An anti-reduction X8R type multilayer ceramic capacitor dielectric material and a preparation method thereof

Abstract

The application belongs to the technical field of ceramic capacitors, and discloses a kind of anti-reduction X8R type multilayer ceramic capacitor dielectric material and preparation method thereof.The dielectric material is prepared from BaTiO3, Re2O3, MgO, MnO2 and SrZrO3;The dosage of each component accounts for the molar percentage of BaTiO3: Re2O3 0.5%~1.5%, MgO 1%~3%, MnO2 0.5%~1.5%, SrZrO3 1%~2%.The application also discloses the preparation method of dielectric material.The application generates lattice distortion by SrZrO3 entering BaTiO3 lattice, makes adjacent titanium oxygen octahedron have larger space, promotes Re to enter Ba site and Ti site, and the generated defect dipole can bind the migration of oxygen vacancy, enhances the short-range jump polarization of oxygen vacancy, improves the dielectric constant, the dielectric loss is low, and the temperature stability of material is good.

Description

Technical Field

[0001] This invention belongs to the field of ceramic capacitor technology, and relates to a reduction-resistant X8R type ceramic capacitor dielectric material and its preparation method. Background Technology

[0002] Multilayer ceramic capacitors (MLCCs), as a fundamental passive electronic component, are widely used in various electronic circuits. Among capacitor classifications, MLCCs hold a dominant position in both production volume and market share. With the continuous development of aerospace, automotive electronics, and oil exploration, the reliability of devices in high-temperature environments has received increasing attention, placing more stringent requirements on the operating temperature range and dielectric properties of ceramic capacitors. The X8R type refers to a capacitance value based on 25℃, with a capacitance change rate (ΔC / C25℃) ≤ ±15% within a temperature range of -55℃ to +150℃. In addition to meeting the service conditions of up to 150℃, the dielectric material also needs to possess a high dielectric constant to adapt to the trend of device miniaturization. With the continuous increase in the number of MLCC layers, the amount of electrode material used is constantly increasing, with a significant rise in the amount of internal electrode material. Due to cost considerations, multilayer ceramic capacitors with base metal internal electrodes, such as copper and nickel, are gradually becoming a research focus. These types of devices typically require sintering in a reducing atmosphere, but the free electrons and oxygen vacancies generated in the BaTiO3 ceramic matrix under reducing conditions reduce the material's temperature stability. Therefore, developing X8R-type MLCC dielectric materials with high-temperature stability, reduction resistance, and high dielectric constant has significant practical application value.

[0003] In previous studies, the introduction of neutral rare earth ions and their simultaneous occupation of A-sites and B-sites has been shown to form defect dipoles, thereby suppressing the long-range migration of oxygen vacancies and increasing the dielectric constant of the material through the short-range jumping polarization of oxygen vacancies. Neutral rare earth ions also reduce the Curie temperature of BaTiO3 materials. Zeng et al.'s work showed that by adjusting the doping concentration of neutral rare earth ions to change their occupation mode, the dielectric constant was observed to increase to 2470 in the experiment. However, when the temperature was below 5℃ or above 107℃, the capacitance change rate exceeded 15%, and the temperature stability of the sample decreased (Zeng M, Liu X, Hao H, et al. Improved dielectric properties and anti-reducing mechanism of Er / Mg Co-dopedBaTiO3-based ceramics produced in reducing atmosphere[J]. CeramicsInternational, 2025, 51(18): 26918-26925.). Furthermore, Kim et al.'s research also found that increasing the concentration of neutral rare earth ions alone reduced the Curie point of BaTiO3 from 125℃ to 85℃, increasing the capacitance change rate in the high-temperature region and leading to a decrease in the material's temperature stability, making it difficult to meet the X8R standard (Kim J, Kim D, Noh T, et al. Microstructure and thermal properties of dysprosium and thulium co-dopedbarium titanate ceramics for high performance multilayer ceramic capacitors[J]. Materials Science and Engineering: B, 2011, 176(15): 1227-1231.). Although doping with neutral rare earth ions can improve the dielectric constant of BaTiO3-based materials through defect dipoles, it also significantly reduces the Curie temperature, leading to an increase in the capacitance change rate in the high-temperature region, thereby weakening the material's temperature stability and making it difficult to meet the application requirements of X8R type ceramic capacitors.

[0004] Therefore, how to utilize neutral rare earth ions to form defect dipoles to improve the dielectric constant while suppressing their effect on lowering the Curie temperature of BaTiO3, thereby reducing the capacitance change rate in the high-temperature region and improving the temperature stability of the material, is a key technical problem that needs to be solved in this field. Furthermore, the aforementioned studies all used relatively expensive rare earth elements as doping components. How to balance low cost and high dielectric constant is the focus of this invention. Summary of the Invention

[0005] The purpose of this invention is to provide a reduction-resistant X8R type ceramic capacitor dielectric material and its preparation method, to solve the problems of low dielectric constant, poor temperature stability, and low reduction resistance of existing BaTiO3-based dielectric materials. This invention uses BaTiO3 as the main component and introduces Re2O3, MnO2, SrZrO3, and MgO as modifying dopants. The dielectric material of this invention does not contain toxic elements such as lead and vanadium, and avoids the use of expensive heavy rare earth oxides, thus possessing good environmental friendliness and cost advantages. In the preparation process of the dielectric material of this invention, the Re in the selected dopant Re2O3 is a neutral rare earth ion with an ionic radius of 0.87–0.94 Å, such as Er, Dy, Tb, Tm, Eu, Y, and Ho, which can enter both Ba and Ti sites. While existing technologies can form defect dipoles in BaTiO3-based dielectric materials through neutral rare-earth ion doping, thereby suppressing long-range migration of oxygen vacancies and increasing the dielectric constant, this also leads to a decrease in the Curie temperature, resulting in reduced temperature stability. It is difficult to balance high dielectric constant with wide-temperature stability, thus limiting its application in X8R type ceramic capacitors. In contrast, the SrZrO3 dielectric material of this invention contains Sr... 2+ and Zr 4+ The process of Re entering the crystal lattice alters the crystal structure, providing more space for adjacent titanium-oxygen octahedra, promoting the simultaneous entry of Re into Ba and Ti sites, and forming defect dipoles. – This not only hinders the migration of oxygen vacancies but also acts as a deep potential trap for electrons, reducing the long-range transition behavior of defect carriers such as oxygen vacancies. Under the influence of an electric field, the synergistic doping of this invention can increase the contribution of short-range jump polarization of oxygen vacancies to the dielectric constant, thereby improving the dielectric constant. Furthermore, the SrZrO3 selected in this invention has a slow diffusion rate during sintering, which helps to form a Sr, Zr, and Re enriched shell layer with Re2O3, encapsulating the BaTiO3 core and thus constructing a unique "core-shell structure." The internal stress generated between the core and shell structures can adjust the cell parameters of BaTiO3, slightly increasing the c-axis and slightly decreasing the a-axis, thereby increasing the tetragonal distortion of the material (increasing the c / a value). This enhanced tetragonality helps to increase the Curie temperature of BaTiO3, thus improving the dielectric stability of the material at high temperatures and reducing the rate of change of volumetric temperature.

[0006] The dopant selected in this invention contains Mn 4+ It will be reduced to Mn in a reducing atmosphere. 3+ and Mn 2+ Both and Mg 2+ Ti enters BaTiO3 as acceptor dopant4+ Acceptor doping can bind free electrons and reduce conductivity. In addition, Mg... 2+ Because of its slow diffusion rate, it can play a role in regulating the volume fraction of the shell in the core-shell structure.

[0007] This invention is achieved through the following technical solution:

[0008] A reduction-resistant X8R type multilayer ceramic capacitor dielectric material is composed of BaTiO3 as the main component and four dopants: Re2O3, MnO2, SrZrO3, and MgO. The Re2O3 accounts for 0.5% to 1.5% (preferably 0.8% to 1.3%) of the molar ratio of BaTiO3, the MgO accounts for 1% to 3% (preferably 1.5% to 2.5%) of the molar ratio of BaTiO3, the MnO2 accounts for 0.5% to 1.5% (preferably 0.5% to 1%) of the molar ratio of BaTiO3, and the SrZrO3 accounts for 1% to 2% of the molar ratio of BaTiO3.

[0009] In Re2O3, Re represents a neutral rare earth ion with an ionic radius of 0.87–0.94 Å, such as Er, Dy, Tb, Tm, Eu, Y, or Ho.

[0010] A method for preparing a reduction-resistant X8R type multilayer ceramic capacitor dielectric material includes the following steps:

[0011] 1) Mix SrZrO3 powder, BaTiO3, MgO, MnO2 and Re2O3, ball mill, dry, granulate, press and debind to obtain green body;

[0012] 2) The blank is placed in an atmosphere of hydrogen / argon or hydrogen / nitrogen mixture with a hydrogen specific gravity of 0.3-1% for sintering at a temperature of 1200-1300℃ and a holding time of 2-4 hours. After cooling, the reduction-resistant X8R type multilayer ceramic capacitor dielectric material is obtained.

[0013] SrZrO3 powder is prepared by the following method: S1. SrCO3 and ZrO2 are ball-milled at a molar ratio of 1:1, dried, and calcined in air to obtain SrZrO3 powder.

[0014] In the preparation of SrZrO3 powder, anhydrous ethanol is used as the milling medium. The mass ratio of powder to milling beads to anhydrous ethanol during milling is 1:2:1-2, and the milling beads are zirconia balls. The calcination temperature is 1000-1150℃, and the holding time is 2-3 hours. The drying conditions are: drying at 90-105℃ for 4-6 hours. The milling time is 3-4 hours.

[0015] The adhesive removal process involves heating the material to 500-600°C at a rate of 2-3°C / min, holding it at that temperature for 2-4 hours, and then cooling it down. The cooling process involves reducing the temperature to 200°C at a rate of 3-5°C / min, followed by furnace cooling or direct natural cooling to room temperature.

[0016] Granulation refers to granulation by adding a polyvinyl alcohol aqueous solution (5-10 wt%); pressing refers to pressing into a preform to be discharged and pressing it into shape under a uniaxial pressure of 5 MPa-15 MPa.

[0017] The milling medium is anhydrous ethanol. During the milling process, the mass ratio of powder to milling beads to anhydrous ethanol is 1:2:1-2, and the milling beads are zirconia balls. The drying conditions are: drying at 90-105℃ for 4-6 hours. The milling time is 3-4 hours.

[0018] Compared with the prior art, the beneficial effects of the present invention are:

[0019] A high-quality EIA X8R standard dielectric ceramic material was obtained by solid-state method based on BaTiO3 through donor-acceptor doping. The process is simple, low-cost, and free of lead, vanadium, and other elements, making it environmentally friendly. The dielectric material of this invention features high dielectric constant and low dielectric loss. At room temperature (25℃) and 1kHz, the dielectric constant is greater than 4500, and the dielectric loss is less than 0.016. Within a temperature range of -55℃ to 150℃, the capacitance change rate is less than or equal to ±15%. It can be applied to Ni-MLCCs, which require lower sintering costs under a reducing atmosphere. The high-temperature stable MLCC provided by this invention meets the performance requirements of electronic materials and has good industrialization prospects. Attached Figure Description

[0020] Figure 1 The image shows the XRD pattern of the dielectric material of the X8R type multilayer ceramic capacitor in Example 1.

[0021] Figure 2 Here is a SEM image of the dielectric material of the X8R type multilayer ceramic capacitor in Example 1;

[0022] Figure 3 This is a TEM image of the dielectric material of the X8R type multilayer ceramic capacitor in Example 1;

[0023] Figure 4 The dielectric constant-temperature diagram of the dielectric material of the X8R type multilayer ceramic capacitor in Example 1 is shown.

[0024] Figure 5 This is a capacitance change rate-temperature graph of the dielectric material of the X8R type multilayer ceramic capacitor in Example 1. Detailed Implementation

[0025] The embodiments of this application will be described in detail below with reference to examples. However, those skilled in the art will understand that the following examples are for illustrative purposes only and should not be considered as limiting the scope of this application. Unless otherwise specified in the examples, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0026] In some possible implementations, the oxide of Re may be selected from one or more rare earth oxides of Er, Dy, Tb, Tm, Eu, Y and Ho.

[0027] For example, the oxide of Re can be selected from Y2O3.

[0028] Tests on samples prepared according to this invention revealed that, compared to samples doped only with Y₂O₃, samples co-doped with Y₂O₃ and SrZrO₃ exhibit both a high Curie temperature (>135°C) and a high dielectric constant (>4000). The capacitance temperature change rate at the high-temperature end decreased from over 40% to less than 15%, dielectric loss was <1.6%, and insulation resistivity was ≥10 Ω·cm. 10 The temperature stability reaches the X8R standard (Ω·cm). Under reducing atmosphere, the material exhibits low dielectric loss and high insulation resistivity, indicating strong resistance to reduction.

[0029] Example 1:

[0030] A method for preparing a reduction-resistant X8R type multilayer ceramic capacitor dielectric material includes the following steps:

[0031] Step 1: Synthesis of SrZrO3

[0032] Weigh SrCO3 and ZrO2 according to a molar ratio of 1:1, place the powder into a ball mill jar, and then add anhydrous ethanol and zirconium oxide grinding beads to the ball mill jar; the mass ratio of powder: grinding beads: anhydrous ethanol is 1:2:1. Place the ball mill jar in a planetary ball mill and ball mill at a speed of 300 rpm / min for 3 hours. After ball milling, place the slurry in a 100℃ oven to dry it thoroughly, then grind it through an 80-mesh sieve, and then calcine the obtained powder at 1000℃ for 2 hours to obtain SrZrO3 powder.

[0033] Step 2: Synthesize BaTiO3 (2 mol%), MgO (1 mol%), Y2O3 (0.5 mol%), MnO2 (1 mol%), and SrZrO3 powder.

[0034] BaTiO3 (0.02 mol), SrZrO3 powder, MgO, MnO2, and Y2O3 powder were placed in a ball mill jar, and then anhydrous ethanol and zirconium oxide grinding beads were added to the jar. The mass ratio of powder to grinding beads to anhydrous ethanol was 1:2:1. The ball mill jar was placed in a planetary ball mill and milled at 300 rpm for 3 hours. After milling, the slurry was placed in a 100℃ oven to dry thoroughly. The percentage of each powder in the molar amount of BaTiO3 was: MgO 2%, Y2O3 1%, MnO2 0.5%, and SrZrO3 powder 1%.

[0035] Step 3, the green body to be sintered

[0036] Add 5wt% polyvinyl alcohol aqueous solution to the mixed powder in step 2, and add 6-10 drops of polyvinyl alcohol (type 17-88, with an average molecular weight of 20,000-150,000) to 1g of powder. Mix and granulate through a 100-mesh sieve. Press the granulated powder into round samples with a diameter of 10mm and a thickness of 0.8mm under a pressure of 10MPa.

[0037] Step 4, Sintering

[0038] The disc sample obtained in step 3 was heated to 550℃ at a heating rate of 3℃ / min and held at that temperature for 2 hours to remove the binder. Then, it was cooled to room temperature at a cooling rate of 5℃ / min (or cooled to 200℃ at a cooling rate of 5℃ / min and then cooled to room temperature in the furnace). The sample was then removed and placed in a tube furnace for sintering at a heating rate of 5℃ / min and a sintering temperature of 1200℃ for 2 hours to form ceramic.

[0039] Figure 1 The image shows the XRD pattern of the dielectric material of the X8R type multilayer ceramic capacitor in Example 1.

[0040] Figure 2 Here is a SEM image of the dielectric material of the X8R type multilayer ceramic capacitor in Example 1;

[0041] Figure 3 This is a TEM image of the dielectric material of the X8R type multilayer ceramic capacitor in Example 1;

[0042] Figure 4 The dielectric constant-temperature diagram of the dielectric material of the X8R type multilayer ceramic capacitor in Example 1 is shown.

[0043] Figure 5 This is a capacitance change rate-temperature graph of the dielectric material of the X8R type multilayer ceramic capacitor in Example 1.

[0044] Example 2

[0045] The difference between Example 2 and Example 1 is that the amount of BaTiO3 used is 0.02 mol, and the molar percentage of other components in BaTiO3 is: MgO 2%, Y2O3 1%, MnO2 0.5%, and SrZrO3 powder 1%.

[0046] Example 3

[0047] The difference between Example 3 and Example 1 is that the amount of BaTiO3 used is 0.02 mol, and the molar percentage of other components in BaTiO3 is: MgO 2%, Ho2O3 1.5%, MnO2 1%, and SrZrO3 powder 1%.

[0048] Example 4

[0049] The difference between Example 4 and Example 1 is that the amount of BaTiO3 used is 0.02 mol, and the molar percentage of other components in BaTiO3 is: MgO 2%, Dy2O3 1%, MnO2 1%, and SrZrO3 powder 2%.

[0050] Comparative Examples 1-5

[0051] The difference between Comparative Examples 1-5 and Example 1 is that the molar ratio of SrZrO3 and Y2O3 was changed in the comparative examples. The specific components are shown in Table 1.

[0052] Table 1. Dosage of each component in Comparative Examples 1-5

[0053]

[0054] The ceramic discs obtained after sintering in Examples 1-4 and Comparative Examples 1-5 were polished, silver-coated, and silver-fired. Their dielectric properties, dielectric constant, dielectric loss, and temperature coefficient of capacitance (TCC) were measured. The results are shown in Table 2.

[0055] Table 2 Performance test data of the dielectric materials prepared in Examples 1-4 and Comparative Examples 1-5

[0056]

[0057] Results analysis:

[0058] Examples 1, 2, 3, and 4, and Comparative Example 3, all exhibit dielectric losses of less than 1.6%, effectively preventing MLCC thermal failure during prolonged operation and reducing energy loss. Furthermore, the temperature stability characteristics of the samples in Examples 1 and 2 meet the EIA X8R standard, and their insulation resistivity is ≥10 Ω·cm. 10 They exhibit good resistance to reduction and all have a dielectric constant >4500 Ω·cm.

[0059] Comparing Examples 1 and 2 with Comparative Examples 1 and 2, it can be seen that increasing the SrZrO3 content within a certain range can appropriately improve the temperature stability of the material. However, at contents of 0% and 3 mol%, the temperature stability does not meet the X8R standard. Nevertheless, the SrZrO3 content plays a crucial role in the formation of the core-shell structure. Compared to samples without any SrZrO3 addition, the temperature stability at both the high-temperature and low-temperature ends of all other samples is improved.

[0060] Data from Comparative Examples 1 and 3 show that increasing the Y₂O₃ content increases the dielectric constant at room temperature. This is because the addition of Y increases the number of free electrons in the system, which undergo long-range migration under an electric field, leading to increased leakage conductance. Simultaneously, some free electrons are confined to local defect structures due to hindered migration at oxygen vacancies, participating only in short-range hopping polarization, thus increasing the dielectric constant. Examples 1 and 1 demonstrate that the dielectric constant reaches 4914 under the synergistic effect of Y₂O₃ and SrZrO₃.

[0061] According to the data from Examples 4 and 5, Ho 3+ and Dy 3+ As a neutral rare earth ion, it also has properties similar to Y. 3+ It has the same effect.

[0062] Comparing Comparative Examples 4 and 5 with Example 1, it can be found that when Mn is missing from the system... 4+ Or Mg 2+ All of these will lead to a decrease in insulation resistivity, an increase in dielectric loss, and a decrease in the system's resistance to reduction.

Claims

1. A reduction-resistant X8R type multilayer ceramic capacitor dielectric material, characterized in that: It includes the main component BaTiO3 and dopants, including Re2O3, MgO, MnO2 and SrZrO3, where Re is a neutral rare earth ion with an ionic radius of 0.87 to 0.94 Å, and Re is Er, Dy, Tb, Tm, Eu, Y or Ho; The molar proportions of Re2O3 in BaTiO3 are 0.5% to 1.5%, MgO is 1% to 3%, MnO2 is 0.5% to 1.5%, and SrZrO3 is 1% to 2%.

2. The anti-reduction X8R type multilayer ceramic capacitor dielectric material according to claim 1, characterized in that: The molar proportion of Re2O3 in BaTiO3 is 0.8-1.3%, the molar proportion of MgO in BaTiO3 is 1.5-2.5%, the molar proportion of MnO2 in BaTiO3 is 0.5-1%, and the molar proportion of SrZrO3 in BaTiO3 is 1%-2%.

3. The method for preparing the anti-reduction X8R type multilayer ceramic capacitor dielectric material according to any one of claims 1 to 2, characterized in that: Includes the following steps: 1) Mix SrZrO3 powder, BaTiO3, MgO, MnO2 and Re2O3, ball mill, dry, granulate, press and debind to obtain green body; 2) The blank is placed in an atmosphere of hydrogen / argon or hydrogen / nitrogen mixture with a hydrogen specific gravity of 0.3-1% for sintering at a temperature of 1200-1300℃ and a holding time of 2-4 hours. After cooling, the reduction-resistant X8R type multilayer ceramic capacitor dielectric material is obtained.

4. The method for preparing the reduction-resistant X8R type multilayer ceramic capacitor dielectric material according to claim 3, characterized in that: SrZrO3 powder is prepared by the following method: S1. Weigh out the corresponding SrCO3 and ZrO2 according to the chemical formula SrZrO3 molar ratio of 1:1, ball mill, dry, and calcine in air to obtain SrZrO3 powder.

5. The method for preparing the reduction-resistant X8R type multilayer ceramic capacitor dielectric material according to claim 4, characterized in that: In the preparation of SrZrO3 powder, the ball milling medium is anhydrous ethanol, and the mass ratio of powder:milling beads:anhydrous ethanol during the ball milling process is 1:2:1~2. The milling beads are zirconia balls. The calcination temperature is 1000~1150℃, and the holding time is 2~3 hours. The drying conditions are: drying at 90~105℃ for 4~6 hours. The ball milling time is 3~4 hours.

6. The method for preparing the reduction-resistant X8R type multilayer ceramic capacitor dielectric material according to claim 3, characterized in that: The glue removal in step 1) involves heating the temperature to 500-600°C at a heating rate of 2-3°C / min and holding it at that temperature for 2-4 hours, followed by cooling. The cooling process involves reducing the temperature to 200°C at a cooling rate of 3-5°C / min, cooling it in the furnace, or cooling it to room temperature at a cooling rate of 3-5°C / min, or allowing it to cool naturally to room temperature.

7. The method for preparing the reduction-resistant X8R type multilayer ceramic capacitor dielectric material according to claim 3, characterized in that: Granulation in step 1) refers to granulation by adding an aqueous solution of polyvinyl alcohol; pressing refers to pressing into a preform to be discharged. The ball milling medium is anhydrous ethanol. During the ball milling process, the mass ratio of mixed powder: ball milling beads: anhydrous ethanol is 1:2:1~2, and the ball milling beads are zirconia balls. The drying conditions in step 1) are: drying at 90~105℃ for 4~6 hours; ball milling time is 3~4 hours.

8. The method for preparing the reduction-resistant X8R type multilayer ceramic capacitor dielectric material according to claim 3, characterized in that: The polyvinyl alcohol solution has a mass fraction of 5-10 wt% and a pressing pressure of 5-15 MPa.

9. The method for preparing the reduction-resistant X8R type multilayer ceramic capacitor dielectric material according to claim 3, characterized in that: The gas flow rate of the mixed gas in step 2) is 30-50 SCCM.

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