CN107805067A - A kind of dielectric constant microwave ceramic medium of zero frequency temperature coefficient and ultra-low loss and preparation method thereof - Google Patents

Abstract

The invention relates to a low dielectric constant microwave dielectric ceramic with zero frequency temperature coefficient and ultra-low loss and a preparation method thereof. The general chemical formula of the microwave dielectric ceramic is xMg ₂ SiO ₄ ‑(1‑x)MgTa ₂ O ₆ +y wt% B, said B is ZnO, CuO, Al ₂ O ₃ , Ga ₂ O ₃ , TiO ₂ , ZrO ₂ , SnO ₂ , MnO ₂ , Nb ₂ O ₅ , Sb ₂ O ₅ and WO ₃ At least one, where x represents the percentage of Mg ₂ SiO ₄ in the total molar mass of Mg ₂ SiO ₄ and MgTa ₂ O ₆ , 0<x<1; y represents the percentage of B in the total mass of Mg ₂ SiO ₄ and MgTa ₂ O ₆ Percentage, 0≤y≤5.

Description

A low dielectric constant microwave dielectric ceramic with zero frequency temperature coefficient and ultra-low loss and its preparation method

technical field

The invention belongs to the technical field of microwave dielectric ceramics, and in particular relates to a microwave dielectric ceramic with low dielectric constant, ultra-low dielectric loss and nearly zero frequency temperature coefficient and a preparation method thereof.

Background technique

In recent years, with the rapid development of 5G communication technology and global positioning technology, the demand for high-performance microwave dielectric ceramics used as wireless communication devices such as microwave filters, resonators and oscillators is increasing, especially ultra-low microwave dielectric loss and Ceramics with near zero frequency temperature coefficient. This kind of ceramic can not only meet the requirements of mobility, portability, miniaturization, and miniaturization of microwave communication equipment, but also meet the requirements of high performance, high reliability, and large-capacity information transmission in the microwave range. extensive attention.

MgTa ₂ O ₆ has a high quality factor Qf value, medium and low dielectric constant ε _r and positive resonant frequency temperature coefficient τ _f (Qf = 60000GHz, ε _r = 30, τ _f = 30ppm/℃) can not meet the actual needs , and Mg ₂ SiO ₄ also has excellent microwave dielectric properties (Qf = 270000 GHz, ε _r = 6.8, τ _f = -67ppm/°C), which cannot meet the application requirements.

Contents of the invention

In view of the above problems, the object of the present invention is to provide a microwave dielectric ceramic with low dielectric constant, ultra-low dielectric loss and nearly zero frequency temperature coefficient and its preparation method.

On the one hand, the present invention provides a microwave dielectric ceramic with low dielectric constant and ultra-low dielectric loss. The general chemical formula of the microwave dielectric ceramic is xMg ₂ SiO ₄ -(1-x)MgTa ₂ O ₆ +y wt% B, said B being at least one of ZnO, CuO, Al ₂ O ₃ , Ga ₂ O ₃ , TiO ₂ , ZrO ₂ , SnO ₂ , MnO ₂ , Nb ₂ O ₅ , Sb ₂ O ₅ and WO ₃ species, where x represents the percentage of Mg ₂ SiO ₄ in the total molar weight of Mg ₂ SiO ₄ and MgTa ₂ O ₆ , 0<x<1; y represents the percentage of B in the total mass of Mg ₂ SiO ₄ and MgTa ₂ O ₆ , 0≤y≤5.

The present invention uses dielectric ceramic composite technology to adjust the dielectric properties of dielectric ceramics in order to meet the application requirements. The mechanism is: using two matrix materials with opposite frequency temperature coefficients (MgTa ₂ O ₆ has a positive resonance frequency temperature coefficient τ _f =30ppm/°C, while Mg ₂ SiO ₄ has a negative frequency temperature coefficient τ _f =-67ppm/°C), by controlling the relative composition content of the two phases (ie molar ratio x: (1-x), 0<x<1) , the result that the frequency temperature coefficient is close to zero is obtained. In addition, an appropriate amount of B substance (the ratio of B to the total mass of Mg ₂ SiO ₄ and MgTa ₂ O ₆ y wt%, 0≤y≤5) is added to the two matrix materials to improve the sintering characteristics of the material and stabilize the dielectric properties of the material performance.

Preferably, the dielectric constant of the microwave dielectric ceramic is 6.9-28.3, the quality factor Qf is 60000-275000 GHz, and the resonant frequency temperature coefficient is -70-55 ppm/°C.

Preferably, 0.5≤x≤0.7 or/and 1≤y≤3.

Also, preferably, when 0.5≤x≤0.7 and 1≤y≤3, the dielectric constant of the microwave dielectric ceramic is 12.1-15.2, preferably 13-15, and the quality factor Qf value is 120000-152000 GHz, preferably 125,000 to 140,000 GHz, and the resonance frequency temperature coefficient is -11 to 18 ppm/°C, preferably 0 to 4 ppm/°C.

In another aspect, the present invention provides a method for preparing the microwave dielectric ceramic as above, comprising:

Weighing and mixing Mg ₂ SiO ₄ powder and MgTa ₂ O ₆ powder according to xMg ₂ SiO ₄ -(1-x)MgTa ₂ O ₆ stoichiometric composition to obtain mixed powder;

Add B and binder to the obtained mixed powder, and after crushing, granulation and molding, a green body is obtained;

The obtained body is sintered at 1300-1450° C. for 4-16 hours to obtain the microwave dielectric ceramic.

Preferably, the Mg ₂ SiO ₄ powder and the MgTa ₂ O ₆ powder are pre-synthesized respectively using MgO, Ta ₂ O ₅ , and SiO ₂ as raw materials.

Also, preferably, after mixing MgO and SiO ₂ , they are calcined at 1000-1250° C. for 4-12 hours to obtain Mg ₂ SiO ₄ .

Also, preferably, after mixing MgO and Ta ₂ O ₅ , calcining at 1000-1250° C. for 4-12 hours to obtain MgTa ₂ O ₆ powder.

Preferably, the mass of B is 0-5 wt%, preferably 1-3 wt%, of the mass of the mixed powder.

Preferably, the binding agent is at least one of polyvinyl alcohol PVA, polyvinyl butyral PVB and sodium carboxymethyl cellulose CMC, and the amount of the binding agent is 2% of the mixed powder quality. ~4wt%.

The advantages of the present invention are: xMg ₂ SiO ₄ -(1-x)MgTa ₂ O ₆ +y wt%B composite microwave dielectric ceramic material has a low dielectric constant, a wide adjustable range of 6.9-28.3, and a high quality factor of 60,000-275,000 GHz , The resonant frequency temperature coefficient is continuously adjustable, which can meet the needs of the new generation of communication.

Detailed ways

The present invention will be further described below through the following embodiments. It should be understood that the following embodiments are only used to illustrate the present invention, not to limit the present invention.

In the present invention, the composite microwave dielectric ceramic with low dielectric constant, high quality factor, and near-zero frequency temperature coefficient can be expressed as xMg ₂ SiO ₄ -(1-x)MgTa ₂ O ₆ + y wt% B. Wherein B can be at least one of ZnO, CuO, Al ₂ O ₃ , Ga ₂ O ₃ , TiO ₂ , ZrO ₂ , SnO ₂ , MnO ₂ , Nb ₂ O ₅ , Sb ₂ O ₅ and WO ₃ . Where x represents the percentage of Mg ₂ SiO ₄ in the total molar weight of Mg ₂ SiO ₄ and MgTa ₂ O ₆ , 0<x<1 (preferably 0.5≤x≤0.7); y represents the percentage of B in Mg ₂ SiO ₄ and MgTa ₂ O The percentage of the total mass of ₆ , 0≤y≤5 (preferably 1≤y≤3). If the added amount of B exceeds 5wt%, new compounds will be generated, and various properties of the microwave dielectric ceramic will deviate from predicted values.

In the present invention, the dielectric constant of the microwave dielectric ceramic is 6.9-28.3, the quality factor Qf is 60000-275000 GHz, and the resonant frequency temperature coefficient is -70-55 ppm/°C. When 0.5≤x≤0.7, 1≤y≤3, within this range, the composite microwave dielectric ceramic has stable dielectric properties and good repeatability, and the dielectric constant of the microwave dielectric ceramic is 12.1 to 15.2, preferably 13 ~15, the quality factor Qf value is 120000~152000GHz, preferably 125000~140000GHz, and the temperature coefficient of resonance frequency is -11~18ppm/℃, preferably 0~4ppm/℃.

The microwave dielectric ceramic of the invention has simple preparation process, good repeatability and excellent microwave dielectric properties. The following exemplifies the preparation method of microwave dielectric ceramics provided by the present invention with low and medium dielectric constant, extremely low dielectric loss, and frequency temperature coefficient near zero.

Preparation of Mg ₂ SiO ₄ powder and MgTa ₂ O ₆ powder. Specifically, using MgO, Ta ₂ O ₅ , and SiO ₂ as raw materials, Mg ₂ SiO ₄ powder and MgTa ₂ O ₆ powder were synthesized in advance, respectively. After mixing MgO and SiO ₂ or MgO and Ta ₂ O ₅ , calcining at 1000-1250° C. for 4-12 hours to obtain Mg ₂ SiO ₄ or MgTa ₂ O ₆ powder. The above-mentioned mixing method may be ball milling and the like. It should be noted that the preparation of Mg ₂ SiO ₄ powder and MgTa ₂ O ₆ powder in the present invention is not limited to the above preparation methods. Mg ₂ SiO ₄ powder and MgTa ₂ O ₆ powder prepared by other methods can also be used in the preparation of this microwave dielectric ceramic.

Weigh the Mg ₂ SiO ₄ powder and MgTa ₂ O ₆ powder according to the stoichiometric composition of xMg ₂ SiO ₄ -(1-x)MgTa ₂ O ₆ , add B and binder to the mixed powder, and crush , after granulation and molding, the desired green body is obtained. The mass of B is 0-5 wt%, preferably 1-3 wt%, of the mass of the mixed powder. The binder may be at least one of polyvinyl alcohol (PVA), polyvinyl butyral (PVB), sodium carboxymethylcellulose (CMC) and the like. The amount of the binder can be 2-4 wt% of the mass of the mixed powder. The forming method can be dry pressing forming, cold isostatic pressing forming and the like.

The obtained green body is sintered at 1300° C. to 1450° C. for 4 to 16 hours to obtain the low dielectric constant microwave dielectric ceramic.

As an example of a preparation method for microwave dielectric ceramics, high-purity (purity>99%) MgO, SiO ₂ and Ta ₂ O ₅ are used as raw materials, and they are synthesized by calcining at 1000-1250°C (preferably 1000-1200°C) for 4-12h Mg ₂ SiO ₄ powder and MgTa ₂ O ₆ powder are weighed according to the stoichiometric composition of xMg ₂ SiO ₄ -(1-x)MgTa ₂ O ₆ , and at the same time, B is added with a mass fraction of y wt%. After crushing, add The binder is granulated and shaped to obtain a green body; the obtained green body is sintered at 1350-1450° C. for 4-16 hours to obtain the microwave dielectric ceramic.

The microwave dielectric properties of the prepared ceramics were tested. The diameter and thickness of the samples were measured using a micrometer. With the help of AgilentE8363A PNA network analyzer, the dielectric constant and dielectric loss of the prepared cylindrical ceramic materials were measured by the cavity method, and the test samples were placed in the ESPEC MC-710F high and low temperature cycle box to measure the temperature coefficient of the resonant frequency. The range is 20~85℃, and the test frequency is in the range of 9~16GHz.

Examples are given below to describe 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 interpreted as limiting the protection scope of the present invention. Some non-essential improvements and adjustments made by those skilled in the art according to the above contents of the present invention all belong to this invention. protection scope of the invention. The specific process parameters and the like in the following examples are only examples of suitable ranges, 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.

The present invention uses high-purity MgO, Ta ₂ O ₅ , SiO ₂ and B as raw materials to prepare xMg ₂ SiO ₄ -(1-x)MgTa ₂ O ₆ +y wt%B ceramics, and specific examples are as follows.

Example 1

(1) Weigh MgO, Ta ₂ O ₅ , and SiO ₂ in molar ratios of MgO:Ta ₂ O ₅ =1:1 and MgO:SiO ₂ =2:1, respectively, and add zirconia balls and deionized water. Ball mill for 1 to 2 hours, dry the ball-milled raw materials in a drying oven, and then calcinate at 1100°C for 4 hours to synthesize MgTa ₂ O ₆ and Mg ₂ SiO ₄ ;

(2) Weigh the synthesized Mg ₂ SiO ₄ and MgTa ₂ O ₆ according to the mole fraction ratio of 0.4:0.6, 0.5:0.5, 0.6:0.4, 0.7:0.3, 0.8:0.2 and add zirconia balls, deionized In the water ball mill tank, ball mill for 1 to 2 hours, after drying, add PVA (polyvinyl alcohol) with a mass fraction of 3% to the powder as a binder to granulate, and press it into a cylindrical embryo body;

(4) Sinter the cylindrical green body at 1350°C for 8 hours to obtain the required composite microwave dielectric ceramics;

(5) Test the microwave dielectric properties of the composite microwave dielectric ceramic prepared in step (4) with a network analyzer and a resonant cavity. See Table 1 for the relevant process parameters and test results of microwave dielectric properties of specific embodiments.

Table 1 is the experimental result involved in embodiment 1:

Example 2

Follow example 1, select x=0.6 component on the basis of example 1, add B substance content in (2) step and be 1wt%, all the other steps are identical with example 1, test result sees table 2 for details.

Table 2 is the experimental result involved in embodiment 2:

Example 3

Follow example 2, on the basis of example 2, select material B as ZnO, change the amount of material B added, the rest of the steps are the same as in example 1, the test results are shown in Table 3.

Table 3 is the experimental result involved in embodiment 3:

Claims (10)

1. the microwave-medium ceramics of a kind of low-k, ultralow dielectric loss, it is characterised in that the microwave-medium ceramics Chemical general formula is xMg₂SiO₄-(1-x)MgTa₂O₆+ y wt% B, the B are ZnO, CuO, Al₂O₃、Ga₂O₃、TiO₂、ZrO₂、 SnO₂、MnO₂、Nb₂O₅、Sb₂O₅And WO₃At least one of, wherein x represents Mg₂SiO₄Account for Mg₂SiO₄And MgTa₂O₆Integral molar quantity Percentage, 0 ＜ x ＜ 1；Y represents B and accounts for Mg₂SiO₄And MgTa₂O₆Gross mass percentage, 0≤y≤5.

2. microwave-medium ceramics according to claim 1, it is characterised in that the dielectric constant of the microwave-medium ceramics is 6.9~28.3, quality factorQfIt is worth for 60000~275000 GHz, temperature coefficient of resonance frequency is -70~55 ppm/ DEG C.

3. microwave-medium ceramics according to claim 1 or 2, it is characterised in that 0.5≤x≤0.7 or/and 1≤y≤3.

4. microwave-medium ceramics according to claim 3, it is characterised in that as 0.5≤x≤0.7 and 1≤y≤3, institute The dielectric constant for stating microwave-medium ceramics is 12.1~15.2, preferably 13~15, quality factorQfBe worth for 120000~ 152000 GHz, preferably 125000~140000 GHz, temperature coefficient of resonance frequency are -11~18 ppm/ DEG C, preferably 0 ~4 ppm/ DEG C.

A kind of 5. preparation method of microwave-medium ceramics as any one of claim 1-4, it is characterised in that including：

By Mg₂SiO₄Powder and MgTa₂O₆Powder presses xMg₂SiO₄-(1-x)MgTa₂O₆Stoichiometric composition is weighed and mixed, and is obtained To mixed powder；

B and binding agent are added in gained mixed powder, through broken, after granulation and shaping, obtains base substrate；

Gained base substrate is sintered into 4~16 h at 1300~1450 DEG C, obtains the microwave-medium ceramics.

6. preparation method according to claim 5, it is characterised in that with MgO, Ta₂O₅、SiO₂For raw material, close in advance respectively Into Mg₂SiO₄Powder and MgTa₂O₆Powder.

7. preparation method according to claim 6, it is characterised in that by MgO and SiO₂After mixing, at 1000~1250 DEG C 4~12h of lower calcining, obtains Mg₂SiO₄。

8. preparation method according to claim 6, it is characterised in that by MgO and Ta₂O₅After mixing, at 1000~1250 DEG C 4~12h of lower calcining, obtains MgTa₂O₆Powder.

9. according to the preparation method described in any one of claim 5-8, it is characterised in that the quality of the B is mixed powder 0~5 wt% of weight, preferably 1~3 wt%.

10. according to the preparation method described in any one of claim 5-9, it is characterised in that the binding agent is polyethylene At least one of alcohol PVA, polyvinyl butyral resin PVB and sodium carboxymethylcellulose CMC, the dosage of preferably described binding agent For 2~4 wt% of mixed powder quality.