Linear dielectric Bi2Ti2O7 ceramic capacitor material and preparation method thereof

Abstract

The invention relates to the technical field of ceramic capacitor materials, and discloses a preparation method of a linear dielectric Bi2Ti2O7 ceramic capacitor material, which comprises the following steps: firstly, mixing sodium bismuthate and titanium oxide according to a chemical ratio, and drying; then adding absolute ethyl alcohol, carrying out ball milling to form slurry, drying and grinding to obtain powder; carrying out compression molding on the powder, carrying out solid-phase reaction, carrying out ball milling again, and drying; the preparation method comprises the following steps: mixing sodium bismuthate and titanium oxide, adding a PVA solution, carrying out ball milling, carrying out compression molding and isostatic pressing molding, carrying out heating treatment to remove PVA, and finally sintering to obtain the Bi2Ti2O7 ceramic capacitor material. Sodium bismuthate and titanium oxide are mixed, and the linear dielectric ceramic with the chemical formula of Bi2Ti2O7 is prepared through a solid-phase reaction and sintering method; the invention provides a linear dielectric Bi2Ti2O7 ceramic capacitor material of which the breakdown strength can reach 350kV / cm, the relative dielectric constant epsilon r at 30 DEG C is equal to 117, and the dielectric loss tan delta is equal to 0.0017.

Description

Technical Field

[0001] The present invention relates to the technical field of ceramic capacitor materials, and in particular to a linear dielectric Bi2Ti2O7 ceramic capacitor material and a preparation method thereof. Background Art

[0002] Dielectric materials are the key core materials for manufacturing capacitors. They have the function of storing charge and are widely used in electronic circuits to realize coupling, filtering, decoupling, high-frequency vibration elimination, resonance, bypass, neutralization, timing, integration, differentiation, compensation, bootstrap, frequency division and other functions. The performance of dielectric materials directly determines the quality of capacitor components. Linear dielectric materials have good dielectric constant stability, do not change with the external electric field, and the polarization intensity has a small hysteresis with the external electric field. Therefore, they have important application value in the preparation of high-stability ceramic capacitors. Currently, commonly used linear dielectric materials include mica, strontium titanate, etc. With the development trend of miniaturization and high integration of electronic products, capacitors are facing the technical challenges of ultra-miniaturization, ultra-large capacity, and ultra-thinness, which puts higher requirements on the dielectric breakdown strength, energy storage efficiency and energy storage density of dielectric materials.

[0003] However, the polarization intensity of ferroelectric ceramics is large, but the hysteresis of the polarization intensity is also large, which results in that although ferroelectric ceramics have a high energy storage density, the energy storage efficiency is relatively low, and the heat generation during the charging and discharging process is serious. In addition, the dielectric breakdown strength of ferroelectric ceramics is low, which limits the further improvement of its energy storage density. Therefore, it is of great value to develop new linear dielectric materials to optimize ferroelectric ceramic materials and meet the growing demand for high breakdown strength. However, the number of linear dielectrics that can meet this demand is relatively small. Summary of the invention

[0004] The purpose of the present invention is to solve the shortcomings of the prior art and to propose a linear dielectric Bi2Ti2O7 ceramic capacitor material and a preparation method.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions: A method for preparing a linear dielectric Bi2Ti2O7 ceramic capacitor material comprises the following steps: Step 1: Mix sodium bismuthate and titanium oxide in a molar ratio according to the chemical formula Bi2Ti2O7 to obtain a mixture, and place the weighed raw materials in an oven to dry; Step 2: Add 1.5 times the mass of anhydrous ethanol to the mixture dried in step 1, and ball-mill until the powders are evenly mixed to form a slurry; Step 3: Place the slurry obtained in step 2 in an oven for constant temperature drying to remove ethanol, and then grind to obtain a uniformly mixed powder; Step 4: placing the powder obtained in step 3 into a mold for pressing and forming, and placing the formed block into a solid phase reaction furnace for solid phase reaction; Step 5: The material blocks after the solid phase reaction are crushed and ground in a mortar to obtain ceramic powder, and 2 times the mass of anhydrous ethanol is added to the obtained ceramic powder, and the ball milling is continued for 8 hours to mix the powders evenly to form a slurry; Step 6: Place the slurry obtained in step 5 in an oven to dry at a constant temperature, remove ethanol, and grind to obtain a uniformly mixed ceramic powder; Step 7: After sieving the ceramic powder obtained in step 6, a PVA solution with a mass concentration of 3% is added to the ceramic powder, and the mixture is ground and sieved to make the PVA evenly mixed in the ceramic powder. The powder particles are placed in a mold and pressed into shape, and then isostatically pressed at 250 MPa to form a ceramic green body; Step 8: heat-treating the ceramic green body obtained in step 7 to discharge the PVA in the ceramic green body to obtain a ceramic green body; Step 9: Sinter the ceramic blank obtained in step 8, and obtain the linear dielectric Bi2Ti2O7 ceramic capacitor material after cooling.

[0006] Preferably, in step 1, the weighed raw materials are placed in an oven and dried at 120° C. for 2 hours.

[0007] Preferably, in step 4, the solid phase reaction is specifically: keeping the temperature at 900° C. for 3 hours in a solid phase reaction furnace.

[0008] Preferably, in step 6, the temperature of the oven is set to 120°C.

[0009] Preferably, in step 7, the ceramic powder obtained in step 6 is sieved through a 150-mesh sieve, and then sieved through a 150-mesh sieve after grinding.

[0010] Preferably, in step 8, the heating treatment is specifically: keeping the ceramic green body at 500° C. for 0.5 hours.

[0011] Preferably, step 9: sintering treatment is specifically: sintering the ceramic blank at 1050° C. for 2 hours.

[0012] A linear dielectric Bi2Ti2O7 ceramic capacitor material is prepared by the above-mentioned method for preparing the linear dielectric Bi2Ti2O7 ceramic capacitor material.

[0013] The beneficial effects of the present invention are: The present invention provides a method for preparing a linear dielectric Bi2Ti2O7 ceramic capacitor material by a solid phase reaction method, wherein NaBiO32H2O and TiO2 are mixed, and a linear dielectric ceramic with a chemical formula of Bi2Ti2O7 is prepared by a solid phase reaction and a sintering method; the present invention provides a linear dielectric ceramic with a breakdown strength of 350 kV / cm and a relative dielectric constant ε at 30°C. r =117, linear dielectric Bi2Ti2O7 ceramic capacitor material with dielectric loss tanδ=0.0017. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 This is a SEM photo of the linear dielectric Bi2Ti2O7 ceramic sheet prepared in Example 1; Figure 2 The XRD spectrum of the linear dielectric Bi2Ti2O7 ceramic sheet prepared in Example 1; Figure 3 The hysteresis loop of the linear dielectric Bi2Ti2O7 ceramic sheet prepared in Example 1; Figure 4 The dielectric constant of the linear dielectric Bi2Ti2O7 ceramic sheet prepared in Example 1 varies with temperature; Figure 5 The dielectric loss curve of the linear dielectric Bi2Ti2O7 ceramic sheet prepared in Example 1 varies with temperature; Figure 6 The temperature stability of the dielectric constant of the linear dielectric Bi2Ti2O7 ceramic sheet prepared in Example 1 at 1 MHz relative to 150°C. DETAILED DESCRIPTION

[0015] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0016] Embodiment 1: Ingredients: Sodium bismuthate and titanium oxide are mixed in a molar ratio according to the chemical formula Bi2Ti2O7 to obtain a mixture, and the weighed raw materials are placed in an oven and dried at 120°C for 2 hours.

[0017] Mixing: Add 1.5 times the mass of anhydrous ethanol to the mixture and continue ball milling for 1 hour to mix the powders evenly to form a slurry.

[0018] Drying: Place the slurry in a 120°C oven to dry at a constant temperature to remove ethanol, and grind it in a mortar to obtain a uniformly mixed powder.

[0019] Solid phase reaction: The uniformly mixed powder is placed in a mold and pressed for 3 minutes, and the formed block is placed in a solid phase reaction furnace and kept at 900°C for 3 hours to cause a solid phase reaction.

[0020] Ball milling: The material blocks after the solid phase reaction are placed in a mortar and crushed to obtain ceramic powder. Two times the mass of anhydrous ethanol is added to the obtained ceramic powder, and the ball milling is continued for 8 hours to mix the powders evenly to form a slurry.

[0021] Drying: Place the slurry in a 120°C oven to dry at a constant temperature to remove ethanol, and grind it with a mortar to obtain a uniformly mixed ceramic powder.

[0022] Granulation: The ceramic powder is passed through a 150-mesh sieve, and then a 3% PVA solution is added thereto. After grinding, the solution is passed through a 150-mesh sieve to allow the PVA to be evenly mixed in the ceramic powder. The powder particles are placed in a mold and pressed into shape, and then isostatically pressed at 250 MPa to form a ceramic green body.

[0023] Debinding: Keep the temperature at 500℃ for 0.5 hours to discharge the PVA in the ceramic green body to obtain a ceramic body.

[0024] Sintering: The ceramic blank is sintered at 1050°C for 2 hours, and after cooling, a linear dielectric Bi2Ti2O7 ceramic sheet is obtained.

[0025] Depend on Figure 1 It can be seen that the SEM microscopic morphology characterization shows that the average size of the ceramic grains is about 1.8μm, dense and without obvious pores; Figure 2 It can be seen that XRD structural characterization shows that the ceramic phase is pure Bi2Ti2O7 phase, without the existence of a second phase; Figure 3 It can be seen that the polarization intensity of Bi2Ti2O7 ceramics shows a good linear relationship with the applied electric field, and the dielectric breakdown strength can reach 350kV / cm; Figure 4 It can be seen that at 30°C, the relative dielectric constant ε of Bi2Ti2O7 ceramics is r =117, has excellent temperature stability in the temperature range of 30℃ to 300℃; Figure 5 It can be seen that at 30°C, Bi2Ti2O7 ceramics have extremely low dielectric loss tanδ=0.0017, and have excellent temperature stability in the temperature range of 30°C to 200°C; Figure 6 It can be seen that the dielectric constant of the linear dielectric Bi2Ti2O7 ceramic changes less than 5% from room temperature to 450°C.

[0026] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A method for preparing a linear dielectric Bi2Ti2O7 ceramic capacitor material, characterized in that: The following steps are involved: Step 1: Mix sodium bismuthate and titanium oxide in a molar ratio according to the chemical formula Bi2Ti2O7 to obtain a mixture, and place the weighed raw materials in an oven to dry; Step 2: Add 1.5 times the mass of anhydrous ethanol to the mixture dried in step 1, and ball-mill until the powders are evenly mixed to form a slurry; Step 3: Place the slurry obtained in step 2 in an oven for constant temperature drying to remove ethanol, and then grind to obtain a uniformly mixed powder; Step 4: placing the powder obtained in step 3 into a mold for pressing and forming, and placing the formed block into a solid phase reaction furnace for solid phase reaction; Step 5: The material blocks after the solid phase reaction are crushed and ground in a mortar to obtain ceramic powder, and 2 times the mass of anhydrous ethanol is added to the obtained ceramic powder, and the ball milling is continued for 8 hours to mix the powders evenly to form a slurry; Step 6: Place the slurry obtained in step 5 in an oven to dry at a constant temperature, remove ethanol, and grind to obtain a uniformly mixed ceramic powder; Step 7: After sieving the ceramic powder obtained in step 6, a PVA solution with a mass concentration of 3% is added to the ceramic powder, and the mixture is ground and sieved to make the PVA evenly mixed in the ceramic powder. The powder particles are placed in a mold and pressed into shape, and then isostatically pressed at 250 MPa to form a ceramic green body; Step 8: heat-treating the ceramic green body obtained in step 7 to discharge the PVA in the ceramic green body to obtain a ceramic green body; Step 9: Sinter the ceramic blank obtained in step 8, and obtain the linear dielectric Bi2Ti2O7 ceramic capacitor material after cooling.

2. The method for preparing the linear dielectric Bi2Ti2O7 ceramic capacitor material according to claim 1, characterized in that: In step 1, the weighed raw materials are placed in an oven and dried at 120° C. for 2 hours.

3. The method for preparing the linear dielectric Bi2Ti2O7 ceramic capacitor material according to claim 1, characterized in that: In step 4, the solid phase reaction is specifically: keeping the temperature at 900° C. for 3 hours in a solid phase reaction furnace.

4. The method for preparing the linear dielectric Bi2Ti2O7 ceramic capacitor material according to claim 1, characterized in that: In step 6, the temperature of the oven is set to 120°C.

5. The method for preparing the linear dielectric Bi2Ti2O7 ceramic capacitor material according to claim 1, characterized in that: In step 7, the ceramic powder obtained in step 6 is passed through a 150-mesh sieve, and then passed through a 150-mesh sieve after grinding.

6. The method for preparing the linear dielectric Bi2Ti2O7 ceramic capacitor material according to claim 1, characterized in that: In step 8, the heating treatment is specifically: keeping the ceramic green body at 500° C. for 0.5 hours.

7. The method for preparing the linear dielectric Bi2Ti2O7 ceramic capacitor material according to claim 1, characterized in that: Step 9: Sintering treatment is specifically as follows: sintering the ceramic blank at 1050° C. for 2 hours.

8. The linear dielectric Bi2Ti2O7 ceramic capacitor material prepared by the method for preparing the linear dielectric Bi2Ti2O7 ceramic capacitor material as described in any one of claims 1 to 7.

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