Ceramic dielectric material with high dielectric constant and preparation method thereof

Abstract

The invention discloses a ceramic dielectric material with a high dielectric constant and a preparation method thereof. The ceramic dielectric material comprises a main body material and a modified additive, the main body material is BaTiO3, and the addition amount of the main body material is 95.5-98.25 mol%; the modified additive is (1) a mixture of SiO2, MgO, CaO and Dy2O3; or, (2) a mixture of SiO2, MgO and Dy2O3; the total addition amount of the modified additive is 1.75-4.5 mol%. The room temperature dielectric constant of the ceramic dielectric material provided by the invention is between 9000 and 13000.

Description

Technical Field

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

[0002] Multilayer ceramic capacitors (MLCCs) are widely used in various devices, primarily in the circuits of communication infrastructure equipment such as communications equipment, automotive electronics, industrial machinery, and medical devices. They can be used as power supply bypass capacitors in liquid crystal modules (LCD drive voltage lines) and high-voltage LSI / IC / OP amplifiers, as well as smoothing capacitors in DC-DC converters (input and output) and switching power supplies (secondary side).

[0003] In recent years, the miniaturization of mobile electronic devices has led to the gradual development of MLCCs in the direction of miniaturization and high capacity. Barium titanate (BaTiO3), the base material of Class II capacitors in MLCCs, has a high dielectric constant. However, to obtain a high-capacity barium titanate-based MLCC, the number of layers must be increased, resulting in a significant decrease in MLCC reliability. In addition, the dielectric constant of barium titanate fluctuates greatly at -90°C, 0°C, and 125°C, which also limits its application range. For example, the dielectric material temperature coefficients of Class II capacitors include X5R, X6T, and X7T. The capacitor specifications of the American Electronics Industry Association state that the capacitance change rate of X6T must be between +22% and -33% at temperatures between -55°C and 105°C. Therefore, research on ceramic dielectric materials with high dielectric constants is of great significance to the development of high-capacity MLCCs. Summary of the Invention

[0004] In order to solve the above technical problems, the present invention provides a ceramic dielectric material with a high dielectric constant and a preparation method thereof. The ceramic dielectric material provided by the present invention not only has a high dielectric constant, but also has a simple and easy-to-operate preparation method, and is suitable for industrial large-scale production.

[0005] The technical problem of the present invention is solved by the following technical solutions:

[0006] In one aspect, the present invention provides a ceramic dielectric material with a high dielectric constant; the ceramic dielectric material includes a main material and a modifying additive; the main material is BaTiO3, and the addition amount is 95.5 to 98.25 mol%; the modifying additive is ① a mixture of SiO2, MgO, CaO and Dy2O3; or, ② a mixture of SiO2, MgO and Dy2O3; the total addition amount of the modifying additive is 1.75 to 4.5 mol%.

[0007] In some specific embodiments, the particle size of the BaTiO3 is 150-250 nm.

[0008] As a preferred embodiment, the amount of SiO2 added is 0.5 to 1.5 mol%;

[0009] and / or, the addition amount of MgO is 0.25 to 1.0 mol%;

[0010] And / or, the addition amount of CaO is 0 to 0.5 mol%;

[0011] And / or, the added amount of Dy2O3 is 0.5 to 1.5 mol%.

[0012] In another aspect, the present invention provides a method for preparing the above-mentioned ceramic dielectric material, comprising the following steps:

[0013] The main material and the modified additive are wet ball-milled and dried to obtain a dielectric powder material; the dielectric powder material is mixed with a binder and then tableted, and sintered to obtain the ceramic dielectric material.

[0014] As a preferred embodiment, the binder is polyvinyl alcohol;

[0015] In some specific embodiments, the binder is a polyvinyl alcohol solution, and the mass fraction of the solute in the polyvinyl alcohol solution is 5% to 10%.

[0016] As a preferred embodiment, the sintering further includes a debinding process before the sintering;

[0017] Preferably, the debinding process comprises the following steps:

[0018] Keep the temperature at 200-300℃ for 60-180min, then raise the temperature to 500-650℃ and keep the temperature for another 60-180min.

[0019] Preferably, the heating rate in the debinding treatment is 0.5-5°C / min.

[0020] As a preferred embodiment, the sintering is carried out in an air atmosphere;

[0021] Preferably, the sintering temperature is 1050-1250°C;

[0022] Preferably, the sintering holding time is 60 to 180 minutes;

[0023] Preferably, the heating rate of the sintering is 1-10°C / min.

[0024] In the technical solution of the present invention, the grain size of the ceramic dielectric material is 0.3-1.8 μm, and the dielectric constant at room temperature is between 9000-13000.

[0025] In another aspect, the present invention provides a use of the above-mentioned ceramic dielectric material in the field of electronic packaging;

[0026] Preferably, the invention is used in the preparation of multilayer ceramic capacitors (MLCC).

[0027] The above technical solution has the following advantages or beneficial effects:

[0028] The present invention provides a ceramic dielectric material with a high dielectric constant and a method for preparing the same. The ceramic dielectric material comprises a main material, BaTiO3, and a modifying additive, wherein the main material is BaTiO3 and the modifying additive is a combination of SiO2, MgO, CaO, and Dy2O3. The BaTiO3 ceramic produced by sintering the ceramic dielectric material, which is obtained through a rationally designed formulation, has a room-temperature dielectric constant of 9,000 to 13,000. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a scanning electron microscope image of the ceramic dielectric material in Example 1 of the present invention.

[0030] Figure 2 This is a scanning electron microscope image of the ceramic dielectric material in Example 2 of the present invention.

[0031] Figure 3 This is a scanning electron microscope image of the ceramic dielectric material in Example 3 of the present invention.

[0032] Figure 4 This is a scanning electron microscope image of the ceramic dielectric material in Example 4 of the present invention.

[0033] Figure 5 This is a ceramic grain size distribution diagram of the ceramic dielectric material in Example 1 of the present invention.

[0034] Figure 6 This is a ceramic grain size distribution diagram of the ceramic dielectric material in Example 2 of the present invention.

[0035] Figure 7 This is a ceramic grain size distribution diagram of the ceramic dielectric material in Example 3 of the present invention.

[0036] Figure 8 This is a ceramic grain size distribution diagram of the ceramic dielectric material in Example 4 of the present invention.

[0037] Figure 9 FIG. 1 is a graph showing the relationship between the dielectric constant of the ceramic dielectric material and temperature in Example 1 of the present invention.

[0038] Figure 10 FIG. 4 is a graph showing the relationship between the dielectric constant of the ceramic dielectric material and temperature in Example 2 of the present invention.

[0039] Figure 11 FIG. 4 is a graph showing the relationship between the dielectric constant of the ceramic dielectric material and temperature in Example 3 of the present invention.

[0040] Figure 12 FIG. 4 is a graph showing the relationship between the dielectric constant of the ceramic dielectric material and temperature in Example 4 of the present invention. DETAILED DESCRIPTION

[0041] The following embodiments are merely some of the embodiments of the present invention, rather than all of them. Therefore, the detailed description of the embodiments of the present invention provided below is not intended to limit the scope of the claimed invention, but rather merely represents selected embodiments of the present invention. All other embodiments derived by those skilled in the art based on the embodiments of the present invention without creative effort are intended to fall within the scope of protection of the present invention.

[0042] In the present invention, unless otherwise specified, all equipment and raw materials can be purchased from the market or are commonly used in the industry. The methods in the following embodiments, unless otherwise specified, are all conventional methods in the art.

[0043] The present invention provides a ceramic dielectric material with a high dielectric constant, which is mainly composed of BaTiO3 and a mixture of SiO2, MgO, CaO and Dy2O3 or a mixture of SiO2, MgO and Dy2O3 as a modifying additive; wherein the addition amount of the main material is 95.5-98.25 mol%, and the total addition amount of the modifying additive is 1.75-4.5 mol%.

[0044] Furthermore, the particle size of the host material is 150-250 nm.

[0045] Furthermore, the added amount of SiO2 is 0.5 to 1.5 mol%.

[0046] Furthermore, the addition amount of MgO is 0.25 to 1.0 mol%.

[0047] Furthermore, the addition amount of CaO is 0 to 0.5 mol%.

[0048] Furthermore, the added amount of Dy2O3 is 0.5 to 1.5 mol%.

[0049] Among the modified additives used in the present invention, Mg 2+ Can replace Ba in barium titanate 2+ site, due to Mg 2+ The ionic radius is smaller than that of Ba 2+ , this substitution may lead to lattice contraction and enhance the polarization ability of the lattice. Therefore, Mg doping affects the symmetry of the lattice and thus changes the dielectric properties of the material. 2+Alternative to Ba 2+ site, due to Ca 2+ The ionic radius of Ba 2+ Similarly, Ca doping may help stabilize the lattice structure and reduce lattice distortion. In addition, Ca doping may promote grain growth. The increase in grain size can reduce grain boundaries, thereby reducing the polarization barrier at the grain boundaries and improving the dielectric constant. 3+ As a rare earth element, it has a large ionic radius and unpaired 4f electrons, which can introduce additional polarization mechanisms such as electronic polarization and ionic polarization. Dy doping may cause lattice distortion, enhance lattice inhomogeneity, and thus increase the dielectric constant of the material. Rare earth elements such as Dy may enhance the dielectric properties of the material by forming defect dipoles (such as electron pinning defect dipoles). Co-doping of the above elements will also produce a synergistic effect, further optimizing the dielectric properties of the material by combining their respective characteristics.

[0050] In the technical solution of the present invention, the above-mentioned ceramic dielectric material can be prepared by the following method: the main material and the modified additive are mixed in proportion, zirconium oxide balls are used as ball milling media, and wet ball milling is performed for, for example, 12 to 36 hours, and the dielectric powder material is obtained after drying; the dielectric powder material is mixed with a binder and then pressed into tablets, and then sintered.

[0051] Furthermore, the binder is polyvinyl alcohol;

[0052] Furthermore, the binder is a polyvinyl alcohol solution with a mass fraction of 5% to 10%.

[0053] Furthermore, before the sintering, a debinding process is also included;

[0054] Preferably, the debinding process comprises the following steps:

[0055] Keep the temperature at 200-300℃ for 60-180min, then raise the temperature to 500-650℃ and keep the temperature for another 60-180min.

[0056] Preferably, the heating rate in the debinding treatment is 0.5-5°C / min.

[0057] Furthermore, the sintering is carried out in an air atmosphere;

[0058] Furthermore, the sintering temperature is 1050-1250°C;

[0059] Furthermore, the sintering holding time is 60 to 180 minutes;

[0060] Furthermore, the heating rate during the sintering is 1-10°C / min.

[0061] The features and properties of the present invention are further described in detail below with reference to the following examples. The components of the ceramic dielectric materials in Examples 1-4 are shown in Table 1.

[0062] Table 1

[0063]

[0064] Example 1

[0065] (1) As shown in Table 1, the main material and the modified additive were mixed in proportion, and zirconia balls were used as ball milling media. The wet ball milling was performed for 24 hours, and the medium powder material was obtained after drying.

[0066] (2) 0.25 g of the dielectric powder material was added to an 8% by mass polyvinyl alcohol (PVA) solution, thoroughly mixed, ground, and granulated, and then formed into a ceramic green body on a tablet press at a pressure of 350 MPa;

[0067] (3) Debinding treatment: The ceramic green body was heated to 300°C in air at a heating rate of 1°C / min and kept at this temperature for 2 h; then the temperature was further increased to 600°C at a heating rate of 1°C / min and kept at this temperature for 2 h;

[0068] (4) The debinding ceramic green body was heated to 1200°C at a heating rate of 1°C / min, kept at that temperature for 2 hours, and then cooled to room temperature in the furnace to obtain a BaTiO3 ceramic dielectric material.

[0069] Example 2

[0070] (1) As shown in Table 1, the main material and the modified additive were mixed in proportion, and zirconia balls were used as ball milling media. The wet ball milling was performed for 24 hours, and the medium powder material was obtained after drying.

[0071] (2) 0.25 g of the dielectric powder material was added to an 8% by mass polyvinyl alcohol (PVA) solution, thoroughly mixed, ground, and granulated, and then formed into a ceramic green body on a tablet press at a pressure of 350 MPa;

[0072] (3) Debinding treatment: The ceramic green body was heated to 300°C in air at a heating rate of 1°C / min and kept at this temperature for 2 h; then the temperature was further increased to 600°C at a heating rate of 1°C / min and kept at this temperature for 2 h;

[0073] (4) The debinding ceramic green body was heated to 1200°C at a heating rate of 1°C / min, kept at that temperature for 2 hours, and then cooled to room temperature in the furnace to obtain a BaTiO3 ceramic dielectric material.

[0074] Example 3

[0075] (1) As shown in Table 1, the main material and the modified additive were mixed in proportion, and zirconia balls were used as ball milling media. The wet ball milling was performed for 24 hours, and the medium powder material was obtained after drying.

[0076] (2) 0.25 g of the dielectric powder material was added to an 8% by mass polyvinyl alcohol (PVA) solution, thoroughly mixed, ground, and granulated, and then formed into a ceramic green body on a tablet press at a pressure of 350 MPa;

[0077] (3) Debinding treatment: The ceramic green body was heated to 300°C in air at a heating rate of 1°C / min and kept at this temperature for 2 h; then the temperature was further increased to 600°C at a heating rate of 1°C / min and kept at this temperature for 2 h;

[0078] (4) The debinding ceramic green body was heated to 1200°C at a heating rate of 1°C / min, kept at that temperature for 2 hours, and then cooled to room temperature in the furnace to obtain a BaTiO3 ceramic dielectric material.

[0079] Example 4

[0080] (1) As shown in Table 1, the main material and the modified additive were mixed in proportion, and zirconia balls were used as ball milling media. The wet ball milling was performed for 24 hours, and the medium powder material was obtained after drying.

[0081] (2) 0.25 g of the dielectric powder material was added to an 8% by mass polyvinyl alcohol (PVA) solution, thoroughly mixed, ground, and granulated, and then formed into a ceramic green body on a tablet press at a pressure of 350 MPa;

[0082] (3) Debinding treatment: The ceramic green body was heated to 300°C in air at a heating rate of 1°C / min and kept at this temperature for 2 h; then the temperature was further increased to 600°C at a heating rate of 1°C / min and kept at this temperature for 2 h;

[0083] (4) The debinding ceramic green body was heated to 1200°C at a heating rate of 1°C / min, kept at that temperature for 2 hours, and then cooled to room temperature in the furnace to obtain a BaTiO3 ceramic dielectric material.

[0084] Figure 1-4 The scanning electron microscope images of the BaTiO3 ceramic dielectric materials prepared by steps (1) to (4) of Examples 1-4 are shown respectively. From the comparison in the images, it can be seen that the BaTiO3 ceramic dielectric material samples of Examples 1-4 all have relatively dense microstructures.

[0085] Figure 5-8These are the grain size distribution diagrams of the BaTiO3 ceramic dielectric materials prepared in Examples 1-4. It can be seen from the diagrams that the grain sizes of the BaTiO3 ceramics prepared in Examples 1-4 are 1.82, 0.28, 1.48 and 0.75 μm, respectively.

[0086] Figure 9-12 The dielectric constant of the BaTiO3 ceramic dielectric material prepared in Examples 1-4 varies with temperature. It can be seen from the figure that the room temperature dielectric constant ε of Examples 1-4 r The higher dielectric constants in Examples 1 and 3 may be due to the fact that defects with different charges further associate to form defect dipoles, such as These defect dipoles can cause electron-pinning defect-dipole (EPDD) effects, thereby increasing the dielectric constant.

[0087] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A ceramic dielectric material with a high dielectric constant, characterized in that: The ceramic dielectric material includes a main material and a modifying additive; the main material is BaTiO3, and the addition amount is 95.5-98.25 mol%; the modifying additive is ① a mixture of SiO2, MgO, CaO and Dy2O3; or, ② a mixture of SiO2, MgO and Dy2O3; the total addition amount of the modifying additive is 1.75-4.5 mol%.

2. The ceramic dielectric material according to claim 1, characterized in that The particle size of the BaTiO3 is 150-250 nm.

3. The ceramic dielectric material according to claim 1, characterized in that The amount of SiO2 added is 0.5 to 1.5 mol%; and / or, the addition amount of MgO is 0.25 to 1.0 mol%; And / or, the addition amount of CaO is 0 to 0.5 mol%; And / or, the added amount of Dy2O3 is 0.5 to 1.5 mol%.

4. The method for preparing a ceramic dielectric material according to any one of claims 1 to 3, characterized in that: The following steps are involved: Wet-milling the main material and the modified additive, and drying to obtain a medium powder material; The dielectric powder material is mixed with a binder, pressed into tablets, and sintered to obtain the ceramic dielectric material.

5. The preparation method according to claim 4, characterized in that The binder is polyvinyl alcohol.

6. The preparation method according to claim 4, characterized in that The process also includes debinding treatment before sintering.

7. The preparation method according to claim 6, characterized in that The debinding process comprises the following steps: Keep the temperature at 200-300℃ for 60-180min, then raise the temperature to 500-650℃ and keep the temperature for another 60-180min.

8. The preparation method according to claim 7, characterized in that The heating rate in the debinding treatment is 0.5-5°C / min.

9. The preparation method according to claim 4, characterized in that The sintering is carried out in an air atmosphere; Preferably, the sintering temperature is 1050-1250°C; Preferably, the sintering holding time is 60 to 180 minutes; Preferably, the heating rate of the sintering is 1-10°C / min.

10. Use of the ceramic dielectric material according to any one of claims 1 to 3 in the field of electronic packaging; Preferably, the invention relates to use in the preparation of multilayer ceramic capacitors.

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