阅读说明：本技术 微波体衰减陶瓷材料及其制备方法和应用 (Microwave attenuation ceramic material and preparation method and application thereof ) 是由 鲁燕萍 杨艳玲 臧向荣 刘钊 王帅 于 2020-07-03 设计创作，主要内容包括：本发明公开了一种微波体衰减陶瓷材料,该陶瓷材料包括基体相和微波衰减相,所述微波衰减相的平均粒径为1-2μm；所述微波衰减相均匀地分布在所述基体相的晶粒间界,形成了晶界网络结构。该微波体衰减材料制备得到的大功率高频微波真空电子器件具有高导热率和好的衰减量。本发明还公开了该微波体衰减陶瓷材料的制备方法和应用。(The invention discloses a microwave attenuation ceramic material, which comprises a matrix phase and a microwave attenuation phase, wherein the average grain diameter of the microwave attenuation phase is 1-2 mu m; the microwave attenuation phase is uniformly distributed at the grain boundaries of the matrix phase to form a grain boundary network structure. The high-power high-frequency microwave vacuum electronic device prepared from the microwave attenuation material has high thermal conductivity and good attenuation. The invention also discloses a preparation method and application of the microwave attenuation ceramic material.)

1. A microwave body attenuating ceramic material comprising a matrix phase and a microwave attenuating phase,

the average grain diameter of the microwave attenuation phase is 1-2 μm;

the microwave attenuating phase is uniformly distributed at the grain boundaries of the matrix phase.

2. A microwave bulk-attenuating ceramic material as claimed in claim 1, wherein the microwave-attenuating phase is uniformly distributed at the bimorph or tricrystal or polycrystal junctions of the matrix phase.

3. A microwave bulk-attenuating ceramic material as claimed in claim 1, wherein the matrix phase is selected from aluminium nitride or aluminium oxide;

preferably, the microwave attenuating phase is selected from one or more of silicon carbide, titanium carbide and titanium nitride.

4. A microwave attenuating ceramic material according to claim 1, characterised in that the ceramic material has a matrix phase content of 55-80 wt% and a microwave attenuating phase content of 20-45 wt%.

5. The microwave attenuation ceramic material of claim 1, further comprising 3-10 wt% of a sintering aid, wherein the sintering aid comprises at least one of magnesium oxide, calcium fluoride, titanium dioxide and aluminum oxide, or one or more of yttrium oxide, yttrium aluminate, yttrium fluoride, or lanthanide metal oxide or fluoride.

6. A method of preparing a microwave body attenuating ceramic material as claimed in any one of claims 1 to 5, comprising the steps of:

mixing the raw materials including the matrix phase and the microwave attenuation phase, and forming to obtain a prefabricated body;

and sintering the prefabricated body at normal pressure to obtain the microwave attenuation ceramic material.

7. The method according to claim 6, wherein the raw material further comprises a sintering aid; the mixing is to mix the matrix phase, the microwave attenuation phase and the sintering aid.

8. The production method according to claim 6, wherein the molding is performed by cold isostatic pressing; preferably, the atmospheric sintering is performed in a nitrogen atmosphere or an argon atmosphere.

9. The method as claimed in claim 6, wherein the sintering temperature is 1600-2000 ℃, and the sintering time is 0.5-6 h;

preferably, when the matrix phase is selected from aluminum nitride, the sintering temperature is 1800-1960 ℃, and the sintering time is 2-4 h;

preferably, when the matrix phase is alumina, the sintering temperature is 1600-.

10. Use of a microwave bulk-attenuating ceramic material according to any one of claims 1 to 4 for the preparation of microwave vacuum electronic devices.

Technical Field

The invention relates to the field of ceramic materials. More particularly, relates to a microwave attenuation ceramic material and a preparation method and application thereof.

Background

In microwave vacuum electronic devices, microwave attenuation materials are required to absorb waves in non-design modes and eliminate sideband oscillation, so that accurate operation of the devices is guaranteed. Since the electromagnetic wave is converted into heat energy after being absorbed by the microwave attenuation material, the microwave attenuation material is required to have good thermal conductivity and high temperature stability in order to prevent the generated heat from affecting the normal operation of the device.

The microwave attenuation materials studied at present can only be well applied to microwave vacuum electronic devices with low or medium-high frequency such as X wave band and K wave band. The research on the microwave attenuation material suitable for the high-frequency, especially the high-power high-frequency W-band microwave vacuum electronic device is relatively few or has high cost. The main reason is that the higher the frequency of the electronic device, the smaller the volume of the electronic device needs to be, the more difficult the electronic device is to be prepared, and thus the microwave attenuation material is required to have higher thermal conductivity and higher attenuation, but in the existing research, the process of improving the thermal conductivity and the attenuation of the microwave attenuation material at the same time is a contradiction process. For example, in the aluminum nitride-silicon carbide complex phase attenuation ceramic, when the microwave attenuation phase silicon carbide content is low (< 20 wt%), the material has better thermal conductivity, but the attenuation of the microwave attenuation phase silicon carbide in a high-frequency wave band is very small; when the content of the microwave attenuation phase silicon carbide is too high, although the attenuation energy of the microwave attenuation phase silicon carbide is improved in a high-frequency band, the reduction of the thermal conductivity is serious, and the sintering temperature required by a material system is high.

Therefore, in view of the above problems, there is a need to provide a new microwave attenuation material suitable for use in high power high frequency microwave vacuum electronic devices.

Disclosure of Invention

The first purpose of the present invention is to provide a microwave attenuation ceramic material, which has high attenuation, good thermal conductivity and high temperature thermal stability when applied to a full frequency band, especially high frequency, especially W band high power high frequency microwave vacuum electronic device.

The second purpose of the invention is to provide a preparation method of the microwave attenuation ceramic material.

A third object of the present invention is to provide a use of a microwave bulk attenuating ceramic material.

In order to achieve the first object, the present invention provides a microwave attenuation ceramic material, which comprises a matrix phase and a microwave attenuation phase, wherein the average particle size of the microwave attenuation phase is 1-2 μm; the microwave attenuating phase is uniformly distributed at the grain boundaries of the matrix phase.

Preferably, the microwave attenuating phase is uniformly distributed at the junction of the twin or triple crystals or polycrystals of the matrix phase.

Preferably, the matrix phase is selected from aluminium nitride or aluminium oxide.

Preferably, the microwave attenuating phase is selected from one or more of silicon carbide, titanium carbide and titanium nitride.

Preferably, the ceramic material has a matrix phase content of 55 to 80 wt% and a microwave attenuating phase content of 20 to 45 wt%.

Preferably, the ceramic material further comprises 3-10 wt% of a sintering aid, wherein the sintering aid comprises at least one of magnesium oxide, calcium fluoride, titanium dioxide and aluminum oxide, or one or more of yttrium oxide, yttrium aluminate, yttrium fluoride or lanthanide metal oxide or fluoride.

In order to achieve the second object, the present invention provides a method for preparing a microwave attenuation ceramic material, comprising the steps of:

mixing the raw materials including the matrix phase and the microwave attenuation phase, and forming to obtain a prefabricated body;

and sintering the prefabricated body at normal pressure to obtain the microwave attenuation ceramic material.

Preferably, the raw materials also comprise a sintering aid; the mixing is to mix the matrix phase, the microwave attenuation phase and the sintering aid.

Preferably, the sintering aid comprises at least one of magnesium oxide, calcium fluoride, titanium dioxide and aluminum oxide, or one or more of yttrium oxide, yttrium aluminate, yttrium fluoride or lanthanide metal oxide or fluoride in combination.

Preferably, the forming mode is cold isostatic pressing.

Preferably, the atmospheric sintering is performed in a nitrogen atmosphere.

Preferably, the sintering temperature is 1600-;

preferably, when the matrix phase is selected from aluminum nitride, the sintering temperature is 1800-1960 ℃ and the sintering time is 2-6h, preferably 2-4 h.

Preferably, when the matrix phase is selected from alumina, the sintering temperature is 1600-.

In order to achieve the third object, the invention also protects the application of the microwave body attenuation ceramic material in the preparation of microwave vacuum electronic devices.

The invention has the following beneficial effects:

in the microwave attenuation ceramic material, the average particle size of the raw powder of the microwave attenuation phase material is controlled to be 1-2 mu m, and the sintered ceramic microwave attenuation phase keeps the particle size of the raw powder and is uniformly distributed in the grain boundaries of the matrix phase to form a compact grain boundary network structure, so that the ceramic material has high attenuation, good thermal conductivity and high-temperature thermal stability at the same time, and can be better suitable for high-frequency, especially W-waveband high-power high-frequency microwave vacuum electronic devices. Furthermore, the microwave attenuation ceramic material for the high-power high-frequency microwave vacuum electronic device has low manufacturing cost and is easy to obtain due to the easily available raw materials.

Drawings

The following describes embodiments of the present invention in further detail with reference to the accompanying drawings.

Fig. 1 shows a microstructure topography of the microwave bulk attenuating ceramic material obtained in example 1.

Fig. 2 shows a microstructure topography of the microwave bulk attenuating ceramic material obtained in example 2.

Fig. 3 shows a microstructure topography of the microwave bulk attenuating ceramic material obtained in example 3.

Fig. 4 shows a microstructure morphology of the microwave bulk damped ceramic material obtained in comparative example 1.

Fig. 5 shows a microstructure morphology of the microwave bulk attenuating ceramic material obtained in comparative example 2.

FIG. 6 is a graph showing the comparison of dielectric properties in the W band between the materials obtained in example 1 and comparative examples 1 and 2.

Fig. 7 shows the test result of practical application of the embodiment of the present invention in the W band.

Detailed Description

In order to more clearly illustrate the invention, the invention is further described below with reference to preferred embodiments and the accompanying drawings. Similar parts in the figures are denoted by the same reference numerals. It is to be understood by persons skilled in the art that the following detailed description is illustrative and not restrictive, and is not to be taken as limiting the scope of the invention.

In one embodiment the present invention provides a microwave bulk attenuating ceramic material comprising a matrix phase and a microwave attenuating phase, the microwave attenuating phase having an average particle size of from 1 to 2 μm; the microwave attenuation phase is uniformly distributed at the grain boundaries of the matrix phase to form a grain boundary network structure.

In the existing microwave attenuation ceramic material taking SiC as an attenuation phase, a nano SiC material is usually adopted as the microwave attenuation phase to reduce the sintering temperature and improve the attenuation amount, namely the loss amount, of the obtained microwave attenuation ceramic material. However, such microwave attenuation ceramic materials are usually sintered by hot pressing, and are generally only suitable for microwave vacuum electronic devices with relatively low frequency, and when the ceramic materials are applied to microwave vacuum electronic devices with high power and high frequency, the problem that high attenuation is difficult to obtain is solved. However, when the particle size of the microwave attenuation phase is too large, the problems of difficult sintering and difficult heat dissipation still exist.

In the embodiment of the invention, the particle size of the initial raw material of the microwave attenuation phase material (such as SiC and the like) directly influences the performance of the obtained ceramic material, and when the particle size of the raw powder is less than 1 μm, the problem that particles are easy to agglomerate and are not easy to disperse uniformly exists in the process of ceramic sintering on one hand; on the other hand, the microwave attenuation phase material particles are easy to be wrapped in the matrix phase grains in the sintering process due to undersize, so that the growth of the ceramic matrix grains is influenced, and meanwhile, the small grains are randomly and disorderly distributed in the matrix grain boundary, so that the overall sintering density of the composite ceramic material is poor, the heat conductivity of the attenuation ceramic obtained when the attenuation phase grain size is smaller is poor, and meanwhile, the insulation resistivity is relatively lower, the insulation performance is poor, and the working stability is poor; when the particle size of the attenuation phase raw powder is larger than 2 mu m, the existence of large crystal grains increases sintering resistance, and hinders the sintering densification process, so that the obtained ceramic material has high porosity and low integral density of the ceramic, and the composite ceramic has poor high-frequency attenuation performance and poor heat conduction performance. When the grain size of the raw material is strictly controlled at 1-2 μm, the sintering process is accompanied with the growth of matrix grains, under the action of sintering thrust, the microwave attenuation phase is uniformly distributed in the grain boundaries (the junctions of bicrystal, tricrystal or polycrystal form a grain boundary network structure) of the aluminum nitride or alumina matrix in an extremely regular and orderly manner in the ceramic material formed after sintering, the grain size of the attenuation phase in the formed ceramic structure still keeps 1-2 μm of the raw material grains, and the obtained two-phase composite ceramic has compact structure and excellent high-frequency attenuation performance and heat dissipation performance of the ceramic material. In addition, the form of the microwave attenuation phase material also affects the distribution of the microwave attenuation phase material in the matrix phase, and ideally, when the form of the attenuation phase raw powder is a spherical or spheroidal structure, the sintering resistance is smaller, a more uniform and compact sintering structure can be obtained, and therefore the high-frequency attenuation performance and the heat dissipation performance of the obtained ceramic material can be further improved to a certain extent. Particularly, when the attenuation phase is in a sphere-like shape, the attenuation phase is positioned at the junction of three crystals or polycrystal, and the composite ceramic structure is more compact. However, since the microwave attenuating phase raw material such as silicon carbide raw material in the present application is obtained by pulverizing natural raw material, it is difficult to obtain a spherical or spheroidal structure in practice; the microwave attenuation ceramic material obtained by replacing the silicon carbide attenuation phase with the titanium nitride or titanium carbide attenuation phase with better sphericity has obviously higher heat conductivity than the microwave attenuation ceramic material added with the silicon carbide attenuation phase.

Therefore, in the technical scheme of the embodiment, the particle size and morphology of the microwave attenuation phase are strictly controlled, and the microwave attenuation phase is uniformly and orderly distributed at the grain boundaries (such as two-phase grain boundaries and three-phase grain boundaries) of the matrix phase in the ceramic sintering process to form a compact two-phase ceramic structure, so that the obtained ceramic material has high attenuation, good thermal conductivity and high-temperature thermal stability, and can be used for high-frequency, especially W-band, high-power and high-frequency microwave vacuum electronic devices.

The matrix phase suitable for the microwave attenuation ceramic material is also the ceramic dielectric phase, and the ceramic dielectric phase can be made of attenuation materials such as aluminum nitride or aluminum oxide.

In a preferred example, the microwave attenuating phase may be made of one or more of silicon carbide, titanium carbide and titanium nitride.

In this embodiment, the microwave attenuation phase of 1 to 2 μm is commercially available, and the above-mentioned material of 1 to 2 μm can be prepared and used as the microwave attenuation phase material.

In a preferred embodiment, the ceramic material has a matrix phase content of 55 to 80 wt% and a microwave attenuating phase content of 20 to 45 wt%. The physical and mechanical properties of the ceramic material formed by the raw materials can be better suitable for being applied to microwave vacuum electronic devices.

Microwave attenuating ceramic materials also typically include a sintering aid to prevent porosity from forming during sintering and to make it difficult to achieve a dense structure. In a preferred example, the material further comprises 3-10 wt% of a sintering aid comprising at least one of magnesium oxide, calcium fluoride, titanium dioxide and aluminum oxide, or at least one of yttrium oxide, yttrium fluoride or a lanthanide metal oxide or fluoride.

In another embodiment of the present invention, a method for preparing the microwave attenuation ceramic material comprises the following steps:

mixing the raw materials including the matrix phase and the microwave attenuation phase, and forming to obtain a prefabricated body;

and sintering the prefabricated body at normal pressure to obtain the microwave attenuation ceramic material.

Wherein the particle size of the microwave attenuation phase is 1-2 μm.

The microwave attenuation phase can be uniformly distributed at the grain boundaries of the ceramic dielectric phase by the preparation method, so that the prepared microwave attenuation ceramic material has the properties mentioned in the first embodiment.

It will be appreciated by those skilled in the art that the preparation method may further include the steps of ball milling, drying, sieving, etc. after mixing the matrix phase and the microwave attenuating phase.

In order to prevent pores from being generated when the material is formed by sintering and difficult to realize a compact structure, the raw material also comprises a sintering aid; the mixing is to mix the matrix phase, the microwave attenuation phase and the sintering aid.

In a preferred example, the forming is performed by cold isostatic pressing.

In a preferred example, the atmospheric sintering is performed in a nitrogen atmosphere.

In a preferred example, when the matrix phase is selected from aluminum nitride, the sintering temperature is 1800-. Sintering at the sintering temperature is more favorable for obtaining the microwave attenuation ceramic material with compact structure. In a further more preferred example, the sintering temperature is 1800-. In this case, the sintering temperature is low, and the microwave attenuation ceramic material obtained is more compact in structure, and has both a higher attenuation and a higher thermal conductivity. In still other specific examples, the sintering temperature includes, but is not limited to, 1810 deg.C, 1820 deg.C, 1830 deg.C, 1840 deg.C, and the like.

In yet another preferred example, when the matrix phase is selected from alumina, the sintering temperature is 1600-.

In a further embodiment of the present invention, there is provided a use of the microwave bulk attenuating ceramic material described above for the preparation of microwave vacuum electronic devices.

The obtained microwave attenuation ceramic material is used for preparing microwave vacuum electronic devices, and the prepared microwave vacuum electronic devices, including high-power microwave vacuum electronic devices, have high attenuation, good thermal conductivity and high-temperature thermal stability when used under the conditions of full frequency bands, particularly high frequency, particularly W band.

The invention is described in detail below with reference to some specific examples: