Low dielectric microwave dielectric ceramic with intrinsic near-zero temperature coefficient of resonance frequency and preparation method thereof

Abstract

The invention discloses a low-dielectric microwave dielectric ceramic with an intrinsic near-zero temperature coefficient of resonance frequency and a preparation method of the low-dielectric microwave dielectric ceramic. Raw materials CaCO3, Ga2O3 and SiO2 are mixed according to the stoichiometric ratio of the chemical formula Ca2Ga2SiO7, and a high-temperature solid-phase synthesis method is adopted for preparation. The preparation method is simple, the dielectric constant (epsilon r) of the prepared low-dielectric microwave dielectric ceramic material is 8.0-10.5, the quality factor (Q * f) is 35000-95000 GHz, and the temperature coefficient of resonance frequency (tau f) is-3.0 ppm / DEG C to + 3.0 ppm / DEG C.

Description

Technical Field

[0001] The invention relates to a microwave dielectric ceramic material for manufacturing microwave components such as ceramic substrates, resonators and filters used at microwave frequencies and a preparation method thereof, belonging to the technical field of microwave dielectric ceramic materials. Background Art

[0002] Microwave dielectric ceramics refer to ceramics used as dielectric materials in microwave frequency band (300MHz~300GHz, corresponding to electromagnetic wavelength of 1m~1mm) circuits and perform certain functions. They are made into dielectric devices such as filters, resonators, duplexers, and dielectric antennas, and are widely used in satellite radar, mobile communications, and global positioning systems. The three main indicators for measuring the performance of microwave dielectric materials are dielectric constant (ε r ), quality factor (Q×f) and resonant frequency temperature coefficient (τ f ). With the development of 5G / 6G communication technology, high frequency and large bandwidth characteristics require more dense macro and micro base stations to ensure full signal coverage, which is bound to bring huge market demand for microwave dielectric ceramic materials and components (dielectric antennas, dielectric filters and substrates). At the same time, with the continuous improvement of communication frequency and device integration, signal delay will become more obvious, the heat generated by system loss will also increase significantly, and the thermal stability of the device will gradually deteriorate. Therefore, it is urgent to have materials with low dielectric constant (ε r <15) reduce signal delay and the exchange coupling loss between materials and electrodes, high quality factor to improve frequency selection characteristics and reduce transmission loss, and near-zero resonant frequency temperature coefficient to ensure the temperature stability of microwave circuits. However, most of the single-phase low-dielectric (ε r <15) Ceramics usually exhibit a large negative τ f Value (-20 ~ -80 ppm / o C), cannot meet the current high standard requirements of 5G. 2 O 3 ε r is 10, Q×f value is as high as 335000 GHz, but τ f A large negative value of -60 ppm / °C; spinel structure (Zn / Mg)Al 2 O 4 Ceramic ε r is between 8.5 and 9.0, and the Q×f value can reach 56000 ~ 100000GHz, but its τ f It is a relatively negative value of -70 ~ -80 ppm / °C; (Zn / Mg) of olivine structure 2 SiO 4 Ceramic ε rThe Q×f value ranges from 22000 to 270000 GHz, but it shows a large negative τ f Value (-61 ~ -67ppm / °C); cubic garnet Y 3 Al 5 O 12 With low ε r (10.5), high Q×f value (440000 GHz) and large negative τ f Value (-60 ppm / °C); clinopyroxene structure CaMgSi 2 O 6 Ceramic ε r The lowest is 7.6, and the Q×f value can be as high as 120000GHz, but τ f Value is -66 ppm / °C; wolframite structure (Mg / Zn) WO 4 Ceramic ε r is between 10 and 13.5, the Q×f value can reach 62800 GHz, τ f The value range is -30~-64 ppm / °C.

[0003] To adjust the resonant frequency temperature coefficient (τ f ) is close to zero to ensure the thermal stability of microwave components. The main method currently used is the composite positive τ f Value materials (such as TiO 2 、CaTiO 3 However, this method may have the following difficulties: 1) The main crystal phase chemically reacts with the Ti-based material and loses the control effect, for example, TiO 2 Regulation of Mg 3 Ga 2 GeO 8 When the reaction generates MgTiO 3 The phase is still negative τ f value; 2) Ti-based materials usually have high ε r and low Q×f value, resulting in the ε r Increase and Q×f value decrease; 3) When sintered at higher temperatures, Ti-based materials are prone to Ti 4+ Partially reduced to Ti 3+ , resulting in a sharp increase in loss. Therefore, a new type of intrinsic τ f Low-K microwave dielectric materials with near-zero resonant frequency and low loss are very necessary. In order to solve the above problems, the present invention provides a low-K microwave dielectric ceramic with an intrinsic near-zero resonant frequency temperature coefficient and a method for preparing the microwave dielectric ceramic. Summary of the invention

[0004] To solve the above problems, the purpose of the present invention is to provide a compound for use in preparing a low dielectric constant microwave dielectric ceramic with an intrinsic near-zero resonant frequency temperature coefficient. The microwave dielectric ceramic of the present invention has a low dielectric constant and a high quality factor, and the resonant frequency temperature coefficient ranges from -3.0 ppm / ℃ to +3.0 ppm / ℃.

[0005] To achieve the above-mentioned purpose, the present invention provides a low-k microwave dielectric ceramic with an intrinsic near-zero resonant frequency temperature coefficient, wherein the chemical formula of the low-k microwave dielectric ceramic is Ca 2 Ga 2 SiO 7 .

[0006] Preferably, the dielectric constant (ε r ) is 8.0 ~ 10.5, the quality factor (Q×f) is 35000 ~ 95000 GHz, and the resonant frequency temperature coefficient (τ f ) is –3.0 ppm / ℃ ~ +3.0 ppm / ℃.

[0007] Furthermore, the present invention also provides a method for preparing the low-k microwave dielectric ceramic having an intrinsic near-zero resonant frequency temperature coefficient, comprising the following steps:

[0008] (1) Weigh CaCO 3 , Ga 2 O 3 and SiO 2 The raw material powder is according to the chemical formula Ca 2 Ga 2 SiO 7 The ingredients are prepared in a stoichiometric ratio, mixed evenly with a dispersant, and then subjected to a first wet ball milling treatment, followed by drying and pre-calcining to obtain a pre-calcined powder;

[0009] (2) The pre-sintered powder obtained in step (1) is mixed evenly with a dispersant and then subjected to a second wet ball milling treatment. After drying, a binder is added to granulate the powder, and the powder is pressed and sintered to obtain the low-k microwave dielectric ceramic.

[0010] Preferably, the dispersant for the first wet ball milling treatment and the second wet ball milling treatment is deionized water. By mass, the amount of deionized water used in the first wet ball milling treatment is twice the total amount of ingredients, and the amount of deionized water used in the second wet ball milling treatment is twice the total amount of ingredients. The ball milling medium is zirconium balls, the ball milling speed is 200 to 360 r / min, and the ball milling time is 3 to 10 h.

[0011] Preferably, in step (1), the pre-firing temperature is 1000 to 1150° C., and the pre-firing time is 3 to 12 h.

[0012] Preferably, in step (2), the adhesive is PVA (polyvinyl alcohol), and the mass fraction of the adhesive is 4 to 10%.

[0013] Preferably, in step (2), the sintering temperature is 1250 to 1450° C., and the sintering time is 3 to 12 h.

[0014] The beneficial effects of the present invention are:

[0015] The present invention uses the chemical formula Ca 2 Ga 2 SiO 7 The compound is used to prepare a low dielectric constant microwave dielectric ceramic with an intrinsic near-zero resonant frequency temperature coefficient, wherein the dielectric constant (ε r ) is between 8.0 and 10.5, the quality factor (Q×f) is between 35000 and 95000 GHz, and the resonant frequency temperature coefficient (τ f ) is between –3.0 ppm / ℃ and +3.0ppm / ℃.

[0016] Microwave dielectric ceramic materials with intrinsic near-zero resonant frequency temperature coefficient can ensure the thermal stability of microwave components. The low dielectric constant characteristic is conducive to reducing signal delay and the mutual coupling loss between the material and the electrode. The high Q×f value is conducive to improving the frequency selection characteristics and reducing the transmission loss. Especially in the field of low dielectric constant materials, there is no intrinsic resonant frequency temperature coefficient (τ f ) is near zero in the existing technology, and the related products designed by the present invention fill the technical gap in the relevant field and provide a new technical solution for ensuring the thermal stability of microwave components. At the same time, the microwave dielectric ceramics prepared by the method for preparing microwave dielectric ceramics proposed by the present invention are single-phase microwave dielectric ceramics, do not contain easily variable valence elements, are not easy to deliquesce, have a stable crystal structure and are suitable for mass production. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 The low dielectric microwave dielectric ceramic Ca having an intrinsic near-zero resonant frequency temperature coefficient prepared in Examples 1-9 of the present invention 2 Ga 2 SiO 7 Preparation flow chart of

[0018] Figure 2 The low dielectric microwave ceramic Ca prepared in Example 5 of the present invention 2 Ga 2 SiO 7X-ray diffraction (XRD) spectrum;

[0019] Figure 3 The low-k microwave dielectric ceramic Ca prepared in Example 5 of the present invention 2 Ga 2 SiO 7 Scanning electron microscope (SEM) surface morphology;

[0020] Figure 4 The low-k microwave dielectric ceramic Ca prepared in Example 5 of the present invention 2 Ga 2 SiO 7 XRD refinement diagram and crystal structure diagram;

[0021] Figure 5 The low-k microwave dielectric ceramic Ca prepared in Example 5 of the present invention 2 Ga 2 SiO 7 High-resolution transmission electron microscopy image. DETAILED DESCRIPTION

[0022] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0023] Example 1

[0024] This embodiment provides a method for preparing a low-K microwave dielectric ceramic having a near-zero resonant frequency temperature coefficient, comprising the following steps:

[0025] (1) CaCO with a purity of 99.99% 3 , Ga 2 O 3 and SiO 2 According to the chemical formula, Ca 2 Ga 2 SiO 7 After being mixed evenly in a stoichiometric ratio, the first wet ball milling is performed with a deionized water dispersant, with zirconium balls as the ball milling medium, and the amount of deionized water added is twice the amount of the ingredients by mass). The powder is mixed and stirred for 6 hours at a speed of 360 r / min using a ball mill; the obtained slurry is dried and pre-fired at 1100 °C for 4 hours to obtain a pre-fired ceramic powder;

[0026] (2) Deionized water dispersant was added to the pre-fired ceramic powder obtained in step (1) for wet ball milling. The amount of deionized water added was twice the total amount of the pre-fired ceramic powder by weight. After drying, 4 wt% of PVA binder was added to the dry powder for granulation. The powder was pressed into a cylindrical green body sample with a thickness to diameter ratio of 0.4 to 0.6 at a pressure of 200 MPa. After pressing, the green body was sintered in air at 1350 °C for 4 h. The properties of the microwave dielectric ceramic obtained are shown in Table 1.

[0027] Examples 2 to 9

[0028] The only difference between Examples 2 to 9 and Example 1 is that the pre-sintering temperature and time when preparing the pre-sintered ceramic powder in step (1) are different, the mass fraction of the binder in step (2) is different, and the sintering temperature and time of the sintering process are different. The other steps are basically the same as those in Example 1 and will not be repeated here. The properties of the prepared microwave dielectric ceramics are shown in Table 1:

[0029] Table 1 Properties of low-k microwave dielectric ceramics obtained in Examples 1 to 9

[0030]

[0031] From the data in Table 1, it can be seen that the Ca 2 Ga 2 SiO 7 Microwave dielectric ceramics have a near-zero resonant frequency temperature coefficient, low dielectric constant and excellent quality factor. r ) is 8.0 ~ 10.5, excellent quality factor (Q×f) is 35000 ~ 115000 GHz, positive resonant frequency temperature coefficient (τ f ) is -3.0 ppm / ℃ ~+3.0 ppm / ℃. In addition, the Ca prepared by the present invention 2 Ga 2 SiO 7 The physical phase of microwave dielectric ceramics is single phase, the relative density is over 90%, it does not contain easily variable valence elements, is not easy to deliquesce, has a stable crystal structure and is suitable for mass production.

[0032] Figure 1 The low dielectric microwave dielectric ceramic Ca having a near-zero resonant frequency temperature coefficient prepared in Examples 1-9 of the present invention 2 Ga 2 SiO 7 Preparation flow chart of .

[0033] Figure 2 The low dielectric microwave dielectric ceramic Ca having a near-zero resonant frequency temperature coefficient prepared in Example 7 of the present invention 2 Ga2 SiO 7 X-ray diffraction (XRD) spectrum. As can be seen from the figure, Ca 2 Ga 2 SiO 7 The phase of microwave dielectric ceramics is pure tetragonal phase of pyrite structure, and Ca 2 Ga 2 SiO 7 The PDF card PDF# 00-043-0634 matches.

[0034] Figure 3 The low-k microwave dielectric ceramic Ca prepared in Example 7 of the present invention 2 Ga 2 SiO 7 SEM scanning electron microscope image. It can be seen from the image that the prepared ceramic has uniform grain size, dense structure and no obvious pores and second phases.

[0035] Figure 4 The low-k microwave dielectric ceramic Ca prepared in Example 7 of the present invention 2 Ga 2 SiO 7 Rietveld XRD refinement diagram and crystal structure diagram. Low dielectric microwave dielectric ceramic Ca with near-zero resonant frequency temperature coefficient 2 Ga 2 SiO 7 The crystal structure is tetragonal chalcedony structure.

[0036] Figure 5 The low-k microwave dielectric ceramic Ca prepared in Example 7 of the present invention 2 Ga 2 SiO 7 High-resolution transmission electron microscopy image.

[0037] In summary, the present invention provides a low dielectric constant microwave dielectric ceramic with a near-zero resonant frequency temperature coefficient, wherein the dielectric constant (ε r ) is 8.0 ~ 10.5, the quality factor (Q×f ) is 35000 ~ 95000GHz, and the resonant frequency temperature coefficient (τ f ) is -3.0 ppm / ℃ ~ +3.0 ppm / ℃. Microwave dielectric ceramic materials with near-zero resonant frequency temperature coefficient can ensure the thermal stability of microwave components. The low dielectric constant characteristic increases the transmission rate of electrical signals in microwave dielectric ceramic materials, and the high Q×f value is conducive to reducing losses. The microwave dielectric ceramic phase composition prepared by the method for preparing microwave dielectric ceramics proposed in the present invention is single-phase, does not contain easily variable valence elements, is not easy to deliquesce, has a stable crystal structure and is suitable for mass production.

[0038] The above content is a further detailed description of the present invention in combination with a specific preferred embodiment. It cannot be determined that the specific embodiments of the present invention are limited to this. For ordinary technicians in the technical field to which the present invention belongs, several simple deductions or substitutions can be made without departing from the concept of the present invention, which should be regarded as belonging to the scope of patent protection determined by the claims submitted by the present invention.

Claims

1. A low-k microwave dielectric ceramic having an intrinsic near-zero resonant frequency temperature coefficient, characterized in that: The chemical formula of the low-dielectric microwave dielectric ceramic is Ca2Ga2SiO7.

2. The low-k microwave dielectric ceramic with intrinsic near-zero resonant frequency temperature coefficient according to claim 1, characterized in that: The dielectric constant (ε r ) ranges from 8.0 to 10.5, the quality factor (Q×f) ranges from 35000 to 95000 GHz, and the resonant frequency temperature coefficient (τ f ) is –3.0 ppm / ℃ ~ +3.0 ppm / ℃.

3. A low-k microwave dielectric ceramic according to any one of claims 1 to 2, characterized in that: The preparation method of the low-k microwave dielectric ceramic comprises the following steps: (1) weighing raw material powders of CaCO3, Ga2O3 and SiO2 and mixing them in a stoichiometric ratio according to a chemical formula of Ca2Ga2SiO7, mixing them evenly with a dispersant, performing a first wet ball milling treatment, and then drying and pre-calcining to obtain a pre-calcined powder; (2) The pre-sintered powder obtained in step (1) is mixed evenly with a dispersant and then subjected to a second wet ball milling treatment. After drying, a binder is added to granulate the powder, and the powder is pressed and sintered to obtain the low-k microwave dielectric ceramic.

4. The method for preparing low-k microwave dielectric ceramics according to claim 3, characterized in that: The dispersant for the first wet ball milling treatment and the second wet ball milling treatment is 200% of the mass of the ingredients in deionized water, the ball milling medium is zirconium balls, the ball milling speed is 200 to 360 r / min, and the ball milling time is 3 to 12 hours.

5. The method for preparing low-k microwave dielectric ceramics according to claim 3, characterized in that: In step (1), the pre-firing temperature is 1000-1100°C, and the pre-firing time is 3-12h.

6. The method for preparing low-k microwave dielectric ceramics according to claim 3, characterized in that: In step (2), the adhesive is PVA (polyvinyl alcohol), and the mass fraction of the adhesive is 4 to 10%.

7. The method for preparing low-k microwave dielectric ceramics according to claim 3, characterized in that: In step (2), the sintering temperature is 1250 to 1450°C, and the sintering time is 3 to 12 hours.

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