Low-dielectric-loss magnesium silicate system microwave dielectric ceramic and low-temperature preparation method thereof
By preparing Mg2.1SiO4.1-xCaTiO3-yLiF multiphase composite microwave dielectric ceramics at low temperature, the problems of high sintering temperature and poor sintering characteristics of Mg2SiO4 ceramics were solved, and microwave dielectric ceramic materials with dielectric constant less than 10 and high quality factor were realized, which are suitable for high-frequency communication components.
Patent Information
- Application Number
- CN202411212535.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2024-08-30
- Publication Date
- 2025-10-21
- Estimated Expiration
- 2044-08-30
AI Technical Summary
Mg2SiO4 ceramics have high sintering temperature, poor sintering characteristics, and large negative temperature coefficient, which limit their application in microwave dielectric ceramic materials.
A low-temperature preparation method was adopted, in which a mixed slurry was formed by primary and secondary ball milling. CaTiO3 and LiF were added to adjust the temperature stability and dielectric loss. Mg2.1SiO4.1-xCaTiO3-yLiF multiphase composite microwave dielectric ceramics were synthesized by traditional solid-state reaction method.
It lowers the sintering temperature of ceramics, improves microwave dielectric properties, has a dielectric constant of less than 10 and is adjustable, has a high quality factor, and a resonant frequency temperature coefficient close to zero, making it suitable for microwave communication components such as dielectric resonators and dielectric filters.
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Figure CN119038979B_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the technical field of wireless communication and electronic ceramic materials, and particularly relates to a magnesium silicate system microwave dielectric ceramic and a low-temperature preparation method thereof. Background Art
[0002] Microwaves, the electromagnetic waves with the shortest wavelength, possess strong penetration, good directionality, robust anti-interference capabilities, and high signal capacity. They are widely used in fields such as radar technology and mobile communications. In recent years, the evolution of mobile communication technology has continuously pushed microwave application frequency bands toward higher frequencies. To meet the development requirements of 5G / 6G communication technologies, microwave dielectric ceramics, as key materials for electronic components, should have a dielectric constant less than 10, a high quality factor, and a resonant frequency temperature coefficient close to zero. A low dielectric constant reduces signal transmission delay, while a high quality factor ensures frequency selectivity during signal transmission. Low-temperature co-fired ceramic (LTCC) technology is a recently developed passive integrated component technology. It embeds various components within a multilayer ceramic substrate, using metals such as silver as electrodes to create high-density circuits or three-dimensional circuit substrates with built-in passive components without interference in three dimensions. ICs and active devices are then mounted on the surface of the substrate to form passive / active integrated functional modules. This further minimizes and increases circuit density, making it particularly suitable for high-frequency communication components. In order to realize the LTCC application of microwave dielectric ceramics, its sintering temperature is required to be lower than the melting point of the Ag electrode (961°C).
[0003] Mg2SiO4 dielectric materials are readily available and inexpensive, and they exhibit a low dielectric constant and a high quality factor. Despite these advantages, conventional solid-phase reaction methods, when used to prepare them, suffer from poor sintering characteristics. Sintered samples are porous, resulting in increased dielectric losses and a significant decrease in quality factor. Furthermore, Mg2SiO4 ceramic samples require high sintering temperatures and exhibit a negative resonant frequency temperature coefficient, significantly limiting their application. Therefore, further research is needed to overcome these limitations and produce microwave dielectric ceramic materials that meet the requirements of communication devices. Summary of the Invention
[0004] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a low-dielectric and low-loss magnesium silicate system microwave dielectric ceramic and a low-temperature preparation method thereof to solve the problems of high sintering temperature, poor sintering characteristics and negative temperature coefficient of Mg2SiO4 ceramics.
[0005] To achieve the above-mentioned object, the technical solution adopted by the present invention is: a low-temperature preparation method of low-dielectric and low-loss magnesium silicate system microwave dielectric ceramics, characterized in that the specific steps are as follows:
[0006] (1) Primary ball milling: MgO and SiO2 are mixed in proportion and then wet-milled to obtain a mixed slurry S1; CaCO3 and TiO2 are mixed in proportion and then wet-milled to obtain a mixed slurry S2, wherein the ball milling time is controlled within 12 to 16 hours;
[0007] (2) Primary drying: The mixed slurry S1 and the mixed slurry S2 are placed in an oven and dried to constant weight to obtain dried mixed materials S1 and S2;
[0008] (3) Pre-calcination: The mixed material S1 is dispersed through a 120-200 mesh standard sieve and then pre-calcined in a high temperature furnace to synthesize
[0009] Mg 2.1 SiO 4.1 Compound powder; the mixed material S2 is dispersed through a 120-200 mesh standard sieve and then pre-calcined in a high-temperature furnace to synthesize a CaTiO3 compound powder;
[0010] (4) Secondary ball milling: Mg 2.1 SiO 4.1 , CaTiO3 and LiF compound powders are mixed in proportion and wet ball milled to form a mixture slurry S3, wherein the ball milling time is controlled within 4 to 6 hours;
[0011] (5) Secondary drying: The mixture slurry S3 is placed in an oven and dried to constant weight to obtain Mg 2.1 SiO 4.1 -xCaTiO3-yLiF mixture powder;
[0012] (6) Granulation: Mg 2.1 SiO 4.1 -xCaTiO3-yLiF mixture powder is passed through a 120-200 mesh standard sieve and then added
[0013] The binder is ground and mixed uniformly using an agate mortar to obtain a powder for pressing;
[0014] (7) Compression molding: Pressing the powder for compression molding into a ceramic green body;
[0015] (8) Debinding sintering: Place the ceramic green body in a high-temperature furnace, heat it to 550-700℃ at a certain heating rate, and then keep it warm to remove the binder. The holding time is 2-3 hours. Then, increase the temperature to 850-1000℃ at the same heating rate and keep it warm for 3-4 hours. Finally, cool it to 200-300℃ at a certain cooling rate and cool it naturally in the furnace.
[0016] Furthermore, in the first ball milling step (1), MgO and SiO2 are subjected to the chemical formula Mg 2.1 SiO 4.1The ingredients are mixed in a stoichiometric ratio, and CaCO3 and TiO2 are mixed in a stoichiometric ratio according to the chemical formula CaTiO3.
[0017] In step (3) pre-firing, the pre-firing temperature of the mixture S1 is controlled to be 1100-1200°C, and the pre-firing temperature of the mixture S2 is controlled to be 1200-1300°C.
[0018] Step (4) During the secondary ball milling, LiF and pre-sintered Mg 2.1 SiO 4.1 、CaTiO3 according to the chemical formula Mg 2.1 SiO 4.1 -xCaTiO3-yLiF is prepared in a stoichiometric ratio, wherein x=0.09-0.13, y=0.05-0.25.
[0019] In the first ball milling of step (1) and the second ball milling of step (4), the wet ball milling uses a polytetrafluoroethylene ball milling jar, zirconia grinding balls and a planetary ball mill, wherein the ball milling aid is anhydrous ethanol. During ball milling, the volume ratio of powder, zirconia grinding balls and anhydrous ethanol is 1:1:(1 to 1.5).
[0020] In the first drying of step (2) and the second drying of step (5), the drying temperature is controlled at 80-110°C.
[0021] In the granulation step (6), the binder is polyvinyl alcohol (PVA), and the weight ratio of the mixture powder to the polyvinyl alcohol is 100:(5-10).
[0022] In step (8) debinding and sintering, the heating rate is 3-5°C / min, and the cooling rate is 2-3°C / min.
[0023] Furthermore, in step (8) of debinding and sintering, when the temperature is raised to 550-700°C, the holding time is preferably 2 hours; when the temperature is raised to 850-1000°C, the holding time is preferably 3 hours.
[0024] The present invention also provides a low-dielectric and low-loss magnesium silicate system microwave dielectric ceramic prepared by the low-temperature preparation method, wherein the dielectric constant is less than 10 and is adjustable within a range of 7.76 to 8.81, the quality factor Q×f=56821 to 105803 GHz, and the resonant frequency temperature coefficient is τ f =-23~-4ppm / ℃.
[0025] The beneficial effects of the present invention are: using Mg2SiO4 ceramic with low dielectric constant as the matrix, 2+ Non-stoichiometric reduction of dielectric loss, CaTiO3 composite to adjust temperature stability, LiF composite to reduce sintering temperature, Mg was synthesized by traditional solid phase reaction method. 2.1SiO 4.1 -xCaTiO3-yLiF multiphase composite microwave dielectric ceramic. The multiphase composite improves the microwave dielectric properties of the ceramic and reduces the sintering temperature of the ceramic sample. This invention provides an alternative material for microwave communication components such as dielectric resonators and dielectric filters, as well as LTCC high-frequency communication components, and has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS
[0026] Figure 1 The Mg content of the preferred sintering temperature of Examples 1 to 6 of the present invention is 2.1 SiO 4.1 -XRD pattern of xCaTiO3-yLiF ceramics.
[0027] Figure 2 The Mg content of the preferred sintering temperature of Examples 1 to 6 of the present invention is 2.1 SiO 4.1 -SEM image of xCaTiO3-yLiF ceramics.
[0028] Figure 3 Mg prepared in Examples 1 to 6 of the present invention 2.1 SiO 4.1 -Graph of the dielectric constant of xCaTiO3-yLiF ceramics.
[0029] Figure 4 Mg prepared in Examples 1 to 6 of the present invention 2.1 SiO 4.1 -Graph showing the quality factor of xCaTiO3-yLiF ceramics.
[0030] Figure 5 Mg prepared in Examples 1 to 6 of the present invention 2.1 SiO 4.1 -Graph showing the resonant frequency temperature coefficient of xCaTiO3-yLiF ceramics. DETAILED DESCRIPTION
[0031] The principles and features of the present invention are described below with reference to the accompanying drawings. The examples given are only used to explain the present invention and are not used to limit the scope of the present invention.
[0032] Example 1
[0033] A low-temperature preparation method for low-dielectric and low-loss magnesium silicate system microwave dielectric ceramics, comprising the following specific steps:
[0034] (1) Primary ball milling: Weigh 105.2720 g of MgO and 74.7280 g of SiO2 into a polytetrafluoroethylene ball mill, use zirconium oxide as grinding balls, and use anhydrous ethanol as a ball milling aid. Wet ball mill the mixture for 12 h in a planetary ball mill. The volume ratio of powder: zirconium oxide grinding balls: anhydrous ethanol is 1:1:1.25 to obtain a mixed slurry S1. Separately, weigh 11.0434 g of CaCO3 and 8.8124 g of TiO2 into a polytetrafluoroethylene ball mill and ball mill the mixture in the same manner as above to obtain a mixed slurry S2.
[0035] (2) Primary drying: pour out the mixed slurry S1 and the mixed slurry S2, place them in an oven at 80°C and dry them to constant weight to obtain dried mixed materials S1 and S2;
[0036] (3) Pre-calcination: The dried mixed material S1 is first passed through a 120-200 mesh standard sieve, dispersed, and then pre-calcined in a high-temperature furnace at a pre-calcination temperature of 1150°C to synthesize Mg 2.1 SiO 4.1 Compound powder; the dried mixture S2 is first passed through a 120-200 mesh standard sieve, dispersed, and then pre-calcined in a high-temperature furnace at a pre-calcination temperature of 1300°C to synthesize CaTiO3 compound powder;
[0037] (4) Secondary ball milling: According to the chemical formula Mg 2.1 SiO 4.1 -0.09CaTiO3-0.11LiF stoichiometric ratio for mixing, weigh Mg 2.1 SiO 4.1 20.0000g of powder, 1.6907g of CaTiO3 powder and 0.4000g of LiF were mixed and added with anhydrous ethanol, and the mixture was placed in a planetary ball mill for wet ball milling for 4h to form Mg 2.1 SiO 4.1 -0.09CaTiO3-0.11LiF mixture slurry S3;
[0038] (5) Secondary drying: Mg 2.1 SiO 4.1 The slurry S3 of the 0.09CaTiO3-0.11LiF mixture was taken out and dried in an oven at 80°C to a constant weight to obtain Mg 2.1 SiO 4.1 -0.09CaTiO3-0.11LiF mixture powder;
[0039] (6) Granulation: The dried Mg 2.1 SiO 4.1The 0.09CaTiO3-0.11LiF mixture powder was first passed through a standard sieve of 120-200 mesh, and then a binder, polyvinyl alcohol, was added at a weight ratio of the mixture powder to polyvinyl alcohol of 100:8. The mixture was ground and mixed uniformly using an agate mortar to obtain a powder for pressing;
[0040] (7) Compression molding: A certain amount of powder was weighed and poured into a mold, and then four ceramic green pieces with a diameter of 12 mm and a height of 7 mm were pressed in a tablet press at a pressure of 100 MPa for 3 min.
[0041] (8) Debinding and sintering: Place the four pressed ceramic green bodies into a high-temperature furnace respectively, set the furnace heating rate to 5℃ / min, heat to 600℃ and keep for 2h to debind, then increase the temperature at the same heating rate, and sinter the four green bodies to 850℃, 900℃, 950℃ and 1000℃ respectively, keep warm for 3h, then cool to 200℃ at a cooling rate of 2℃ / min, stop the program and let the furnace cool down naturally; take out the sample, grind it to 1000 mesh with sandpaper, and finally ultrasonically clean it. In this example, the preferred sintering temperature is 950℃. The XRD spectrum of the ceramics prepared at this temperature is shown in Figure 1 、SEM images see Figure 2 .
[0042] Example 2
[0043] A low-temperature preparation method for low-dielectric and low-loss magnesium silicate system microwave dielectric ceramics, comprising the following specific steps:
[0044] (1)-(3) are the same as in Example 1.
[0045] (4) Secondary ball milling: According to the chemical formula Mg 2.1 SiO 4.1 The ingredients were prepared in a stoichiometric ratio of -0.10CaTiO3-0.11LiF, and 1.8785g of CaTiO3 powder was weighed. Other ingredients were the same as in Example 1.
[0046] (5) Secondary drying: The drying temperature is 110° C., and the rest is the same as in Example 1.
[0047] (6) Granulation: Same as Example 1.
[0048] (7) Compression molding: Same as Example 1.
[0049] (8) Debinding sintering: the heating rate is 3°C / min, and the rest is the same as in Example 1.
[0050] Example 3
[0051] A low-temperature preparation method for low-dielectric and low-loss magnesium silicate system microwave dielectric ceramics, comprising the following specific steps:
[0052] (1)-(3) are the same as in Example 1.
[0053] (4) Secondary ball milling: According to the chemical formula Mg 2.1 SiO 4.1 The ingredients were prepared in a stoichiometric ratio of -0.11CaTiO3-0.11LiF, and 2.0664g of CaTiO3 powder was weighed. Other ingredients were the same as in Example 1.
[0054] (5) Secondary drying: The drying temperature is 110° C., and the rest is the same as in Example 1.
[0055] (6) Granulation: The weight ratio of the mixture powder to polyvinyl alcohol is 100:8, and the rest is the same as in Example 1.
[0056] (7)-(8): Same as Example 1.
[0057] Example 4
[0058] A low-temperature preparation method for low-dielectric and low-loss magnesium silicate system microwave dielectric ceramics, comprising the following specific steps:
[0059] (1)-(3) are the same as in Example 1.
[0060] (4) Secondary ball milling: According to the chemical formula Mg 2.1 SiO 4.1 The ingredients were prepared in a stoichiometric ratio of -0.12CaTiO3-0.11LiF, and 2.2543g of CaTiO3 powder was weighed. During ball milling, the volume ratio of powder: zirconium oxide grinding balls: anhydrous ethanol was 1:1:1. Other parameters were the same as in Example 1.
[0061] (5)-(8): Same as Example 1.
[0062] Example 5
[0063] A low-temperature preparation method for low-dielectric and low-loss magnesium silicate system microwave dielectric ceramics, comprising the following specific steps:
[0064] (1)-(3) are the same as in Example 1.
[0065] (4) Secondary ball milling: According to the chemical formula Mg 2.1 SiO 4.1 The ingredients were prepared in a stoichiometric ratio of -0.13CaTiO3-0.11LiF, and 2.4420g of CaTiO3 powder was weighed. Other ingredients were the same as in Example 1.
[0066] (5)-(8): Same as Example 1.
[0067] In this case, the ceramic sample exhibits excellent comprehensive dielectric properties, with a dielectric constant ε r =8.61, Q×f up to 82236GHz, τf =-4ppm / ℃, and the sintering temperature is only 950℃.
[0068] Example 6
[0069] A low-temperature preparation method for low-dielectric and low-loss magnesium silicate system microwave dielectric ceramics, comprising the following specific steps:
[0070] (1)-(3) are the same as in Example 1.
[0071] (4) Secondary ball milling: According to the chemical formula Mg 2.1 SiO 4.1 The ingredients were prepared in a stoichiometric ratio of -0.09CaTiO3-0.22LiF, and 0.8000g of LiF was weighed. Other ingredients were the same as in Example 1.
[0072] (5) Secondary drying: Same as Example 1.
[0073] (6) Granulation: The weight ratio of the mixture powder to polyvinyl alcohol is 100:6, and the rest is the same as in Example 1.
[0074] (7)-(8): Same as Example 1.
[0075] In this example, the preferred sintering temperature is 900° C. As the LiF doping amount increases, a glass phase is easily formed during sintering at a higher temperature, which affects the microwave dielectric properties.
[0076] Example 7: Figure 1-Figure 5 As shown, the present invention also provides a low-dielectric and low-loss magnesium silicate system microwave dielectric ceramic prepared by the low-temperature preparation method, whose dielectric constant is less than 10 and is adjustable in the range of 7.76 to 8.81, the quality factor Q×f=56821~105803GHz, and the resonant frequency temperature coefficient is τ f =-23~-4ppm / ℃.
[0077] Figure 1 In the experiment, XRD analysis revealed that ceramic samples with multiphase coexistence of Mg2SiO4, CaTiO3, Mg2TiO4 and CaF2 were obtained, while the Li element volatilized during sintering. Figure 2 It can be concluded that the main phase of the sample Mg2SiO4 has a large grain distribution, and a small amount of pores are left after the Li element evaporates. 2.1 SiO 4.1 -xCaTiO3-yLiF ceramic system, the sample has excellent dielectric properties, its dielectric constant is less than 10 and adjustable, the adjustable range is 7.76 ~ 8.81 (see Figure 3 ) and excellent quality factor (Q×f=56821~105803GHz) (see Figure 4). While having a small dielectric constant, it also has a resonant frequency temperature coefficient close to zero (τ f =-23~-4ppm / ℃)(See Figure 5 ).
[0078] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.
Claims
1. A low-temperature preparation method for low-dielectric and low-loss magnesium silicate system microwave dielectric ceramics, characterized in that: The specific steps are as follows: (1) Primary ball milling: MgO and SiO2 were mixed in proportion and then wet-milled to obtain a mixed slurry S1; CaCO3 and TiO2 were mixed in proportion and then wet-milled to obtain a mixed slurry S2. The ball milling time was controlled at 12 to 16 h. Among them, MgO and SiO2 are chemically 2.1 SiO 4.1 The ingredients are mixed in a stoichiometric ratio, and CaCO3 and TiO2 are mixed in a stoichiometric ratio according to the chemical formula CaTiO3; (2) Primary drying: The mixed slurry S1 and the mixed slurry S2 are placed in an oven and dried to constant weight to obtain dried mixed materials S1 and S2; (3) Pre-burning: The mixed material S1 is dispersed through a 120-200 mesh standard sieve and then pre-burned in a high temperature furnace to synthesize Mg 2.1 SiO 4.1 Compound powder; the mixture S2 is dispersed through a 120~ 200 mesh standard sieve and then pre-calcined in a high-temperature furnace to synthesize a CaTiO3 compound powder; (4) Secondary ball milling: Mg 2.1 SiO 4.1 , CaTiO3 and LiF compound powders are mixed in proportion and wet ball milled to form a mixture slurry S3, wherein the ball milling time is controlled within 4 to 6 hours; Among them, LiF and pre-calcined Mg 2.1 SiO 4.1 、CaTiO3 according to the chemical formula Mg 2.1 SiO 4.1 - x CaTiO3- y The stoichiometric ratio of LiF is used for batching, where x = 0.09 ~ 0.13, y = 0.05 ~ 0.25; (5) Secondary drying: Place the mixture slurry S3 in an oven and dry it to constant weight to obtain Mg 2.1 SiO 4.1 -xCaTiO3-yLiF mixture powder; (6) Granulation: Mg 2.1 SiO 4.1 The xCaTiO3-yLiF mixture powder was passed through a standard sieve of 120-200 mesh, and then a binder was added. The mixture was ground and mixed uniformly using an agate mortar to obtain a powder for pressing. (7) Pressing: Pressing the powder for pressing into a ceramic green body; (8) Debinding sintering: Place the ceramic green body in a high-temperature furnace, heat it to 550-700 °C at a certain heating rate, and then keep it warm to remove the binder. The holding time is 2-3 h. Then, increase the temperature to 850-1000 °C at the same heating rate and keep it warm for 3-4 h. Finally, cool it down to 200-300 °C at a certain cooling rate and then cool it naturally in the furnace. The magnesium silicate system microwave dielectric ceramic prepared by the method has a dielectric constant of less than 10 and is adjustable in the range of 7.76 to 8.81, and a quality factor Q× f =56821 ~ 105803 GHz, the resonant frequency temperature coefficient is τ f = -23 ~ -4 ppm / ℃.
2. The low-temperature preparation method of the low-dielectric and low-loss magnesium silicate system microwave dielectric ceramic according to claim 1, characterized in that: In the pre-firing step (3), the pre-firing temperature of the mixture S1 is controlled to be 1100 ~ 1200 °C, and the pre-firing temperature of the mixture S2 is controlled to be 1200 ~ 1300 °C.
3. The low-temperature preparation method of the low-dielectric and low-loss magnesium silicate system microwave dielectric ceramic according to claim 1, characterized in that: In the first ball milling of step (1) and the second ball milling of step (4), the wet ball milling uses a polytetrafluoroethylene ball milling jar, zirconia grinding balls and a planetary ball mill, wherein the ball milling aid is anhydrous ethanol. During ball milling, the volume ratio of powder, zirconia grinding balls and anhydrous ethanol is 1:1:(1-1.5).
4. The low-temperature preparation method of the low-dielectric and low-loss magnesium silicate system microwave dielectric ceramic according to claim 1, characterized in that: In the first drying of step (2) and the second drying of step (5), the drying temperature is controlled at 80-110°C.
5. The low-temperature preparation method of the low-dielectric and low-loss magnesium silicate system microwave dielectric ceramic according to claim 1, characterized in that: In the granulation step (6), the binder is polyvinyl alcohol, and the weight ratio of the mixture powder to the polyvinyl alcohol is 100:(5-10).
6. The low-temperature preparation method of the low-dielectric and low-loss magnesium silicate system microwave dielectric ceramic according to claim 1, characterized in that: In the debinding sintering step (8), the heating rate is 3 to 5 °C / min, and the cooling rate is 2 to 3 °C / min.
7. The low-temperature preparation method of the low-dielectric and low-loss magnesium silicate system microwave dielectric ceramic according to any one of claims 1 to 6, characterized in that: In the debinding sintering step (8), when the temperature is raised to 550-700°C, the holding time is 2 h; when the temperature is raised to 850-1000°C, the holding time is 3 h.