CN106587991B - Low-temperature sintered composite microwave dielectric ceramic material and preparation method thereof - Google Patents

Abstract

The invention belongs to the field of electronic ceramics and manufacture thereof, and particularly relates to a low-temperature sintered composite microwave dielectric ceramic material and a preparation method thereof. Of the materials of the inventionThe base material is BaTi₅O₁₁nCuO-xM, n is more than or equal to 0.005 and less than or equal to 0.020 weight ratio, M is a burning reducing agent, and x is more than or equal to 0.010 and less than or equal to 0.075 weight ratio. M is specifically: ba of 27.25% or more₂CO₃≤46.74％、4.25％≤Li₂CO₃≤7.47％、8.65％≤SiO₂≤9.19％、25.59％≤B₂O₃≤38.29％、20.88％≤ZnO≤32.95％、1.58％≤Al₂O₃≤9.83％、0.29％≤MnCO₃Less than or equal to 0.95 percent. The material provided by the invention has the advantages of compact system, dielectric constant (30-40) and loss (less than or equal to 10) at the sintering temperature (875-920 ℃), and^‑4) And Qxf (GHz) 20000 to 30000, can be co-fired with silver well in LTCC process, and is easy for industrial production. The low-temperature high-dielectric-constant microwave dielectric core material can be widely applied to microwave devices such as dielectric resonators, filters, oscillators and the like in satellite communication, and has important industrial application value.

Description

Low-temperature sintered composite microwave dielectric ceramic material and preparation method thereof

Technical Field

The invention belongs to the field of electronic ceramics and manufacture thereof, and relates to a composite microwave dielectric ceramic material, in particular to a low-temperature sintered composite microwave dielectric ceramic material and a preparation method thereof.

Background

The microwave dielectric ceramic is used as a dielectric material and can perform one or more functions in a microwave (300MHz to 300GHz) frequency band circuit, is a key basic material in modern communication technology, and is widely applied to microwave components such as dielectric resonators, filters, dielectric substrates, dielectric waveguide loops, microwave capacitors, duplexers, antennas and the like.

The dielectric ceramic applied to the microwave frequency band meets the following requirements: (1) appropriate dielectric constant to facilitate miniaturization of the device (size of dielectric component and dielectric constant epsilon)_rIs inversely proportional to the square root of); (2) a high quality factor Q is required to reduce loss, and Q x f is generally equal to or greater than 3000GHz (where f is the resonant frequency). (ii) a (3) A stable frequency temperature coefficient close to zero to ensure the temperature stability of the device; (4) has good cofiring property with silver or copper. In recent years, the development of electronic information technology is moving to high frequency and digitalizationThe demand for miniaturization, integration and modularization of components is also more and more urgent. Low Temperature cofired ceramic LTCC (Low Temperature Co-fired Ceramics) has become one of the main technologies for electronic device modularization due to its excellent electrical, mechanical, thermal and process characteristics. Researchers at home and abroad in recent years have conducted extensive research and study on some low-burning system materials. Ceramic BaO-TiO in microwave medium₂In the system, BaTi₅O₁₁Has good microwave dielectric property, but has high sintering temperature (more than 1100 ℃), can not be directly co-sintered with low-melting-point metals such as Ag, Cu and the like, thereby greatly limiting the application of the low-melting-point metals in the field of LTCC. Therefore, how to reduce the sintering temperature of the microwave dielectric material becomes a research focus, and currently, generally adopted methods for reducing the sintering temperature of the microwave dielectric material include: (1) the preparation process is improved, such as the preparation by adopting a chemical synthesis method, the sintering temperature is reduced, but the method has complex process and increased manufacturing period; (2) the superfine powder is used as a raw material, so that the activity of the powder is improved, and the sintering temperature of the ceramic is reduced, but the method has high cost; (3) the low-melting-point oxide or the low-melting-point glass sintering aid is added, and the low-melting-point oxide or the low-melting-point glass sintering aid forms a liquid phase in the sintering process, so that the cooling effect is obvious, the process is simple, and the batch production is easy. Therefore, in order to reduce the manufacturing cost, the third method is mostly adopted to reduce the sintering temperature of the microwave dielectric material.

For BaO-TiO₂The microwave dielectric ceramic system is generally prepared by adding low-melting point oxide, such as B₂O₃And V₂O₅Can reduce BaO-TiO₂The sintering temperature of the system. But added low-melting oxides, B₂O₃And V₂O₅In the later casting process, the slurry is easy to cause overlarge viscosity and instability, and is not matched with an industrial casting process, so that the practical application of the slurry is limited. And low-temperature sintering affects BaO-TiO₂The compactness of the microwave dielectric ceramic system can cause silver infiltration in the LTCC process, and the ceramic cannot be co-fired with silver well. The other method is to mix low-melting glass, but the existence of the glass phase greatly improves the dielectric loss of the material, and the glass has unstable performance and higher cost in the smelting process,greatly limit BaO-TiO₂In view of the above, the development of system materials and microwave multilayer devices has enabled industrial application of how to prepare a stable, low temperature sinterable, dense composite microwave dielectric ceramic material. [1]H.f.Zhou,X.b.Liu,H.Wang,L.Fang,X.l.Chen,Phase stability,lowtemperature cofiring and microwave dielectric properties of BaTi₅O₁₁ceramicswith BaCu(B₂O₅) addition, J Mater Sci Mater Electron (2013)24: 299-304 discloses a BaTi₅O₁₁After the sintering temperature is reduced from 1100 ℃ to 925 ℃ after the sintering reducing agent is added into the microwave ceramic material, the microwave dielectric property is obtained: epsilon_r＝37.4，Qxf＝25502GHz。

The above document reduces BaTi₅O₁₁The sintering temperature of 925 ℃ is still relatively high in the application of LTCC, which limits the application of LTCC.

Disclosure of Invention

Aiming at the problems or the defects, the invention provides a low-temperature sintered composite microwave dielectric ceramic material and a preparation method thereof; the sintering temperature (875 ℃ -920 ℃) of the material is compact, the material has medium dielectric constant (30-40) and low loss (less than or equal to 10)^-4) And Qxf (GHz) 20000 to 30000, can be co-fired with silver well in LTCC process, and is easy for industrial production.

The chemical composition of the low-temperature sintered composite microwave dielectric ceramic material is as follows: BaTi₅O₁₁nCuO-xM, n is more than or equal to 0.005 and less than or equal to 0.020 weight ratio, M is a burning reducing agent, and x is more than or equal to 0.010 and less than or equal to 0.075 weight ratio.

The weight percentage of the raw materials of the combustion reducing agent M is as follows: BaCO not less than 27.25%₃≤46.74％、4.25％≤Li₂CO₃≤7.47％、8.65％≤SiO₂≤9.19％、25.59％≤B₂O₃≤38.29％、20.88％≤ZnO≤32.95％、1.58％≤Al₂O₃≤9.83％、0.29％≤MnCO₃≤0.95％。

The preparation method of the low-temperature sintered composite microwave dielectric ceramic material comprises the following steps:

step 1, mixing BaCO₃、CuO、TiO₂According to BaTi₅O₁₁-nCuO, wherein n is more than or equal to 0.005 and less than or equal to 0.020 in weight ratio, then wet-grinding and mixing for 3-5 hours by taking deionized water as a medium, drying at 80-120 ℃ after taking out, sieving by using a 40-100 mesh sieve, and then presintering for 5-8 hours in an atmosphere at 800-1200 ℃ to synthesize a main crystal phase BaTi₅O₁₁Phase, i.e. the base.

Step 2, the raw materials are as follows by mass percent: BaCO not less than 27.25%₃≤46.74％、4.25％≤Li₂CO₃≤7.47％、8.65％≤SiO₂≤9.19％、25.59％≤B₂O₃≤38.29％、20.88％≤ZnO≤32.95％、1.58％≤Al₂O₃≤9.83％、0.29％≤MnCO₃Batching less than or equal to 0.95 percent, wet-milling and mixing for 3-7 hours by taking deionized water as a medium, sieving by using a 40-100 mesh sieve after drying, pre-burning for 2-8 hours at 500-800 ℃, and preparing the combustion reducing agent M powder for later use.

And 3, adding the sintering agent powder which is prepared in the step 2 and accounts for 1-7.5 percent of the total mass percent into the base material prepared in the step 1, uniformly mixing, wet-grinding and mixing for 3-5 hours by taking alcohol as a medium, taking out, drying at 80-120 ℃, granulating by taking an acrylic acid solution which accounts for 2-5 percent of the total mass of the raw materials as a binder, performing compression molding, and sintering for 1-3 hours in an atmosphere of 875-920 ℃ to prepare the microwave medium ceramic material.

In summary, compared with the prior art, the invention has the beneficial effects that:

1. the formula of the invention does not contain heavy metal components, can be applied to products in the high-frequency field, is green, environment-friendly and pollution-free, and meets the strict standard requirements of the latest RHOS and WEEE in the European Union.

2. The sintering temperature is 875-920 ℃, the further reduction is realized, and the energy saving advantage is achieved.

3. The sintering aid uses the composite eutectic point oxide and the additive, and improves the low-melting point oxide (B) which can not be matched with the casting process in the traditional sintering aid₂O₃And V₂O₅) And/or high cost and unstable performance.

4. The dielectric constant of the material is adjustable from 30 to 40, and the loss is low (less than or equal to 10)^-4)，Qxf(GHz)20000～30000。

5. The invention can be widely applied to low-temperature high-dielectric constant microwave dielectric core materials in microwave devices such as dielectric resonators, filters, oscillators and the like in satellite communication, and has important industrial application value.

Drawings

Figure 1 is the XRD pattern of the examples.

Detailed Description

The invention is described in further detail below with reference to the figures and the specific embodiments.

The material of the invention is prepared from 92.5-97.5 percent of BaTi by mass percent₅O₁₁Base material and 1-7.5 wt% of combustion reducing agent, BaTi₅O₁₁The base material consists of BaTi₅O₁₁-nCuO, wherein: n is more than or equal to 0.005 and less than or equal to 0.020 by weight, and the composition of the combustion reducing agent is more than or equal to 27.25 percent of BaCO₃≤46.74％、4.25％≤Li₂CO₃≤7.47％、8.65％≤SiO₂≤9.19％、25.59％≤B₂O₃≤38.29％、20.88％≤ZnO≤32.95％、1.58％≤Al₂O₃≤9.83％、0.29％≤MnCO₃≤0.95％。

Table 1 shows data of several specific examples of the contents of the respective components constituting the present invention, and Table 2 shows the microwave dielectric properties of the respective examples.

The preparation method comprises the following steps:

step 1, mixing BaCO₃、CuO、TiO₂According to BaTi₅O₁₁-nCuO, wherein: n is more than or equal to 0.005 and less than or equal to 0.020 by weight ratio, deionized water is used as a medium for wet grinding and mixing for 4 hours, the mixture is taken out and dried at 100 ℃, a 60-mesh screen is used for sieving, and then the mixture is presintered in the atmosphere of 900 ℃ for 6 hours to synthesize the main crystal phase BaTi₅O₁₁Phase, i.e. the base;

step 2, the raw materials are as follows by mass percent: BaCO not less than 27.25%₃≤46.74％、4.25％≤Li₂CO₃≤7.47％、8.65％≤SiO₂≤9.19％、25.59％≤B₂O₃≤38.29％、20.88％≤ZnO≤32.95％、1.58％≤Al₂O₃≤9.83％、0.29％≤MnCO₃Batching at less than or equal to 0.95 percent, wet-milling and mixing for 6 hours by taking deionized water as a medium, drying, sieving by a 60-mesh sieve, pre-burning for 4 hours at 600 ℃, and preparing into sintering agent powder for later use;

and step 3: adding the sintering agent powder which is prepared in the step 2 and accounts for 1-7.5 percent of the total mass into the base material prepared in the step 1, uniformly mixing, wet-grinding and mixing for 4 hours by taking alcohol as a medium, drying at 80 ℃, granulating by taking an acrylic acid solution which accounts for 5 percent of the total mass of the raw materials as a binder, performing compression molding, and finally sintering for 1 hour in the atmosphere of 875-920 ℃ to prepare the microwave medium ceramic material.

The microwave dielectric property is evaluated by a cylindrical dielectric resonator method, and the detection method is GB/T7265.2-1987 open cavity method.

TABLE 1

TABLE 2

As can be seen from the table above, the addition of the sintering reducing agent provided by the invention enables the system to be sintered and compact at low temperature, and medium dielectric constant (30-40) and excellent microwave dielectric property to be obtained. It can be seen from the XRD diffraction patterns (FIG. 1) of examples 4 and 8 that the system can obtain pure BaTi during low-temperature sintering₅O₁₁Crystalline phase, no hetero-phase is generated. The sintering reducing agent is stated to be effective in promoting sintering without introducing a heterogeneous phase.

Claims (2)

1. A low-temperature sintered composite microwave dielectric ceramic material is characterized in that:

the raw material composition is BaTi₅O₁₁-nCuO-xM,0.0125N is more than or equal to 0.020 weight ratio, M is a combustion reducing agent, x is more than or equal to 0.010 and less than or equal to 0.075 weight ratio;

the combustion reducing agent comprises the following components in percentage by weight: BaCO not less than 27.25%₃≤46.74％、4.25％≤Li₂CO₃≤7.47％、8.65％≤SiO₂≤9.19％、25.59％≤B₂O₃≤38.29％、20.88％≤ZnO≤32.95％、1.58％≤Al₂O₃≤9.83％、0.29％≤MnCO₃Less than or equal to 0.95 percent, and the sum of the percentages of the components meets 100 percent;

the sintering temperature of the ceramic material is 875-920 ℃, and the dielectric constant is not less than 30 epsilon_rNot more than 40, Qxf (GHz) 20000 to 30000, and frequency temperature coefficient tau_f30-40 ppm/DEG C, loss less than or equal to 10^-4；

The low-temperature sintering composite microwave dielectric ceramic material does not contain heavy metal components, can be applied to products in the high-frequency field, is matched with a subsequent casting process, and has stable performance.

2. The preparation method of the low-temperature sintered composite microwave dielectric ceramic material as claimed in claim 1, comprising the following steps:

step 1, according to BaTi₅O₁₁-nCuO ingredient, n is more than or equal to 0.0125 and less than or equal to 0.020 in weight ratio, then the raw materials are wet-milled and mixed for 3 to 5 hours by taking deionized water as a medium, the mixture is taken out and dried at 80 to 120 ℃, sieved by a 40 to 100-mesh screen, and then presintered for 5 to 8 hours in the atmosphere at 800 to 1200 ℃ to synthesize a main crystal phase BaTi₅O₁₁Phase, i.e. the base;

step 2, according to mass percent: BaCO not less than 27.25%₃≤46.74％、4.25％≤Li₂CO₃≤7.47％、8.65％≤SiO₂≤9.19％、25.59％≤B₂O₃≤38.29％、20.88％≤ZnO≤32.95％、1.58％≤Al₂O₃≤9.83％、0.29％≤MnCO₃Batching less than or equal to 0.95 percent, wet-milling and mixing for 3-7 hours by taking deionized water as a medium, sieving by using a 40-100 mesh sieve after drying, pre-burning for 2-8 hours at 500-800 ℃, and preparing into sintering agent reducing powder for later use;

and 3, adding the sintering agent powder which is prepared in the step 2 and accounts for 1-7.5 percent of the total mass percent into the base material prepared in the step 1, uniformly mixing, wet-grinding and mixing for 3-5 hours by taking alcohol as a medium, taking out, drying at 80-120 ℃, granulating by taking an acrylic acid solution which accounts for 2-5 percent of the total mass of the raw materials as a binder, performing compression molding, and sintering for 1-3 hours in an atmosphere of 875-920 ℃ to prepare the microwave medium ceramic material.

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