Temperature-stable microwave dielectric material and preparation method thereof

Abstract

The present application belongs to the field of electronic ceramics. Specifically, a temperature-stable microwave dielectric material and a preparation method thereof are provided. The material has a chemical formula of CaB2O4+x wt% TiO2, wherein 10<=x<=15. The material has a main crystal phase of CaB2O4 and a secondary crystal phase of TiO2. The sintering temperature is 900-950 DEG C. The present application aims to solve the problem that microwave dielectric materials cannot be applied in devices due to a too large temperature coefficient of resonant frequency. In particular, when 11<=x<=14 and the sintering temperature is 950 DEG C, the dielectric constant is 7-9, the Qxf value is 14000 GHz-19000 GHz, and the temperature coefficient of resonant frequency is -7-2 ppm / DEG C. Meanwhile, the microwave dielectric material has a simple preparation process, low raw material price, and abundant reserves, and is conducive to industrialized production.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of electronic ceramics, and particularly relates to a temperature-stable microwave dielectric material and a preparation method thereof. BACKGROUND

[0002] Microwave dielectric materials are widely used in microwave devices such as radars, antennas, resonators and filters, and play a vital role in the field of electronic information. Borate ceramics have the advantages of low sintering temperature and low cost, and have great potential in the field of electronic ceramics. A microwave dielectric material CaB2O4 with good dielectric properties is prepared in the paper Microwave Dielectric Ceramic Ca3B2O6 and Low-Firing Improvement Studied by P-V-L Bond Theory. 3- x B2O 6-x -0.7Li, ε r = 7.62, Qxf = 40426 GHz, tau f = -53.12 ppm / ℃, but the temperature coefficient of the resonant frequency of the material is too large, which does not meet the design requirements of devices, and temperature-stable microwave dielectric materials with near-zero temperature coefficient need to be researched.

[0003] Based on the background, the application provides a temperature-stable microwave dielectric material and a preparation method thereof. SUMMARY

[0004] The application provides a temperature-stable microwave dielectric material CaB2O4+xwt%TiO2.

[0005] To achieve the above-mentioned purpose, the application realizes the technical scheme as follows:

[0006] Step 1. Analytically pure Ca(OH)2 and H3BO3 are used as raw materials to prepare CaB2O4 according to the chemical formula, and H3BO3 needs to be compensated by 10% excess because boron volatilizes at high temperature and causes loss;

[0007] Step 2. The mixed material is placed in a ball mill tank, anhydrous ethanol is used as a solvent, and zirconium balls are used as a medium, and the material is discharged after ball milling for 7 hours and dried in an oven at 70℃;

[0008] Step 3. The dried material is sieved and placed in a crucible, and is pre-sintered at 700-800℃ for 3-4 hours to obtain pre-sintered material CaB2O4;

[0009] Step 4. The pre-sintered material CaB2O4 is prepared according to the mass ratio of the chemical formula CaB2O4+xwt%TiO2;

[0010] Step 5. Put the mixture into a ball mill tank, take zirconium ball as medium, and ball mill for 7 hours with anhydrous ethanol as solvent, and then discharge and dry in an oven at 70℃;

[0011] Step 6. Mix the dried mixture with acrylic acid, and then granulate and press at 20MPa to obtain a cylindrical green body;

[0012] Step 7. After the green body is deformed, sinter it at 900-950℃ for 4-5 hours to obtain the microwave dielectric material.

[0013] Further, the present application has the following beneficial effects:

[0014] The microwave dielectric material CaB2O4+xwt%TiO2 provided by the present application has a sintering temperature of 900-950℃, a dielectric constant of 7-9, a Qxf value of 14000-19000GHz, and a resonance frequency temperature coefficient of -7-2ppm / ℃. The microwave dielectric material has a near-zero resonance frequency temperature coefficient, and can be widely used in microwave components such as resonators and filters. The preparation process of the microwave dielectric material is simple, and the raw material cost is low, which is conducive to industrialized production. BRIEF DESCRIPTION OF DRAWINGS

[0015] Figure 1 The XRD pattern of the microwave dielectric material CaB2O4+11wt%TiO2 prepared in Example 1 is shown in the figure.

[0016] Figure 2 The SEM pattern of the microwave dielectric material CaB2O4+11wt%TiO2 prepared in Example 1 is shown in the figure. DETAILED DESCRIPTION

[0017] The present application will be further described in detail below in combination with the drawings and examples.

[0018] The present application provides four examples, and the chemical formula of the microwave dielectric material is respectively: CaB2O4+11wt%TiO2, CaB2O4+12wt%TiO2, CaB2O4+13wt%TiO2, and CaB2O4+14wt%TiO2. The specific steps for preparation are as follows:

[0019] Step 1. Take analytically pure Ca(OH)2 and H3BO3 as raw materials, and prepare them according to the chemical formula CaB2O4. Since boron volatilizes at high temperature, H3BO3 needs to be compensated by 10% excess.

[0020] Step 2. Put the mixture into a ball mill tank, take zirconium ball as medium, and ball mill for 7 hours with anhydrous ethanol as solvent, and then discharge and dry in an oven at 70℃;

[0021] Step 3. The sieved dried material is placed in a crucible and pre-fired at 700-800℃ for 3-4 hours to obtain pre-fired material CaB2O4;

[0022] Step 4. The pre-fired material CaB2O4 is mixed with TiO2 according to the mass ratio of CaB2O4+xwt%TiO2;

[0023] Step 5. The mixed material is placed in a ball mill tank, using anhydrous ethanol as solvent and zirconium balls as medium, and ball-milled for 7h, and then dried at 70℃ in an oven;

[0024] Step 6. The dried material is mixed with acrylic acid and granulated, and then pressed at 20MPa to obtain a cylindrical green body;

[0025] Step 7. After the green body is degreased, it is sintered at 900-950℃ for 4-5 hours to obtain the microwave dielectric material.

[0026] The temperature-stable microwave dielectric ceramic prepared in the above Examples 1-4 is tested, and the microwave performance is shown in the following table:

[0027]

[0028] As shown in the above table, the temperature-stable microwave dielectric ceramic provided by the present application has excellent microwave dielectric performance: dielectric constant is 7-9, Qxf value is 14000-19000GHz, and resonance frequency temperature coefficient is -7-2ppm / ℃.

[0029] The above is merely a specific implementation of the present application, and any feature disclosed in the present specification can be replaced by other equivalent or similar purpose alternative features, unless specifically described; all features disclosed, or steps in all methods or processes, except for mutually exclusive features and / or steps, can be combined in any manner.

Claims

1. A temperature-stable microwave dielectric material, characterized in that, The microwave dielectric material has the chemical formula CaB₂O₄ + xwt%TiO₂, where 10 ≤ x ≤ 15; it is characterized in that the main crystalline phase of the microwave dielectric material is CaB₂O₄ and the secondary crystalline phase is TiO₂; and it is characterized in that the sintering temperature of the microwave dielectric material is 900~950℃, and the dielectric constant is 7~9. Q×f The value is 14000~19000GHz, and the temperature coefficient of the resonant frequency is -7~2ppm / ℃; characterized in that the microwave dielectric material is prepared by the following method: Step 1. Use analytical grade Ca(OH)2 and H3BO3 as raw materials and prepare the mixture according to the chemical formula CaB2O4. Since boron will be lost due to volatilization at high temperature, H3BO3 needs to be in excess by 10% to compensate. Step 2. Place the mixture in a ball mill jar, use anhydrous ethanol as solvent and zirconium balls as medium, ball mill for 7 hours, then discharge the material and dry it in an oven at 70°C. Step 3. After sieving the dried material, place it in a crucible and pre-calcine it at 700~800℃ for 3~4 hours to obtain pre-calcined material CaB2O4; Step 4. Mix the pre-calcined CaB2O4 and TiO2 according to the mass ratio of CaB2O4 + x wt% TiO2; Step 5. Place the mixture in a ball mill jar, use anhydrous ethanol as solvent and zirconium balls as medium, ball mill for 7 hours, and then dry it in an oven at 70°C. Step 6. Mix the dried material with acrylic acid and granulate it, then press it at 20 MPa to obtain a cylindrical green body; Step 7. After removing the binder from the green body, sinter at 900~950℃ for 4~5 hours to obtain the microwave dielectric material.

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