Dielectric ceramic material and preparation method thereof

Abstract

The invention discloses a dielectric ceramic material and a preparation method thereof, and relates to the technical field of dielectric ceramic materials, and the technical key points are as follows: the dielectric ceramic material comprises barium titanate (BaTiO3) which accounts for 80-99 wt% of the weight of the finished dielectric ceramic material; the dielectric ceramic material also comprises a dopant, and the dopant accounts for 1-20wt% of the weight of the dielectric ceramic material finished product. The doping agent comprises silicon dioxide (SiO2), magnesium carbonate (MgCO3), manganous-manganic oxide (Mn3O4), barium titanate (BaCO3) and rare earth oxide D2O3; wherein D represents any one or more of yttrium (Y), holmium (Ho), ytterbium (Yb), gadolinium (Gd) and dysprosium (Dy); the invention provides a dielectric ceramic material which meets the EIAX7R standard and still has a high IR characteristic and a low dielectric loss factor (tan delta) in a high-temperature environment and a preparation method of the dielectric ceramic material.

Description

Technical Field

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

[0002] As a high-performance electronic component, multilayer ceramic capacitors (MLCC) play a vital role in modern electronic devices. Its small size, long life, and easy surface mount technology (SMT) processing make MLCC excellent in solving the problem of circuit board space limitations. MLCC is widely used in many fields such as industrial power supply, module power supply, LED lighting, automotive hernia lamp, negative ion generator and electronic ballast, especially in industrial power supply such as AT power supply, ATX power supply and MicroATX power supply, as a key component of power supply filtering, voltage reduction and voltage doubling, its importance is self-evident.

[0003] As the application scenarios continue to expand, the market demand for MLCC continues to expand, and the requirements for its large-scale production and stability are also increasing. In order to meet the needs of high dielectric constant and good temperature stability of capacitors in high temperature environments, the US Electronics Industry Association (EIA) has formulated the X7R specification, which requires capacitors to maintain stable performance in the temperature range of -55℃ to 125℃.

[0004] However, the existing dielectric ceramic materials are mainly made of barium titanate (BaTiO3) as the main component and doped with oxides of zirconium, barium, manganese and silicon. Although the performance of the capacitor has been improved to a certain extent, there is still a significant insulation resistance (IR) degradation problem under high temperature conditions. This degradation not only shortens the service life of the capacitor, but also reduces its reliability. In order to improve the IR degradation and reliability at high temperatures, a class of special ceramic materials such as CaZrO3, SrCaTiZrO3, Ca(TiZr)O3, etc. have been proposed, but these materials have low dielectric constants (usually less than 100), so they are not suitable for preparing large-capacity capacitors.

[0005] In addition, the performance of multilayer ceramic capacitors is also affected by the temperature characteristics of its materials. The temperature characteristics of dielectric ceramic materials refer to the characteristics of the capacitor's capacity changing with temperature, which is one of the important indicators for evaluating the stability of capacitors. At the same time, insulation resistance and dielectric loss are also key parameters for measuring capacitor performance. Insulation resistance reflects the insulation ability of the capacitor's dielectric under the action of an electric field, while dielectric loss represents the energy consumed by the capacitor due to heat during operation. Summary of the invention

[0006] In view of the fact that the existing dielectric ceramic materials are prone to significant degradation of the insulation resistance which cannot be restored when an electric field is applied at high temperature, there are problems of short IR life and low reliability; a type of ceramic (CaZrO3, SrCaTiZrO3, Ca(TiZr)O3) can improve the high temperature IR degradation and reliability problems, but the dielectric constant is low (less than 100), and it is not suitable for preparing large-capacity capacitors. The purpose of the present invention is to provide a dielectric ceramic material that meets the EIAX7R standard and still has high IR characteristics and low dielectric loss factor (tanδ) in a high temperature environment and a preparation method thereof.

[0007] To achieve the above object, the present invention provides the following technical solutions:

[0008] A dielectric ceramic material:

[0009] The invention comprises barium titanate (BaTiO3), wherein the barium titanate accounts for 80 to 99 wt% of the finished dielectric ceramic material;

[0010] Also includes a dopant, the dopant accounts for 1 to 20 wt% of the weight of the finished dielectric ceramic material;

[0011] The dopants include silicon dioxide (SiO2), magnesium carbonate (MgCO3), manganese tetraoxide (Mn3O4), barium titanate (BaCO3) and rare earth oxide D2O3; wherein D represents any one or more of yttrium (Y), holmium (Ho), ytterbium (Yb), gadolinium (Gd) and dysprosium (Dy).

[0012] Preferably, based on the weight of the barium titanate as 100 parts by mass, the amount of silicon dioxide added in the dopant is 0.05-2wt%, the amount of magnesium carbonate added is 0.4-0.6wt%, the amount of manganese tetraoxide added is 0.03-0.05wt%, the amount of barium titanate added is 1.3-2.3wt%, and the amount of rare earth oxide D2O3 added is 0.2-3wt%.

[0013] A method for preparing a dielectric ceramic material comprises the following steps:

[0014] Step 1: Mixing and grinding: Mixing and grinding barium titanate particles, dopant particles and dispersant to obtain a powder mixture;

[0015] Step 2, mixing slurry: adding a binder and a solvent to the powder mixture, stirring and mixing to obtain a ceramic slurry;

[0016] Step three, preliminary shaping and drying: shaping and drying the ceramic slurry to obtain a sheet;

[0017] Step 4, sintering and forming; sintering the sheet to obtain a finished dielectric ceramic material; the sintering temperature is 1200-1420° C., the sintering atmosphere is 0.5-3.5% H2-N2, and the sintering time is 0.5-4.5 hours.

[0018] Preferably, the barium titanate particles have a particle size of 150-250 nm and are prepared by a solid phase method.

[0019] Preferably, the dispersant is a polyethylene oxide resin, and the amount of the dispersant added is usually 0.5 to 5 wt % based on 100 parts by weight of the barium titanate particles.

[0020] Preferably, the binder is a polyvinyl acetal resin, and the added amount of the binder is 5 to 15 wt % based on 100 parts by weight of the barium titanate particles.

[0021] Preferably, the solvent is one or more of water, ethanol and toluene.

[0022] Preferably, in step three, an extrusion molding machine is used to extrude the ceramic slurry, and in step three, a drying box is used to dry the formed ceramic slurry.

[0023] Preferably, the sintering temperature is 1340-1360° C., the sintering atmosphere is 0.9-1.1% H 2 —N 2 , and the sintering time is 0.9-1.1 hours.

[0024] The present invention has the following beneficial effects:

[0025] 1. Improving dielectric properties: Through the optimization of reasonable additive composition and addition amount, the dielectric ceramic material prepared by the present invention has excellent dielectric properties within the temperature range of -55°C to 125°C, meeting the EIA-X7R standard.

[0026] 2. Improve temperature stability: Mg 2+ The addition of and the formation of a "core-shell" structure enable the material to maintain stable dielectric properties over an ultra-wide temperature range, effectively solving the problem of large fluctuations in dielectric properties of traditional barium titanate-based ceramics at high temperatures.

[0027] 3. Improve the insulation resistance (IR) characteristics: The introduction of Mn3O4 reduces the semiconductivity problem at high temperatures, improves the insulation resistance characteristics of the material, and extends the service life.

[0028] 4. Reduce dielectric loss factor (tanδ): The doping of D2O3 reduces the dielectric loss factor at high temperatures and improves the overall performance of the material.

[0029] 5. Enhanced reliability: Based on the above improvements, the dielectric ceramic material prepared by the present invention can still maintain excellent performance in harsh environments such as high temperature and high electric field, which significantly improves the reliability of the product. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0031] Figure 1 The process flow chart of an embodiment of the present invention. DETAILED DESCRIPTION

[0032] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0033] A dielectric ceramic material: including barium titanate (BaTiO3), which accounts for 80-99wt% of the weight of the finished dielectric ceramic material; also including a dopant, which accounts for 1-20wt% of the weight of the finished dielectric ceramic material; the dopant includes silicon dioxide (SiO2), magnesium carbonate (MgCO3), manganese tetraoxide (Mn3O4), barium titanate (BaCO3) and rare earth oxide D2O3; wherein D represents any one or more of yttrium (Y), holmium (Ho), ytterbium (Yb), gadolinium (Gd), and dysprosium (Dy).

[0034] This application is for dielectric materials of multilayer ceramic capacitors with X7R characteristics. The core of this application is to optimize the composition and amount of additives in the BaTiO3 matrix to solve the semiconductivity problem that traditional X7R ceramic dielectric materials are prone to in the high temperature range (-55℃~125℃), and to improve the dielectric properties and capacitance-temperature characteristics after sintering. This dielectric material is mainly composed of BaTiO3, Mn3O4, MgCO3, D2O3 (where D represents rare earth elements such as Y, Ho, Yb, Gd, Dy, etc.) and BaCO3. The following is a detailed description of its working principle:

[0035] First, BaTiO3 (barium titanate) as a matrix material has excellent dielectric properties, but it is easy to become a semiconductor due to high-temperature oxygen loss when sintered in a reducing atmosphere, resulting in a decrease in dielectric properties. In order to solve this problem, a variety of additives have been introduced.

[0036] Second, the role of magnesium carbonate: magnesium carbonate decomposes into MgO and Mg at high temperature. 2+ The ions enter the BaTiO3 lattice to perform acceptor substitution. This substitution can improve the material's anti-reduction properties and prevent semiconductivity caused by oxygen volatilization at high temperatures.

[0037] Grain growth suppression and “core-shell” structure: Mg 2+ It can also inhibit the excessive growth of BaTiO3 grains and promote the formation of a "core-shell" structure. This structure helps to improve the dielectric temperature stability of ceramics in an ultra-wide temperature range.

[0038] Tc peak shifts left: Mg 2+ The addition of will also shift the Curie temperature (Tc) peak of the material to the left, which may further optimize the dielectric properties of the material.

[0039] Third, the role of manganese tetraoxide: During the calcination of Mn3O4, Mn ions will present +2 and +3 valences. In the reoxidation stage, low-valent manganese ions will be oxidized, and this process reduces the concentration of oxygen vacancies used to compensate for acceptor defects. Oxygen vacancies are an important cause of semiconductivity at high temperatures, so the addition of Mn3O4 helps reduce the problem of high-temperature semiconductivity.

[0040] Fourth, the role of rare earth oxides: D2O3 (where D represents rare earth elements) as amphoteric rare earth ions can simultaneously perform donor doping and acceptor doping, and produce defect association. This doping method helps to reduce the dielectric loss factor (tanδ) at high temperatures and improve the material's anti-reduction performance and life. The introduction of rare earth elements also enhances the stability and reliability of the material.

[0041] Fifth, the role of barium titanate: The addition of BaCO3 mainly plays the role of regulating the atmosphere during the sintering process, which helps to maintain the chemical balance during the sintering process, promote the densification of the material, and thus improve the dielectric properties.

[0042] Taking barium titanate as 100 parts by mass, the amount of silicon dioxide added in the dopant is 0.05-2wt%, the amount of magnesium carbonate added is 0.4-0.6wt%, the amount of manganese tetraoxide added is 0.03-0.05wt%, the amount of barium titanate added is 1.3-2.3wt%, and the amount of rare earth oxide D2O3 added is 0.2-3wt%.

[0043] BaTiO3, as a matrix material, has excellent dielectric properties and is an important raw material for making multilayer ceramic capacitors. SiO2 (silicon dioxide): As a sintering aid, the addition of SiO2 can promote the densification process of ceramics, reduce porosity, and improve the mechanical strength and dielectric properties of the material. In addition, SiO2 can also adjust the sintering temperature range to a certain extent to prevent over-burning or under-burning. MgCO3 (magnesium carbonate): decomposes into MgO and MgCO3 at high temperatures. 2+ The ions enter the BaTiO3 lattice to perform acceptor substitution, inhibit excessive grain growth, and promote the formation of a "core-shell" structure, thereby improving the dielectric temperature stability and anti-reduction properties of the material.

[0044] Mn3O4 (manganese tetraoxide): During the sintering process, it releases oxygen to compensate for oxygen vacancies and inhibit the occurrence of semiconductivity at high temperatures. At the same time, Mn ions can also improve the dielectric constant and dielectric loss of the material and improve the electrical performance of the capacitor. BaCO3 (barium titanate): As one of the sintering aids, the addition of BaCO3 helps to maintain the chemical balance during the sintering process and promote the densification of the material. In addition, BaCO3 can also adjust the Curie temperature of the material to a certain extent and optimize the dielectric properties. D2O3 (rare earth oxide): Through donor and acceptor doping, D2O3 can reduce the dielectric loss factor at high temperatures and improve the material's anti-reduction performance and life. The introduction of rare earth elements can also enhance the stability and reliability of the material. The synergistic effect of these additives enables BaTiO3-based ceramic materials to maintain excellent dielectric properties and stability in harsh environments such as high temperature and high humidity. At the same time, by optimizing the composition and addition amount of additives, the comprehensive performance of the material can be further improved to meet the use requirements of multilayer ceramic capacitors.

[0045] A method for preparing a dielectric ceramic material, such as Figure 1 As shown, the following steps are included:

[0046] Step 1: Mixing and grinding: Mix and grind barium titanate particles, dopant particles and dispersant to obtain a powder mixture; the purpose of this step is to fully mix and grind barium titanate particles (BaCO3, as the main component), dopant particles (such as SiO2, MgCO3, Mn3O4, D2O3, etc., used to improve dielectric properties and stability) and dispersant to obtain a uniform powder mixture. The addition of dispersant helps prevent particle agglomeration and improve mixing uniformity.

[0047] Step 2: Mixing slurry: Add binder and solvent to the powder mixture, stir and mix to obtain ceramic slurry. The addition of binder enables the powder particles to bond with each other, forming a slurry with certain strength and toughness, which provides a basis for subsequent molding. The solvent plays a role in adjusting the viscosity and fluidity of the slurry.

[0048] Step 3: Preliminary forming and drying: The ceramic slurry is formed and dried to obtain a sheet; the ceramic slurry is formed (such as casting, pressing, etc.) to form a sheet with a certain shape and size. Then, a drying process is performed to remove the solvent and water in the slurry, so that the sheet is solidified and has a certain strength.

[0049] Step 4, sintering and forming; sintering the sheet to obtain the finished dielectric ceramic material, sintering the sheet at high temperature so that the powder particles therein undergo a solid phase reaction to form a dense dielectric ceramic material. The selection of sintering temperature, atmosphere and time has an important influence on the performance of the final product. The sintering temperature used in this method is 1200-1420°C, which belongs to the category of high temperature sintering; the sintering atmosphere is an N2 atmosphere containing 0.5-3.5% H2. This reducing atmosphere helps to reduce oxygen vacancies in the material and improve the anti-reduction performance; the sintering time is 0.5-4.5 hours, which is adjusted according to the specific formula and material properties. In this process, the low melting point substance will preferentially melt into a liquid phase, wrapping the BaTiO3 grains that have not yet fully grown, forming a shell-core structure, thereby inhibiting the further growth of the grains, and finally forming a fine-grained dielectric ceramic. This structure not only improves the temperature stability of the material, but also improves its dielectric properties.

[0050] The particle size of barium titanate particles is 150-250nm and is made by the solid phase method. The particle size of barium titanate particles is controlled in the range of 150-250nm, and this particle size range helps to obtain a higher specific surface area and better sintering performance. Fine particles can shorten the diffusion distance during sintering, promote densification, and may improve the dielectric properties of the material. The solid phase preparation process is relatively simple and mature, and it is easy to achieve industrial production. By optimizing the process parameters of key steps such as grinding and sintering, production efficiency can be further improved and production costs can be reduced.

[0051] The dispersant is a polyethylene oxide resin, and the amount of the dispersant added is usually 0.5-5wt% based on the weight of the barium titanate particles as 100 parts by weight. The polyethylene oxide resin is used as a dispersant, and the amount of the dispersant added is 0.5-5wt% based on the weight of the barium titanate particles. The function of the dispersant is to prevent the particles from agglomerating during the mixing and grinding process and ensure the uniform dispersion of the raw materials. The right amount of dispersant can significantly improve the uniformity and stability of the mixture.

[0052] The binder is a polyvinyl alcohol acetal resin, and the amount of the binder added is 5 to 15 wt% based on the weight of the barium titanate particles as 100 parts by mass. The polyvinyl alcohol acetal resin is selected as the binder, and the amount of the binder added is 5 to 15 wt% of the weight of the barium titanate particles. The binder plays a bridging role in the ceramic slurry, allowing the powder particles to bond to each other to form a slurry with certain strength and toughness. An appropriate amount of binder can ensure that the slurry maintains a stable shape during the molding process and forms a dense ceramic body after sintering.

[0053] The solvent is one or more of water, ethanol and toluene. The selection of the solvent should take into account its solubility, volatility and environmental friendliness to the raw materials. Water as a solvent has the advantages of low cost and no pollution; ethanol and toluene may have better solubility and volatility, which helps to adjust the viscosity and fluidity of the slurry.

[0054] In step 3, the ceramic slurry is extruded and molded using an extrusion molding machine, and the molded ceramic slurry is dried using a drying oven in step 3. The ceramic slurry is extruded and molded using an extrusion molding machine to obtain a sheet having a desired shape and size. Extrusion molding can ensure the dimensional accuracy and shape consistency of the product. The molded ceramic slurry is then dried using a drying oven to remove solvents and moisture, so that the sheet is solidified and has a certain strength.

[0055] A better choice is to select a sintering temperature of 1340-1360°C (especially 1350°C), which can fully sinter the barium titanate-based ceramic material without over-burning or under-burning. The sintering atmosphere is 0.9-1.1% H2-N2 (especially 1% H2-N2). The reducing atmosphere helps to reduce oxygen vacancies and defects in the material and improve the dielectric properties. The sintering time is 0.9-1.1 hours (especially 1 hour) to ensure that the material achieves the best sintering effect in a shorter time.

[0056] The specific embodiments of the present invention are as follows:

[0057] Example 1

[0058] Mix 100 mass percent of barium titanate particles with an average particle size of 0.15μm to 0.25μm, a certain mass percent of dopant and 2 mass percent of (dispersant), and grind them in a ball mill for 1 hour to obtain a powder mixture. Then add 8 weight percent of (binder) to the powder mixture and mix evenly to obtain a slurry. The components of the above-mentioned dopants are listed in Table 1 below. The slurry is extruded and dried to obtain a sheet. The test sheet is sintered at 1350°C for 1 hour in a 1% H2-N2 atmosphere to obtain a dielectric ceramic material. Then, copper end electrodes are added to the corresponding two sides of the dielectric ceramic material to carry out the evaluation test described later, and the evaluation results are listed in Table 1 below.

[0059] Examples 2-5 and Comparative Examples 1-7

[0060] Examples 2-5 and Comparative Examples 1-7 were all manufactured in a similar manner to Example 1. The difference is that the dosage of the dopant was changed in Examples 2-5 and Comparative Examples 1-7. The specific conditions and evaluation results are shown in Table 1 below.

[0061] Table 1

[0062]

[0063] Referring to Table 1, compared with Comparative Examples 1-7, the capacitance temperature coefficient of the dielectric ceramic materials of Examples 1-5 at -55°C to 125°C is not greater than 15%, and the dielectric constant is greater than 2600, and the dielectric loss factor is less than 1.54. It can be seen that the dopant containing a specific composition can reduce the capacitance temperature coefficient of the prepared dielectric ceramic material, increase the dielectric constant and reduce the dielectric loss factor.

[0064] The above are only specific embodiments of the present invention, but the technical features of the present invention are not limited thereto. Any simple changes, equivalent replacements or modifications made based on the present invention to solve basically the same technical problems and achieve basically the same technical effects are all within the scope of protection of the present invention.

Claims

1. A dielectric ceramic material, Features: Including barium titanate (BaTiO 3 ), the barium titanate accounts for 80-99wt% of the weight of the finished dielectric ceramic material; and also includes a dopant, the dopant accounts for 1-20wt% of the weight of the finished dielectric ceramic material; The dopant includes silicon dioxide (SiO 2 ), magnesium carbonate (MgCO 3 ), manganese tetraoxide (Mn 3 O 4 ), barium titanate (BaCO 3 ) and rare earth oxides D 2 O 3 ; wherein D represents any one or more of yttrium (Y), holmium (Ho), ytterbium (Yb), gadolinium (Gd), and dysprosium (Dy).

2. A dielectric ceramic material according to claim 1, Features: Based on the weight of the barium titanate as 100 parts by mass, the addition amount of silicon dioxide in the dopant is 0.05-2wt%, the addition amount of magnesium carbonate is 0.4-0.6wt%, the addition amount of manganese tetraoxide is 0.03-0.05wt%, the addition amount of barium titanate is 1.3-2.3wt%, and the rare earth oxide D 2 O 3 The addition amount is 0.2~3wt%.

3. A method for preparing a dielectric ceramic material, applied to a dielectric ceramic material as claimed in any one of claims 1 to 2, Features: The following steps are involved: Step 1, mixing and grinding; The barium titanate particles, the dopant particles and the dispersant are mixed and ground to obtain a powder mixture; Step 2, mixing slurry: adding a binder and a solvent to the powder mixture, stirring and mixing to obtain a ceramic slurry; Step three, preliminary shaping and drying: shaping and drying the ceramic slurry to obtain a sheet; Step 4: sintering and forming; sintering the sheet to obtain a finished dielectric ceramic material; the sintering temperature is 1200-1420°C, and the sintering atmosphere is 0.5-3.5% H 2 -N 2 The sintering time is 0.5 to 4.5 hours.

4. A method for preparing a dielectric ceramic material according to claim 3, Features: The barium titanate particles have a particle size of 150-250 nm and are prepared by a solid phase method.

5. The method for preparing a dielectric ceramic material according to claim 3, Features: The dispersant is a polyethylene oxide resin. The amount of the dispersant added is usually 0.5 to 5 wt % based on 100 parts by weight of the barium titanate particles.

6. A method for preparing a dielectric ceramic material according to claim 3, Features: The binder is a polyvinyl acetal resin, and the addition amount of the binder is 5-15wt% based on 100 parts by weight of the barium titanate particles.

7. A method for preparing a dielectric ceramic material according to claim 3, Features: The solvent is one or more of water, ethanol and toluene.

8. A method for preparing a dielectric ceramic material according to claim 3, Features: In the step three, an extrusion molding machine is used to extrude the ceramic slurry, and in the step three, a drying box is used to dry the formed ceramic slurry.

9. The method for preparing a dielectric ceramic material according to claim 3, Features: The sintering temperature is 1340-1360°C, and the sintering atmosphere is 0.9-1.1% H 2 -N 2 , the sintering time is 0.9 to 1.1 hours.

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