Microwave ceramic dielectric material and method for preparing the same

Abstract

The application discloses a microwave ceramic dielectric material and a preparation method thereof, and belongs to the field of microwave ceramic dielectric materials. The microwave ceramic dielectric material comprises a main crystal phase, and the expression of the main crystal phase is aRCO3-bLn2O3-cBi2O3-dTiO2, wherein R is Ca or Sr, Ln is La or Sm, and a:b:c:d=(3-4):(0.2-1):(1-2):(4-5). The microwave ceramic dielectric material can be sintered at 1000-1100 DEG C by adopting a specific main crystal phase and modified additives and sintering aids, and can keep a high Qf value.

Description

Technical Field

[0001] This invention relates to the field of microwave ceramic dielectric materials, and specifically to a microwave ceramic dielectric material and its preparation method. Background Technology

[0002] Microwave ceramics are core materials for microwave devices. In the past decade or so, the rapid development of microwave technology and equipment towards miniaturization and integration, especially towards mass production and low prices for consumer products, coupled with the significant progress in electronic ceramics over the past thirty years, has led to rapid advancements in the research and practical application of microwave ceramics. Currently, a large number of microwave ceramic dielectric materials suitable for various microwave frequency bands have been developed. Dielectric ceramics used in microwave circuits, while satisfying the dielectric constant ε... r Under the premise of meeting the requirements of the temperature coefficient τf of the resonant frequency, materials are required to have a higher quality factor Q to improve the signal-to-noise ratio. With the rapid development of mobile communication, satellite communication, and especially digital satellite television, there is an increasing amount of research on microwave dielectric ceramics with medium to high dielectric constants and quality factors, which are widely used in mobile communication base stations, digital television receiving systems, and military radar.

[0003] CN105254293A discloses a microwave dielectric ceramic material, which includes a matrix and a sintering aid: the matrix is ​​(1-α)Ba 6-3x Nd8+2xTi 18 O 54-α Zn 2-y SiO 4-y The sintering aids are at least one of Li₂CO₃, CuO, and Bi₂O₃, where 0.50≤x≤1.0, 0≤y≤0.50, and 0.2≤α≤0.6. This microwave dielectric material has a Qf value as high as 9000-11000 GHz and a resonant frequency temperature coefficient of ±10 ppm / ℃, but its relative permittivity is only 65-75. Currently, there are not many known microwave dielectric ceramic materials with high permittivity, especially those with permittivity exceeding 100. Therefore, research on high permittivity microwave dielectric ceramic materials has become a hot topic in microwave dielectric material research both domestically and internationally in recent years. CaTiO₃ is a type of microwave dielectric ceramic material with a high permittivity of 170, but its temperature coefficient is as high as 744 ppm / ℃. It is necessary to find ways to add other components to reduce the resonant frequency temperature coefficient to near zero without significantly deteriorating the permittivity and dielectric loss of CaTiO₃ ceramics, and to appropriately lower its sintering temperature.

[0004] To address the problems existing in the aforementioned microwave ceramic dielectric materials, developing a low-temperature microwave ceramic dielectric material that can reduce the sintering temperature of microwave ceramic dielectric materials while still maintaining a high Q value is currently a key research focus. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a low-temperature microwave ceramic dielectric material and its preparation method that can reduce the sintering temperature of microwave ceramic dielectric materials but still have a high Q value.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] In a first aspect, the present invention provides a microwave ceramic dielectric material comprising a main crystalline phase, wherein the expression of the main crystalline phase is aRCO3-bLn2O3-cBi2O3-dTiO2, wherein R is Ca or Sr, Ln is La or Sm, and a:b:c:d=(3-4):(0.2-1):(1-2):(4-5).

[0008] The main crystalline phase material described in this invention is obtained using a rapid pre-sintering solid-state process, resulting in a fine-grained main crystalline phase material that is stable and highly active. The main crystalline phase material is placed in a microwave sintering kiln or a high-temperature tunnel furnace and heated from room temperature to a high-temperature zone temperature, then held at that high temperature, and finally cooled back to room temperature. The heating process takes 3-5 hours, the holding process takes 2.5-5 hours, the room temperature is 20±20℃, and the high-temperature zone temperature is 1050±50℃. Compared with traditional solid-state processes, the rapid pre-sintering process reduces the time by more than one-third, and the resulting product has uniform and fine-grained particles, while also saving energy.

[0009] The dielectric material described in this invention is also applicable to traditional pre-firing processes; the modifier and sintering flux are free of lead (Pb), cadmium (Cd), mercury (Hg), and chromium (Cr). +6 The material eliminates harmful elements that are detrimental to the environment, allowing the ceramic material to be sintered at 1000–1100℃, saving production costs while maintaining a high Q value. Furthermore, the sintered ceramic body of this low-temperature microwave dielectric material exhibits uniform and dense grain growth, free of impurities and with few defects, resulting in stable performance of components manufactured using this material.

[0010] As a preferred embodiment of the microwave ceramic dielectric material of the present invention, the microwave ceramic dielectric material further includes a modifying additive, which is a mixture of BaO, Nb2O5, and MgO or a mixture of BaO, Nb2O5, MgO, and Y2O3.

[0011] As a more preferred embodiment of the microwave ceramic dielectric material of the present invention, the modified additives contain BaO with a molar percentage of 0.2%-1.5%, Nb2O5 with a molar percentage of 0.2%-1%, MgO with a molar percentage of 0.1%-1%, and Y2O3 with a molar percentage of 0-1%.

[0012] As a preferred embodiment of the microwave ceramic dielectric material of the present invention, the microwave ceramic dielectric material further includes a sintering flux, wherein the sintering flux is a mixture of K2O, ZnO, Li2O and SiO2 or a mixture of MnO2, ZnO, Li2O, K2O and SiO2.

[0013] As a more preferred embodiment of the microwave ceramic dielectric material of the present invention, the sintering flux contains K2O with a molar percentage of 0.8%-1.5%, ZnO with a molar percentage of 1.2%-1.9%, Li2O with a molar percentage of 0.6%-1.3%, MnO2 with a molar percentage of 0-1.0%, and SiO2 with a molar percentage of 0.9%-1.8%.

[0014] As a preferred embodiment of the microwave ceramic dielectric material of the present invention, the main crystalline phase has a molar percentage content of 90%-95%, the modified additive has a molar percentage content of 0.5%-4.5%, and the sintering flux has a molar percentage content of 3.5%-7.5%. The inventors have found through a large number of experiments that under the above conditions, the sintering temperature of the microwave ceramic dielectric material can be reduced, but a relatively high Q value is still maintained.

[0015] As a more preferred embodiment of the microwave ceramic dielectric material of the present invention, the microwave ceramic dielectric material has a molar percentage content of 90%-95% for the main crystalline phase, a molar percentage content of 0.5%-4.5% for the modified additive, and a molar percentage content of 3.5%-7.5% for the sintering flux. The inventors have found through a large number of experiments that under the above conditions, the sintering temperature of the microwave ceramic dielectric material can be reduced to a greater extent, while still maintaining a relatively high Q value.

[0016] In a second aspect, the present invention provides a method for preparing microwave ceramic dielectric material as described in the first aspect. The preparation method includes the following steps: mixing the raw materials, adding deionized water, and grinding for 10-20 hours to obtain a mixture; adding polyvinyl alcohol to the mixture for granulation, and sintering to remove the polyvinyl alcohol, thereby obtaining the microwave ceramic dielectric material.

[0017] In a preferred embodiment of the preparation method of the microwave ceramic dielectric material of the present invention, the sintering temperature is 1000-1100℃ and the holding time is 3-5h.

[0018] In a preferred embodiment of the preparation method of the microwave ceramic dielectric material of the present invention, the heating rate during sintering is 3.5-6.4℃ / min.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0020] This invention provides a microwave ceramic dielectric material, which uses a specific main crystalline phase combined with modified additives and sintering flux to enable the microwave ceramic dielectric material to be sintered at 1000-1100℃ while maintaining a high Qf value. Detailed Implementation

[0021] The technical solution of the present invention will be further described below with reference to the embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention. Unless otherwise specified, the methods or operations used in the embodiments are conventional methods or operations in the art.

[0022] Examples 1-6

[0023] Examples 1-6 are microwave ceramic dielectric materials of the present invention. The composition and molar percentage of the microwave ceramic dielectric materials of Examples 1-6 are shown in Table 1.

[0024] The preparation method of the microwave ceramic dielectric material described in Examples 1-6 includes the following steps:

[0025] After weighing the raw materials according to the formula, place them in zirconia balls as the grinding medium, add deionized water as the solvent, and grind for 10-20 hours to obtain a homogeneous mixture. Dry the mixture using a bread oven or spray tower to obtain a dry powder. Then, place the obtained dry powder in a microwave sintering kiln or high-temperature tunnel furnace, heating it from room temperature to the high-temperature zone temperature, holding it at high temperature, and finally cooling it back to room temperature. The heating process takes 3-5 hours, the holding process takes 2.5-5 hours, the room temperature is 20±20℃, and the high-temperature zone temperature is 1050±50℃. The resulting calcined powder (i.e., the main crystalline phase) is then weighed according to the formula, along with modifying additives and sintering aids, and placed in zirconia balls as the grinding medium again. Deionized water is added as the solvent, and grinding for 10-20 hours to obtain a homogeneous mixture. Polyvinyl alcohol is added to the mixture, followed by granulation, pressing, and sintering at 1000-1100℃ for 3-5 hours to finally obtain the microwave ceramic dielectric material of this invention.

[0026] Table 1

[0027]

[0028]

[0029] Examples 7-12

[0030] Examples 7-12 are microwave ceramic dielectric materials of the present invention. The composition and molar percentage of the microwave ceramic dielectric materials of Examples 7-12 are shown in Table 2.

[0031] The preparation method of the microwave ceramic dielectric material described in Examples 7-12 includes the following steps:

[0032] After weighing the raw materials according to the formula, place them in zirconia balls as the grinding medium, add deionized water as the solvent, and grind for 10-20 hours to obtain a homogeneous mixture. Dry the mixture using a bread oven or spray tower to obtain a dry powder. Then, place the obtained dry powder in a microwave sintering kiln or high-temperature tunnel furnace, heating it from room temperature to the high-temperature zone temperature, holding it at high temperature, and finally cooling it back to room temperature. The heating process takes 3-5 hours, the holding process takes 2.5-5 hours, the room temperature is 20±20℃, and the high-temperature zone temperature is 1050±50℃. The resulting calcined powder (i.e., the main crystalline phase) is then weighed according to the formula, along with modifying additives and sintering aids, and placed in zirconia balls as the grinding medium again. Deionized water is added as the solvent, and grinding for 10-20 hours to obtain a homogeneous mixture. Polyvinyl alcohol is added to the mixture, followed by granulation, pressing, and sintering at 1000-1100℃ for 3-5 hours to finally obtain the microwave ceramic dielectric material of this invention.

[0033] Table 2

[0034]

[0035]

[0036] Comparative Example 1: Main crystalline phase: 3.7CaCO3-0.3La2O3-Bi2O3-5TiO2 95%, Li2O 5%.

[0037] The only difference between this comparative example and Example 6 is that only Li2O was added as a sintering aid.

[0038] Comparative Example 2: Main crystalline phases: 3.7CaCO3-0La2O3-1.3Bi2O3-5TiO2 90%, BaO 0.8%, Nb2O5 0.7%, MgO 0.8%, Y2O3 0.7%, ZnO 1.8%, MnO2 1.0%, Li2O 1.1%, K2O 1.4%, SiO2 1.7%.

[0039] The only difference between this comparative example and Example 1 is that the expression of the main crystalline phase is 3.7CaCO3-0La2O3-1.3Bi2O3-5TiO2.

[0040] Comparative Example 3: Main crystalline phase 3.7CaCO3-0.3La2O3-Bi2O3-5TiO2 90%, BaO 0%, Nb2O5 0.9%, MgO 1.1%, Y2O3 1.0%, ZnO 1.8%, MnO2 1.0%, Li2O 1.1%, K2O 1.4%, SiO2 1.7%.

[0041] The only difference between this comparative example and Example 1 is that BaO is 0%.

[0042] Comparative Example 4: Main crystalline phase 3.7CaCO3-0.3La2O3-Bi2O3-5TiO2 90%, BaO 0.8%, Nb2O5 0.7%, MgO 0.8%, Y2O3 0.7%, ZnO 2.1%, MnO2 1.4%, Li2O 1.5%, K2O 0%, SiO2 2.0%. The only difference between this comparative example and Example 1 is the presence of 0% K2O.

[0043] Performance testing

[0044] The dielectric constant and Qf value of the microwave ceramic dielectric materials in the above embodiments and comparative examples were tested using an Agilent network analyzer and the planar method, and the τf value was tested using the closed-cavity method. The product performance test parameters are shown in Table 3.

[0045] Table 3

[0046]

[0047]

[0048] As can be seen from Table 3, when the technical solution of the present invention is adopted, the obtained microwave ceramic dielectric material has a high Q value, specifically 3500-4600 GHz.

[0049] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A microwave ceramic dielectric material, characterized in that, The microwave ceramic dielectric material is composed of modified additives, sintering flux, and a main crystalline phase. The molar percentage of the main crystalline phase is 90%-95%, the molar percentage of the modified additives is 0.5%-4.5%, the molar percentage of the sintering flux is 3.5%-7.5%, and the expression of the main crystalline phase is aCaCO3-bLa2O3-cBi2O3-dTiO2, where a:b:c:d=(3-4):(0.2-1):(1-2):(4-5). The modified additive is a mixture of BaO, Nb2O5, MgO and Y2O3, wherein the molar percentage of BaO is 0.2%-1.5%, the molar percentage of Nb2O5 is 0.2%-1%, the molar percentage of MgO is 0.1%-1%, and the molar percentage of Y2O3 is 0-1%. The sintering flux is a mixture of MnO2, ZnO, Li2O, K2O and SiO2, wherein the molar percentage of K2O is 0.8%-1.5%, the molar percentage of ZnO is 1.2%-1.9%, the molar percentage of Li2O is 0.6%-1.3%, the molar percentage of MnO2 is 0-1.0%, and the molar percentage of SiO2 is 0.9%-1.8%.

2. The microwave ceramic dielectric material according to claim 1, characterized in that, In the microwave ceramic dielectric material, the molar percentage content of the main crystalline phase is 90.5%-94.5%, the molar percentage content of the modifying additive is 0.8%-4.2%, and the molar percentage content of the sintering flux is 4.0%-7.0%.

3. The method for preparing microwave ceramic dielectric material according to claim 1 or 2, characterized in that, The preparation method includes the following steps: mixing the raw materials, adding deionized water, and grinding for 10-20 hours to obtain a mixture; adding polyvinyl alcohol to the mixture for granulation, and sintering to remove the polyvinyl alcohol, thereby obtaining the microwave ceramic dielectric material.

4. The method for preparing microwave ceramic dielectric material according to claim 3, characterized in that, The sintering temperature is 1000-1100℃, and the holding time is 3-5h.

5. The method for preparing microwave ceramic dielectric material according to claim 3, characterized in that, The heating rate during sintering is 3.5-6.4℃ / min.

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