CN108455979B

CN108455979B - Microwave dielectric ceramic material with ultralow dielectric constant and preparation method thereof

Info

Publication number: CN108455979B
Application number: CN201810349610.0A
Authority: CN
Inventors: 王哲飞; 余磊; 孙跃; 罗嵘潇; 王旭红; 殷仕龙; 胡秀丽
Original assignee: Changshu Institute of Technology
Current assignee: Changshu Institute of Technology
Priority date: 2018-04-18
Filing date: 2018-04-18
Publication date: 2020-06-30
Anticipated expiration: 2038-04-18
Also published as: CN108455979A

Abstract

The invention discloses an ultralow dielectric constant microwave dielectric ceramic material which is prepared by sintering the following raw materials in percentage by mass: 93-95% of fused silica micropowder, 2-4% of nano quartz powder and CaF₂0.5-2.5% of MnO₂0.5-2.5%, wherein the main phase of the ultralow dielectric constant microwave dielectric ceramic material is crystalline SiO₂. The invention also discloses a preparation method of the microwave dielectric ceramic material with the ultralow dielectric constant, S1, grinding and mixing CaF₂And MnO₂Powder; s2, mixing the fused silica powder and the nano quartz powder, and adding the CaF obtained in the step S1₂And MnO₂Carrying out wet ball milling on the mixed powder to obtain a mixture; s3, drying the mixture obtained in the step S2, granulating and pressing the mixture into a blank, and sintering the blank to obtain the ceramic material. The microwave dielectric ceramic material with the ultralow dielectric constant is wide in raw material source, simple and convenient in preparation method, beneficial to practical production and application, low in dielectric constant and near-zero in resonant frequency temperature coefficient, and can be widely applied to manufacturing microwave devices such as microwave substrates and missile radomes.

Description

Microwave dielectric ceramic material with ultralow dielectric constant and preparation method thereof

Technical Field

The invention relates to a ceramic material and a preparation method thereof, in particular to a microwave dielectric ceramic material with an ultralow dielectric constant and a preparation method thereof.

Background

In a microwave communication system, a microwave dielectric material is used as a main body manufacturing material of various microwave components, and the performance of the microwave dielectric material plays a key role in the stability and the communication quality of the whole communication system. In recent years, with the rapid development of technologies such as wireless communication, wireless networks, direct broadcast of satellite television, bluetooth, global positioning system, military guidance and the like, the trend of high frequency, integration, high stability and low cost of microwave equipment has become inevitable, and the communication frequency is continuously improved nowadays, so that a series of problems such as signal delay, increased equipment heat productivity, poor system stability and the like are increasingly obvious.

In the microwave dielectric material, the low dielectric constant material can reduce the interactive coupling effect between the dielectric material and the electrodes, improve the signal transmission rate, and improve the stability of the system by the near-zero temperature coefficient of the resonant frequency. In a plurality of microwave dielectric material systems, SiO₂The ceramic material has the advantages of low cost, reliable performance and the like, and is a low dielectric constant microwave dielectric ceramic material with great commercial potential. However, preparation of high performance SiO₂The microwave dielectric ceramic material has the following problems: SiO 2₂Can be sintered into porcelain at temperature above 1600 ℃, has low density, can reduce sintering temperature by introducing the auxiliary agent, but can also cause great increase of dielectric constant, can not improve the signal transmission rate of electronic elements, and simultaneously SiO₂The ceramic negative temperature coefficient of the resonant frequency easily causes the unstable working frequency of the ceramic, and the accurate receiving and transmitting of signals cannot be ensured. Therefore, research and development of SiO with ultralow dielectric constant and near-zero temperature coefficient of resonant frequency₂The microwave dielectric ceramic material is a key problem to be solved at present.

Disclosure of Invention

Aiming at the defects of the prior art, the invention provides an ultralow dielectric constant microwave dielectric ceramic material which has an ultralow dielectric constant and a resonant frequency temperature coefficient close to zero, and solves the problems of high dielectric constant and resonant frequency temperature coefficient, poor sintering property and the like of the existing material. The invention also provides a preparation method of the microwave dielectric ceramic material with the ultralow dielectric constant.

The technical scheme of the invention is as follows: an ultralow dielectric constant microwave dielectric ceramic material is prepared by sintering the following raw materials in percentage by mass: 93-95% of fused silica micropowder, 2-4% of nano quartz powder and CaF₂0.5-2.5% of MnO₂0.5-2.5% of the ultralow dielectric constant microwave dielectric ceramic materialThe main phase being crystalline SiO₂。

Furthermore, the ultralow dielectric constant microwave dielectric ceramic material has a dielectric constant of 2.4-2.7, a quality factor of 21628-34451 GHz, and a temperature coefficient of resonance frequency of-5-7 ppm/DEG C.

Preferably, the purity of the fused silica powder is more than 99%, the crystallinity is 0-5%, the granularity is 1-1.5 μm, the purity of the nano quartz powder is more than 99.9%, and the granularity is 500-600 nm.

Preferably, said CaF₂And MnO₂For analytical purification.

A preparation method of an ultralow dielectric constant microwave dielectric ceramic material comprises the following steps: s1 grinding and mixing CaF₂And MnO₂Powder; s2, mixing the fused silica powder and the nano quartz powder, and adding the CaF obtained in the step S1₂And MnO₂Carrying out wet ball milling on the mixed powder to obtain a mixture; s3, drying the mixture obtained in the step S2, granulating and pressing the mixture into a blank, and sintering the blank to obtain a ceramic material, wherein the raw materials in percentage by mass are as follows: 93-95% of fused silica micropowder, 2-4% of nano quartz powder and CaF₂0.5-2.5% of MnO₂0.5-2.5%.

Further, the grinding and mixing in the step S1 is manual grinding in a mortar, the grinding time is 20-30 min, and the step S2 of mixing the fused silica powder and the nano quartz powder adopts dry horizontal tumbling for 9-12 h.

Further, in the step S2, the fused silica micro powder and the nano quartz powder are mixed and then subjected to wet ball milling for 1-2 hours by using ethanol as a medium, and then CaF is added₂And MnO₂And carrying out wet ball milling on the powder for 5-8 h.

Further, the step S3 granulation is to add a binder into the mixture obtained in the step S2 in an amount of 1.5-3% by mass of the mixture for granulation, wherein the binder is methyl cellulose or stearic acid, the binder accounting for 40-60% by mass of the total binder is mixed with the mixture obtained in the step S2, and the rest of the binder is slowly added dropwise in the granulation process.

Further, after granulation in the step S3, 150 to 400 mesh granules are selected and pressed into a blank.

Preferably, the temperature is increased from room temperature to 1020-1025 ℃ at the temperature rising speed of 3-4 ℃/min during sintering, then is increased to 1220-1320 ℃ at the temperature rising speed of 1-1.5 ℃/min, the temperature is kept for 1-3 h, and furnace cooling is carried out after the temperature is kept.

The technical scheme provided by the invention has the advantages that: sintering aid CaF₂And MnO₂And the addition of the nano quartz powder can reduce the dielectric constant of the material to below 2.7 under the microwave frequency range, thereby ensuring the high-speed transmission of electronic signals in the device. The addition of the nano quartz powder can ensure that SiO is generated₂The resonant frequency temperature coefficient of the ceramic material is near zero, and the sintering compactness of the block is greatly improved. The nano quartz powder is uniformly dispersed in the fused silica powder in a premixing mode, so that the stability of the modification effect of the ceramic material is ensured. The sintering process with the slowly rising high temperature section can prevent the silicon micro powder from generating cracks during crystallization and improve the compactness of the material. The invention has wide raw material source and simple and convenient preparation method, is beneficial to practical production and application, and the obtained ceramic material has low dielectric constant and near zero temperature coefficient of resonance frequency, and can be widely applied to the manufacture of microwave devices such as microwave substrates, missile radomes and the like.

Drawings

FIG. 1 is an XRD spectrum of the ultra-low dielectric constant microwave dielectric ceramic material of the present invention.

FIG. 2 is a SEM picture of the ultralow dielectric constant microwave dielectric ceramic material of the present invention.

Detailed Description

The present invention is further illustrated by the following examples, which are not to be construed as limiting the invention thereto.

Example 1

Weighing sintering aid analytically pure CaF₂0.5g, analytically pure MnO₂2.5g, placing the mixture in an agate mortar for manual grinding for 20min for later use, weighing 95g of fused silica micropowder with the purity of more than 99 percent, the crystallinity of 0-5 percent, the granularity of 1-1.5 mu m, 2g of nano quartz powder with the purity of more than 99.9 percent and the granularity of 500nm, placing the mixture in a tumbling jar for tumbling for 9h, taking out the mixed powder, placing the mixed powder in the tumbling jar, mixing the powder for 1h by taking ethanol as a medium, taking out the mixed powder, and adding the mixed powder into the slurryAdding the manually ground CaF₂+MnO₂And (2) continuing ball milling for 5 hours after the powder of the aid is ground, adding methyl cellulose accounting for 0.6 wt% of the powder into the dried powder, mixing, slowly and dropwise adding the methyl cellulose accounting for 0.9 wt% of the powder in the granulation process to granulate, sieving the granulated material to obtain coarse powder of 150-400 meshes, then putting the coarse powder into a metal mold to be cold-pressed and molded, putting the molded block into a high-temperature furnace, heating the molded block to 1020 ℃ at 3 ℃/min, then heating the molded block to 1220 ℃ at 1 ℃/min, preserving the heat for 1 hour, and then cooling the molded block along with the furnace. The microwave dielectric property of the prepared microwave dielectric ceramic material with ultralow dielectric constant is as follows: dielectric constant ε_r2.7, quality factor Q × f 34451GHz, temperature coefficient of resonance frequency τ_f-5ppm/° c, and the XRD pattern and SEM picture are shown in fig. 1 and fig. 2, respectively.

Example 2

Weighing sintering aid analytically pure CaF₂1g, analytical pure MnO₂2g, placing the mixture in an agate mortar for manual grinding for 25min for later use, weighing 94.5g of fused silica powder with the purity of more than 99 percent, the crystallinity of 0-5 percent, the granularity of 1-1.5 mu m, 2.5g of nano quartz powder with the purity of more than 99.9 percent and the granularity of 500nm, placing the fused silica powder in a tumbling tank for tumbling for 10h, taking out the mixed powder, placing the mixed powder in the tumbling tank, mixing the powder for 1h by using ethanol as a medium, taking out the mixed powder, adding the manually ground CaF into the slurry₂+MnO₂And (2) continuing ball milling for 6 hours after the powder of the assistant is ground, adding methyl cellulose accounting for 1.5 wt% of the powder into the dried powder, mixing, slowly and dropwise adding the methyl cellulose accounting for 1.5 wt% of the powder in the granulation process to granulate, sieving the granulated material to obtain coarse powder of 150-400 meshes, then putting the coarse powder into a metal mold to be cold-pressed and molded, putting the molded block into a high-temperature furnace, heating the molded block to 1025 ℃ at the rate of 3 ℃/min in the high-temperature furnace, heating to 1250 ℃ at the rate of 1.5 ℃/min, preserving heat for 2 hours, and then cooling along with the furnace. The microwave dielectric property of the prepared microwave dielectric ceramic material with ultralow dielectric constant is as follows: dielectric constant ε_r2.6, quality factor Q × f 30561GHz, temperature coefficient of resonance frequency τ_f＝-2ppm/℃。

Example 3

Weighing sintering aid analytically pure CaF₂1.5g, analytically pure MnO₂1.5g, placing the mixture in an agate mortar for manual grinding for 30min for later use, weighing 94g of fused silica micropowder with the purity of more than 99 percent, the crystallinity of 0-5 percent, the granularity of 1-1.5 mu m, 3g of nano quartz powder with the purity of more than 99.9 percent and the granularity of 500nm, placing the mixture in a tumbling jar for tumbling for 11h, taking out the mixed powder, placing the mixed powder in the tumbling jar, mixing the powder for 1.5h by taking ethanol as a medium, taking out the mixed powder, adding the manually ground CaF into the slurry₂+MnO₂And (2) continuing ball milling for 7 hours after the powder of the assistant is ground, firstly adding stearic acid accounting for 0.6 wt% of the powder into the dried powder, mixing, slowly and dropwise adding stearic acid accounting for 0.9 wt% of the powder in the granulation process, granulating, screening the granulated material to obtain coarse powder of 150 meshes to 400 meshes, then putting the coarse powder into a metal mold for cold press molding, putting the molded block into a high-temperature furnace, heating the molded block to 1020 ℃ at 3.5 ℃/min, then heating the molded block to 1260 ℃ at 1 ℃/min, preserving heat for 2 hours, and then cooling along with the furnace. The microwave dielectric property of the prepared microwave dielectric ceramic material with ultralow dielectric constant is as follows: dielectric constant ε_r2.6, quality factor Q × f 27258GHz, temperature coefficient of resonance frequency τ_f＝0ppm/℃

Example 4

Weighing sintering aid analytically pure CaF₂2g, analytical pure MnO₂1g, placing the mixture in an agate mortar for manual grinding for 25min for later use, weighing 93.5g of fused silica powder with the purity of more than 99 percent, the crystallinity of 0-5 percent, the granularity of 1-1.5 mu m and 3.5g of nano quartz powder with the purity of more than 99.9 percent and the granularity of 500nm, placing the fused silica powder in a tumbling tank for tumbling for 12h, taking out the mixed powder, placing the mixed powder in the tumbling tank, mixing the powder with ethanol as a medium for 1.5h, taking out the mixed powder, adding the manually ground CaF into slurry₂+MnO₂And (2) continuing ball milling for 8 hours after the powder of the aid is ground, adding stearic acid accounting for 1.2 wt% of the powder into the dried powder, mixing, slowly and dropwise adding stearic acid accounting for 0.8 wt% of the powder in the granulation process, granulating, screening the granules to obtain coarse powder of 150-400 meshes, then putting the coarse powder into a metal mold, cold-pressing and molding, putting the molded block into a high-temperature furnace, heating the molded block to 1025 ℃ at 4 ℃/min in the high-temperature furnace, subsequently heating to 1280 ℃ at 1.5 ℃/min, preserving heat for 3 hours, and then cooling along with the furnace. To obtain ultra-low dielectricThe microwave dielectric property of the constant microwave dielectric ceramic material is as follows: dielectric constant ε_r2.5, quality factor Q × f 24120GHz, temperature coefficient of resonance frequency tau_f＝3ppm/℃。

Example 5

Weighing sintering aid analytically pure CaF₂2.5g, analytically pure MnO₂0.5g, placing the mixture in an agate mortar for manual grinding for 20min for later use, weighing 93g of fused silica micropowder with the purity of more than 99 percent, the crystallinity of 0-5 percent, the granularity of 1-1.5 mu m and 4g of nano quartz powder with the purity of more than 99.9 percent and the granularity of 500nm, placing the mixture in a tumbling jar for tumbling for 10h, taking out the mixed powder, placing the mixed powder in the tumbling jar, mixing the powder for 2h by taking ethanol as a medium, taking out the mixed powder, adding the manually ground CaF into the slurry₂+MnO₂And (2) continuing ball milling for 8 hours after the powder of the assistant is ground, adding stearic acid accounting for 1.5 wt% of the powder into the dried powder, mixing, slowly and dropwise adding the stearic acid accounting for 1.5 wt% of the powder in the granulation process, granulating, screening the granulated material to obtain coarse powder of 150-400 meshes, then putting the coarse powder into a metal mold for cold press molding, putting the molded block into a high-temperature furnace, heating the molded block into 1020 ℃ at 3 ℃/min, then heating the molded block into 1320 ℃ at 1 ℃/min, preserving the heat for 2 hours, and then cooling the molded block along with the furnace. The microwave dielectric property of the prepared microwave dielectric ceramic material with ultralow dielectric constant is as follows: dielectric constant ε_r2.4, quality factor Q × f 21628GHz, temperature coefficient of resonance frequency τ_f＝7ppm/℃。

Claims

1. The microwave dielectric ceramic material with the ultralow dielectric constant is characterized by being prepared by sintering the following raw materials in percentage by mass: 93-95% of fused silica micropowder, 2-4% of nano quartz powder and CaF₂0.5-2.5% of MnO₂0.5-2.5%, wherein the main phase of the ultralow dielectric constant microwave dielectric ceramic material is crystalline SiO₂。

2. The microwave dielectric ceramic material with ultralow dielectric constant as claimed in claim 1, wherein the dielectric constant of the microwave dielectric ceramic material with ultralow dielectric constant is 2.4-2.7, the quality factor is 21628-34451 GHz, and the temperature coefficient of resonance frequency is-5-7 ppm/° C.

3. The microwave dielectric ceramic material with the ultralow dielectric constant as claimed in claim 1, wherein the purity of the fused silica powder is more than 99%, the crystallinity is 0-5%, the particle size is 1-1.5 μm, the purity of the nano quartz powder is more than 99.9%, and the particle size is 500-600 nm.

4. The ultralow dielectric constant microwave dielectric ceramic material of claim 1 wherein said CaF₂And MnO₂For analytical purification.

5. A preparation method of an ultralow dielectric constant microwave dielectric ceramic material is characterized by comprising the following steps: s1 grinding and mixing CaF₂And MnO₂Powder; s2, mixing the fused silica powder and the nano quartz powder, and adding the CaF obtained in the step S1₂And MnO₂Carrying out wet ball milling on the mixed powder to obtain a mixture; s3, drying the mixture obtained in the step S2, granulating and pressing the mixture into a blank, and sintering the blank to obtain a ceramic material, wherein the raw materials in percentage by mass are as follows: 93-95% of fused silica micropowder, 2-4% of nano quartz powder and CaF₂0.5-2.5% of MnO₂0.5-2.5%.

6. The preparation method of the microwave dielectric ceramic material with the ultralow dielectric constant as claimed in claim 5, wherein the grinding and mixing in step S1 is manual grinding in a mortar for 20-30 min, and the step S2 is dry horizontal roller grinding for 9-12 h for mixing the fused silica powder and the nano quartz powder.

7. The preparation method of the microwave dielectric ceramic material with the ultralow dielectric constant as claimed in claim 5, wherein the step S2 is to mix the fused silica powder and the nano quartz powder, perform wet ball milling for 1-2 h by using ethanol as a medium, and then add CaF₂And MnO₂And carrying out wet ball milling on the powder for 5-8 h.

8. The method for preparing microwave dielectric ceramic material with ultralow dielectric constant as claimed in claim 5, wherein the step S3 granulation is carried out by adding a binder into the mixture obtained in the step S2 in an amount of 1.5-3% by mass, wherein the binder is methylcellulose or stearic acid, the binder accounting for 40-60% by mass of the total mass of the binder is mixed with the mixture obtained in the step S2, and the rest of the binder is slowly added dropwise in the granulation process.

9. The preparation method of the microwave dielectric ceramic material with the ultralow dielectric constant as in claim 5, wherein after the granulation in the step S3, 150-400 mesh granules are selected and pressed into a blank.

10. The preparation method of the microwave dielectric ceramic material with the ultralow dielectric constant as claimed in claim 5, wherein the temperature is raised from room temperature to 1020-1025 ℃ at a heating rate of 3-4 ℃/min, then raised to 1220-1320 ℃ at a heating rate of 1-1.5 ℃/min, and the temperature is kept for 1-3 h, and then the ceramic material is cooled along with the furnace after the temperature is kept.