Microwave dielectric ceramic material and preparation method thereof

Abstract

The invention discloses a microwave dielectric ceramic material and a preparation method thereof. The microwave dielectric ceramic material consists of the following components: a main crystalline phase raw material: 60-80% of BaTiO3 (barium titanate); a fluxing agent: 5%-15% of Bi2O3 (bismuth oxide); a doping agent: 0.1%-5% of Nb2O5 (niobium pentoxide); the additive comprises 1%-3% of MnO2 (manganese dioxide); 2%-5% of TiO2 (titanium dioxide); 1%-3% of Y2O3 (yttrium oxide); and 0.5%-2% of MoS2 (molybdenum disulfide). According to the microwave dielectric ceramic material and the preparation method thereof, the microwave dielectric ceramic material has extremely low dielectric loss (# imgabs0 # = 0.0022), so that the energy loss is greatly reduced in a microwave signal transmission process. In an actual communication system, such as a signal transmitting and receiving device of a 5G base station, a microwave element made of the material can effectively reduce attenuation of signals on a transmission path, the signals can reach a receiving end with higher strength and integrity, the communication quality is greatly improved, the bit error rate is reduced, and the service life of the microwave element is prolonged. And smooth proceeding of high-speed data services such as high-definition video transmission and rapid downloading of large files is ensured.

Description

Technical Field

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

[0002] In today's information age, the rapid development of 5G and, in the future, 6G communication technologies is placing extremely stringent demands on the performance of electronic equipment. Microwave dielectric ceramic materials, as one of the core foundational materials, play a crucial role in microwave communications. They are widely used in key microwave components such as filters, resonators, and antennas. The performance of these components directly determines the signal transmission quality, bandwidth, and anti-interference capabilities of communication systems, as well as the degree of device integration and miniaturization. Ideal microwave dielectric ceramic materials should have a series of excellent properties. High relative dielectric constant ( ) is a key factor in achieving miniaturization of electronic components. As communication equipment develops towards miniaturization and lightweight, high The material can effectively reduce the size of components, integrate more functions in a limited space, and meet the demand for compact structure of portable devices. For example, in mobile terminals such as mobile phones and tablets, high Filters made of microwave dielectric ceramics can work efficiently in a small motherboard space, improving the communication performance of the equipment. Low dielectric loss ( ) is crucial for reducing energy loss during signal transmission. In long-distance communications and high-frequency signal transmission scenarios, such as satellite communications and 5G base station signal coverage, low-loss materials ensure high signal strength and integrity during transmission, reduce signal attenuation, improve signal transmission efficiency, and avoid signal distortion and communication quality degradation caused by energy loss. Near zero resonant frequency temperature coefficient ( ) is a key indicator to ensure the stable operation of electronic components in different temperature environments. From the cold polar regions to the hot desert areas, communication equipment may face huge temperature changes. The microwave dielectric ceramic material can keep the resonant frequency of the component relatively stable when the temperature fluctuates, ensuring that the equipment can operate normally in various complex environments, greatly improving the reliability and stability of the communication system. However, the existing microwave dielectric ceramic materials have many limitations in terms of performance. Although some traditional materials have a high dielectric constant, the dielectric loss is too large. For example, some materials based on the barium strontium titanate (BST) system have can reach higher values, but It is also relatively high, which results in a large amount of energy loss and rapid weakening of signal strength during high-frequency signal transmission, severely limiting its application in 5G and future communication technologies that have extremely high requirements for signal transmission quality. However, some low-loss materials have relatively low dielectric constants, which makes it difficult to meet the urgent demand for miniaturization of electronic components. For example, some alumina-based ceramic materials, Low, small signal transmission loss, but The value is not high, which makes it difficult to further reduce the size of components and cannot adapt to the development trend of increasingly miniaturized communication equipment. Existing processes also present significant challenges in their preparation methods. Traditional processes are often complex, involving multiple high-temperature treatments, complex chemical synthesis steps, and precise control procedures. This not only increases energy consumption and production costs, but also places extremely high demands on production equipment and the technical expertise of operators. Furthermore, these complex processes are prone to introducing impurities, resulting in unstable product quality. Summary of the Invention

[0003] To address the shortcomings of existing technologies, the present invention provides a microwave dielectric ceramic material and its preparation method, addressing the performance deficiencies and preparation process issues of existing microwave dielectric ceramic materials. This material exhibits a high relative permittivity, low dielectric loss, and a near-zero resonant frequency temperature coefficient. Furthermore, the preparation method is simple, low-cost, and amenable to industrial production.

[0004] To achieve the above object, the present invention provides the following technical solution: A microwave dielectric ceramic material, comprising the following components by mass percentage: Main crystal phase raw material: BaTiO3 (barium titanate) 60%-80%; Flux: Bi2O3 (bismuth oxide) 5%-15%; Dopant: Nb2O5 (niobium pentoxide) 0.1%-5%; The balance is additives, which include: MnO2 (manganese dioxide) 1%-3%; TiO2 (titanium dioxide) 2%-5%; Y2O3 (yttrium oxide) 1%-3%; MoS2 (molybdenum disulfide) 0.5%-2%.

[0005] Preferably, the main crystalline phase raw material BaTiO3 is processed by a high-temperature solid-phase reaction method to have a perovskite crystal structure, a particle size distribution of 0.5-2 μm, and a purity of 99.5%.

[0006] Preferably, the flux Bi2O3 can significantly reduce the sintering temperature of the material in the temperature range of 800-1000°C without introducing impurities that affect the electrical properties of the material, and its melting point range is 820-860°C.

[0007] Preferably, the dopant Nb2O5 can form a specific defect structure of oxygen vacancies in the material lattice, thereby regulating the material microstructure and electrical properties, reducing dielectric loss and optimizing the resonant frequency temperature coefficient. The ion radius is compatible with the BaTiO3 main crystal phase lattice in the range of 0.64-0.72Å.

[0008] Preferably, the additive Y2O3 can refine ceramic grains, improve the microstructural uniformity of the material, and enhance the thermal stability of the material. It exists in the material in the form of a solid solution, is evenly distributed in the main crystal phase lattice gaps, or replaces some cation positions.

[0009] Preferably, the additive MoS2 has a layered structure, which can form a lubricating layer at the grain boundary, reduce the grain boundary resistance, and enhance the mechanical properties of the material. During the sintering process, MoS2 is partially decomposed, and the sulfur element participates in the regulation of lattice defects, thereby improving the electrical properties of the material.

[0010] A method for preparing a microwave dielectric ceramic material comprises the following steps: S1: Raw material preparation: Accurately weigh each raw material according to the mass percentage, crush and grind the main crystal phase raw material BaTiO3, flux Bi2O3, dopant Nb2O5, and additives MnO2, TiO2, Y2O3 and MoS2 respectively to a particle size of 0.1-0.5μm to ensure the uniformity of subsequent mixing; S2: Mixing: Use wet ball milling to mix the pretreated raw materials evenly. Add appropriate amount of dispersant (such as ammonium polyacrylate) and ball milling medium (such as zirconia balls) during the ball milling process. Control the ball milling time to 12-24 hours and the speed to 300-500r / min to ensure that all raw materials are fully mixed to form a uniform mixed slurry; S3: Drying: Drying the mixed slurry by spray drying. During spray drying, the air inlet temperature is controlled at 180-220°C and the air outlet temperature is controlled at 80-100°C to remove moisture from the slurry and obtain a dry mixed powder. S4: Pre-sintering: The dried mixed powder is pre-sintered at 900-1100°C for 2-4 hours. The purpose of pre-sintering is to promote the initial solid-phase reaction of the raw materials, form part of the main crystal phase, stabilize the chemical composition of the material, and reduce shrinkage and deformation during the subsequent sintering process. S5: Secondary ball milling: The pre-calcined powder is subjected to secondary ball milling to further refine the powder particles. The secondary ball milling also adopts wet ball milling, with the ball milling time controlled to 6-10h and the rotation speed to 350-450r / min to improve the powder uniformity; S6: Molding: The powder after secondary ball milling is formed into the desired shape by an appropriate molding method. When dry pressing is used, the molding pressure is controlled at 100-200 MPa and the holding time is 3-5 minutes; when isostatic pressing is used, the pressure is 200-300 MPa and the holding time is 5-8 minutes; when injection molding is used, the injection temperature is 150-180°C and the injection pressure is 50-80 MPa to ensure the density and dimensional accuracy of the green body; S7: Sintering: The formed green body is sintered at 1200-1400℃ for 4-6h. During the sintering process, nitrogen is used as the protective atmosphere. By controlling the sintering temperature and time, the material is fully densified to form a microwave dielectric ceramic with excellent performance.

[0011] Preferably, the mass percentage of the dispersant ammonium polyacrylate in the ball mill slurry is 0.5%-1.5%, which can prevent the raw material particles from agglomerating and ensure mixing uniformity.

[0012] Preferably, the mass ratio of the ball milling medium zirconium oxide balls to the raw materials is 3:1-5:1, which can crush and mix the raw material particles during the ball milling process.

[0013] Preferably, the purity of the nitrogen in the protective atmosphere reaches 99.9%, which can prevent material oxidation or the introduction of other impurities during the sintering process.

[0014] Compared with the prior art, the present invention provides a microwave dielectric ceramic material and a preparation method thereof, which has the following beneficial effects: 1. By using the extremely low dielectric loss in the second embodiment ( =0.0022), significantly reducing energy loss during microwave signal transmission. In practical communication systems, such as the signal transmission and reception equipment of 5G base stations, microwave components made of this material can effectively reduce signal attenuation along the transmission path. Signals can reach the receiving end with greater strength and integrity, significantly improving communication quality, reducing bit error rates, and ensuring smooth high-speed data services such as high-definition video transmission and fast large file downloads.

[0015] 2. By adopting a conventional and easy-to-use preparation process, from raw material preparation, mixing, drying, to pre-calcination, secondary ball milling, molding, and sintering, each step utilizes equipment and technologies widely used in the field of ceramic material preparation. For example, planetary ball mills, spray drying equipment, and high-temperature furnaces are used, eliminating the need for expensive and complex specialized equipment. This simple process route lowers the technical barriers to production, making it easy for small and medium-sized enterprises to start production, which is conducive to the promotion of technology and the popularization of the industry. DETAILED DESCRIPTION

[0016] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention. Example 1

[0017] A microwave dielectric ceramic material, comprising the following components by mass percentage: main crystal phase raw material: BaTiO3 (barium titanate) 60%; Flux: Bi2O3 (bismuth oxide) 10%; Dopant: Nb2O5 (niobium pentoxide) 2%; The balance is additives, which include: MnO2 (manganese dioxide) 2%; TiO2 (titanium dioxide) 3%; Y2O3 (yttrium oxide) 2%; MoS2 (molybdenum disulfide) 1%.

[0018] The remainder is other additives and impurities (assumed to be 0.01%, the impact can be ignored).

[0019] The main crystal phase raw material BaTiO3 is treated by high-temperature solid-phase reaction method and has a perovskite crystal structure with a particle size of 1μm and a purity of 99.5%.

[0020] The flux Bi2O3 can significantly reduce the sintering temperature of the material in the temperature range of 800-1000℃ without introducing impurities that affect the electrical properties of the material. Its melting point range is 820-860℃.

[0021] The dopant Nb2O5 can form a specific defect structure of oxygen vacancies in the material lattice, thereby regulating the material's microstructure and electrical properties, reducing dielectric loss and optimizing the resonant frequency temperature coefficient. Its ion radius is compatible with the BaTiO3 main crystal phase lattice in the range of 0.64-0.72Å.

[0022] The additive Y2O3 can refine the ceramic grains, improve the microstructural uniformity of the material, and enhance the thermal stability of the material. It exists in the material in the form of a solid solution, evenly distributed in the lattice gaps of the main crystal phase or replacing some cation positions.

[0023] The additive MoS2 has a layered structure and can form a lubricating layer at the grain boundary, reducing the grain boundary resistance while enhancing the mechanical properties of the material. During the sintering process, MoS2 partially decomposes, and the sulfur element participates in the regulation of lattice defects, improving the electrical properties of the material.

[0024] A method for preparing a microwave dielectric ceramic material comprises the following steps: S1: Raw material preparation: Accurately weigh each raw material according to the mass percentage, crush and grind the main crystal phase raw material BaTiO3, flux Bi2O3, dopant Nb2O5, and additives MnO2, TiO2, Y2O3 and MoS2 respectively to a particle size of 0.4μm to ensure the uniformity of subsequent mixing; S2: Mixing: Use wet ball milling to mix the pretreated raw materials evenly. Add appropriate amount of dispersant (such as ammonium polyacrylate) and ball milling medium (such as zirconia balls) during the ball milling process. Control the ball milling time to 24 hours and the speed to 400r / min to ensure that all raw materials are fully mixed to form a uniform mixed slurry; S3: Drying: Drying the mixed slurry by spray drying. During spray drying, the air inlet temperature is controlled at 200°C and the air outlet temperature is controlled at 100°C to remove moisture from the slurry and obtain a dry mixed powder. S4: Pre-sintering: The dried mixed powder is pre-sintered at 1000°C for 3 hours. The purpose of pre-sintering is to promote the initial solid-phase reaction of the raw materials, form part of the main crystal phase, stabilize the chemical composition of the material, and reduce shrinkage and deformation during the subsequent sintering process. S5: Secondary ball milling: The pre-calcined powder is subjected to secondary ball milling to further refine the powder particles. The secondary ball milling also uses wet ball milling, with a controlled ball milling time of 8 hours and a rotation speed of 400 r / min to improve powder uniformity; S6: Molding: The powder after secondary ball milling is molded into the desired shape by an appropriate molding method. When dry pressing is used, the molding pressure is controlled at 180 MPa and the holding time is 4 minutes; when isostatic pressing is used, the pressure is 260 MPa and the holding time is 6 minutes; when injection molding is used, the injection temperature is 170°C and the injection pressure is 70 MPa to ensure the density and dimensional accuracy of the green body; S7: Sintering: The formed green body is sintered at 1300°C for 5 hours. During the sintering process, nitrogen is used as a protective atmosphere. By controlling the sintering temperature and time, the material is fully densified to form a microwave dielectric ceramic with excellent performance.

[0025] The mass percentage of the dispersant ammonium polyacrylate in the ball mill slurry is 1%, which can prevent the raw material particles from agglomerating and ensure mixing uniformity; the mass ratio of the ball mill medium zirconium oxide balls to the raw materials is 4:1, which can crush and mix the raw material particles during the ball milling process; the purity of the protective atmosphere nitrogen reaches 99.9%, which can prevent material oxidation or the introduction of other impurities during the sintering process.

[0026] Relative dielectric constant ( ): Measured by network analyzer, in the microwave frequency range of 1-10GHz, the capacitance and inductance of the test sample are calculated according to the formula ( is the capacitance, is the vacuum dielectric constant, A is the electrode area, and d is the sample thickness). The average value is taken after multiple measurements and calculated. It is 85.

[0027] Dielectric loss ( ): Also using the network analyzer, the energy loss of the sample during microwave signal transmission is measured and calculated. It is 0.0025.

[0028] Resonant frequency temperature coefficient ( ): Place the sample in a temperature-controlled environment box, measure the resonant frequency every 10℃ in the temperature range of -50℃ to 150℃, and use the formula ( is the resonant frequency at different temperatures, is the corresponding temperature), calculate and get +300ppm / ℃. Example 2

[0029] A microwave dielectric ceramic material, comprising the following components by mass percentage: main crystal phase raw material: BaTiO3 (barium titanate) 55%; Flux: Bi2O3 (bismuth oxide) 12%; Dopant: Nb2O5 (niobium pentoxide) 3%; The balance is additives, which include: MnO2 (manganese dioxide) 1.5%; TiO2 (titanium dioxide) 4%; Y2O3 (yttrium oxide) 2.5%; MoS2 (molybdenum disulfide) 1.5%.

[0030] The remainder is other additives and impurities (assumed to be 0.01%, the impact can be ignored).

[0031] The main crystal phase raw material BaTiO3 is treated by high-temperature solid-phase reaction method and has a perovskite crystal structure with a particle size of 1μm and a purity of 99.5%.

[0032] The flux Bi2O3 can significantly reduce the sintering temperature of the material in the temperature range of 800-1000℃ without introducing impurities that affect the electrical properties of the material. Its melting point range is 820-860℃.

[0033] The dopant Nb2O5 can form a specific defect structure of oxygen vacancies in the material lattice, thereby regulating the material's microstructure and electrical properties, reducing dielectric loss and optimizing the resonant frequency temperature coefficient. Its ion radius is compatible with the BaTiO3 main crystal phase lattice in the range of 0.64-0.72Å.

[0034] The additive Y2O3 can refine the ceramic grains, improve the microstructural uniformity of the material, and enhance the thermal stability of the material. It exists in the material in the form of a solid solution, evenly distributed in the lattice gaps of the main crystal phase or replacing some cation positions.

[0035] The additive MoS2 has a layered structure and can form a lubricating layer at the grain boundary, reducing the grain boundary resistance while enhancing the mechanical properties of the material. During the sintering process, MoS2 partially decomposes, and the sulfur element participates in the regulation of lattice defects, improving the electrical properties of the material.

[0036] A method for preparing a microwave dielectric ceramic material comprises the following steps: S1: Raw material preparation: Accurately weigh each raw material according to the mass percentage, crush and grind the main crystal phase raw material BaTiO3, flux Bi2O3, dopant Nb2O5, and additives MnO2, TiO2, Y2O3 and MoS2 respectively to a particle size of 0.4μm to ensure the uniformity of subsequent mixing; S2: Mixing: Use wet ball milling to mix the pretreated raw materials evenly. Add appropriate amount of dispersant (such as ammonium polyacrylate) and ball milling medium (such as zirconia balls) during the ball milling process. Control the ball milling time to 24 hours and the speed to 400r / min to ensure that all raw materials are fully mixed to form a uniform mixed slurry; S3: Drying: Drying the mixed slurry by spray drying. During spray drying, the air inlet temperature is controlled at 200°C and the air outlet temperature is controlled at 100°C to remove moisture from the slurry and obtain a dry mixed powder. S4: Pre-sintering: The dried mixed powder is pre-sintered at 1000°C for 3 hours. The purpose of pre-sintering is to promote the initial solid-phase reaction of the raw materials, form part of the main crystal phase, stabilize the chemical composition of the material, and reduce shrinkage and deformation during the subsequent sintering process. S5: Secondary ball milling: The pre-calcined powder is subjected to secondary ball milling to further refine the powder particles. The secondary ball milling also uses wet ball milling, with a controlled ball milling time of 8 hours and a rotation speed of 400 r / min to improve powder uniformity; S6: Molding: The powder after secondary ball milling is molded into the desired shape by an appropriate molding method. When dry pressing is used, the molding pressure is controlled at 180 MPa and the holding time is 4 minutes; when isostatic pressing is used, the pressure is 260 MPa and the holding time is 6 minutes; when injection molding is used, the injection temperature is 170°C and the injection pressure is 70 MPa to ensure the density and dimensional accuracy of the green body; S7: Sintering: The formed green body is sintered at 1300°C for 5 hours. During the sintering process, nitrogen is used as a protective atmosphere. By controlling the sintering temperature and time, the material is fully densified to form a microwave dielectric ceramic with excellent performance.

[0037] Relative dielectric constant ( ): After testing and calculation with a network analyzer, in the 1-10GHz microwave frequency band, It is 82.

[0038] Dielectric loss ( ): Calculated by measurement It is 0.0022. Resonant frequency temperature coefficient ( ): Calculated and tested in the temperature range of -50℃ to 150℃, τf is +25ppm / ℃. Example 3

[0039] A microwave dielectric ceramic material, comprising the following components by mass percentage: main crystal phase raw material: BaTiO3 (barium titanate) 65%; Flux: Bi2O3 (bismuth oxide) 8%; Dopant: Nb2O5 (niobium pentoxide) 1%; The balance is additives, which include: MnO2 (manganese dioxide) 2.5%; TiO2 (titanium dioxide) 2.5%; Y2O3 (yttrium oxide) 1.5%; MoS2 (molybdenum disulfide) 0.8%. The balance is other additives and impurities (assumed to be 0.01%, the impact of which can be ignored).

[0040] The main crystal phase raw material BaTiO3 is treated by high-temperature solid-phase reaction method and has a perovskite crystal structure with a particle size of 1μm and a purity of 99.5%.

[0041] The flux Bi2O3 can significantly reduce the sintering temperature of the material in the temperature range of 800-1000℃ without introducing impurities that affect the electrical properties of the material. Its melting point range is 820-860℃.

[0042] The dopant Nb2O5 can form a specific defect structure of oxygen vacancies in the material lattice, thereby regulating the material's microstructure and electrical properties, reducing dielectric loss and optimizing the resonant frequency temperature coefficient. Its ion radius is compatible with the BaTiO3 main crystal phase lattice in the range of 0.64-0.72Å.

[0043] The additive Y2O3 can refine the ceramic grains, improve the microstructural uniformity of the material, and enhance the thermal stability of the material. It exists in the material in the form of a solid solution, evenly distributed in the lattice gaps of the main crystal phase or replacing some cation positions.

[0044] The additive MoS2 has a layered structure and can form a lubricating layer at the grain boundary, reducing the grain boundary resistance while enhancing the mechanical properties of the material. During the sintering process, MoS2 partially decomposes, and the sulfur element participates in the regulation of lattice defects, improving the electrical properties of the material.

[0045] A method for preparing a microwave dielectric ceramic material comprises the following steps: S1: Raw material preparation: Accurately weigh each raw material according to the mass percentage, crush and grind the main crystal phase raw material BaTiO3, flux Bi2O3, dopant Nb2O5, and additives MnO2, TiO2, Y2O3 and MoS2 respectively to a particle size of 0.4μm to ensure the uniformity of subsequent mixing; S2: Mixing: Use wet ball milling to mix the pretreated raw materials evenly. Add appropriate amount of dispersant (such as ammonium polyacrylate) and ball milling medium (such as zirconia balls) during the ball milling process. Control the ball milling time to 24 hours and the speed to 400r / min to ensure that all raw materials are fully mixed to form a uniform mixed slurry; S3: Drying: Drying the mixed slurry by spray drying. During spray drying, the air inlet temperature is controlled at 200°C and the air outlet temperature is controlled at 100°C to remove moisture from the slurry and obtain a dry mixed powder. S4: Pre-sintering: The dried mixed powder is pre-sintered at 1000°C for 3 hours. The purpose of pre-sintering is to promote the initial solid-phase reaction of the raw materials, form part of the main crystal phase, stabilize the chemical composition of the material, and reduce shrinkage and deformation during the subsequent sintering process. S5: Secondary ball milling: The pre-calcined powder is subjected to secondary ball milling to further refine the powder particles. The secondary ball milling also uses wet ball milling, with a controlled ball milling time of 8 hours and a rotation speed of 400 r / min to improve powder uniformity; S6: Molding: The powder after secondary ball milling is molded into the desired shape by an appropriate molding method. When dry pressing is used, the molding pressure is controlled at 180 MPa and the holding time is 4 minutes; when isostatic pressing is used, the pressure is 260 MPa and the holding time is 6 minutes; when injection molding is used, the injection temperature is 170°C and the injection pressure is 70 MPa to ensure the density and dimensional accuracy of the green body; S7: Sintering: The formed green body is sintered at 1300°C for 5 hours. During the sintering process, nitrogen is used as a protective atmosphere. By controlling the sintering temperature and time, the material is fully densified to form a microwave dielectric ceramic with excellent performance.

[0046] Relative dielectric constant ( ): After testing and calculation with a network analyzer, in the 1-10GHz microwave frequency band, It is 88.

[0047] Dielectric loss ( ): Measured and calculated It is 0.0028. Resonant frequency temperature coefficient ( ): Calculated and tested in the temperature range of -50℃ to 150℃, τf is +35ppm / ℃.

[0048] Comprehensive comparison of the performance data of the three embodiments: Dielectric constant: Example 3 The highest is 88, which is conducive to the miniaturization of electronic components. Dielectric loss: Example 2 The lowest is 0.0022, and the signal transmission energy loss is the smallest. Resonant frequency temperature coefficient: Example 2 It is +25ppm / ℃, which is closest to zero and has the best working stability at different temperatures. Taking all factors into consideration, low dielectric loss and a resonant frequency temperature coefficient close to zero are often more critical for microwave dielectric ceramic materials to ensure efficient and stable signal transmission. Therefore, the second embodiment has the best overall performance among the three embodiments and can be regarded as the best embodiment.

[0049] 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 microwave dielectric ceramic material, characterized in that: The main crystalline phase raw materials are composed of the following components by mass percentage: BaTiO3 (barium titanate) 60%-80%; Flux: Bi2O3 (bismuth oxide) 5%-15%; Dopant: Nb2O5 (niobium pentoxide) 0.1%-5%; The balance is additives, which include: MnO2 (manganese dioxide) 1%-3%; TiO2 (titanium dioxide) 2%-5%; Y2O3 (yttrium oxide) 1%-3%; MoS2 (molybdenum disulfide) 0.5%-2%.

2. The microwave dielectric ceramic material according to claim 1, characterized in that: The main crystal phase raw material BaTiO3 is processed by a high-temperature solid-phase reaction method to have a perovskite crystal structure, a particle size distribution of 0.5-2 μm, and a purity of 99.5%.

3. The microwave dielectric ceramic material according to claim 1, characterized in that: The flux Bi2O3 can significantly reduce the sintering temperature of the material in the temperature range of 800-1000°C without introducing impurities that affect the electrical properties of the material. Its melting point range is 820-860°C.

4. The microwave dielectric ceramic material according to claim 1, characterized in that: The dopant Nb2O5 can form a specific defect structure of oxygen vacancies in the material lattice, thereby regulating the material's microstructure and electrical properties, reducing dielectric loss and optimizing the resonant frequency temperature coefficient. Its ion radius is compatible with the BaTiO3 main crystal phase lattice in the range of 0.64-0.72Å.

5. The microwave dielectric ceramic material according to claim 1, characterized in that: The additive Y2O3 can refine ceramic grains, improve the microstructural uniformity of the material, and enhance the thermal stability of the material. It exists in the material in the form of a solid solution, is evenly distributed in the main crystal phase lattice gaps, or replaces some cation positions.

6. The microwave dielectric ceramic material according to claim 1, characterized in that: The additive MoS2 has a layered structure and can form a lubricating layer at the grain boundary, reducing the grain boundary resistance while enhancing the mechanical properties of the material. During the sintering process, MoS2 is partially decomposed, and the sulfur element participates in the regulation of lattice defects, thereby improving the electrical properties of the material.

7. The method for preparing a microwave dielectric ceramic material according to any one of claims 1 to 6, characterized in that: The following steps are involved: S1: Raw material preparation: Accurately weigh the raw materials according to the mass percentage in claim 1, crush and grind the main crystal phase raw material BaTiO3, flux Bi2O3, dopant Nb2O5 and additives MnO2, TiO2, Y2O3 and MoS2 respectively to a particle size of 0.1-0.5μm to ensure the uniformity of subsequent mixing; S2: Mixing: Use wet ball milling to mix the pretreated raw materials evenly. Add appropriate amount of dispersant (such as ammonium polyacrylate) and ball milling medium (such as zirconia balls) during the ball milling process. Control the ball milling time to 12-24 hours and the speed to 300-500r / min to ensure that all raw materials are fully mixed to form a uniform mixed slurry; S3: Drying: Drying the mixed slurry by spray drying. During spray drying, the air inlet temperature is controlled at 180-220°C and the air outlet temperature is controlled at 80-100°C to remove moisture from the slurry and obtain a dry mixed powder. S4: Pre-sintering: The dried mixed powder is pre-sintered at 900-1100°C for 2-4 hours. The purpose of pre-sintering is to promote the initial solid-phase reaction of the raw materials, form part of the main crystal phase, stabilize the chemical composition of the material, and reduce shrinkage and deformation during the subsequent sintering process. S5: Secondary ball milling: The pre-calcined powder is subjected to secondary ball milling to further refine the powder particles. The secondary ball milling also adopts wet ball milling, with the ball milling time controlled to 6-10h and the rotation speed to 350-450r / min to improve the powder uniformity; S6: Molding: The powder after secondary ball milling is formed into the desired shape by an appropriate molding method. When dry pressing is used, the molding pressure is controlled at 100-200 MPa and the holding time is 3-5 minutes; when isostatic pressing is used, the pressure is 200-300 MPa and the holding time is 5-8 minutes; when injection molding is used, the injection temperature is 150-180°C and the injection pressure is 50-80 MPa to ensure the density and dimensional accuracy of the green body; S7: Sintering: The formed green body is sintered at 1200-1400℃ for 4-6h. During the sintering process, nitrogen is used as the protective atmosphere. By controlling the sintering temperature and time, the material is fully densified to form a microwave dielectric ceramic with excellent performance.

8. The method for preparing a microwave dielectric ceramic material according to claim 7, characterized in that: The mass percentage of the dispersant ammonium polyacrylate in the ball mill slurry is 0.5%-1.5%, which can prevent the raw material particles from agglomerating and ensure mixing uniformity.

9. The method for preparing a microwave dielectric ceramic material according to claim 7, wherein: The mass ratio of the ball milling medium zirconium oxide balls to the raw materials is 3:1-5:1, and the raw material particles can be crushed and mixed during the ball milling process.

10. The method for preparing a microwave dielectric ceramic material according to claim 7, wherein: The nitrogen purity of the protective atmosphere reaches 99.9%, which can prevent material oxidation or the introduction of other impurities during the sintering process.

Images