A medium-low dielectric constant pyrochlore structure microwave dielectric material, a preparation method and application thereof

Abstract

The application relates to a medium-low dielectric constant pyrochlore structure microwave dielectric material, a preparation method thereof and application. 2‑ x Zr2O 7‑1.5x a main phase and a second phase; the second phase comprises MgO and La2MgZrO6 phases; wherein, 0<=x<=0.2; the molar content of the MgO phase is 0-47 mol%, the molar content of the La2MgZrO6 phase is 0-16 mol%, and the molar contents of the MgO phase and the La2MgZrO6 phase are not both 0.

Description

TECHNICAL FIELD

[0001] The present application relates to a kind of low dielectric constant pyrochlore structure microwave dielectric material and its preparation method and application, belong to ceramic material field. BACKGROUND

[0002] Microwave dielectric ceramic (MWDC) is a kind of functional ceramics applied in microwave frequency band as the core device of dielectric filter in electronic circuit, with the continuous development of communication industry, in the aspect of circuit integration, traditional metal cavity resonator is gradually replaced by microwave dielectric ceramic with small size and light weight.In recent years, with the explosive development of 5G era, the types and demand of microwave dielectric ceramic are millions.

[0003] Suitable dielectric constant, higher quality factor (Qxf), resonant frequency temperature coefficient close to 0 are three main performance characteristics of microwave dielectric ceramic.Dielectric constant series is used for devices of different signal frequency bands, and the size of dielectric constant is adjusted to meet the requirements of devices of different sizes;Higher quality factor can ensure that the device has excellent frequency selection characteristics during use;Resonant frequency temperature coefficient close to 0 is an important guarantee for stable operation of the device.At present, as the core device of filter, microwave dielectric ceramic is widely used in military, civil, aerospace and other fields.The application field is different, and the corresponding microwave frequency band is also different.Therefore, on the basis of the present stage, the microwave dielectric ceramic material system is further expanded to meet the application requirements of functional ceramic devices.

[0004] In order to further meet the use requirements of microwave dielectric ceramic for 5G communication, we need to ensure that the material has a specific dielectric constant and has a high Qxf value to ensure the use requirements of high frequency and large flux of microwave communication equipment.Pyrochlore structure (A2B2O7) compound has various compositions and potential application value.The research on pyrochlore structure compound in the field of microwave dielectric ceramic with low dielectric constant is very few.La2Zr2O7 compound is a representative of pyrochlore microwave dielectric ceramic with low dielectric constant, and La2Zr2O7 ceramic is successfully prepared and its dielectric properties are studied. SUMMARY

[0005] Therefore, the present application provides a kind of low dielectric constant pyrochlore structure microwave dielectric material and its preparation method and application.

[0006] In a first aspect, the present application provides a kind of low dielectric constant pyrochlore structure microwave dielectric material, comprising: La 2- x Zr2O 7-1.5x Main phase and second phase;The second phase includes MgO phase and La2MgZrO6 phase;Wherein, 0≤x≤0.2.

[0007] the molar content of the MgO phase is 0-47 mol%, the molar content of the La2MgZrO6 phase is 0-16 mol%, and the molar contents of the MgO phase and the La2MgZrO6 phase are not both 0;

[0008] Preferably, the molar content of the MgO phase is 17-47 mol%, and the molar content of the La2MgZrO6 phase is 0-16 mol%.

[0009] More preferably, the molar content of the MgO phase is 29-47 mol%, and the molar content of the La2MgZrO6 phase is 0-11 mol%.

[0010] In the present application, La2Zr2O7-MgO ceramic is obtained by adding MgO to La2Zr2O7 ceramic, thereby improving the dielectric properties. Preferably, La2Zr2O7-MgO ceramic is prepared by studying the non-stoichiometric ratio of La in La2Zr2O7-MgO ceramic, and the dielectric properties are further improved. 2-x Zr2O 7-1.5x -MgO ceramic (0≤x≤0.2), inhibiting the formation of La2MgZrO6 and further improving the dielectric properties.

[0011] Preferably, x=0.12-0.2, and more preferably x=0.16.

[0012] Preferably, the dielectric constant of the pyrochlore-structured microwave dielectric material is 22.3-24.9, and the Qxf value is 17100-59200.

[0013] Preferably, the density of the pyrochlore-structured microwave dielectric material is 5.66-6.07 g / cm 3 .

[0014] In a second aspect, the present application provides a preparation method of a low-mid dielectric constant pyrochlore-structured microwave dielectric material, comprising:

[0015] (1) weighing and mixing a Mg source, a La source and a Zr source according to the chemical formula aLa 2-x Zr2O 7-1.5x -bMgO to obtain a mixed powder;

[0016] (2) pre-sintering the mixed powder at 1250-1300°C for at least 4 hours to obtain a synthesized powder;

[0017] (3) after ball milling, granulating and forming the synthesized powder, a ceramic green body is obtained;

[0018] (4) After the ceramic green body is de-glued, it is firstly heated to 1550-1675 ℃ and kept for 4-6 hours, and then cooled to 1000-1200 ℃ and kept for 4-6 hours, to obtain the medium-low dielectric constant pyrochlore structure microwave dielectric material.

[0019] In the present application, the pyrochlore structure La2Zr2O7 ceramic is successfully prepared, the dielectric property thereof is studied, and it is found that the sintering temperature range thereof is wide. By adding MgO, the dielectric property is improved, and a new second phase La2MgZrO6 is found. Preferably, by reducing the La source in a non-stoichiometric ratio, La 2-x Zr2O 7-1.5x -MgO ceramic, the La2MgZrO6 phase in the La 2- x Zr2O 7-1.5x -MgO ceramic, the content of the La2MgZrO6 phase is reduced, which is helpful to further reduce the dielectric constant, improve the Qxf value, and expand the application of the pyrochlore structure ceramic in the medium-low dielectric constant ceramic field, and expand the application market.

[0020] Preferably, in the step (1), the Mg source is MgO powder or basic MgCO3 powder; the La source is La2O3 powder; and the Zr source is ZrO2 powder.

[0021] Preferably, in the step (1), x=0-0.2, preferably x=0.12-0.2, and more preferably x=0.16.

[0022] Preferably, in the step (1), a=0.5-0.9 and b=0.1-0.5.

[0023] Preferably, in the step (2), a binder needs to be added during granulation, and the binder is polyvinyl alcohol aqueous solution; and the concentration of the polyvinyl alcohol aqueous solution is 4-8 wt%.

[0024] Preferably, in the step (3), the de-gluing temperature is 400-600 ℃, and the time is 1-2 hours; the heating rate is 4-10 ℃ / min; and the cooling rate is 1-5 ℃ / min.

[0025] In a third aspect, the present application provides an application of the medium-low dielectric constant pyrochlore structure microwave dielectric material in the microwave communication field.

[0026] Beneficial effects:

[0027] The prepared pyrochlore structure La2Zr2O7 microwave dielectric ceramic material has a dielectric constant of 24.7, a resonance temperature coefficient of -41.69 ppm / ℃, a Qxf value of 18300 GHz and a sintering schedule of 1575℃ / 4h. The dielectric performance can be optimized by adding MgO in La2Zr2O7, and a new second phase La2MgZrO6 is generated. The content of La is reduced by using a non-stoichiometric ratio for La, and La 2-x Zr2O 7-1.5x -MgO ceramic, the La2MgZrO6 phase in the La 2-x Zr2O 7-1.5x -MgO ceramic decreases with the decrease of the content of La, which helps to further reduce the dielectric constant and improve the Qxf value. Finally, the best La 1.84 Zr2O 6.76 -MgO ceramic has a dielectric constant of 22.9, a Qxf value of 59200 GHz and a resonance temperature coefficient of -44.6 ppm / ℃. The application of pyrochlore structure ceramic in the field of medium and low dielectric constant ceramic is widened, which can be used as a key core material of microwave mobile communication antenna, substrate and other electronic components, and is widely used in the fifth generation mobile communication industry. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 The XRD pattern of La2Zr2O7, La2Zr2O7-MgO ceramic prepared in Example 1 and Example 2;

[0029] Figure 2 The XRD pattern of La 2-x Zr2O 7-1.5x -MgO (0≤x≤0.2) ceramic;

[0030] Figure 3 The dielectric constant, Qxf and density value of La2Zr2O7 ceramic prepared in Example 1, wherein the abscissa is the sintering temperature (℃);

[0031] Figure 4 The dielectric constant, Qxf and density value of La2Zr2O7, La 2-x Zr2O 7-1.5x The dielectric constant value of La2Zr2O7-MgO (0≤x≤0.2) ceramic, wherein the abscissa is the sintering temperature (℃) and the ordinate is the dielectric constant;

[0032] Figure 5 The dielectric constant, Qxf and density value of La2Zr2O7, La2-x Zr2O 7-1.5x Q x f value of -MgO (0≤x≤0.2) ceramic, wherein the abscissa is sintering temperature (℃). DETAILED DESCRIPTION

[0033] The present application is further illustrated by the following embodiments, which should be understood as merely illustrative of the present application, but not limiting the present application.

[0034] In the present disclosure, pyrochlore structure La2Zr2O7 ceramic dielectric properties are successfully prepared and studied, and its dielectric properties are improved by adding MgO. After adding MgO, the second phase La2MgZrO6 is found to be formed, and La 2-x Zr2O 7-1.5x -MgO ceramic, wherein 0≤x≤0.2, the generation of La2MgZrO6 phase is inhibited, and the dielectric properties are further improved.

[0035] In the present disclosure, the low dielectric constant pyrochlore structure microwave dielectric material is composed of La 2-x Zr2O 7-1.5x -MgO system, and the main body is a microwave dielectric material containing Mg, La, Zr and O elements. Preferably, Q x f is not less than 54000.

[0036] Preferably, the non-stoichiometric ratio of La deficiency is 0-0.2, preferably 0.12-0.2, and more preferably 0.16. The present application improves its dielectric properties by adding MgO and non-stoichiometric ratio of La position. It should be noted that excessive La deficiency can easily lead to deterioration of material properties, and appropriate deficiency can improve Q x f value.

[0037] The preparation method of the low dielectric constant pyrochlore structure microwave dielectric material provided by the present application is exemplarily described as follows.

[0038] Preparation of synthetic powder. According to La 2-x Zr2O 7-1.5x -MgO, the Mg source, La source and Zr source are mixed, and then pre-sintered and synthesized to obtain the synthetic powder. The molar amount of the La deficiency is between 0 and 0.2. The Mg source can be MgO or basic MgCO3. The La source is La2O3. The Zr source can be ZrO2. As an example, the raw materials of the microwave dielectric material are mixed according to the molar ratio La 2-x Zr2O 7-1.5x-MgO is weighed, then alcohol is added, and the slurry is ground in a planetary ball mill with zirconium balls, then dried, calcined and synthesized to obtain the synthesized powder. The temperature for pre-synthesizing is 1250-1300℃, and the holding time is not less than 4 hours. Preferably, the pre-synthesizing temperature is 1300℃.

[0039] The synthesized powder is ball-milled, granulated and formed to obtain a ceramic green body.

[0040] The ceramic green body is sintered under a specific sintering system to obtain the microwave dielectric material with a low dielectric constant and a pyrochlore structure. The specific sintering system includes: first, increasing the temperature to 1550-1675℃ at a rate of 5-10℃ / min, holding for 4-6 hours, then decreasing the temperature to 1000-1200℃ at a rate of 1℃ / min, and holding for 4-6 hours to end.

[0041] In the present application, the dielectric constant of the microwave dielectric material with a low dielectric constant and a pyrochlore structure is tested by using a vector network analyzer. The dielectric loss of the microwave dielectric material with a low dielectric constant and a pyrochlore structure is tested by using a vector network analyzer. The density of the microwave dielectric material with a low dielectric constant and a pyrochlore structure is tested by using the Archimedes drainage method. The relative density of the microwave dielectric material with a low dielectric constant and a pyrochlore structure is tested by using the Archimedes drainage method. The Qxf of the microwave dielectric material with a low dielectric constant and a pyrochlore structure is tested by using a vector network analyzer.

[0042] The following examples are further illustrated to explain the present application in detail. It should also be understood that the following examples are only used to further illustrate the present application, and cannot be understood as limiting the protection scope of the present application. Some non-essential improvements and adjustments made by those skilled in the art according to the above content of the present application all belong to the protection scope of the present application. The specific process parameters in the following examples are only one example in the appropriate range, i.e. those skilled in the art can select within the appropriate range according to the description herein, and are not limited to the specific values in the following examples.

[0043] Example 1

[0044] (1) Accurately weigh La2O3 1.0 moL with a purity of greater than 99.9%, ZrO2 2.0 moL, add nylon ball mill tank, pour into deionized water with zirconium oxide balls with a diameter of 10mm, and the weight ratio of material: ball: alcohol is 1:2:1.5; the ball milling time is 4h, and after the ball milling is completed, the slurry is dried in a 120℃ oven for one night. The dried powder is loaded into a sagger, calcined at 850℃ for 4h, and then cooled in the furnace to obtain a synthesized powder;

[0045] (2) Take 100 g of the synthetic powder and put it into a nylon ball mill tank, pour in alcohol and zirconium oxide balls with a diameter of 10 mm. The weight ratio of the material: ball: alcohol = 1:2:1.5. The ball milling time is 4 h. After the ball milling, pour the slurry into a porcelain dish and put it into an oven to dry at a temperature of 130 °C. Granulate the powder with a PVA water solution. Put the granulated powder into a mold with a diameter of 6 mm under a pressure of 100 MPa. Set the height of the formed sample to 4 mm to obtain a ceramic green body;

[0046] (3) Put the ceramic green body into a muffle furnace, first increase the temperature to 600 °C at a rate of 4 °C / min, and keep the temperature for 2 h to perform a degassing treatment. Then increase the temperature to 1575 °C at a rate of 4 °C / min, and keep the temperature for 4 h. Then decrease the temperature to 1000 °C at a rate of 1 °C / min, and keep the temperature for 5 h to end the process. The microwave dielectric material is obtained, and its properties are shown in Table 1.

[0047] Example 2

[0048] In this example 2, the preparation process of the microwave dielectric material is similar to that of Example 1, except that in step (1), 1.0 moL of La2O3 with a purity of more than 99.9%, 1.0 moL of basic MgCO3, and 2.0 moL of ZrO2 are accurately weighed. Then four samples are prepared by increasing the temperature to 1600 °C, 1625 °C, 1650 °C, and 1675 °C at a rate of 4 °C / min, respectively, and keeping the temperature for 4 h. Then decrease the temperature to 1000 °C at a rate of 1 °C / min, and keep the temperature for 5 h to end the process. The microwave dielectric material is obtained. Meanwhile, 0.1 moL and 0.3 moL of basic MgCO3 with different molar contents are used to replace 1.0 moL in step (1) above, 0.9 moL and 0.7 moL of La2O3 with different molar contents, and 1.8 moL and 1.4 moL of ZrO2 with different molar contents are used to synthesize aLa2Zr2O7-bMgO (a = 0.1, 0.3, b = 0.9, 0.7), and then the temperature is increased to 1650 °C and kept for 4 h. Then decrease the temperature to 1000 °C at a rate of 1 °C / min, and keep the temperature for 5 h to end the process. The microwave dielectric material is obtained.

[0049] Example 3

[0050] In this example 3, the preparation process of the microwave dielectric material is similar to that of Example 1, except that in step (1), the molar concentrations of La2O3 1.0 moL, basic MgCO3 1.0 moL, and ZrO2 2.0 moL are replaced by La2O3 0.9 moL, basic MgCO3 0.9 moL, and ZrO2 1.8 moL, respectively. 2-x Zr2O 7-1.5xMgO ceramic, wherein x = 0, 0.04, 0.08, 0.12, 0.16, 0.2 are weighed in the proportion. Then the samples are respectively heated to 1600°C, 1625°C, 1650°C, 1675°C, and kept for 4h at a rate of 4°C / min, then decreased to 1000°C at a rate of 1°C / min, and kept for 5h to end, to prepare microwave dielectric materials.

[0051] Table 1 is the composition and performance of the microwave dielectric materials prepared by the present application

[0052]

[0053]

Claims

1. A mid-low dielectric constant pyrochlore-structured microwave dielectric material, characterized in that, The molar content of the MgO phase is 17-47 mol%, and the molar content of the La2MgZrO6 phase is 0-16 mol%. La 2-x Zr2O 7-1.5x a primary phase and a second phase; the second phase comprising a MgO phase and a La2MgZr06phase; wherein 0≤x≤0.2; The molar content of the MgO phase is 29-47 mol%, and the molar content of the La2MgZrO6 phase is 0-11 mol%.

2. The mid- to low dielectric constant pyrochlore-structure microwave dielectric material of claim 1, wherein, The dielectric constant of the pyrochlore-structure microwave dielectric material is 22.3-24.9, and the Qxf value is 17100-59200.

3. The mid- to low dielectric constant pyrochlore-structure microwave dielectric material of claim 1, wherein, x=0.12～0.2。 4. The mid- to low-dielectric constant pyrochlore-structure microwave dielectric material according to claim 3, wherein x=0.16。 5. The mid- to low dielectric constant pyrochlore-structure microwave dielectric material of claim 1, wherein, The molar content of the MgO phase is 17-47 mol%, and the molar content of the La2MgZrO6 phase is 0-16 mol%. The pyrochlore structure microwave dielectric material has a density of 5.66-6.07 g / cm 3 .

6. A method for preparing a low dielectric constant pyrochlore-structured microwave dielectric material, characterized by, (2) The mixed powder is pre-fired at 1250-1300℃ for at least 4 hours to obtain a synthesis powder; (1) Mg source, La source and Zr source are weighed and mixed according to the chemical formula aLa 2-x Zr2O 7-1.5x -bMgO to obtain a mixed powder; wherein, a = 0.1-0.5, b = 0.5-0.9, and x = 0-0.

2. (3) The obtained synthesis powder is ball-milled, granulated and formed to obtain a ceramic green body; (4) The ceramic green body is degreased, and then heated to 1550-1675℃ for 4-6 hours, and then cooled to 1000-1200℃ for 4-6 hours to obtain the low-mid dielectric constant pyrochlore-structure microwave dielectric material. In step (1), the Mg source is MgO powder or basic MgCO3 powder; the La source is La2O3 powder; and the Zr source is ZrO2 powder.

7. The production method according to claim 6, wherein In step (1), x=0.12-0.

2.

8. The production method according to claim 6, characterized by, In step (2), a binder needs to be added during granulation, and the binder is polyvinyl alcohol aqueous solution; the concentration of the polyvinyl alcohol aqueous solution is 4-8 wt%.

9. The production method according to claim 8, characterized by, x=0.16。 10. The method of claim 6, wherein, In step (3), the degreasing temperature is 400-600℃, and the time is 1-2 hours; the heating rate is 4-10℃ / min; and the cooling rate is 1-5℃ / min.

11. The preparation method according to claim 6, characterized in that, 12. Application of the low-mid dielectric constant pyrochlore-structure microwave dielectric material of any one of claims 1-5 in the field of microwave communication. ​

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