Low dielectric constant and low loss microwave dielectric ceramic and preparation method thereof

Abstract

The application discloses a microwave dielectric ceramic with low dielectric constant and low loss and a preparation method thereof.The chemical composition expression of the microwave dielectric ceramic is CaLaAl3O7, the microwave dielectric ceramic has low dielectric constant (5.8-6.3), low loss (7.2*10 ‑4 ) and negative resonance frequency temperature coefficient (-37-31ppm / ℃). The microwave dielectric ceramic has low dielectric constant and low loss, is an ideal candidate material of low dielectric microwave ceramic in the field of wireless communication, is prepared by using a traditional solid-phase reaction method, has mature process and can be produced industrially, has strong repeatability and can synthesize stable pure phase.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of electronic ceramics and its manufacturing, in particular, the present application relates to a new type of low dielectric constant and low loss microwave dielectric ceramic and its preparation method. BACKGROUND

[0002] Microwave dielectric ceramic refers to the key dielectric material applied in microwave frequency band (300MHz-300GHz) circuit as a passive device (such as resonator, filter, antenna, etc.) in microwave communication system. According to different use scenarios, having suitable dielectric constant, low dielectric loss, near-zero resonance frequency temperature coefficient is the most important three performance evaluation indexes of microwave dielectric ceramic.

[0003] In order to meet the needs of the ever-advancing society, it is essential to design and deploy special devices with artificial intelligence technology. These cutting-edge devices working in the field of high-frequency signal transmission require fast propagation and strong anti-interference ability, while also pursuing higher transmission efficiency and operation stability. The transmission time of signal is directly affected by the square root of dielectric constant. This correlation shows that the lower the dielectric constant, the faster the propagation speed. Therefore, in order to effectively meet the development requirements of the new generation of electronic technology, it is essential to develop low dielectric constant materials, which can reduce transmission delay and achieve high-speed and efficient signal propagation.

[0004] Under this background, a series of low-dielectric microwave dielectric ceramic systems have been widely studied, such as silicates, aluminates and molybdates (such as Chinese patents CN115286375A, CN106966713A). Aluminates have lower ionic polarization rate than silicates and molybdates, and are more likely to prepare microwave dielectric ceramics with ultra-low dielectric constant. However, there are few studies on the preparation of yellow long stone structure microwave dielectric ceramics with chemical formula ABC3O7 in aluminates. In the yellow long stone structure, the alkali earth cation of site A and the rare earth cation of site B can be replaced by the transition metal of site C. This substitution feature gives it important research significance. Therefore, it is of great scientific research and practical application value to study the microwave dielectric ceramic of yellow long stone structure aluminates system. SUMMARY

[0005] In order to overcome the shortcomings of the prior art, the purpose of the present application is to provide a low dielectric constant and low loss microwave dielectric ceramic and its preparation method.

[0006] To solve the above problems, the technical scheme adopted by the present application is as follows:

[0007] The application provides a microwave dielectric ceramic with low dielectric constant and low loss, the chemical composition expression of the microwave dielectric ceramic is CaLaAl3O7, and the microwave dielectric ceramic has low dielectric constant (5.8-6.3), low loss (7.2*10-4) and negative resonance frequency temperature coefficient (-37--31ppm / ℃).

[0008] The application also provides a preparation method of the microwave dielectric ceramic with low dielectric constant and low loss.

[0009] (1) raw powder preparation: according to the chemical formula of CaLaAl3O7, CaCO3, La2O3 and Al2O3 initial raw materials are weighed; the obtained mixture is ball milled with anhydrous ethanol to obtain a slurry-like raw material, which is dried to constant weight, and finally sieved to obtain uniformly dried raw powder mixture.

[0010] (2) prepared powder preparation: the raw powder in step (1) is pre-fired, and CaLaAl3O7 prepared powder is obtained after reaction; the prepared powder is secondarily ball milled with alcohol to form uniformly dispersed slurry, which is dried to constant weight, and finally sieved to obtain uniformly dried CaLaAl3O7 compound prepared powder.

[0011] (3) forming and sintering: the compound prepared powder in step (2) is added to PVA aqueous solution and granulated, and then pressed into a ceramic embryo, and then the embryo is subjected to degassing and sintering treatment to obtain microwave dielectric ceramic CaLaAl3O7.

[0012] Preferably, in steps (1) and (2), zirconium oxide ball milling beads are used, and the mass ratio of raw powder mixture, ball milling beads and anhydrous ethanol is 1:5:2.

[0013] Preferably, the pre-firing temperature is 1350-1450℃, the heating rate is 2℃ / min-5℃ / min, and the holding time is 3-5h, and the pre-firing is naturally cooled to room temperature after the pre-firing.

[0014] Preferably, in step (3), the mass fraction of the PVA aqueous solution is 50%, and the aqueous solution addition amount is 10% of the mass of the mixture.

[0015] Preferably, in step (3), the degassing treatment temperature is 450-600℃, the heating rate is 1℃ / min-3℃ / min, the holding time is 2-4h, and the degassing treatment is followed by a sintering process.

[0016] Preferably, in step (3), the sintering treatment temperature is 1500-1600℃, the heating rate is 1℃ / min-3℃ / min, the holding time is 3-5h, and the sintering treatment is naturally cooled to room temperature after the sintering treatment.

[0017] Preferably, in step (3), the diameter of the green blank is 12 mm, the height is 6 mm, and the pressing pressure is a uniaxial pressure of 160-200 MPa.

[0018] Compared with the prior art, the technical effects of the present invention are reflected in:

[0019] The microwave dielectric ceramic of the present invention has the chemical composition formula CaLaAl3O7. The microwave dielectric ceramic has a low dielectric constant (5.8 to 6.3), low loss (7.2 × 10-4) and a negative temperature coefficient of resonant frequency (-37 to -31 ppm / ℃), making it an ideal candidate material for low dielectric microwave ceramics in the field of wireless communication.

[0020] It is prepared using the traditional solid-phase reaction method, which is a mature process that can be industrialized, has strong reproducibility, and can synthesize stable pure phases.

[0021] Some of the additional advantages, objectives and features of the present invention will be described in detail below, which will enable those skilled in the art to clearly understand the essence of the invention and guide related research or practice.

[0022] Please note that the scope of application of this invention is not limited to the specific description above, and the various objectives and advantages that this invention can achieve can be more fully understood based on the detailed description below, including but not limited to the above content. Attached Figure Description

[0023] Figure 1 XRD patterns of pre-sintered CaLaAl3O7 powder and sintered ceramics.

[0024] Figure 2 The images show the SEM and EDS spectra of CaLaAl3O7 ceramics. Detailed Implementation

[0025] The present invention will now be described in detail with reference to the accompanying drawings and embodiments. By reading this specification, those skilled in the art will easily understand other advantages and functions of the present invention. It is worth noting that the present invention can be implemented or applied through a variety of different specific embodiments. Furthermore, the details in this specification can be appropriately adjusted or modified according to different viewpoints and applications without departing from the core concept of the present invention.

[0026] It should be noted that the process equipment or apparatus not specifically mentioned in the following embodiments are all conventional equipment or apparatus in the art.

[0027] In addition, it needs to be understood that one or more method steps mentioned in the present application do not exclude the existence of other method steps, which can be inserted before or after the combination steps, or between the explicitly mentioned steps, provided that there is no other indication. In addition, their relative relationship can be adjusted or changed without substantial change in technical content, which still belongs to the implementation scope of the present application.

[0028] The embodiment of the present application provides a low dielectric constant and low loss microwave dielectric ceramic, which has a chemical composition expression of CaLaAl3O7, low dielectric constant (5.8-6.3), low loss (7.2*10 -4 ) and negative resonance frequency temperature coefficient (-37-31 ppm / ℃).

[0029] The embodiment of the present application also provides a low dielectric constant and low loss microwave dielectric ceramic and a preparation method thereof, which comprises the following steps:

[0030] (1) Preparation of raw powder: according to the chemical formula of CaLaAl3O7, CaCO3, La2O3 and Al2O3 initial raw materials are weighed; the obtained mixture is ball milled with anhydrous ethanol to obtain a slurry-like raw material, which is dried to constant weight, and finally uniformly dried raw powder mixture is obtained through sieving. Preferably, high-purity powder raw materials are selected, the purity of CaCO3 powder is 99.9%, the purity of La2O3 powder is 99.9%, and the purity of Al2O3 powder is 99.9%; zirconia milling beads are used in the ball milling process, and the mass ratio of raw powder mixture, ball milling beads and anhydrous ethanol is 1:5:2; a planetary ball mill is used for the ball mill, the rotation speed ranges from 150 r / min to 200 r / min, and 80-mesh screen is used for dispersion treatment.

[0031] (2) Preparation of cooked powder: the raw powder is pre-fired, and CaLaAl3O7 cooked powder is obtained after reaction; the cooked powder is secondarily ball milled with alcohol to form uniformly dispersed slurry, which is dried to constant weight, and finally uniformly dried CaLaAl3O7 compound cooked powder is obtained through sieving. Preferably, the pre-firing temperature is 1350-1450℃, the heating rate is 2-5℃ / min, the holding time is 3-5h, the pre-firing is naturally cooled to room temperature after pre-firing, and 80-mesh screen is used for dispersion treatment.

[0032] (3) forming sintering: the compound powder is added into PVA aqueous solution to form granules, and then the granules are pressed into ceramic green bodies, and then the green bodies are subjected to degassing sintering treatment to obtain microwave dielectric ceramic CaLaAl3O7; preferably, the PVA aqueous solution used has a mass fraction of 50%, and the addition amount is 10% of the mass of the mixture; the degassing treatment is performed at a temperature of 450-600°C, a temperature rising rate of 1-3°C / min, and a holding time of 2-4h; during the sintering process, the sintering temperature is 1500-1600°C, the temperature rising rate is 1-3°C / min, and the holding time is 3-5h, and after the sintering is completed, the sintering product is naturally cooled to room temperature; during the degassing process, the diameter of the green body is 12mm, the height is 6mm, and the uniaxial pressure during the pressing is 160-200Mpa.

[0033] The process parameters and microwave dielectric properties of each embodiment are as follows:

[0034]

[0035] According to the XRD and refinement results of Figure 1 , it can be seen that the diffraction peaks of Example 4 correspond to the standard PDF card, and there are no other diffraction peaks, indicating that Example 4 basically generates CaLaAl3O7 pure phase; according to the SEM and EDS results of Figure 2 , it can be seen that the atomic molar ratio of E and F points in the unit cell of Example 4 and Example 5 is very close to CaLaAl3O7, and combined with XRD, it can be considered that both of them sinter out full CaLaAl3O7 grains, wherein the grains in Example 4 grow uniformly, and some abnormal grains in size and shape are observed in Example 5, which may be caused by excessive sintering.

[0036] From the above table, it can be seen that the dielectric constant of the CaLaAl3O7 microwave dielectric ceramic prepared by Example 1-Example 5 of the present application at different sintering temperatures is between 5.8-6.3; in addition, the quality factor of the ceramic obtained by Example 4 at the optimal sintering temperature is above 20000GHz, showing low dielectric loss, indicating that the microwave dielectric ceramic of the present application has a wide application prospect in the field of microwave communication.

[0037] Although specific embodiments have been described, it should be understood that the present application has greater flexibility and adaptability. Any modification, equivalent change or improvement based on the core technology of the present application should be considered as within the scope of protection of the present application.

Claims

1. Application of CaLaAl307 ceramic as low dielectric constant and low loss microwave dielectric ceramic, which has low dielectric constant (5.8-6.3), low loss (7.2x10 -4 ) and negative resonance frequency temperature coefficient (-37-31 ppm / ℃).

2. Use of the CaLaAl307 ceramic according to claim 1 as low dielectric constant low loss microwave dielectric ceramic, characterized in that, The preparation comprises the following steps: (1) green powder preparation: according to the chemical formula of CaLaAl3O7, CaCO3, La2O3, Al2O3 initial raw materials are weighed; the obtained mixture is ball milled with anhydrous ethanol to obtain a slurry-like raw material, which is dried to constant weight, and finally sieved to obtain uniform dry green powder mixture; (2) preparation of calcined powder: the green powder is pre-fired, and CaLaAl3O7 calcined powder is obtained after reaction, which is secondarily ball milled with alcohol to form a uniformly dispersed slurry, dried to constant weight, and finally sieved to obtain uniform dry CaLaAl3O7 compound calcined powder; (3) forming and sintering: the compound calcined powder is added to PVA aqueous solution, granulated, pressed into a ceramic body, and then the body is subjected to degassing and sintering treatment to obtain microwave dielectric ceramic CaLaAl3O7.

3. Use of the CaLaAl307 ceramic according to claim 2 as low dielectric constant low loss microwave dielectric ceramic, characterized in that, In steps (1) and (2), zirconia milling beads are used, and the mass ratio of green powder mixture, milling beads and anhydrous ethanol is 1:5:

2.

4. Use of the CaLaAl307 ceramic according to claim 2 as low dielectric constant low loss microwave dielectric ceramic, characterized in that, In step (2), the pre-firing temperature is 1350-1450℃, the heating rate is 2-5℃ / min, and the holding time is 3-5h, and the pre-firing is naturally cooled to room temperature after pre-firing.

5. Use of the CaLaAl307 ceramic according to claim 2 as low dielectric constant low loss microwave dielectric ceramic, characterized in that, In step (3), the mass fraction of PVA aqueous solution is 50%, and the PVA aqueous solution addition amount is 10% of the mass of the pre-fired powder.

6. Use of the CaLaAl307 ceramic according to claim 2 as low dielectric constant low loss microwave dielectric ceramic, characterized in that, In step (3), the temperature of the degassing treatment is 450-600℃, the heating rate is 1-3℃ / min, the holding time is 2-4h, and the degassing treatment is followed by sintering.

7. Use of the CaLaAl307 ceramic according to claim 2 as low dielectric constant low loss microwave dielectric ceramic, characterized in that, In step (3), the sintering temperature is 1500-1600℃, the heating rate is 1-3℃ / min, the holding time is 3-5h, and the sintering is naturally cooled to room temperature after sintering.

8. Use of the CaLaAl307 ceramic according to claim 2 as low dielectric constant low loss microwave dielectric ceramic, characterized in that, In step (3), the diameter of the green body formed by pressing is 12mm, the height is 6mm, and the uniaxial pressure used for pressing is 160-200Mpa.

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