A high-strength low-dielectric composite microwave dielectric ceramic material and preparation method thereof

Abstract

The present invention relates to a high-strength low-dielectric composite microwave dielectric ceramic material and a preparation method thereof. The high-strength low-dielectric composite microwave dielectric ceramic material comprises an Al2O3 phase and a RAl2Si2O8 phase, wherein R=at least one of Ba, Ca, and Sr; the molar ratio of the Al2O3 phase to the RAl2Si2O8 phase is 1:(0.2-3); preferably, the Al2O3 phase contains flaky aluminum oxide.

Description

Technical Field

[0001] The invention relates to a high-strength low-dielectric composite microwave dielectric ceramic material and a preparation method thereof, and belongs to the field of electronic communications. Background Art

[0002] Information functional ceramic technology is the key technology of the new generation of chip electronic components. In order to adapt to the arrival of the era of integration of various electronic devices, electronic devices have put forward higher requirements for the development of circuits towards miniaturization, high density, multifunctionality, high reliability, high speed and high power. This has posed challenges to information functional ceramics while also providing good development opportunities. With the increasingly rapid development of microwave communication technology, some equipment used in microwave communication (such as high-frequency substrates, antennas, resonators and filters, etc.) require microwave dielectric ceramics to have a low relative dielectric constant (ε r <10)、small dielectric loss (tanδ<10 -3 ) and the near-zero resonant frequency temperature coefficient (τ f ≈0), which is due to the signal delay of microwave dielectric materials and the dielectric constant ε r In order to reduce this delay, people have paid more and more attention to some ε r A microwave dielectric material that is smaller and has lower loss.

[0003] However, with the continuous increase in communication frequency and capacity, in addition to requiring ceramic materials to have excellent dielectric properties, they also need excellent mechanical and thermal properties to cope with problems such as temperature shock and high-intensity vibration in harsh working environments. Summary of the invention

[0004] In response to the above technical problems, the present invention discloses a high-strength, low-dielectric composite microwave dielectric ceramic material and a preparation method thereof. The material has excellent adjustable dielectric properties, excellent mechanical properties and thermal conductivity, and has potential application prospects in mobile communications, navigation antennas, high-temperature co-fired ceramics, high-temperature sensors and other fields.

[0005] On the one hand, the present invention provides a high-strength, low-dielectric composite microwave dielectric ceramic material, which comprises the coexistence of Al2O3 phase and RAl2Si2O8 phase, wherein R=at least one of Ba, Ca, and Sr; the molar ratio of the Al2O3 phase to the RAl2Si2O8 phase is 1:(0.2~3); preferably, the Al2O3 phase contains flaky aluminum oxide.

[0006] Preferably, the present invention prepares the oriented arrangement of flake aluminum oxide (such as Figure 2) of a high-strength microwave dielectric ceramic material having excellent dielectric, thermal and mechanical properties: the relative density of the composite microwave dielectric ceramic material is ≥98%;

[0007] The dielectric constant of the composite microwave dielectric ceramic material is 6 to 8.5, and the dielectric loss is less than 0.005;

[0008] The thermal conductivity of the composite microwave dielectric ceramic material is greater than 5 W / m·K;

[0009] The flexural strength of the composite microwave dielectric ceramic material is ≥300MPa, and the Young's modulus is ≥200GPa.

[0010] On the other hand, the present invention provides a method for preparing a high-strength, low-dielectric composite microwave dielectric ceramic material, which uses Al source, Si source and R source as raw powders, and performs in-situ sintering under the action of a sintering aid to obtain a high-strength, low-dielectric composite microwave dielectric ceramic material in which Al2O3 phase and RAl2Si2O8 phase coexist; preferably, the sintering aid contains a high-melting point Ln2O3-RO-SiO2-B2O3-Al2O3 microcrystalline glass powder, and the mass of the high-melting point Ln2O3-RO-SiO2-B2O3-Al2O3 microcrystalline glass powder does not exceed 10wt% of the total mass of the raw powder.

[0011] Preferably, the Al source is at least one of irregularly shaped alumina powder with a particle size of 0.3 to 5 μm, aluminum hydroxide, or / and flaky alumina powder with a diameter of 1 to 30 μm and a thickness of more than 100 nm;

[0012] The R source is at least one of an oxide of R, a carbonate of R, a nitrate of R, and a hydroxide of R;

[0013] The Si source is SiO2 powder with a particle size of 0.5 to 5 μm.

[0014] Preferably, the molar ratio of the Al source, the R source and the Si source is 2:(0.1-1):(0.1-0.5).

[0015] Preferably, when the Al source is irregular alumina powder Al2O3 and flaky alumina powder, the mass ratio of the irregular alumina powder Al2O3 to the flaky alumina powder in the Al source is 1:(0.1-3). In the present invention, flaky alumina has poor sintering activity and generally does not participate in the reaction. By adopting the above mass ratio, it is possible to ensure that there is enough alumina powder to form the RAl2Si2O8 phase while retaining the presence and directional arrangement of flaky alumina to improve the mechanical properties of the material.

[0016] Preferably, the composition of the high melting point Ln2O3-RO-SiO2-B2O3-Al2O3 glass-ceramics powder is aLn2O3-bRO-cSiO2-dB2O3-eAl2O3, wherein Ln=at least one of Sc, Y, La, Ce, Pr, Nd, Sm, Eu, Cd, Tb, Dy, Ho, Er, Tm, Yb, and Lu, R=at least one of Ca, Ba, and Sr, a=0 to 10, b=20 to 45, c=25 to 50, d=0 to 10, e=5 to 20, and a+b+c+d+e=100. The particle size of the high melting point Ln2O3-RO-SiO2-B2O3-Al2O3 glass-ceramics powder is D 90 <2μm;Preferably, the precipitated crystal phase in the high melting point Ln2O3-RO-SiO2-B2O3-Al2O3 glass-ceramic powder includes at least one of celsium feldspar, calcium feldspar, strontium feldspar, barium silicate (BaSiO3 and / or BaSi2O5), and calcium silicate (CaSiO3 and / or CaSi2O5). In the present invention, a high melting point Ln2O3-RO-SiO2-B2O3-Al2O3 glass-ceramic powder with a specific content and a specific composition is selected as a sintering aid. Since the composition of the above-mentioned sintering aid is in the same ratio as RAl2Si2O8, it can not only assist the mass transfer of the glass liquid phase to play a role in rapid sintering, but also precipitate the same RAl2Si2O8 crystal phase, and no other impurities will appear, thereby achieving the sintering density and excellent dielectric properties of the composite microwave dielectric ceramic material with coexistence of Al2O3 phase and RAl2Si2O8 phase.

[0017] Preferably, the second sintering aid powder includes at least one of MgO, Y2O3, ZrO2, AlF3, and CaF2; the second sintering aid; the particle size D of the second sintering aid powder is 90 <2μm.

[0018] Preferably, the method comprises the following steps:

[0019] (1) mixing raw material powder, a binder, a dispersant, a plasticizer and an organic solvent to obtain a mixed slurry; preferably, the viscosity of the mixed slurry is 4 to 8 KPa·S;

[0020] (2) After filtering and vacuum degassing the mixed slurry, the mixed slurry is subjected to tape casting using a tape casting device to obtain a raw tape; preferably, the drying temperature of the tape casting device is set to 40 to 60° C.;

[0021] (3) Cutting and laminating the obtained raw tape, and then hot isostatic pressing and in-situ sintering are performed to obtain the high-strength low-dielectric composite microwave dielectric ceramic material.

[0022] Preferably, the in-situ sintering system includes: continuously heating up to 1550-1650°C at a heating rate of 3-10°C / min, keeping the temperature for 3-6 hours for in-situ sintering, and then cooling down to below 1000°C at a cooling rate of 2-5°C / min.

[0023] Preferably, before in-situ sintering, the temperature is first increased to 250-350°C at a rate of 0.5-2°C / min and kept at that temperature for 2-4 hours, and then increased to 450-550°C at a rate of 0.5-2°C / min and kept at that temperature for 2-4 hours.

[0024] Beneficial effects of the present invention:

[0025] This high-temperature substrate ceramic material has excellent dielectric, thermal and mechanical properties. The dielectric constant is adjustable between 6 and 8.5, the dielectric loss is lower than 0.005, the thermal conductivity is higher than 5W / m·K, the flexural strength is ≥300MPa, and the Young's modulus is ≥200GPa. It has excellent co-firing matching with tungsten slurry and is a high-temperature co-fired ceramic material with great potential application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 The XRD patterns of the corresponding samples prepared in Examples 2-4 and Comparative Example 1 show that the ceramics prepared by this method are composed of Al2O3 and BaAl2Si2O8 phases, and there are no crystallization peaks of other crystalline phases; and as the molar ratio of BaO increases, the diffraction peak of the BaAl2Si2O8 phase is enhanced, and the peak intensity of the Al2O3 phase decreases, indicating that the dielectric constant of the composite ceramic can be controlled by adjusting the ratio of the two phases of Al2O3 and BaAl2Si2O8;

[0027] Figure 2 and 3 The SEM images of the corresponding samples prepared in Examples 4 and 8 respectively show that the Al2O3 and BaAl2Si2O8 bionic composite ceramic materials with oriented arrangement of flaky aluminum oxide (gray) are obtained, indicating that the oriented arrangement of flaky aluminum oxide can be achieved by the tape casting-lamination method, thereby improving its mechanical properties;

[0028] Figure 4 The SEM image of the corresponding sample prepared in Example 12 shows that the Al2O3 and CaAl2Si2O8 bionic composite ceramic material with oriented arrangement of flaky aluminum oxide (gray) is obtained, indicating that the oriented arrangement of flaky aluminum oxide can be achieved by the tape casting-lamination method, thereby improving its mechanical properties;

[0029] Figure 5: This is the SEM image of the sample corresponding to Comparative Example 2. It can be seen from the figure that when no sintering aid is added, there are a large number of 5-20um pores in the microstructure of the composite ceramic obtained, and the crystal phase is irregularly arranged, indicating that in the absence of a sintering aid, a dense composite ceramic material cannot be obtained by the in-situ sintering method at 1600°C;

[0030] Figure 6 This is the SEM picture of the sample corresponding to Comparative Example 3. It can be seen from the picture that a high-density (99.5%) ceramic material can be obtained by sintering Al2O3 at 1550°C.

[0031] Figure 7 This is the SEM image of the sample corresponding to Comparative Example 6. It can be seen from the figure that the sample has many pores and stratification occurs, which means that if the sintering aid is not selected properly, the sample will not be sintered densely and will not achieve the purpose of improving the mechanical properties. DETAILED DESCRIPTION

[0032] The present invention is further described below by the following embodiments. It should be understood that the following embodiments are only used to illustrate the present invention, but not to limit the present invention.

[0033] The present invention provides a composite microwave dielectric ceramic material which comprises two phases of aluminum oxide and RAl2Si2O8 phase (R=Ba, Ca, Sr), wherein the molar ratio of Al2O3 phase:RAl2Si2O8 phase is preferably 1:(0.2-3).

[0034] In the present invention, by using Al source (for example, Al2O3, etc.), Si source (for example, SiO2, etc.) and R source (R = Ba, Ca, Sr) as raw materials and in-situ sintering under the action of sintering aids, a composite microwave dielectric ceramic in which Al2O3 phase and RAl2Si2O8 phase coexist is obtained, and the dielectric constant is adjustable between 6 and 8.5, the dielectric loss is less than 0.001, and the thermal conductivity is higher than 5W / m·K.

[0035] At the same time, in the present invention, by adjusting the mass ratio of irregular shaped alumina powder to flaky alumina powder in the composite material Al source (alumina phase), and obtaining a pearl layer-like material in which flaky alumina can be oriented by a casting method, the comprehensive mechanical properties of the Al2O3 / RAl2Si2O8 phase composite microwave dielectric ceramic material are achieved: flexural strength ≥300MPa, Young's modulus ≥200GPa.

[0036] In the present invention, the raw materials include: irregularly shaped alumina powder and aluminum hydroxide with a particle size of 0.3 to 5 μm, one or more, flaky alumina powder with a diameter of 1 to 30 μm and a thickness of more than 100 nm, R source (R = Ba, Ca, Sr), 0.5 to 5 μm SiO2 powder. The sintering aid includes high melting point Ln2O3-RO-SiO2-B2O3-Al2O3 microcrystalline glass powder and oxide powder.

[0037] Preferably, the Al source may be aluminum oxide or aluminum hydroxide. More preferably, the mass ratio of irregularly shaped aluminum oxide powder to flaky aluminum oxide powder in Al2O3 may be 1:(0.1-3).

[0038] Preferably, the R source includes one or more of oxides, carbonates, nitrates, hydroxides.

[0039] Preferably, the molar ratio of Al2O3:RO:SiO2 may be in the range of 3:(0.1-1):(0.1-0.5).

[0040] Preferably, the composition of the high melting point glass-ceramics powder in the sintering aid is aLn2O3-bRO-cSiO2-dB2O3-eAl2O3 (Ln=Sc、Y、La、Ce、Pr、Nd、Sm、Eu、Cd、Tb、Dy、Ho、Er、Tm、Yb、Lu、R=Ca、Ba、Sr), a=0~10, b=20~40, c=25~35, d=0~10, e=0~10, and a+b+c+d+e=100. Preferably, the crystalline phases that can be precipitated in the glass-ceramics include one or more phases of celsium feldspar, calcium feldspar, mullite, and barium silicate (BaSiO3, BaSi2O5). The particle size of the high melting point glass-ceramics powder is D90<2um. The addition amount of the high melting point glass-ceramics powder is 3~7wt% of the total mass of the raw materials.

[0041] Preferably, the sintering aid also includes a second aid, preferably at least one of MgO, Y2O3, ZrO2, and ZrSiO4, with a powder particle size D 90 <2um, and the added amount can be 0~5wt% of the total mass of the raw materials.

[0042] The following is an exemplary description of a method for preparing a composite microwave dielectric ceramic material.

[0043] Preparation of Ln2O3-RO-SiO2-B2O3-Al2O3 microcrystalline glass powder. Specifically, Ln source, R source, Si source, Al source, and B source are mixed in a molar ratio of (0-10): (20-40): (25-35): (0-10): (0-10) to obtain a raw material mixture A; the raw material mixture A is melted and quenched to obtain glass fragments; and the glass fragments are ball-milled and sand-milled, dried, and sieved to obtain the above-mentioned glass powder. In the process of preparing Ln2O3-RO-SiO2-B2O3-Al2O3 glass powder, the Al source is one or more Ln2O3 with a purity greater than 99%, the R source is one or more RCO3, R(NO3)2 and RCl2 with a purity greater than 99%, the Al source is one or more Al2O3 and Al(OH)3 with a purity greater than 99%, the B source is H3BO3 with a purity greater than 99%, and the Si source is SiO2 with a purity greater than 99%. The use of raw materials with a purity greater than 99% to prepare Ln2O3-RO-SiO2-B2O3-Al2O3 glass powder can ensure the stability of the glass crystallization phase and reduce the influence of impurities on dielectric properties. The temperature of the glass melting is 1500-1650°C and the time is 1.5-4 hours.

[0044] Aluminum source, flaky alumina powder, R source, silica powder, glass powder and other sintering aids are mixed in a certain mass ratio and dried to obtain a mixed material.

[0045] The mixed material powder is evenly mixed with a binder, a dispersant, a plasticizer, and an organic solvent by planetary ball milling to obtain a high viscosity casting slurry (for example, 4 to 8 kPa·S). The ball milling process for preparing microwave dielectric ceramics is divided into two steps. The first step is to mix the powder, solvent and dispersant evenly and ball mill for 1 to 3 hours at a speed of 300 to 500 rpm. The second step is to add a binder and a plasticizer and ball mill for 1 to 3 hours at a speed of 450 to 550 rpm. The solid content of the mixed slurry can be 60 to 70wt%. The content of organic solvent (alcohol and benzene mixed solvent) in the mixed slurry can be 25 to 30wt%. The content of polyvinyl butyral binder in the mixed slurry can be 7 to 10wt%. The content of BYK system and fish oil dispersant in the mixed slurry can be 0.5 to 2wt%. The content of dioctyl phthalate mixed plasticizer in the mixed slurry can be 1 to 3wt%.

[0046] After filtering and vacuum degassing the mixed slurry, the raw tape is obtained by tape casting using a tape casting device. The drying temperature of the tape casting device is set at 40 to 60°C. During the tape casting process, the bottom mold moves at a speed of 0.2 to 0.4 m / min, and the slurry thickness is controlled to 50 to 200 μm by a scraper.

[0047] The raw material strip is cut and laminated, and then hot isostatic pressing is performed to form a green body, and a debinding-sintering process is performed to obtain a high-strength, low-dielectric Al2O3 / RAl2Si2O8 composite microwave dielectric ceramic material. The parameters of the hot isostatic pressing include: the pressure can be 20-40MPa, and the temperature can be 50-80°C. The sintering process includes: first heating up to 1550-1650°C at a heating rate of 3-10°C / min and keeping warm for 3-6 hours, and then cooling down to 1000°C at a cooling rate of 2-5°C / min. Debinding is preferably performed before sintering. The debinding process includes: first heating up to 250-350°C at a heating rate of 0.5-2°C / min and keeping warm for 2-4 hours, and then heating up to 450-550°C at a heating rate of 0.5-2°C / min and keeping warm for 2-4 hours to fully remove organic matter.

[0048] In the present invention, the rapid chemical reaction of alumina and silicon dioxide is achieved by mass transfer between glass and ceramic liquid phase to produce RAl2Si2O8 phase. According to the microwave dielectric properties of the composite material (Al2O3 ceramic: εr = 9.8, tanδ < 1×10 -4 , RAl2Si2O8 ceramics: εr = 6 ~ 7, tanδ < 5 × 10 -4 ) The mixing rule can make the dielectric constant of the obtained composite material adjustable and lower than 10; on the other hand, the directional arrangement of flake aluminum oxide is achieved through the casting-lamination method to obtain a new type of bionic microwave dielectric ceramic material that imitates pearl layer, further improving the mechanical properties (bending strength 300-500MPa).

[0049] In the present invention, the prepared raw ceramic powder and sintering aid are mixed according to the mass ratio, tape-casted and laminated, and sintered at 1500-1650°C to form a microwave dielectric ceramic material. In the present invention, the microwave dielectric properties, mechanical properties and thermal properties of the microwave dielectric ceramic material can be adjusted by adjusting the molar ratio of the aluminum source, the silicon source and the R source, the mass ratio of the irregular alumina and the flaky alumina, and the tape-casting directional arrangement process: the dielectric constant can be adjusted between 6.5 and 8.5, and the dielectric loss tanδ is less than 5×10 -3 , thermal expansion coefficient 5 ~ 8ppm / ℃, thermal conductivity higher than 5W / m K, flexural strength ≥ 300MPa, Young's modulus ≥ 200GPa, and the preparation process is simple, pollution-free, low cost, can be used for the manufacture of high-temperature co-fired ceramic systems, multilayer dielectric resonators, microwave antennas, filters and other microwave devices. It is a low-temperature co-fired ceramic material with great potential application value.

[0050] High-strength low-dielectric composite microwave dielectric ceramic material performance test:

[0051] (1) Performance characterization: The thermal expansion coefficient of the obtained ceramic material was tested using a thermal expansion meter. The bending strength and Young's modulus of the obtained ceramic material were tested using a 5566 universal testing machine. The thermal conductivity of the obtained ceramic material was tested using a laser thermal conductivity meter. The phase and morphology of the ceramic material were tested using a high-resolution powder X-ray diffractometer and a field emission scanning electron microscope;

[0052] (2) Microwave dielectric properties: The plate method was used to measure the relative dielectric constant εr and dielectric loss tan quality factor Q×f of the sample at microwave frequency. The instrument used was Agilent E8362B vector network analyzer, and the test sample size was 10×10×0.9 mm.

[0053] The following further examples are given to illustrate the present invention in detail. It should also be understood that the following examples are only used to further illustrate the present invention and cannot be understood as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the above content of the present invention belong to the scope of protection of the present invention. The specific process parameters and the like in the following examples are also only examples within a suitable range, that is, those skilled in the art can make a selection within a suitable range through the description herein, and are not limited to the specific values ​​​​exemplified below.

[0054] Example 1

[0055] (1) According to the glass ratio of 5La2O3-40BaO-35SiO2-5B2O3-15Al2O3 (total 100 mol%), weigh 43.34 g of lanthanum oxide, 446.26 g of barium carbonate, 130.02 g of aluminum oxide, 76.99 g of boric acid, and 303.39 g of silicon dioxide, pour the prepared materials into a mortar, add an appropriate amount of deionized water, stir evenly, and place in a platinum crucible at 1550°C for 2 h, then directly pour the molten glass into deionized water for quenching to obtain a glass sample;

[0056] (2) putting 1000 g of glass fragments obtained in step (1) + 3600 g of zirconium oxide balls + 600 mL of anhydrous ethanol into an alumina ceramic jar, and milling them in a planetary ball mill at a speed of 450 rpm for 2 h to obtain a glass powder slurry, which was then sieved through a 120-mesh sieve;

[0057] (3) placing the glass powder slurry ball-milled in step (2) in a sand mill and grinding at a speed of 2000 rpm for 3 h, and then passing the slurry through a 400-mesh sieve and placing it in a 110° C. constant temperature drying oven for 12 h to obtain glass powder (particle size D90≈2±0.5 μm) for later use;

[0058] (4) According to the proportions in Table 1, 82.52 g of alumina powder, 82.52 g of flaky alumina, 10.64 g of barium carbonate, 25.12 g of silicon oxide powder, and 10 g of glass powder were weighed, 210 g of the material + 300 g of zirconium oxide balls + 100 mL of anhydrous ethanol were added to a polyethylene tetrachloride tank, and the mixture was ball milled in a planetary ball mill at a speed of 450 rpm for 1 h. After drying, the mixture was sieved through a 100-mesh sieve to obtain a uniformly mixed powder;

[0059] (5) 200 g of the powder obtained in step (4) was placed in a nylon jar together with 20 g of anhydrous ethanol, 20 g of xylene and 2 g of BYK-255 dispersant, and subjected to planetary milling at a speed of 450 rpm for 1 hour, and then 14 g of PVB 98 binder and 6.8 g of S160 plasticizer were added, and the mixture was further subjected to planetary milling at a speed of 300 rpm for 1 hour to obtain a casting slurry;

[0060] (6) filtering the casting slurry and the grinding balls through a 100-mesh sieve and performing vacuum degassing treatment;

[0061] (7) The slurry is poured onto the PCB bottom mold for casting, and is driven forward by the PCB bottom mold at a speed of 0.25 m / min. The slurry thickness is controlled at 100 μm by a scraper, and the temperature in the casting chamber is controlled at 65°C. After the slurry is formed into a film tape, the bottom mold is removed to obtain a green body (green ceramic sheet);

[0062] (8) The blank was simply cut according to the XY axis shrinkage rate of 14.5% and the Z axis shrinkage rate of 30%, the sample for dielectric property test was cut according to the size of 12×12×1.2 mm, laminated and hot isostatic pressing was performed, the sample for mechanical property test was cut according to the size of 42×42×4 mm, laminated and hot isostatic pressing was performed, and the sample for thermal conductivity test was cut according to the size of 10×10×2.8 mm, laminated and hot isostatic pressing was performed, wherein the hot isostatic pressing pressure was controlled at 35 MPa, the temperature was 80° C., and the holding time was 30 minutes;

[0063] (9) The sample was placed in a muffle furnace and heated to 300 °C at a rate of 1 °C / min and kept at that temperature for 4 hours. The sample was then heated to 500 °C at a rate of 1 °C / min and kept at that temperature for 2 hours to fully remove organic matter. The sample was then heated to 1550 °C at a rate of 5 °C / min and kept at that temperature for 4 hours to sinter. The sample was then cooled to below 1000 °C at a rate of 1 °C / min.

[0064] Example 2

[0065] The preparation process of the sealing member in Example 2 of the present invention refers to that in Example 1, the difference is: 78.35 g of aluminum oxide powder, 78.35 g of flaky aluminum oxide, 20.22 g of barium carbonate, 23.08 g of silicon oxide powder, and 10 g of glass powder.

[0066] Example 3

[0067] The preparation process of the sealing member in Example 3 of the present invention refers to that in Example 1, except that: 74.58 g of aluminum oxide powder, 74.58 g of flaky aluminum oxide, 28.86 g of barium carbonate, 21.96 g of silicon oxide powder, and 10 g of glass powder.

[0068] Example 4

[0069] The preparation process of the sealing member in Example 4 of the present invention refers to that in Example 1, the difference is: 71.16 g of aluminum oxide powder, 71.16 g of flaky aluminum oxide, 36.72 g of barium carbonate, 20.96 g of silicon oxide powder, and 10 g of glass powder.

[0070] Example 5

[0071] The preparation process of the sealing member in Example 5 of the present invention refers to that in Example 1, except that: 77.41 g of aluminum oxide powder, 77.41 g of flaky aluminum oxide, 29.96 g of barium carbonate, 14.13 g of silicon oxide powder, and 10 g of glass powder.

[0072] Table 1 shows the composition and corresponding properties of the composite materials prepared in Examples 1-5:

[0073] Example 1 Example 2 Example 3 Example 4 Example 5 Alumina 3 3 3 3 3 Silicon dioxide 0.75 0.75 0.75 0.75 0.5 Barium Oxide 0.1 0.2 0.3 0.4 0.3 Alumina: flake alumina mass ratio 1:1 1:1 1:1 1:1 1:1 Glass phase / wt% 5 5 5 5 5 Second auxiliary agent / wt% 0 0 0 0 0 Sintering temperature / ℃ 1550 1550 1550 1550 1550 <![CDATA[Al2O3 phase: RAl2Si2O8 phase]]> 1:0.25 1:0.6 1:1.5 1:2 1:1.25 Dielectric constant 8.187 7.984 8.145 7.703 8.553 <![CDATA[Dielectric loss / 10 -3 > 1.566 1.235 0.499 0.127 0.127 <![CDATA[Density (g / cm 3 )]]> 3.709 3.655 3.592 3.541 3.612 Relative density / % 99.3 99.2 98.95 98.92 99.01 Thermal conductivity W / m·K 19.124 14.841 12.381 10.234 13.819 Bending strength / MPa 482±10 446±10 430±10 392±10 450±15

[0074] Example 6

[0075] The preparation process of the sealing member in Example 6 of the present invention refers to that in Example 1, the difference is: 71.94 g of aluminum oxide powder, 71.94 g of flaky aluminum oxide, 27.84 g of barium carbonate, 28.26 g of silicon oxide powder, and 10 g of glass powder.

[0076] Example 7

[0077] The preparation process of the sealing member in Example 7 of the present invention refers to that in Example 1, except that: 69.49 g of aluminum oxide powder, 69.49 g of flaky aluminum oxide, 26.9 g of barium carbonate, 34.12 g of silicon oxide powder, and 10 g of glass powder.

[0078] Example 8

[0079] The preparation process of the sealing component in Example 8 of the present invention refers to that in Example 1, except that: 67.2 g of aluminum oxide powder, 67.2 g of flaky aluminum oxide, 26 g of barium carbonate, 39.6 g of silicon oxide powder, and 10 g of glass powder.

[0080] Example 9

[0081] The preparation process of the sealing member in Example 9 of the present invention refers to that in Example 1, except that: 59.47 g of aluminum oxide powder, 59.47 g of flaky aluminum oxide, 46.03 g of barium carbonate, 35.04 g of silicon oxide powder, and 10 g of glass powder.

[0082] Example 10

[0083] The preparation process of the sealing component in Example 10 of the present invention refers to that in Example 1, except that: 55.23 g of aluminum oxide powder, 55.23 g of flaky aluminum oxide, 57 g of barium carbonate, 32.54 g of silicon oxide powder, and 10 g of glass powder.

[0084] Table 2 shows the composition and corresponding properties of the composite materials prepared in Examples 6-10:

[0085] Example 6 Example 7 Example 8 Example 9 Example 10 Alumina 3 3 3 3 3 Silicon dioxide 1 1.25 1.5 1.5 1.5 Barium Oxide 0.3 0.3 0.3 0.6 0.8 Alumina: flake alumina mass ratio 1:1 1:1 1:1 1:1 1:1 Glass phase / wt% 5 5 5 5 5 Second auxiliary agent / wt% 0 0 0 0 0 Sintering temperature / ℃ 1550 1550 1550 1550 1550 <![CDATA[Al2O3 phase: RAl2Si2O8 phase]]> 1:2.3 1:2.75 1:3 1:2.5 1:2 Dielectric constant 7.529 7.271 6.707 7.494 7.624 <![CDATA[Dielectric loss / 10 -3 > 1.12 1.959 2.341 0.522 0.413 <![CDATA[Density (g / cm 3 )]]> 3.510 3.436 3.354 3.261 3.181 Relative density / % 98.95％ 98.96％ 99.11％ 98.92％ 99.21％ Thermal conductivity W / m·K 10.15 8.565 7.152 6.911 5.109 Bending strength / MPa 416±10 406±10 380±10 353±10 320±10

[0086] Embodiment 11

[0087] The preparation process of the sealing component in Example 11 of the present invention refers to that in Example 1, except that: 78.35 g of aluminum oxide powder, 78.35 g of flaky aluminum oxide, 20.48 g of calcium carbonate, 23.05 g of silicon oxide powder, and 10 g of glass powder.

[0088] Example 12

[0089] The preparation process of the sealing member in Example 12 of the present invention refers to that in Example 1, the difference is: 74.61 g of aluminum oxide powder, 74.61 g of flaky aluminum oxide, 28.81 g of strontium carbonate, 21.98 g of silicon oxide powder, and 10 g of glass powder.

[0090] Example 13

[0091] The preparation process of the sealing component in Example 13 of the present invention refers to that in Example 1, except that: 74.53 g of aluminum oxide powder, 74.53 g of flaky aluminum oxide, 19.23 g of barium carbonate, 9.75 g of calcium carbonate, 21.96 g of silicon oxide powder, and 10 g of glass powder.

[0092] Embodiment 14

[0093] The preparation process of the sealing component in Example 14 of the present invention refers to Example 4, with the following differences: 71.16g of aluminum oxide powder, 71.16g of flaky aluminum oxide, 36.72g of barium carbonate, 20.96g of silicon oxide powder, 5g of glass powder, and 5g of magnesium oxide.

[0094] Embodiment 15

[0095] The preparation process of the sealing member in Example 4 of the present invention refers to that in Example 4, the difference is: 94.88g of aluminum oxide powder, 47.44g of flaky aluminum oxide, 36.72g of barium carbonate, 20.96g of silicon oxide powder, and 10g of glass powder.

[0096] Table 3 shows the composition and corresponding properties of the composite materials prepared in Examples 11-15:

[0097] Embodiment 11 Example 12 Example 13 Embodiment 14 Embodiment 15 Alumina 3 3 3 3 3 Silicon dioxide 0.75 0.75 0.75 0.75 0.75 Barium Oxide 0 0 0.2 0.4 0.4 Calcium Oxide 0.4 0 0.2 0 0 Strontium oxide 0 0.4 0 0 0 Alumina: flake alumina mass ratio 1:1 1:1 1:1 1:1 1:0.5 Glass phase / wt% 5 5 5 2.5 5 Second auxiliary agent / wt% 0 0 0 2.5MgO 0 Sintering temperature / ℃ 1550 1550 1550 1525 1550 <![CDATA[Al2O3 phase: RAl2Si2O8 phase]]> 1:2 1:2 1:2 1:2 1:2 Dielectric constant 7.929 7.771 8.817 7.494 7.529 <![CDATA[Dielectric loss / 10 -3 > 1.02 1.059 1.054 0.522 0.412 <![CDATA[Density (g / cm 3 )]]> 3.588 3.542 3.484 3.461 3.510 Relative density / % 98.92％ 98.96％ 98.96％ 99.12％ 99.41％ Thermal conductivity (W / m·K) 10.89 10.96 10.52 9.911 10.15 Bending strength / MPa 408±10 415±10 403±10 353±10 340±10

[0098] Example 16

[0099] The preparation process of the sealing component in Example 16 of the present invention refers to that in Example 4, except that: 47.44 g of aluminum oxide powder, 94.88 g of flaky aluminum oxide, 36.72 g of barium carbonate, 20.96 g of silicon oxide powder, and 10 g of glass powder.

[0100] Embodiment 17

[0101] The preparation process of the sealing component in Example 17 of the present invention refers to Example 4, with the following differences: 35.58g of aluminum oxide powder, 106.74g of flaky aluminum oxide, 36.72g of barium carbonate, 20.96g of silicon oxide powder, and 10g of glass powder.

[0102] Embodiment 18

[0103] The preparation process of the sealing component in Example 18 of the present invention refers to Example 4, with the following differences: 106.74g of aluminum oxide powder, 35.58g of flaky aluminum oxide, 36.72g of barium carbonate, 20.96g of silicon oxide powder, and 10g of glass powder.

[0104] Embodiment 19

[0105] The preparation process of the sealing component in Example 19 of the present invention refers to that in Example 4, except that: 118.60 g of aluminum oxide powder, 23.72 g of flaky aluminum oxide, 36.72 g of barium carbonate, 20.96 g of silicon oxide powder, and 10 g of glass powder.

[0106] Embodiment 20

[0107] The preparation process of the sealing component in Example 20 of the present invention refers to Example 4, with the following differences: 71.16g of aluminum oxide powder, 71.16g of flaky aluminum oxide, 36.72g of barium carbonate, 20.96g of silicon oxide powder, and 5g of glass powder.

[0108] Table 4 shows the composition and corresponding properties of the composite materials prepared in Examples 16-20:

[0109]

[0110]

[0111] Embodiment 21

[0112] The preparation process of the sealing component in Example 21 of the present invention refers to Example 4, with the following differences: 71.16g of aluminum oxide powder, 71.16g of flaky aluminum oxide, 36.72g of barium carbonate, 20.96g of silicon oxide powder, and 15g of glass powder.

[0113] Embodiment 22

[0114] The preparation process of the sealing component in Example 22 of the present invention refers to Example 4, with the following differences: 71.16g of aluminum oxide powder, 71.16g of flaky aluminum oxide, 36.72g of barium carbonate, 20.96g of silicon oxide powder, and 20g of glass powder.

[0115] Embodiment 23

[0116] The sealing component preparation process in Example 23 of the present invention refers to Example 4, with the difference that the composition of the glass powder is a1Y2O3-a2La2O3-bRO-cSiO2-dB2O3-eAl2O3, wherein a1=2.5, a2=7.5, b=35, c=35, d=2.5, e=17.5, and a+b+c+d+e=100.

[0117] Comparative Example 1

[0118] The preparation process of the sealing member in Comparative Example 1 of the present invention refers to that of Example 4, except that: 142.32 g of aluminum oxide powder, 36.72 g of barium carbonate, 20.96 g of silicon oxide powder, and 10 g of glass powder.

[0119] Comparative Example 2

[0120] The preparation process of the sealing member in Comparative Example 2 of the present invention refers to that of Example 4, except that: 142.32 g of aluminum oxide powder, 36.72 g of barium carbonate, and 20.96 g of silicon oxide powder.

[0121] Table 5 shows the composition and corresponding properties of the composite materials prepared in Examples 21-23 and Comparative Examples 1-2:

[0122]

[0123]

[0124] Comparative Example 3

[0125] (1) 200 g of alumina powder was first placed in a nylon jar together with 20 g of anhydrous ethanol, 20 g of xylene and 2 g of BYK-255 dispersant, and the mixture was subjected to planetary milling at a speed of 450 rpm for 1 hour. Then, 14 g of PVB 98 binder and 6.8 g of S160 plasticizer were added and the mixture was subjected to planetary milling at a speed of 300 rpm for 1 hour to obtain a casting slurry;

[0126] (2) filtering the casting slurry and the grinding balls through a 100-mesh sieve and performing vacuum degassing treatment;

[0127] (3) The slurry is poured onto the PCB bottom mold for casting, and is driven forward by the PCB bottom mold at a speed of 0.25 m / min. The slurry thickness is controlled at 100 μm by a scraper, and the temperature in the casting chamber is controlled at 65°C. After the slurry is formed into a film tape, the bottom mold is removed to obtain a green body (green ceramic sheet);

[0128] (4) The blank was simply cut according to the XY axis shrinkage rate of 14.5% and the Z axis shrinkage rate of 30%. The samples for dielectric performance test were cut, laminated and hot isostatically pressed according to the size of 12×12×1.2 mm, the samples for mechanical performance test were cut, laminated and hot isostatically pressed according to the size of 42×42×4 mm, and the samples for thermal conductivity test were cut, laminated and hot isostatically pressed according to the size of 10×10×2.8 mm, wherein the hot isostatic pressing pressure was controlled at 35 MPa, the temperature was 80° C., and the holding time was 30 minutes;

[0129] (5) Place the sample in a muffle furnace and heat it to 300 °C at a rate of 1 °C / min and keep it at that temperature for 4 hours. Then heat it to 500 °C at a rate of 1 °C / min and keep it at that temperature for 2 hours to fully remove organic matter. Then heat it to 1550 °C at a rate of 5 °C / min and keep it at that temperature for 4 hours to sinter. Then cool it down to below 1000 °C at a rate of 1 °C / min.

[0130] Comparative Example 4

[0131] The preparation process of the sealing member in Comparative Example 4 of the present invention refers to that in Example 1, the difference is: 149.16 g of aluminum oxide powder, 28.86 g of barium carbonate, 21.96 g of silicon oxide powder, and 10 g of glass powder.

[0132] Comparative Example 5

[0133] The preparation process of the sealing member in Comparative Example 5 of the present invention refers to that in Example 4, the difference is: 71.16 g of aluminum oxide powder, 71.16 g of flaky aluminum oxide, 36.72 g of barium carbonate, 20.96 g of silicon oxide powder, and 25 g of glass powder.

[0134] Comparative Example 6

[0135] The sealing component preparation process in Comparative Example 6 of the present invention refers to Example 4, except that the composition of the glass powder is aLn2O3-bRO-cSiO2-dB2O3-eAl2O3, wherein a=0, b=15, c=30, d=5, e=50, and a+b+c+d+e=100.

[0136] Table 6 shows the composition and corresponding properties of the composite materials prepared in Comparative Examples 3-6:

[0137] Comparative Example 3 Comparative Example 4 Comparative Example 5 Comparative Example 6 Alumina 1 3 3 3 Silicon dioxide 0 0.75 0.75 0.75 Barium Oxide 0 0.3 0.4 0.4 Calcium Oxide 0 0 0 0 Strontium oxide 0 0 0 0 Alumina: flake alumina mass ratio 0 1:0 1:1 1:1 Glass phase / wt% 0 5 12.5 5 Second auxiliary agent / wt% 0 0 0 0 Sintering temperature / ℃ 1550 1575 1550 1550 <![CDATA[Molar ratio of Al2O3 phase to RAl2Si2O8 phase]]> 1:0 1:1.5 1:2 1:2 Dielectric constant 9.9 7.529 7.221 - <![CDATA[Dielectric loss / 10 -3 > 0.05 11.2 51.89 - <![CDATA[Density (g / cm 3 )]]> 3.78 3.510 3.655 - Relative density / % 99.52％ 98.91％ 98.86％ 95％ Thermal conductivity (W / m·K) 26.12 10.15 4.82 - Bending strength / MPa 480±10 320±10 350±10 200±10

Claims

1. A high-strength low-dielectric composite microwave dielectric ceramic material, characterized in that: The high-strength low-dielectric composite microwave dielectric ceramic material comprises an Al2O3 phase and a RAl2Si2O8 phase, wherein R=at least one of Ba, Ca, and Sr; the molar ratio of the Al2O3 phase to the RAl2Si2O8 phase is 1:(0.2-3); the Al2O3 phase contains flaky aluminum oxide; The preparation method of the high-strength low-dielectric composite microwave dielectric ceramic material comprises: mixing Al source, Si source, R source and sintering aid to prepare a mixed slurry, and performing tape casting, lamination and in-situ sintering to obtain a high-strength low-dielectric composite microwave dielectric ceramic material in which Al2O3 phase and RAl2Si2O8 phase coexist; wherein, The Al source includes: irregularly shaped alumina powder with a particle size of 0.3 to 5 μm and flaky alumina powder with a diameter of 1 to 30 μm and a thickness of more than 100 nm, and the mass ratio of the two is 1: (0.1 to 3); The in-situ sintering system includes: firstly heating the temperature to 1550-1650°C at a heating rate of 3-10°C / min and keeping the temperature for 3-6 hours for in-situ sintering, and then cooling the temperature to below 1000°C at a cooling rate of 2-5°C / min.

2. The high-strength low-dielectric composite microwave dielectric ceramic material according to claim 1, characterized in that: The relative density of the composite microwave dielectric ceramic material is ≥98%; The dielectric constant of the composite microwave dielectric ceramic material is 6 to 8.5, and the dielectric loss is less than 0.005; The thermal conductivity of the composite microwave dielectric ceramic material is greater than 5 W / m·K; The composite microwave dielectric ceramic material has a flexural strength of ≥300 MPa and a Young's modulus of ≥200 GPa.

3. The high-strength low-dielectric composite microwave dielectric ceramic material according to claim 1, characterized in that: The sintering aid comprises high melting point Ln2O3-RO-SiO2-B2O3-Al2O3 glass-ceramics powder, and the mass of the high melting point Ln2O3-RO-SiO2-B2O3-Al2O3 glass-ceramics powder does not exceed 10wt% of the total mass of the raw material powder.

4. The high-strength low-dielectric composite microwave dielectric ceramic material according to claim 1, characterized in that: The R source includes at least one of an oxide of R, a carbonate of R, a nitrate of R, and a hydroxide of R; The Si source includes SiO2 powder with a particle size of 0.5 to 5 μm.

5. The high-strength low-dielectric composite microwave dielectric ceramic material according to claim 1, characterized in that: The molar ratio of the Al source, the R source and the Si source is 3:(0.1-1):(0.1-0.5).

6. The high-strength low-dielectric composite microwave dielectric ceramic material according to claim 3, characterized in that: The composition of the high melting point Ln2O3-RO-SiO2-B2O3-Al2O3 glass-ceramics powder is aLn2O3-bRO-cSiO2-dB2O3-eAl2O3, wherein Ln=at least one of Sc, Y, La, Ce, Pr, Nd, Sm, Eu, Cd, Tb, Dy, Ho, Er, Tm, Yb, and Lu, R=at least one of Ca, Ba, and Sr, a=0-10, b=20-45, c=25-50, d=0-10, and e=5-20, and a+b+c+d+e=100, and a and d are not 0; The particle size of the high melting point Ln2O3-RO-SiO2-B2O3-Al2O3 glass-ceramic powder is D 90 <2μm.

7. The high-strength low-dielectric composite microwave dielectric ceramic material according to claim 6, characterized in that: The crystalline phases precipitated in the high-melting-point Ln2O3-RO-SiO2-B2O3-Al2O3 glass-ceramics powder include at least one of celsium feldspar, calcium feldspar, strontium feldspar, barium silicate, and calcium silicate phases; wherein the barium silicate is BaSiO3 and / or BaSi2O5; and the calcium silicate is CaSiO3 and / or CaSi2O5.

8. The high-strength low-dielectric composite microwave dielectric ceramic material according to any one of claims 3 to 5, characterized in that: The sintering aid further comprises a second aid powder, wherein the second aid powder comprises at least one of MgO, Y2O3, ZrO2, AlF3, and CaF2; the content of the second aid powder does not exceed 5wt% of the total mass of the raw material powder; The particle size D of the second auxiliary agent powder 90 <2μm.

9. A method for preparing a high-strength low-dielectric composite microwave dielectric ceramic material as claimed in any one of claims 1 to 8, characterized in that: The steps include: (1) mixing raw material powder, a binder, a dispersant, a plasticizer and an organic solvent to obtain a mixed slurry; (2) After filtering and vacuum degassing the mixed slurry, tape casting is performed using a tape casting device to obtain a raw tape; (3) Cutting and stacking the obtained raw tape, and then hot isostatic pressing and in-situ sintering are performed to obtain the high-strength low-dielectric composite microwave dielectric ceramic material.

10. The preparation method according to claim 9, characterized in that: The viscosity of the mixed slurry is 4-8 KPa·S; in the casting device, the drying temperature is set at 40-60°C.

11. The preparation method according to claim 9 or 10, characterized in that: Before in-situ sintering, the temperature is first increased to 250-350°C at a rate of 0.5-2°C / min and kept at that temperature for 2-4 hours, and then increased to 450-550°C at a rate of 0.5-2°C / min and kept at that temperature for 2-4 hours.

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