Anti-surge ceramic capacitor material and preparation method thereof

Abstract

The invention discloses an anti-surge ceramic capacitor material and a preparation method thereof, and belongs to the technical field of electronic ceramic materials. The material is prepared by taking high-purity barium titanate (BaTiO3) as a basic raw material and cooperatively doping lanthanide oxide (La2O3) and transition metal carbonate (MnCO3) as a grain boundary regulating agent through a solid phase method. The ceramic capacitor material is prepared from the following components in mol percent: 96 to 98 mol percent of BaTiO3, 1 to 2.5 mol percent of La2O3 and 0.5 to 2 mol percent of MnCO3, and the sum of the mol percent of all the components is 100 percent. According to the invention, La < 3 + > and Mn < 2 + > are synergistically segregated on a grain boundary, so that a compact grain boundary layer is formed, grains are refined, defects are inhibited, and the surge breakdown resistance (greater than or equal to 10 kV / mm) is remarkably improved. The material has a wide application prospect in surge frequency scenes such as an alternating current circuit and a power supply module.

Description

Technical Field

[0001] This invention relates to the field of electronic ceramic materials technology, specifically to a surge-resistant ceramic capacitor material and its preparation method, which is particularly suitable for electronic circuit scenarios with high surge tolerance requirements. Background Technology

[0002] Ceramic capacitors are widely used in electronic devices such as power supply filtering and signal coupling due to their advantages of large capacitance, small size, and good frequency characteristics. Barium titanate (BaTiO3), as a typical perovskite ferroelectric material, has a high dielectric constant and is the core raw material for ceramic capacitors.

[0003] However, traditional barium titanate-based ceramic capacitors are prone to grain boundary breakdown under surge voltage, mainly due to problems such as uneven grain growth, numerous grain boundary pores, and impurity segregation. For example, while conventional doping schemes (such as single doping with MgO or Y2O3) can improve the dielectric constant, the optimization of grain boundary structure is limited, and the surge voltage resistance is usually below 8kV / mm. Although solid-state processes are mature, grain boundary control is difficult, and there is a lack of effective synergistic doping strategies.

[0004] Solid-state processing is the mainstream technology for preparing barium titanate-based ceramics, characterized by low cost, mature technology, and suitability for mass production. However, controlling grain boundaries in materials prepared by traditional solid-state methods is difficult, and optimizing the grain boundary structure cannot be achieved simply by adjusting process parameters. In existing technologies, doping modification is the main means to improve the performance of barium titanate ceramics, but most doping schemes focus on improving the dielectric constant, with limited research on grain boundary structure regulation to enhance surge resistance, and a lack of effective schemes for synergistic doping to regulate grain boundaries. Summary of the Invention

[0005] Technical Problem: To address the issue of poor surge resistance performance of existing barium titanate-based ceramic capacitors, this invention provides a surge-resistant ceramic capacitor material with optimized grain boundary structure through synergistic doping and its solid-state preparation process, from the perspective of grain boundary control. This solves the technical pain points of traditional materials having many grain boundary defects and insufficient surge breakdown resistance.

[0006] Technical Solution: The core innovation of this invention lies in controlling the grain boundary structure of barium titanate ceramics through synergistic doping of specific elements. The specific technical solution is as follows: The ceramic capacitor material composition is as follows: High-purity barium titanate is used as the base material, with La₂O₃ and MnCO₃ selected as synergistic grain boundary modifiers. The material composition, in molar percentage, is: BaTiO₃ 96-98 mol%, La₂O₃ 1-2.5 mol%, MnCO₃ 0.5-2 mol%. La 3+ The ionic radius of Ba 2+ It is close to and easily replaces Ba in the BaTiO3 lattice. 2+A solid solution is formed, with the remaining La 3+ It selectively segregates at grain boundaries, inhibiting abnormal grain growth and refining grain size; Mn 2+ As transition metal ions, they form an oxidation gradient layer at the grain boundaries, filling grain boundary pores and reducing impurity segregation, thus densifying the grain boundary structure. Under the synergistic effect of both, the grain boundaries become a "barrier layer" that hinders current conduction, significantly improving the material's resistance to surge breakdown.

[0007] Solid-phase preparation: The key process steps and parameter designs all revolve around grain boundary optimization: 1. Ingredient mixing: Precise control of raw material ratios and high-speed ball milling to achieve uniform dispersion of raw materials, laying the foundation for uniform grain boundary formation in the subsequent process; 2. Drying and pre-firing: Pre-firing at 900-1000℃ promotes the initial reaction between raw materials and avoids abnormal grain growth during sintering; 3. Secondary ball milling: refines the particle size of the pre-fired powder, increases the molding density, and reduces internal defects in the green body; 4. Forming: Medium pressure pressing ensures uniform density of the green body and avoids stress defects at grain boundaries after sintering; 5. Sintering: Control the heating rate and sintering temperature, hold at 1250-1350℃ for 3-4 hours to promote grain boundary densification, hold at 600-700℃ to remove binder and avoid residual impurities affecting grain boundary performance, cool to room temperature with furnace to obtain ceramic matrix; 6. Electrode preparation: Low-temperature sintering of silver paste avoids damage to the grain boundary structure caused by high temperature.

[0008] Beneficial effects:

[0009] 1. Breakthrough in surge resistance performance: Through La 3+ With Mn 2+ Co-doping increases the grain boundary breakdown voltage to over 10kV / mm, which is more than 30% higher than that of traditional materials, and the grain boundary structure remains stable under surge impact.

[0010] 2. Excellent capacitor performance: dielectric constant ≥3000, temperature coefficient of capacitance ≤±15%, suitable for a wide temperature range.

[0011] 3. Economical and efficient process: Based on solid-state optimization, no new equipment is required, resulting in low cost and suitability for mass production.

[0012] 4. Innovative Synergistic Effect: This invention proposes a La-Mn synergistic doping grain boundary control scheme for the first time, addressing the shortcomings of traditional doping grain boundary optimization. The core innovation of this invention lies in achieving precise control of the grain boundary structure of barium titanate ceramics through the synergistic doping of La2O3 and MnCO3.

[0013] Invention innovations: 1.La 3+ By replacing Ba 2+ Mn segregates at grain boundaries, inhibiting grain growth; 2+ An oxidation gradient layer is formed at the grain boundaries, filling the pores and reducing impurity segregation.

[0014] 2. Under the synergistic effect of the two, a continuous and dense "barrier layer" is formed at the grain boundary, which significantly hinders the conduction of surge current, something that cannot be achieved by traditional single doping.

[0015] 3. In the preparation process, the uniformity of the powder is optimized by pre-firing and secondary ball milling, and the densification of grain boundaries is controlled by sintering process to ensure that the synergistic doping effect is fully exerted. Attached Figure Description

[0016] Figure 1 The image shown is a scanning electron microscope (SEM) image of the ceramic material prepared in Example 1 of this invention. It can be seen that the material has fine and uniform grains and dense grain boundaries without obvious pores. Detailed Implementation

[0017] The present invention will be described in detail below through specific embodiments, but these embodiments do not limit the scope of protection of the present invention.

[0018] Example 1 1. Ingredients: Weigh out the following ingredients by molar percentage: 97 mol% BaTiO3, 2 mol% La2O3, and 1 mol% MnCO3, wherein the purity of BaTiO3 is 99.9% and the particle size is 2 μm, the purity of La2O3 is 99.5%, and the purity of MnCO3 is 99.0%. 2. First ball milling: Add 1.8 times the total mass of the raw material of deionized water and zirconia balls (ball-to-material ratio 3:1), and ball mill at 350 r / min for 7 hours; 3. Drying and pre-firing: Dry at 85℃ for 5 hours, pass through a 200-mesh sieve, and pre-firing at 950℃ for 2.5 hours; 4. Secondary ball milling: Add deionized water and zirconia balls, ball mill for 9 hours, dry at 90℃ and pass through a 300-mesh sieve; 5. Molding: Granulate with 6wt% PVA binder and press into Φ10mm×2mm green bodies under 18MPa pressure; 6. Sintering: In an air atmosphere, the heating rate is 6℃ / min, and the temperature is held at 650℃ for 1h to remove PVA. The temperature is then increased to 1300℃ and held for 3.5h, followed by furnace cooling. 7. Electrode preparation: Coat with silver paste and calcine at 880℃ for 18 min to obtain ceramic capacitor samples.

[0019] Example 2 The difference from Example 1 is in the material composition: BaTiO3 95mol%, La2O3 3mol%, MnCO3 2mol%, sintering temperature 1350℃, and the remaining steps and parameters are the same.

[0020] Example 3 The difference from Example 1 lies in the material composition: BaTiO3 98.5 mol%, La2O3 1 mol%, MnCO3 0.5 mol were weighed by molar percentage, the sintering temperature was 1250℃, and the remaining steps and parameters were the same.

[0021] Comparative Example Ceramic capacitor samples were prepared using pure BaTiO3 as raw material, without doping with La2O3 and MnCO3, and using the same solid-state process as in Example 1.

[0022] Performance testing: Test conditions: Surge voltage withstand: in accordance with IEC 61000-4-5 standard; Dielectric constant: Measured at 1 kHz using an LCR meter; Capacitor temperature coefficient: based on EIA RS-198 standard.

[0023] The performance of the samples from Examples 1-3 and the comparative examples was tested, and the results are as follows: Test Project Example 1 Example 2 Example 3 Comparative Example Surge voltage withstand (kV / mm) 11.2 10.8 10.3 7.8 Dielectric constant (1kHz, 25℃) 3200 3100 3300 2800 Capacitor temperature coefficient (-55~125℃) ±12% ±13% ±11% ±18% .

[0024] Test results show that the present invention significantly improves the surge resistance of barium titanate ceramics through the synergistic doping of La2O3 and MnCO3, while maintaining good dielectric properties and temperature stability.

Claims

1. A surge-resistant ceramic capacitor material, characterized in that, Using barium titanate as the base material, a grain boundary regulator is doped with a lanthanide oxide and a transition metal carbonate. The material composition, by molar percentage, is as follows: BaTiO3 96-98 mol%, La2O3 1-2.5 mol%, MnCO3 0.5-2 mol%, with the total molar percentage of each component being 100%. The grain boundary regulator is obtained by doping with La... 3+ With Mn 2+ The synergistic segregation at the grain boundaries forms a dense grain boundary layer, which inhibits abnormal grain growth, reduces grain boundary defects, and improves the material's surge resistance.

2. The surge-resistant ceramic capacitor material according to claim 1, characterized in that, The BaTiO3 has a particle size of 1-3 μm and a purity of ≥99.9%.

3. The surge-resistant ceramic capacitor material according to claim 1, characterized in that, The purity of the La2O3 is ≥99.5%, and the purity of the MnCO3 is ≥99.0%.

4. A method for preparing the surge-resistant ceramic capacitor material as described in any one of claims 1-3, employing a solid-state method, characterized in that, Includes the following steps: 1) Ingredient mixing: Weigh BaTiO3, La2O3, and MnCO3 raw materials according to the above molar percentages, add deionized water and zirconia balls, ball mill for 6-8 hours, with a ball-to-material ratio of 3:1 and a rotation speed of 300-400 r / min; 2) Drying and pre-calcining: The ball-milled slurry is dried at 80-100℃ for 4-6 hours, passed through a 200-mesh sieve, and then pre-calcined at 900-1000℃ for 2-3 hours to obtain pre-calcined powder; 3) Secondary ball milling: Add deionized water and zirconia balls to the pre-calcined powder again, ball mill for 8-10 hours, dry and pass through a 300-mesh sieve to obtain refined powder; 4) Molding: Add 5-8 wt% polyvinyl alcohol (PVA) binder to the refined powder, granulate, and then press to form a green body at a pressure of 15-20 MPa. 5) Sintering: The green body is heated in air at a rate of 5-8℃ / min and held at 1250-1350℃ for 3-4 hours. It is then cooled to room temperature in the furnace to obtain the ceramic matrix. 6) Electrode preparation: Silver paste is coated on both ends of the ceramic substrate and sintered at 850-900℃ for 15-20 min to prepare surge-resistant ceramic capacitors.

5. The preparation method according to claim 4, characterized in that, The amount of deionized water added in step 1) is 1.5-3 times the total mass of the raw materials.

6. The preparation method according to claim 4, characterized in that, In step 5), during the sintering process, the temperature is maintained at 600-700℃ for 1 hour to remove the PVA binder.

Images