Intermediate dielectric microwave ceramic material with near-zero temperature coefficient and preparation method thereof

Abstract

The invention provides an intermediate dielectric microwave ceramic material with a near-zero temperature coefficient and a preparation method thereof, and relates to the field of ceramic materials. The material comprises the following components in percentage by weight: 97 to 98.5 percent of main crystal phase, 0.1 to 1.0 percent of Mg-Ca-Si-O glass phase and 0.5 to 2.5 percent of modified additive (selected from BaCO3, SrCO3 and the like), the core chemical formula of the main crystal phase is (MxCaLnz) TiO3, and during preparation, Mg / Zn salt, Ca salt, rare earth and TiO2 are mixed and calcined for 1-4 h at the temperature of 1050-1250 DEG C, and the main crystal phase is obtained; melting the Mg-Ca-Si-O mixture, and performing water quenching to obtain a glass phase; the three components are mixed in proportion, molded under 10MPa, and sintered at 1280-1400 DEG C for 2-5 hours. The room temperature dielectric constant of the material is 25-33, Qf is larger than or equal to 25000GHz, tau f (-40-110 DEG C)-10-30ppm / DEG C is adjustable, the cost is low, the sintering applicability is high, the requirements of microwave devices are met, the overall preparation steps are simple, key parameters (temperature, time, pressure and the like) are definite, the repeatability is good, and the industrial stable production requirements can be met.

Description

Technical Field

[0001] This invention relates to the field of ceramic dielectric technology, and more specifically, to a near-zero temperature coefficient dielectric microwave ceramic material and its preparation method. Background Technology

[0002] With the development of microwave communication technology, devices such as dielectric antennas and filters have higher requirements for the tunability of dielectric constant, temperature stability (temperature drift) and cost economy of materials: materials need to have a suitable dielectric constant to achieve reasonable device shape design and miniaturization, and the temperature coefficient needs to be controllable to ensure the stable performance of the device in a wide temperature range (such as -40~110℃).

[0003] In the existing technology, although Ta-based microwave ceramics have a suitable dielectric constant (25~30) and an extremely high Qf value (quality factor × frequency), they have two major drawbacks: First, the high cost of elements in the Ta system leads to high material and device manufacturing costs; second, the stringent requirements for sintering processes limit their application to the preparation of extremely small ceramic sheets, which cannot meet the needs of conventional antennas and filters for large-size, high-volume products, thus restricting their large-scale application.

[0004] In addition, single-component ceramics are difficult to balance dielectric constant and temperature coefficient: MgTiO3 has a low dielectric constant, which cannot meet the requirements of device miniaturization; although CaTiO3 and Ln2 / 3TiO3 (Ln=La, Sm, Nd) have high dielectric constants, their temperature coefficients are singular, making it difficult to adapt to the temperature drift requirements of different scenarios.

[0005] Therefore, there is an urgent need to develop a low-cost, temperature-coefficient, sintering-compatible, and microwave-performance dielectric microwave ceramic material. Summary of the Invention

[0006] This invention provides a near-zero temperature coefficient dielectric microwave ceramic material and its preparation method. This dielectric ceramic material has low dielectric loss, excellent microwave performance, and can obtain the required dielectric parameters and a highly adjustable temperature coefficient. At the same time, the preparation method is simple, easy to operate, and suitable for stable production.

[0007] To solve the above-mentioned technical problems, the present invention provides a near-zero temperature coefficient dielectric microwave ceramic material, wherein the dielectric microwave ceramic material comprises, by mass fraction, 97-98.5% main crystalline phase material, 0.1-1.0% glass phase material, and 0.5-2.5% modifying additives; The main crystalline phase material is prepared according to the stoichiometric formula (M) x Ca Ln z TiO3 is used as an ingredient in the batch; Among them, in (M) x Ca Ln z In TiO3, M is a mixture of 90%-100% Mg salt and 0-10% Zn salt, Ln is one or more of La, Sm, and Nd, and 0.6% Zn is a Mg salt. <x<0.92、0.03<y<0.3、0.03<z<0.3,x+y+z=1.0; The glass phase material B is a Mg-Ca-Si-O compound, comprising 40-60% MgO and CaO, and 40-60% SiO2, wherein, on a molar ratio basis, MgO / CaO = 2:1.

[0008] As a further optimization, the modified additive is one or more of BaCO3, SrCO3, CaTiO3, SrTiO3, Mn salt, Co salt, cerium oxide, and nickel salt.

[0009] As a further optimization, the mass fraction range of each component in the modified additive is: BaCO3 0~0.5%, SrCO3 0~0.5%, CaTiO3 0~2.5%, SrTiO3 0~2.5%, Mn salt 0~0.5%, Co salt 0~0.5%, cerium oxide 0~0.5%, and nickel salt 0~0.5%.

[0010] As a further optimization, the Mg salt is Mg(OH)2, the Zn salt is ZnO, the Ca salt is CaCO3, the Ln compound is Ln2O3, the Mn salt is MnO2, and the Co salt is Co2O3.

[0011] This application also provides a method for preparing the near-zero temperature coefficient dielectric microwave ceramic material as described in any one of the above claims, comprising the following steps: S1: Press (M) x Ca Ln z TiO3 is stoichiometrically mixed with Mg salt, Zn salt, Ca salt, Ln compound and TiO2, water is added and wet ball milling is performed. After drying, it is calcined in air at 1050~1250℃ for 1~4 hours to obtain the main crystalline phase material. S2: Mix Mg source, Ca source and Si source to obtain Mg-Ca-Si-O mixture, melt at 950~1050℃ for 15~45 minutes and then rapidly cold extract to obtain glass phase material; S3: Mix the main crystalline phase material, glass phase material and modifying additives in a mass ratio of (97~98.5%): (0.1~1.0%): (0.5~2.5%), add water and perform wet ball milling, and then dry to obtain ceramic powder; S4: Additives are added to ceramic powder, which is then ball-milled into a slurry, dried to obtain spherical particles, and pressed into green bodies under 10MPa. S5: Heat the green body to 1280~1400℃ at a rate of 100~200℃ / h, hold for 2~5 hours, and sinter into porcelain.

[0012] As a further optimization, in step S1, the mass ratio of the mixture to water is 1:(0.8~1.6), the calcination temperature is 1100~1150℃, and the calcination time is 3 hours.

[0013] As a further optimization, in step S2, the melting temperature is 980~1020℃, the melting time is 30 minutes, and the cold extraction water temperature is -5~25℃.

[0014] As a further optimization, in step S3, the mass ratio of the mixture to water is 1:(0.5~1.2), and the average particle size of the powder after ball milling is 0.55~0.85μm.

[0015] As a further optimization, in step S4, the additives include binders, plasticizers, and dispersants.

[0016] As a further optimization, in step S4, the green blank is a cylindrical green blank of 15×8mm.

[0017] By adopting the above technical solution, the present invention can achieve the following technical effects: This application provides a near-zero temperature coefficient dielectric microwave ceramic material and its preparation method. This material system does not contain precious metals such as Ta and Ge, resulting in low raw material costs and suitability for large-scale applications. By adjusting the proportions of Mg, Ca, and Ln in the main crystalline phase and the type / content of modifying additives, the temperature coefficient τf (-40~110℃) can be adjusted as needed within the range of -10~30ppm / ℃, meeting the temperature drift requirements of different microwave devices and exhibiting excellent temperature stability. At room temperature, the relative permittivity is 25~33 (suitable for miniaturized adapter designs), and the Qf value is ≥25000GHz (low dielectric loss), ensuring efficient signal transmission. The sintering temperature is 1280~1400℃ (conventional sintering range), enabling the preparation of large-size, high-volume products (such as antenna sheets), solving the problem that traditional Ta systems are only suitable for small-sized ceramic sheets. The overall preparation steps are simple, key parameters are clearly defined (temperature, time, pressure, etc.), and repeatability is good, meeting the requirements for stable industrial production. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention. Therefore, the following detailed description of the embodiments of the present invention is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0019] The present invention provides a near-zero temperature coefficient dielectric microwave ceramic material comprising 97-98.5% by mass of main crystalline phase material, 0.1-1.0% by mass of glassy phase material, and 0.5-2.5% by mass of modifying additives.

[0020] Preferably, the main crystalline phase material is prepared according to the stoichiometric formula (M... x Ca Ln z TiO3 is used as the feedstock. M is a mixture of 90%-100% Mg salt and 0-10% Zn salt, and Ln is one or more of La, Sm, and Nd, with a concentration of 0.6%. <x<0.92、0.03<y<0.3、0.03<z<0.3,x+y+z=1.0。

[0021] In a preferred embodiment, the Mg salt is Mg(OH)2, the Zn salt is ZnO, the Ca salt is CaCO3, the Ln compound is Ln2O3, the Mn salt is MnO2, and the Co salt is Co2O3.

[0022] In a preferred embodiment, the modifying additive is selected from one or more of BaCO3, SrCO3, CaTiO3, SrTiO3, Mn salt, Co salt, cerium oxide, and nickel salt.

[0023] The mass fraction range of each component in the modified additive is: BaCO3 0~0.5%, SrCO3 0~0.5%, CaTiO3 0~2.5%, SrTiO3 0~2.5%, Mn salt 0~0.5%, Co salt 0~0.5%, cerium oxide 0~0.5%, and nickel salt 0~0.5%.

[0024] Preferably, the glass phase material B is a Mg-Ca-Si-O compound, comprising 40-60% MgO and CaO, and 40-60% SiO2, wherein, on a molar ratio basis, MgO / CaO = 2:1.

[0025] Under the specified ratio of the main crystalline phase material and the appropriate additive, ceramic materials can be effectively modified, resulting in ceramic materials with a room temperature dielectric constant between 25 and 33, a quality factor Qf value greater than or equal to 25000 GHz, and a temperature coefficient τ. f (-40~110℃): -10~30ppm / ℃, adjustable as needed.

[0026] By optimizing the selection and proportion of modifying additives, the performance of this ceramic material can be further improved, for example, by further increasing the Qf value of the ceramic material.

[0027] This invention also provides a method for preparing the above-mentioned near-zero temperature coefficient dielectric microwave ceramic material, comprising the following steps: S1: Press (M) x Ca Ln z TiO3 is stoichiometrically mixed with Mg salt, Zn salt, Ca salt, Ln compound and TiO2, water is added and wet ball milling is performed. After drying, it is calcined in air at 1050~1250℃ for 1~4 hours to obtain the main crystalline phase material.

[0028] In a preferred embodiment, the mass ratio of the mixture to water is 1:(0.8~1.6), the calcination temperature is 1100~1150℃, and the calcination time is 3 hours.

[0029] S2: Mix Mg source, Ca source and Si source to obtain Mg-Ca-Si-O mixture, melt at 950~1050℃ for 15~45 minutes and then rapidly cold extract to obtain glass phase material.

[0030] In a preferred embodiment, the melting temperature is 980~1020℃, the melting time is 30 minutes, and the cold extraction water temperature is -5~25℃.

[0031] S3: Mix the main crystalline phase material, glass phase material and modifying additives in a mass ratio of (97~98.5%): (0.1~1.0%): (0.5~2.5%), add water and perform wet ball milling, and then dry to obtain ceramic powder.

[0032] In a preferred embodiment, the mass ratio of the mixture to water is 1:(0.5~1.2), and the average particle size of the powder after ball milling is 0.55~0.85μm.

[0033] In a preferred embodiment, the amount of glass phase material added is 0.2~0.5 wt%.

[0034] S4: Additives are added to ceramic powder, which is then ball-milled into a slurry, dried to obtain spherical particles, and pressed into green bodies under 10 MPa.

[0035] The additives include adhesives, plasticizers, and dispersants.

[0036] Specifically, as a preferred embodiment, the adhesive may be polyvinyl alcohol, the plasticizer may be polyethylene glycol, and the dispersant may be an ammonium carboxylate dispersant.

[0037] The pressed green body is cylindrical, measuring 15×8mm.

[0038] S5: After the green body is debonded and sintered, the product is obtained.

[0039] Specifically, the green body is heated to 1280-1400℃ in air at a rate of 100-200℃ / h, held at that temperature for 2-5 hours, and then sintered into ceramic to obtain ceramic material products.

[0040] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0041] Example This embodiment provides a near-zero temperature coefficient dielectric microwave ceramic material, which is prepared according to the following steps: (1) As shown in Table 1, according to the stoichiometric ratio of the main crystalline phase material, the corresponding oxides, carbonates, and alkali compounds were placed in a ball mill and wet ball milled at a mass ratio of 1:1.5 of the mixture and deionized water. After uniform mixing and spray drying, the mixture was calcined in an air furnace at 1150°C for 3 hours to synthesize the main crystalline phase material.

[0042] Table 1. Main Crystal Phase Material Proportioning Table

[0043] In this case, Ln is La:Nd = 50:1 in number 1; Sm:La = 2:1 in number 2; and Sm:La = 50:1 in number 3.

[0044] (2) According to the composition ratio in Table 2 below, add the modifying additives to the main crystalline phase material, and add deionized water at a mass ratio of 1:0.7 for wet ball milling. Ball mill until the volume average particle size of the powder reaches 0.55~0.85um.

[0045] Table 2 Ceramic Material Proportioning Table

[0046] (3) Add appropriate amounts of binder, plasticizer and dispersant to the powder obtained in step (2), and ball mill in a ball mill jar for 2 hours using zirconia balls as the ball milling medium to obtain a slurry. Centrifuge and spray dry the slurry to obtain spherical particles with good flowability.

[0047] (4) The spherical particles obtained in step (3) are pressed into a cylindrical green body with a size of 15*8mm under a pressure of 5~10MPa.

[0048] (5) The green body obtained in step (4) is sintered in an air atmosphere. The temperature is rapidly increased to 1280-1400℃ at a heating rate of 100℃~200℃ / h, and the holding time is 3~5h.

[0049] Numbered ceramic device samples with each component ratio were obtained.

[0050] Test case For the samples obtained in the examples, the performance was tested using an Agilent network analyzer with the parallel plate resonance method. The test results are shown in Table 3:

[0051] Table 3 Performance Test Results As shown in Table 3, the microwave dielectric ceramic material obtained by the above preparation method can be sintered at 1280-1400℃ to form microwave dielectric ceramic devices. By adjusting the material synthesis ratio, a room temperature dielectric constant of 25~33, a temperature coefficient τf (-40~110℃): -10~30ppm / ℃, and a Qf value ≥25000GHz can be formed, which meets the performance requirements of microwave devices.

[0052] In summary, the near-zero temperature coefficient dielectric microwave ceramic material and its preparation method provided in this application have a material system free of precious metals such as Ta and Ge, resulting in low raw material costs and suitability for large-scale applications. By adjusting the proportions of Mg, Ca, and Ln in the main crystal phase and the type / content of modifying additives, the temperature coefficient τf (-40~110℃) can be adjusted as needed within the range of -10~30ppm / ℃, meeting the temperature drift requirements of different microwave devices. The relative permittivity at room temperature is 25~33 (suitable for miniaturized adapter design), and the Qf value is ≥25000GHz (low dielectric loss), ensuring the signal transmission efficiency of the device. The sintering temperature is 1280~1400℃ (conventional sintering range), enabling the preparation of large-size, high-volume products (such as antenna sheets), solving the problem that traditional Ta systems are only suitable for small-sized ceramic sheets. The overall preparation steps are simple, the key parameters are clearly defined (temperature, time, pressure, etc.), and the repeatability is good, meeting the requirements for stable industrial production.

[0053] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the invention by those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the invention should be included within the scope of protection of the invention.

Claims

1. A near-zero temperature coefficient dielectric microwave ceramic material, characterized in that, The dielectric microwave ceramic material, by mass fraction, comprises 97-98.5% main crystalline phase material, 0.1-1.0% glassy phase material, and 0.5-2.5% modifying additives; The main crystalline phase material is prepared according to the stoichiometric formula (M) x Ca Ln z TiO3 is used as an ingredient in the batch; Among them, in (M) x Ca Ln z In TiO3, M is a mixture of 90%-100% Mg salt and 0-10% Zn salt, Ln is one or more of La, Sm, and Nd, and 0.6% Zn is a Mg salt. <x<0.92、0.03<y<0.3、0.03<z<0.3,x+y+z=1.0; The glass phase material B is a Mg-Ca-Si-O compound, comprising 40-60% MgO and CaO, and 40-60% SiO2, wherein, on a molar ratio basis, MgO / CaO = 2:

1.

2. The near-zero temperature coefficient dielectric microwave ceramic material according to claim 1, characterized in that... The modified additive is one or more of BaCO3, SrCO3, CaTiO3, SrTiO3, Mn salt, Co salt, cerium oxide, and nickel salt.

3. The near-zero temperature coefficient dielectric microwave ceramic material according to claim 2, characterized in that... The mass fraction range of each component in the modified additive is as follows: BaCO3 0~0.5%, SrCO3 0~0.5%, CaTiO3 0~2.5%, SrTiO3 0~2.5%, Mn salt 0~0.5%, Co salt 0~0.5%, cerium oxide 0~0.5%, and nickel salt 0~0.5%.

4. The near-zero temperature coefficient dielectric microwave ceramic material according to claim 1, characterized in that... ,in, Mg salt is Mg(OH)2, Zn salt is ZnO, Ca salt is CaCO3, Ln compound is Ln2O3, Mn salt is MnO2, and Co salt is Co2O3.

5. A method for preparing a near-zero temperature coefficient dielectric microwave ceramic material as described in any one of claims 1 to 4, characterized in that... This includes the following steps: S1: Press (M) x Ca Ln z TiO3 is stoichiometrically mixed with Mg salt, Zn salt, Ca salt, Ln compound and TiO2, water is added and wet ball milling is performed. After drying, it is calcined in air at 1050~1250℃ for 1~4 hours to obtain the main crystalline phase material. S2: Mix Mg source, Ca source and Si source to obtain Mg-Ca-Si-O mixture, melt at 950~1050℃ for 15~45 minutes and then rapidly cold extract to obtain glass phase material; S3: Mix the main crystalline phase material, glass phase material and modifying additives in a mass ratio of (97~98.5%): (0.1~1.0%): (0.5~2.5%), add water and perform wet ball milling, and then dry to obtain ceramic powder; S4: Additives are added to ceramic powder, which is then ball-milled into a slurry, dried to obtain spherical particles, and pressed into green bodies under 10MPa. S5: Heat the green body to 1280~1400℃ at a rate of 100~200℃ / h, hold for 2~5 hours, and sinter into porcelain.

6. The method for preparing the near-zero temperature coefficient dielectric microwave ceramic material according to claim 5, characterized in that... In step S1, the mass ratio of the mixture to water is 1:(0.8~1.6), the calcination temperature is 1100~1150℃, and the calcination time is 3 hours.

7. The method for preparing the near-zero temperature coefficient dielectric microwave ceramic material according to claim 5, characterized in that... In step S2, the melting temperature is 980~1020℃, the melting time is 30 minutes, and the cold extraction water temperature is -5~25℃.

8. The method for preparing the near-zero temperature coefficient dielectric microwave ceramic material according to claim 5, characterized in that... In step S3, the mass ratio of the mixture to water is 1:(0.5~1.2), and the average particle size of the powder after ball milling is 0.55~0.85μm.

9. The method for preparing the near-zero temperature coefficient dielectric microwave ceramic material according to claim 5, characterized in that... In step S4, the additives include adhesives, plasticizers, and dispersants.

10. The method for preparing the near-zero temperature coefficient dielectric microwave ceramic material according to claim 5, characterized in that... In step S4, the green blank is a cylindrical green blank of 15×8mm.

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