate systems. The crystal structures of these candidate materials are mainly composed of tetrahedral structural units (such as AlO4 and SiO4). From a crystallographic perspective, the small inter-tetrahedral gaps provide limited space for cation vibrations, resulting in weak polarization of ions or electrons and thus exhibiting a low dielectric constant. However, aluminate and silicate materials typically require sintering at high temperatures (up to 1500°C) to obtain a dense ceramic body. This limits their feasibility in practical applications to some extent.

[0005] Magnesia olivine (Mg₂SiO₄) ceramics possess excellent microwave dielectric properties. Specifically, their dielectric constant... The value is between 6 and 7. However, the preparation and application of forsterite Mg2SiO4 ceramics still face severe challenges: First, its sintering temperature is too high (usually >1400°C), resulting in low ceramic density and easy formation of pores at grain boundaries, which seriously degrades its inherent excellent microwave dielectric properties; second, during high-temperature sintering, MgSiO3 impurity phases with poor microwave dielectric properties are easily generated, and these impurity phases are difficult to eliminate, thus significantly reducing the overall quality factor of the material. Q × f (Value). Therefore, how to effectively reduce the sintering temperature and suppress the formation of harmful impurity phases without significantly damaging the inherent low dielectric constant and quality factor of magnesium olivine materials has become a key technical problem that urgently needs to be solved in this field. Summary of the Invention

[0006] To overcome the shortcomings of the prior art, the present invention aims to provide a low-dielectric-constant olivine-structured microwave dielectric ceramic material and its preparation method. The material, through an anion substitution strategy, significantly reduces the sintering temperature while maintaining excellent microwave dielectric properties.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: On the one hand, the present invention provides a low dielectric constant olivine structure microwave dielectric ceramic material with the general chemical formula Mg2SiO. 4-x F 2x , where 0 < x < 0.5. This material is processed using F... - Partially replaces O in the olivine structure 2- This forms a structurally stable solid solution.

[0008] Secondly, the present invention provides a method for preparing the above-mentioned ceramic material, comprising the following steps: (1) According to the chemical formula Mg2SiO 4-xF 2x According to the stoichiometric ratio, weigh out and mix the SiO2, MgO and MgF2 raw material powders; (2) The raw materials from step (1) are mixed by wet ball milling, and the dried powder is heated to 900°C at a heating rate of 5°C / min and pre-calcined in an atmospheric atmosphere for 2 hours to obtain powder; (3) After adding a binder to the powder obtained in step (2), the powder is granulated and then dry-pressed. Finally, the powder is heated to 1110~1130℃ at a heating rate of 5℃ / min and sintered in an atmospheric atmosphere for 4 hours to obtain the Mg2SiO. 4-x F 2x ceramics.

[0009] In step (2), the ball milling time is 12 hours and the ball milling medium is anhydrous ethanol.

[0010] Furthermore, the binder mentioned in step (3) accounts for 1.5% of the total mass of the powder prepared in step (2).

[0011] Furthermore, the adhesive is a 5% polyvinyl alcohol (PVA) solution by mass concentration.

[0012] Furthermore, the dry pressing equipment is a single-axis hydraulic press with a pressing pressure of 80 MPa.

[0013] Furthermore, the pre-firing in step (2) and the sintering in step (3) are both carried out in a muffle furnace.

[0014] Thirdly, the present invention provides the application of the above-mentioned low dielectric constant olivine structure microwave dielectric ceramic material in the preparation of microblog communication devices.

[0015] Specifically, the microwave communication device is a device suitable for the 300 MHz to 300 GHz frequency band, preferably a 5G / 6G mobile communication base station device, a satellite communication medium component, a microwave filter, a dielectric resonator, or a dielectric antenna.

[0016] The beneficial effects of this invention are as follows: pass" The charge balance of F is replaced by F. - By introducing the Mg2SiO4 lattice, Mg2SiO4 was successfully constructed. 4- x F 2x Solid solution. Due to F - Ionic radius and O 2- Similarly, this substitution can be achieved without causing drastic structural distortion. -The higher electronegativity enhances the ionicity of the metal-fluorine bond, helping to suppress dielectric loss caused by lattice vibrations and optimizing sintering kinetics. This design fundamentally solves the problems raised in the background art: 1) Significantly reduced sintering temperature: the optimal sintering temperature range is reduced to 1110°C–1130°C, far lower than the sintering temperature of pure phase Mg2SiO4 (>1400°C); 2) Effective suppression of impurity phases: it promotes the formation of a single olivine phase and avoids the formation of harmful impurity phases such as MgSiO3; 3) Excellent performance retention: while achieving low-temperature sintering, the material still possesses a low dielectric constant (…). ε r = 6.5–6.7), high quality factor (highest) Q × f This invention provides an effective and reliable method for the low-temperature fabrication of high-performance, low-loss microwave dielectric ceramics, achieving a resonant frequency of up to 60831 GHz and a controllable temperature coefficient of resonant frequency.

[0017] Based on the above-mentioned excellent comprehensive performance, the Mg2SiO provided by this invention 4-x F 2x Ceramic materials are particularly suitable for high-frequency microwave devices with extremely high requirements for signal transmission delay, loss and stability, such as dielectric filters and dielectric resonators in fifth-generation / sixth-generation mobile communication (5G / 6G) base stations, and dielectric waveguide structures in satellite communication systems, providing key material solutions for the miniaturization and performance improvement of devices in these cutting-edge communication technologies. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 Example 1: Mg2SiO sintered at 1130℃ 4-x F 2x (x=0.1) Microscopic images of ceramic materials; Figure 2 Example 2: Mg2SiO sintered at 1110℃ 4-x F 2x (x=0.2) Microscopic images of ceramic materials; Figure 3 Example 3: Mg2SiO sintered at 1120℃ 4-x F 2x (x=0.3) Microscopic images of ceramic materials; Figure 4 Example 4: Mg2SiO sintered at 1110℃ 4-x F 2x (x=0.4) Microscopic images of ceramic materials. Detailed Implementation

[0020] The embodiments of the present invention are further illustrated by the following examples, but the present invention is not limited to these examples.

[0021] A method for preparing a low dielectric constant olivine-type microwave dielectric ceramic material with the chemical formula Mg₂SiO₃ 3.9 F 0.2 (x=0.1), the preparation method includes the following steps: (1) Mix SiO2 with a purity of 99.99%, MgO with a purity of 98%, and MgF2 with a purity of 97.5% according to the formula Mg2SiO 3.9 F 0.2 Composition, weighing, and mixing of ingredients; (2) The raw materials from step (1) are mixed by wet ball milling for 12 hours. The ball milling medium is anhydrous ethanol. The dried powder is heated to 900°C at a heating rate of 5°C / min and pre-calcined in an atmospheric atmosphere for 2 hours to obtain powder. (3) After adding a binder to the powder obtained in step (2), the powder is granulated and then dry-pressed. The binder is PVA with a mass concentration of 5% and the amount added is 1.5% of the total mass of the powder. Finally, the powder is sintered in an atmospheric atmosphere at 1130°C for 4 hours at a heating rate of 5°C / min to obtain the Mg2SiO. 3.9 F 0.2 ceramics.

[0022] Mg2SiO prepared in Example 1 3.9 F 0.2 Microstructure diagram of ceramic materials can be found Figure 1 This indicates good crystallinity of the ceramic, with no obvious second-phase grains, suggesting that a single-phase olivine ceramic can be formed at this temperature. Dielectric constant. Quality factor GHz, temperature coefficient of resonant frequency .

[0023] Example 2 A method for preparing a low dielectric constant olivine-type microwave dielectric ceramic material with the chemical formula Mg₂SiO₃ 3.8 F 0.4 (x=0.2), the preparation method includes the following steps: (1) Mix SiO2 with a purity of 99.99%, MgO with a purity of 98%, and MgF2 with a purity of 97.5% according to the formula Mg2SiO 3.8 F 0.4Composition, weighing, and mixing of ingredients; (2) The raw materials from step (1) are mixed by wet ball milling for 12 hours. The ball milling medium is anhydrous ethanol. The dried powder is heated to 900°C at a heating rate of 5°C / min and pre-calcined in an atmospheric atmosphere for 2 hours to obtain powder. (3) After adding a binder to the powder obtained in step (2), the powder is granulated and then dry-pressed. The binder is PVA with a mass concentration of 5% and the amount added is 1.5% of the total mass of the powder. Finally, the powder is heated to 1100℃ at a heating rate of 5℃ / min and sintered in an atmospheric atmosphere for 4 hours to obtain the Mg2SiO. 3.8 F 0.4 ceramics.

[0024] Mg2SiO prepared in Example 2 3.8 F 0.4 Microstructure diagram of ceramic materials can be found Figure 2 This indicates good crystallinity of the ceramic, with no obvious pores or second-phase grains, suggesting that a single-phase olivine ceramic can be formed at this temperature. Dielectric constant Quality factor GHz, temperature coefficient of resonant frequency This combination of characteristics makes it ideal for designing 5G communication medium filters with center frequencies in the millimeter-wave band (such as 28 GHz or 39 GHz), enabling low insertion loss while meeting the requirements for device miniaturization.

[0025] Example 3 A method for preparing a low dielectric constant olivine-type microwave dielectric ceramic material with the chemical formula Mg₂SiO₃ 3.7 F 0.6 (x=0.3), the preparation method includes the following steps: (1) Mix SiO2 with a purity of 99.99%, MgO with a purity of 98%, and MgF2 with a purity of 97.5% according to the formula Mg2SiO 3.7 F 0.6 Composition, weighing, and mixing of ingredients; (2) The raw materials from step (1) are mixed by wet ball milling for 12 hours. The ball milling medium is anhydrous ethanol. The dried powder is heated to 900°C at a heating rate of 5°C / min and pre-calcined in an atmospheric atmosphere for 2 hours to obtain powder. (3) After adding a binder to the powder obtained in step (2), the powder is granulated and then dry-pressed. The binder is PVA with a mass concentration of 5% and the amount added is 1.5% of the total mass of the powder. Finally, the powder is heated to 1120°C at a heating rate of 5°C / min and sintered in an atmospheric atmosphere for 4 hours to obtain the Mg2SiO. 3.7 F 0.6 ceramics.

[0026] Mg2SiO prepared in Example 3 3.7 F 0.6 Microstructure diagram of ceramic materials can be found Figure 3 This indicates good crystallinity of the ceramic, with no obvious pores or second-phase grains, suggesting that a single-phase olivine ceramic can be formed at this temperature. Dielectric constant Quality factor GHz, temperature coefficient of resonant frequency .

[0027] Example 4 A method for preparing a low dielectric constant olivine-type microwave dielectric ceramic material with the chemical formula Mg₂SiO₃ 3.6 F 0.8 (x=0.4), the preparation method includes the following steps: (1) Mix SiO2 with a purity of 99.99%, MgO with a purity of 98%, and MgF2 with a purity of 97.5% according to the formula Mg2SiO 3.6 F 0.8 Composition, weighing, and mixing of ingredients; (2) The raw materials from step (1) are mixed by wet ball milling for 12 hours. The ball milling medium is anhydrous ethanol. The dried powder is pre-calcined in an atmospheric atmosphere at 900°C for 2 hours at a heating rate of 5°C / min to obtain powder. (3) After adding a binder to the powder obtained in step (2), the powder is granulated and then dry-pressed. The binder is PVA with a mass concentration of 5% and the amount added is 1.5% of the total mass of the powder. Finally, the powder is heated to 1110°C at a heating rate of 5°C / min and sintered in an atmospheric atmosphere for 4 hours to obtain the Mg2SiO. 3.6 F 0.8 ceramics.

[0028] Mg2SiO prepared in Example 4 3.6 F 0.8 Microstructure diagram of ceramic materials can be found Figure 4 This indicates good crystallinity of the ceramic, with no obvious pores or second-phase grains, suggesting that a single-phase olivine ceramic can be formed at this temperature. Dielectric constant Quality factor GHz, temperature coefficient of resonant frequency .

[0029] As shown in Table 1, Mg2SiO 4-x F 2x Ceramic microwave dielectric properties

[0030] Comparative Example 1 A method for preparing a low dielectric constant olivine-type microwave dielectric ceramic material with the chemical formula Mg₂SiO₃ 3.5 F (x=0.5), the preparation method includes the following steps: (1) Mix SiO2 with a purity of 99.99%, MgO with a purity of 98%, and MgF2 with a purity of 97.5% according to the formula Mg2SiO 3.7 F 0.6 Composition, weighing, and mixing of ingredients; (2) The raw materials from step (1) are mixed by wet ball milling for 12 hours. The ball milling medium is anhydrous ethanol. The dried powder is heated to 900°C at a heating rate of 5°C / min and pre-calcined in an atmospheric atmosphere for 2 hours to obtain powder. (3) After adding a binder to the powder obtained in step (2), the powder is granulated and then dry-pressed. The binder is PVA with a mass concentration of 5% and the amount added is 1.5% of the total mass of the powder. Finally, the powder is heated to 1120°C at a heating rate of 5°C / min and sintered in an atmospheric atmosphere for 4 hours to obtain the Mg2SiO. 3.5 F ceramics.

[0031] Mg2SiO prepared in Comparative Example 1 3.5 The microwave dielectric properties of F-ceramic materials deteriorate significantly, especially the quality factor. GHz, dielectric constant Temperature coefficient of resonant frequency .

Claims

1. A low-dielectric-constant olivine-structured microwave dielectric ceramic material, characterized in that, The chemical formula of the ceramic material is Mg2SiO. 4-x F 2x In the ceramic system, the value of x is 0 < x < 0.

5.

2. The method for preparing the ceramic material as described in claim 1, characterized in that, Includes the following steps: (1) Mix SiO2 with a purity of 99.99%, MgO with a purity of 98%, and MgF2 with a purity of 97.5% according to the formula Mg2SiO 4-x F 2x The stoichiometric ratio is used to weigh and prepare the ingredients; (2) The raw materials from step (1) are mixed by wet ball milling, and the dried powder is heated to 900°C at a heating rate of 5°C / min and pre-calcined in an atmospheric atmosphere for 2 hours to obtain powder; (3) After adding a binder to the powder obtained in step (2), the powder is granulated and then dry-pressed. Finally, the powder is heated to 1110~1130℃ at a heating rate of 5℃ / min and sintered in an atmospheric atmosphere for 4 hours to obtain the Mg2SiO. 4-x F 2x ceramics.

3. The preparation method according to claim 2, characterized in that, In step (2), the ball milling time is 12 hours and the ball milling medium is anhydrous ethanol.

4. The preparation method according to claim 2, characterized in that, The binder mentioned in step (3) accounts for 1.5% of the total mass of the powder prepared in step (2).

5. The preparation method according to claim 4, characterized in that, The adhesive is a 5% polyvinyl alcohol (PVA) solution by mass concentration.

6. The preparation method according to claim 2, characterized in that, The dry pressing equipment is a single-axis hydraulic press with a pressing pressure of 80 MPa.

7. The preparation method according to claim 2, characterized in that, The pre-firing in step (2) and the sintering in step (3) are both carried out in a muffle furnace.

8. The application of the low dielectric constant olivine structure microwave dielectric ceramic material according to claim 1 in the fabrication of microblog communication devices.

9. The application according to claim 8, characterized in that, The microwave communication device is a device suitable for the 300 MHz to 300 GHz frequency band, preferably a 5G / 6G mobile communication base station device, a satellite communication medium component, a microwave filter, a medium resonator, or a medium antenna.

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