A ceramic raw material for capacitors and its preparation method and application

Abstract

The present invention relates to the field of capacitor ceramic materials, and provides a ceramic raw material for capacitors and a preparation method thereof, aiming to solve the problem that traditional ceramic materials are difficult to achieve a balance between high dielectric constant and temperature stability. X Sr X TiO3 gradient layered particles are primarily composed of rare earth oxides, transition metal oxides, alkaline earth metal oxides, low-melting-point sintering aids, and organic processing aids. These gradient particles exhibit a concentric core-intermediate-shell structure, with the x value increasing radially, resulting in a continuous Curie temperature distribution. Their preparation involves precursor co-precipitation, calcination, layer-by-layer deposition, and secondary calcination. Wet ball milling and rheological manipulation are then used to achieve a highly uniform ceramic raw material. This material combines high dielectric properties with wide temperature stability, making it suitable for a variety of capacitor devices and promising application prospects.

Description

Technical Field

[0001] The present invention relates to the field of capacitor ceramic materials, and in particular to a ceramic raw material for capacitors and a preparation method and application thereof. Background Art

[0002] As fundamental components in electronic information technology, capacitors are widely used in key areas such as communications terminals, automotive electronics, power equipment, smart home appliances, and aerospace. High-performance products such as multilayer ceramic capacitors (MLCCs), temperature-compensated capacitors, and radio frequency filters place increasingly stringent performance requirements on the ceramic dielectric materials used. In practical applications, capacitors must operate stably and for extended periods under frequent start-stop cycles, electrothermal coupling, and wide temperature ranges. This places dual demands on the dielectric properties of ceramic materials: on the one hand, a high dielectric constant is required to achieve greater capacitance density and device miniaturization; on the other hand, excellent temperature stability is required across a wide temperature range, from -55°C to +125°C, to ensure that capacitance variations remain within standard tolerances. Furthermore, ceramic materials must exhibit excellent sintering density, structural uniformity, and process adaptability to meet the high reliability and batch consistency requirements of modern electronic manufacturing processes. Therefore, focusing on these two key indicators, high dielectric constant and temperature stability, in material design and structural control, is not only a key path to improving the overall performance of capacitors but also a crucial support for promoting the localization and intelligent development of high-end electronic devices.

[0003] At present, although BaTiO3-based ceramics have been widely studied as mainstream dielectric materials in recent years, the existing technology still has significant deficiencies in simultaneously meeting high dielectric constant and temperature stability. This is mainly due to the insufficient understanding of the coupling mechanism of the two properties in material design, which often leads to the sacrifice of another property when improving one property. For example, the Chinese patent with publication number N105084891A discloses a medium-temperature sintered lead-free multilayer ceramic capacitor dielectric material, which is used in multilayer ceramic capacitors. Although its dielectric constant has been improved, the capacitance fluctuates greatly within a wide temperature range, making it difficult to meet the temperature tolerance requirements of X7R or X8R capacitors. This is fundamentally due to the uneven lattice distortion and unstable local polarization response caused by disordered doping inside the material. On the other hand, there are also studies that attempt to use a solid solution control strategy to introduce SrTiO3 components to improve temperature stability, but they fail to achieve composition gradient control. There are still obvious stress concentration and uneven thermal expansion problems inside the material, which limit the synergistic improvement of its overall performance. Therefore, there is an urgent need to construct a multilayer ceramic particle structure with a gradient distribution through new structural design methods, and to achieve continuous composition transition and stress release at the microscale, so as to essentially achieve the coordinated optimization of dielectric constant and temperature stability. Summary of the Invention

[0004] (1) Technical problems solved

[0005] The purpose of the present invention is to provide a ceramic raw material for capacitors and a preparation method and application thereof, so as to solve the problem that the current ceramic raw materials for capacitors have insufficient high dielectric constant and temperature stability.

[0006] (2) Technical solution

[0007] In order to achieve the above object, the present invention provides the following technical solutions:

[0008] A ceramic raw material for capacitors, comprising the following raw materials in parts by weight:

[0009] Ba1- X Sr X 85-95 parts of TiO3 gradient layered particles; 1.3-3.5 parts of rare earth oxide; 2.0-4.9 parts of transition metal oxide; 2.5-6.0 parts of alkaline earth metal oxide; 2.5-6.5 parts of low melting point sintering aid; 4.8-9.8 parts of organic processing aid; 25-40 parts of solvent;

[0010] The Ba1- X Sr X The TiO3 gradient layered particles are characterized in that the particles present a concentric layered structure, including an inner core layer, an intermediate transition layer, and an outer shell layer, wherein the x value of the inner core layer is 0.05-0.10, the x value of the intermediate transition layer gradually increases radially from the inside to the outside, the x value of the outer shell layer is 0.25-0.30, and the thickness ratio of the inner core layer, the intermediate transition layer, and the outer shell layer is 6.0-7.0:1.0-1.2:1.4-1.6;

[0011] The Ba1- X Sr X The average size of TiO3 gradient layered particles is 0.5~0.8 μm.

[0012] Furthermore, the Ba1- X Sr X The preparation of TiO3 gradient layered particles comprises the following steps:

[0013] A1. BaTiO3 precursor and SrTiO3 precursor were prepared by co-precipitation method;

[0014] A2. calcining the BaTiO3 precursor at 800-850°C for 2-4 hours to obtain BaTiO3 core particles;

[0015] A3. Using the layer-by-layer deposition method, BaTiO3 core particles are used as the substrate, and Ba1- X Sr XTiO3 intermediate layer and Sr-rich Ba1- X Sr X TiO3 outer layer;

[0016] A4. The resulting particles were calcined at 900-950 ° C for 3 to 5 hours and then lightly ground to obtain Ba1- X Sr X TiO3 gradient layered particles.

[0017] Furthermore, the detailed process of A1 is as follows: 10.0-12.0 parts of butyl titanate and 40.0-50.0 parts of anhydrous ethanol are weighed in parts by weight, and stirred at a rate of 450-550 rpm for 10-15 min in an ice-water bath at 4-8°C to form a titanium source solution; at the same time, 7.5-8.5 parts of barium nitrate are dissolved in 25.0-30.0 parts of deionized water to prepare a barium source solution, and 6.0-7.0 parts of strontium nitrate are dissolved in 20.0-25.0 parts of deionized water to prepare a strontium source solution; under continuous stirring, the barium source solution is slowly added to the titanium source solution at a drop rate of 3-5 mL / min, and after reacting for 30-40 min, 25.0-28.0 parts of 25-28 wt% ammonia water was added to adjust the pH value to 10.0~11.0 to form a white BaTiO3 precursor suspension; the strontium source solution was added dropwise to another titanium source solution in the same way to prepare a SrTiO3 precursor suspension; the two suspensions were aged at room temperature for 15~20 h, then filtered and washed with deionized water 6~8 times until the pH value of the filtrate was 7.0~7.5. The obtained filter cake was dried at 80~90℃ for 12~16 h and ground through a 400-mesh sieve to obtain BaTiO3 precursor powder and SrTiO3 precursor powder, respectively.

[0018] Furthermore, the detailed process of A2 is as follows: BaTiO3 precursor powder is placed in a high-purity alumina crucible, heated to 800~850℃ in a tube furnace at a heating rate of 2.0~2.5℃ / min, calcined at a constant temperature for 2~4 hours in an air atmosphere, and then cooled to room temperature at a cooling rate of 1.0~1.5℃ / min; the calcined BaTiO3 powder is mixed with anhydrous ethanol in a weight ratio of 1:5, placed in a polyurethane-lined ball mill, and zirconia balls with a diameter of 3~5 mm are added as grinding media. The ball-to-material ratio is 5:1, and wet ball milling is carried out at a speed of 150~180 rpm for 40~48 hours; the suspension after ball milling is sieved through a 200-mesh sieve to remove large particles, filtered and washed with ethanol 34 times, and the filter cake is dried under a vacuum environment at 60~70℃ for 10~12 hours to obtain an average particle size.

[0019] Furthermore, the detailed process of A3 is as follows: three kinds of Ba1-X Sr X The TiO3 precursor solution is specifically as follows: BaTiO3 precursor and SrTiO3 precursor are mixed in mass ratios of 9:1, 8:2 and 7:3, and a mixed solvent of anhydrous ethanol and glacial acetic acid with a volume ratio of 4:1 is added respectively, and the sol concentration is 0.10~0.15 mol / L; 8.0~10.0 parts of BaTiO3 core particles are dispersed in 100~120 parts of ethanol, and ultrasonic treatment is performed for 15~20 minutes to form a uniform suspension; 30~35 parts of the first precursor solution are slowly added dropwise to the BaTiO3 core particle suspension at a rate of 2~3 mL / min at 35~45°C, the pH value is controlled at 9.5~10.5, and stirring is performed for 60~90 minutes to allow the precursor to be uniformly deposited on the surface of the core particles; centrifugation is performed at a centrifugal speed of 5000~6000 rpm for 10~15 minutes, the precipitate is washed with ethanol three times, and dried at 60°C for 4~6 h; Using the same method, the second and third precursor solutions were used for coating treatment in sequence; finally, the obtained particles were dispersed in ethanol and 25-30 parts of Ba1- X Sr X A TiO3 precursor solution is prepared by mixing a BaTiO3 precursor and a SrTiO3 precursor in a mass ratio of 6:4 for outermost layer deposition, maintaining a pH value at 10.0-11.0, stirring for 4-6 hours, centrifuging, washing, and drying at 70°C for 8-10 hours to obtain composite particles with a multilayer structure.

[0020] Furthermore, the detailed process of A4 is as follows: in parts by weight, the multilayer composite particles obtained in A3 are placed in a high-purity alumina crucible, heated to 900-950°C in a tube furnace at a heating rate of 1.5-2.0°C / min, and calcined at a constant temperature for 3-5 hours in a mixed atmosphere of nitrogen and oxygen with a volume ratio of 95:5 at a flow rate of 80-100 mL / min to promote the diffusion of elements between the layers to form a continuous gradient structure; after calcination, the temperature is cooled to 600°C at a cooling rate of 1.0-1.5°C / min, and then cooled to room temperature at a rate of 2.0-3.0°C / min; Ba1- is obtained after light grinding. X Sr X TiO3 gradient layered particles.

[0021] The present invention adopts Ba1- X Sr XThe design of TiO3 gradient layered particles is mainly used to enhance the dielectric properties and temperature stability of ceramic raw materials in capacitor applications. By rationally constructing a triple structure of inner core layer, intermediate transition layer and outer shell layer, the Sr element is distributed in a step-by-step transition from core to shell within the particle, effectively regulating the local lattice environment and polarization behavior of the material, thereby achieving a synergistic improvement in dielectric properties and thermal stability as a whole. The inner core layer in the gradient layered structure is mainly composed of BaTiO3 with a low Sr content, maintaining a high dielectric response capability; the intermediate transition layer forms a buffer zone by moderately increasing the Sr ratio, reducing the lattice discontinuity caused by compositional mutations; the outer shell is rich in Sr components, which helps to optimize the thermal response characteristics and temperature tolerance of the material. The above design precisely controls the composition of each layer through a layer-by-layer deposition process, and combines the calcination and diffusion process to form a gradient structure with a continuous transition and a clear interface. While improving the overall performance of the material, it avoids the contradiction between the dielectric constant and temperature stability in single-component ceramics. Furthermore, the synergistic effect of gradient particles with components such as rare earth oxides, transition metal oxides, alkaline earth metal oxides, and low-melting-point sintering aids further optimizes the structural uniformity and molding stability of the ceramic raw material while ensuring adaptability to high-density sintering processes. This technical solution demonstrates significant advantages in material microstructure control, process adaptability, and synergistic performance integration, providing an effective solution for meeting the comprehensive performance requirements of dielectric materials for high-reliability capacitors.

[0022] Furthermore, the rare earth oxide is selected from one or more of La2O3, Gd2O3 and Y2O3.

[0023] The transition metal oxide is selected from one or more of ZrO2, MnO2 and CuO.

[0024] The alkaline earth metal oxide is selected from one or more of MgO, CaO and Al2O3.

[0025] The low melting point sintering aid is selected from Bi2O3-ZnO-B2O3 composite oxide, and the mass ratio thereof is (1.0~2.0):(0.8~1.5):(0.7~1.0).

[0026] The organic processing aid includes a dispersant, a binder, a plasticizer, an antistatic agent and a defoamer, wherein the dispersant is 1.0-2.0 parts of ammonium polyacrylate, the binder is 2.0-4.0 parts of hydroxypropyl methylcellulose, the plasticizer is 1.5-3.0 parts of polyethylene glycol 600, the antistatic agent is 0.2-0.5 parts of sodium dodecylbenzene sulfonate, and the defoamer is 0.1-0.3 parts of polydimethylsiloxane.

[0027] The solvent is a mixture of deionized water, ethanol and acetone, with a volume ratio of (3.0-4.0):1:1.

[0028] The present invention also provides a method for preparing a ceramic raw material for a capacitor, characterized by comprising the following steps:

[0029] S1, dry material pretreatment: Ba1- X Sr X TiO3 gradient layered particles were dried at 80-90°C and -0.08-0.09 MPa in a vacuum environment for 12-16 hours. Rare earth oxides, transition metal oxides, alkaline earth metal oxides, and low-melting-point sintering aids were dried at 105-110°C for 4-6 hours. All dried powders were sieved through a 400-mesh sieve to remove agglomerates.

[0030] S2. Dry material mixing: Place the pretreated inorganic raw materials in a polytetrafluoroethylene mixer according to the proportion, and dry mix them at 30-40 rpm for 2-3 hours in a nitrogen atmosphere with a humidity of 15-20% to ensure uniform distribution of the components;

[0031] S3. Preparation of organic additive solution: First, prepare a deionized water / ethanol / acetone mixed solvent; directly dissolve the ammonium polyacrylate dispersant, dissolve the hydroxypropyl methylcellulose binder, polyethylene glycol 600 plasticizer, sodium dodecylbenzene sulfonate antistatic agent, and polydimethylsiloxane defoamer separately, then combine and stir at 450-550 rpm for 1.5-2 hours to form a homogeneous solution;

[0032] S4. Wet mixing: Transfer the dry mix into a polyurethane ball mill, add the organic additive solution and 3-5 mm zirconia balls, set the ball-to-material ratio to 2:1, and ball mill at 150-200 rpm for 18-24 hours in a sealed state to achieve nano-scale dispersion;

[0033] S5. Post-processing: The ball-milled slurry was filtered through a 100-mesh sieve, and then degassed at -0.08 to -0.09 MPa in a vacuum atmosphere for 15 to 20 minutes. The slurry was allowed to stand for 24 hours to achieve rheological equilibrium, thereby obtaining a ceramic raw material for capacitors.

[0034] The invention also discloses an application of a ceramic raw material for a capacitor in a dielectric constant ceramic capacitor, a temperature compensation capacitor, a radio frequency ceramic capacitor and a high frequency filter.

[0035] The present invention utilizes a multi-component synergistic doping and multi-step composite dispersion design, primarily designed to enhance the comprehensive properties of ceramic raw materials in capacitor applications, including molding stability, sintering adaptability, and microstructural uniformity. By rationally combining rare earth oxides, transition metal oxides, and alkaline earth metal oxides with a Bi2O3-ZnO-B2O3 composite low-melting-point sintering aid, the introduction of multiple functional ions synergistically regulates the lattice structure and sintering behavior of the ceramic matrix. The rare earth oxides contribute to stabilizing the crystal phase and adjusting the dielectric response, while the transition metal oxides play a role in regulating grain boundary activity and charge migration. The alkaline earth metal oxides enhance overall microscopic uniformity by influencing grain growth during sintering. Together with the low-melting-point composite sintering aid, they improve the material's densification process and interfacial bonding, effectively reducing the sintering temperature and enhancing structural integrity. During the processing, a composite organic additive system for dispersing, bonding, plasticizing, antistatic and defoaming composed of ammonium polyacrylate, hydroxypropyl methylcellulose, polyethylene glycol 600, sodium dodecylbenzene sulfonate and polydimethylsiloxane is used to improve the rheological stability and wettability of the slurry on the basis of the complementary functions of multiple additives. A composite solvent environment constructed by deionized water, ethanol and acetone in a specific volume ratio is used to effectively improve the distribution uniformity and interfacial wetting ability of the powder during the mixing and dispersion process. In the preparation process, the raw materials are initially homogenized by low-speed dry mixing, and then combined with wet ball milling, vacuum degassing and rheological standing steps to ensure that the slurry has good fluidity and molding consistency in the nano-scale dispersion state. The various components not only complement each other in function, but also achieve a high degree of integration and synergy at the structural level, thereby significantly improving the adaptability and practical application stability of ceramic raw materials in various capacitor products.

[0036] (3) Beneficial technical effects

[0037] 1. The present invention is achieved by Ba1- X Sr X The TiO3 gradient structure is synergistically designed with a variety of functional oxides to achieve simultaneous improvements in dielectric properties and temperature stability, significantly enhancing the structural uniformity and application stability of capacitor materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 Ba1- prepared in Example 1 of the present invention X Sr X Morphology of TiO3 gradient layered particles. DETAILED DESCRIPTION

[0039] To make the purpose, technical solutions and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.

[0040] Example 1: A ceramic raw material for a capacitor, comprising the following raw materials in parts by weight:

[0041] Ba1- X Sr X TiO3 gradient layered particles 85 parts; rare earth oxide 1.3 parts; transition metal oxide 2.0 parts; alkaline earth metal oxide 2.5 parts; low melting point sintering agent 2.5 parts; organic processing aid 4.8 parts; solvent 25 parts;

[0042] Ba1- X Sr X The characteristics of TiO3 gradient layered particles are: the particles have a concentric layered structure, including an inner core layer, an intermediate transition layer and an outer shell layer, wherein the x value of the inner core layer is 0.05, the x value of the intermediate transition layer gradually increases from the inside to the outside along the radial direction, the x value of the outer shell layer is 0.25, and the thickness ratio of the inner core layer, the intermediate transition layer and the outer shell layer is 6.0:1.0:1.4; Ba1- X Sr X The average size of the TiO3 gradient layered particles is 0.5 μm.

[0043] Ba1- X Sr X The preparation of TiO3 gradient layered particles comprises the following steps:

[0044] A1. BaTiO3 precursor and SrTiO3 precursor were prepared by coprecipitation method. The detailed process was as follows: 10.0 parts of butyl titanate and 40.0 parts of anhydrous ethanol were weighed and stirred at 450 rpm for 10 min in an ice-water bath at 4°C to form a titanium source solution. At the same time, 7.5 parts of barium nitrate were dissolved in 25.0 parts of deionized water to prepare a barium source solution, and 6.0 parts of strontium nitrate were dissolved in 20.0 parts of deionized water to prepare a strontium source solution. Under continuous stirring, the barium source solution was slowly added to the titanium source solution at a drop rate of 3 mL / min. After reacting for 30 min, 25.0 parts of 25 wt% ammonia water was added to adjust the pH value to 10.0 to form a white BaTiO3 precursor suspension. The strontium source solution was added dropwise to another part of the titanium source solution using the same method to prepare a SrTiO3 precursor suspension. The two suspensions were aged at room temperature for 15 h, and then filtered and washed with deionized water 6 times until the pH value of the filtrate was 7.0. The filter cake was dried at 80 ° C for 12 h and ground through a 400 mesh sieve to obtain BaTiO3 precursor powder and SrTiO3 precursor powder, respectively.

[0045] A2. The BaTiO3 precursor was calcined at 800°C for 2 hours to obtain BaTiO3 core particles. The detailed process was as follows: the BaTiO3 precursor powder was placed in a high-purity alumina crucible, heated to 800°C in a tube furnace at a heating rate of 2.0°C / min, calcined at a constant temperature for 2 hours in an air atmosphere, and then cooled to room temperature at a cooling rate of 1.0°C / min. The calcined BaTiO3 powder was mixed with anhydrous ethanol in a weight ratio of 1:5, placed in a polyurethane-lined ball mill, and zirconia balls with a diameter of 3 mm were added as grinding media. The ball-to-material ratio was 5:1, and wet ball milling was carried out at a speed of 150 rpm for 40 hours. The suspension after ball milling was sieved through a 200-mesh sieve to remove large particles, filtered and washed with ethanol three times, and the filter cake was dried at 60°C in a vacuum environment for 10 hours to obtain an average particle size.

[0046] A3. Using the layer-by-layer deposition method, BaTiO3 core particles are used as the substrate, and Ba1- X Sr X TiO3 intermediate layer and Sr-rich Ba1- X Sr X TiO3 outer layer; the detailed process is: in parts by weight, three different Sr contents of Ba1- X Sr X TiO3 precursor solution, specifically: BaTiO3 precursor and SrTiO3 precursor are mixed in mass ratios of 9:1, 8:2 and 7:3, and a mixed solvent of anhydrous ethanol and glacial acetic acid with a volume ratio of 4:1 is added respectively, and the sol concentration is 0.10 mol / L; 8.0 parts of BaTiO3 core particles are dispersed in 100 parts of ethanol and ultrasonically treated for 15 minutes to form a uniform suspension; at 35°C, 30 parts of the first precursor solution are slowly added dropwise to the BaTiO3 core particle suspension at a rate of 2 mL / min, the pH value is controlled at 9.5, and stirred for 60 minutes to allow the precursor to be uniformly deposited on the surface of the core particles; centrifuged at a centrifugal speed of 5000 rpm for 10 minutes, the precipitate is washed with ethanol 3 times, and dried at 60°C for 4 hours; the second and third precursor solutions are used in the same way for coating treatment; finally, the obtained particles are dispersed in ethanol, and 25 parts of Ba1- X Sr X A TiO3 precursor solution was prepared by mixing a BaTiO3 precursor and a SrTiO3 precursor in a mass ratio of 6:4 for outermost layer deposition, maintaining a pH value at 10.0, stirring for 4 hours, centrifuging, washing, and drying at 70°C for 8 hours to obtain composite particles with a multilayer structure.

[0047] A4. The resulting particles were calcined at 900 ° C for 3 hours and then lightly ground to obtain Ba1- X Sr X TiO3 gradient layered particles. The detailed process is as follows: in parts by weight, the multilayer composite particles obtained by A3 are placed in a high-purity alumina crucible, heated to 900°C in a tube furnace at a heating rate of 1.5°C / min, and calcined at a constant temperature for 3 hours in a nitrogen and oxygen mixed atmosphere with a volume ratio of 95:5 and a flow rate of 80 mL / min to promote the diffusion of elements between each layer to form a continuous gradient structure; after calcination, the temperature is cooled to 600°C at a cooling rate of 1.0°C / min, and then cooled to room temperature at a rate of 2.0°C / min; after light grinding, Ba1- X Sr X TiO3 gradient layered particles.

[0048] In this embodiment, the rare earth oxide is selected from La2O3; the transition metal oxide is selected from ZrO2; the alkaline earth metal oxide is selected from MgO; and the low-melting-point sintering aid is selected from Bi2O3-ZnO-B2O3 composite oxide, with a mass ratio of 1.0:0.8:0.7.

[0049] The organic processing aids in this embodiment include a dispersant, a binder, a plasticizer, an antistatic agent and a defoaming agent, wherein the dispersant is 1.0 part of ammonium polyacrylate, the binder is 2.0 parts of hydroxypropyl methylcellulose, the plasticizer is 1.5 parts of polyethylene glycol 600, the antistatic agent is 0.2 parts of sodium dodecylbenzene sulfonate, and the defoaming agent is 0.1 parts of polydimethylsiloxane.

[0050] The solvent in this embodiment is a mixture of deionized water, ethanol and acetone, with a volume ratio of 3.0:1:1.

[0051] A method for preparing a ceramic raw material for a capacitor according to this embodiment is characterized by comprising the following steps:

[0052] S1, dry material pretreatment: Ba1- X Sr X TiO3 gradient layered particles were dried at 83°C and -0.08 MPa in a vacuum environment for 13 hours. Rare earth oxides, transition metal oxides, alkaline earth metal oxides, and low-melting-point sintering aids were dried at 107°C for 5 hours. All dried powders were sieved through 400 mesh to remove agglomerates.

[0053] S2. Dry material mixing: Place the pretreated inorganic raw materials in a polytetrafluoroethylene mixer according to the proportion, and dry mix them at 33 rpm for 2 hours in a nitrogen atmosphere with 17% humidity to ensure uniform distribution of the components;

[0054] S3. Preparation of organic additive solution: First, prepare a deionized water / ethanol / acetone mixed solvent; directly dissolve the ammonium polyacrylate dispersant, dissolve the hydroxypropyl methylcellulose binder, polyethylene glycol 600 plasticizer, sodium dodecylbenzene sulfonate antistatic agent, and polydimethylsiloxane defoamer separately, then combine and stir at 480 rpm for 1.7 hours to form a homogeneous solution;

[0055] S4, wet mixing: the dry mix was transferred to a polyurethane ball mill, and the organic additive solution and 4 mm zirconia balls were added, with a ball-to-material ratio of 2:1. The mixture was ball-milled at 165 rpm for 20 h in a sealed state to achieve nano-scale dispersion;

[0056] S5. Post-processing: The ball-milled slurry was filtered through a 100-mesh sieve, degassed at -0.08 MPa in vacuum for 17 minutes, and finally allowed to stand for 24 hours to achieve rheological equilibrium, thereby obtaining a ceramic raw material for capacitors.

[0057] Figure 1 Shows the Ba1- prepared in Example 1 of the present invention X Sr X The typical morphological characteristics of TiO3 gradient layered particles are that the particles are spherical and uniform in size, and the concentric layered structure consisting of an inner core layer, an intermediate transition layer and an outer shell layer is clearly visible on the surface, indicating that the layer-by-layer deposition and controlled calcination process used can successfully construct a gradient structure with continuous transition of composition, providing a structural basis for the coordinated optimization of the dielectric properties and temperature stability of the material.

[0058] Example 2: A ceramic raw material for a capacitor, comprising the following raw materials in parts by weight:

[0059] Ba1- X Sr X TiO3 gradient layered particles 88 parts; rare earth oxide 2.0 parts; transition metal oxide 2.9 parts; alkaline earth metal oxide 3.6 parts; low melting point sintering agent 3.7 parts; organic processing aid 6.3 parts; solvent 30 parts;

[0060] Ba1- X Sr X The characteristics of TiO3 gradient layered particles are: the particles have a concentric layered structure, including an inner core layer, an intermediate transition layer and an outer shell layer, wherein the x value of the inner core layer is 0.07, the x value of the intermediate transition layer gradually increases from the inside to the outside along the radial direction, the x value of the outer shell layer is 0.27, and the thickness ratio of the inner core layer, the intermediate transition layer and the outer shell layer is 6.3:1.1:1.5; Ba1- X Sr X The average size of the TiO3 gradient layered particles is 0.6 μm.

[0061] Ba1- X SrX The preparation of TiO3 gradient layered particles comprises the following steps:

[0062] A1. BaTiO3 precursor and SrTiO3 precursor were prepared by coprecipitation method. The detailed process was as follows: 10.6 parts of butyl titanate and 43.0 parts of anhydrous ethanol were weighed and stirred at 480 rpm for 12 min in an ice-water bath at 5°C to form a titanium source solution. At the same time, 7.8 parts of barium nitrate were dissolved in 26.5 parts of deionized water to prepare a barium source solution, and 6.3 parts of strontium nitrate were dissolved in 21.5 parts of deionized water to prepare a strontium source solution. Under continuous stirring, the barium source solution was slowly added to the titanium source solution at a drop rate of 4 mL / min. After reacting for 33 min, 25.9 parts of 26 wt% ammonia water was added to adjust the pH value to 10.3 to form a white BaTiO3 precursor suspension. The strontium source solution was added dropwise to another part of the titanium source solution using the same method to prepare a SrTiO3 precursor suspension. The two suspensions were aged at room temperature for 17 h, and then filtered and washed with deionized water 7 times until the pH value of the filtrate was 7.2. The filter cake was dried at 83 ° C for 13 h and ground through a 400 mesh sieve to obtain BaTiO3 precursor powder and SrTiO3 precursor powder, respectively.

[0063] A2. The BaTiO3 precursor was calcined at 815°C for 3 hours to obtain BaTiO3 core particles. The detailed process was as follows: the BaTiO3 precursor powder was placed in a high-purity alumina crucible, heated to 815°C in a tube furnace at a heating rate of 2.2°C / min, calcined at a constant temperature for 3 hours in an air atmosphere, and then cooled to room temperature at a cooling rate of 1.2°C / min. The calcined BaTiO3 powder was mixed with anhydrous ethanol in a weight ratio of 1:5, placed in a polyurethane-lined ball mill, and zirconia balls with a diameter of 4 mm were added as grinding media. The ball-to-material ratio was 5:1, and wet ball milling was carried out at a speed of 159 rpm for 42 hours. The suspension after ball milling was sieved through a 200-mesh sieve to remove large particles, filtered and washed with ethanol three times, and the filter cake was dried at 63°C in a vacuum environment for 11 hours to obtain an average particle size.

[0064] A3. Using the layer-by-layer deposition method, BaTiO3 core particles are used as the substrate, and Ba1- X Sr X TiO3 intermediate layer and Sr-rich Ba1- X Sr X TiO3 outer layer; the detailed process is: in parts by weight, three different Sr contents of Ba1- X Sr XTiO3 precursor solution, specifically: BaTiO3 precursor and SrTiO3 precursor are mixed in mass ratios of 9:1, 8:2 and 7:3, and a mixed solvent of anhydrous ethanol and glacial acetic acid with a volume ratio of 4:1 is added respectively, and the sol concentration is 0.12 mol / L; 8.6 parts of BaTiO3 core particles are dispersed in 106 parts of ethanol and ultrasonically treated for 17 minutes to form a uniform suspension; at 38°C, 32 parts of the first precursor solution are slowly added dropwise to the BaTiO3 core particle suspension at a rate of 2 mL / min, the pH value is controlled at 9.8, and stirred for 69 minutes to allow the precursor to be uniformly deposited on the surface of the core particles; centrifuged at a centrifugal speed of 5300 rpm for 12 minutes, the precipitate is washed with ethanol 3 times, and dried at 60°C for 5 hours; the second and third precursor solutions are used in the same way for coating treatment; finally, the obtained particles are dispersed in ethanol, and 27 parts of Ba1- X Sr X A TiO3 precursor solution was prepared by mixing a BaTiO3 precursor and a SrTiO3 precursor in a mass ratio of 6:4 for outermost layer deposition, maintaining a pH value at 10.3, stirring for 5 h, centrifuging, washing, and drying at 70°C for 9 h to obtain composite particles with a multilayer structure.

[0065] A4. The resulting particles were calcined at 915 ° C for 4 hours and then lightly ground to obtain Ba1- X Sr X TiO3 gradient layered particles. The detailed process is as follows: in parts by weight, the multilayer composite particles obtained from A3 are placed in a high-purity alumina crucible, heated to 915°C in a tube furnace at a heating rate of 1.7°C / min, and calcined at a constant temperature for 4 hours in a nitrogen and oxygen mixed atmosphere with a volume ratio of 95:5 and a flow rate of 86 mL / min to promote the diffusion of elements between each layer to form a continuous gradient structure; after calcination, the temperature is cooled to 600°C at a cooling rate of 1.2°C / min, and then cooled to room temperature at a rate of 2.3°C / min; Ba1- X Sr X TiO3 gradient layered particles.

[0066] In this embodiment, the rare earth oxide is selected from Gd2O3; the transition metal oxide is selected from ZrO2; the alkaline earth metal oxide is selected from CaO; and the low-melting-point sintering aid is selected from Bi2O3-ZnO-B2O3 composite oxide, with a mass ratio of 1.3:1.0:0.8.

[0067] The organic processing aids in this embodiment include a dispersant, a binder, a plasticizer, an antistatic agent and a defoaming agent, wherein the dispersant is 1.3 parts of ammonium polyacrylate, the binder is 2.6 parts of hydroxypropyl methylcellulose, the plasticizer is 1.9 parts of polyethylene glycol 600, the antistatic agent is 0.3 parts of sodium dodecylbenzene sulfonate, and the defoaming agent is 0.2 parts of polydimethylsiloxane.

[0068] The solvent in this embodiment is a mixture of deionized water, ethanol and acetone, with a volume ratio of 3.3:1:1.

[0069] A method for preparing a ceramic raw material for a capacitor according to this embodiment is characterized by comprising the following steps:

[0070] S1, dry material pretreatment: Ba1- X Sr X TiO3 gradient layered particles were dried at 80°C and -0.08 MPa in a vacuum environment for 12 hours. Rare earth oxides, transition metal oxides, alkaline earth metal oxides, and low-melting-point sintering aids were dried at 105°C for 4 hours. All dried powders were sieved through 400 mesh to remove agglomerates.

[0071] S2. Dry material mixing: Place the pretreated inorganic raw materials in a polytetrafluoroethylene mixer according to the proportion, and dry mix them at 30 rpm for 2 hours in a nitrogen atmosphere with 15% humidity to ensure uniform distribution of the components;

[0072] S3. Preparation of organic additive solution: First, prepare a deionized water / ethanol / acetone mixed solvent; directly dissolve the ammonium polyacrylate dispersant, dissolve the hydroxypropyl methylcellulose binder, polyethylene glycol 600 plasticizer, sodium dodecylbenzene sulfonate antistatic agent, and polydimethylsiloxane defoamer separately, then combine and stir at 450 rpm for 1.5 hours to form a homogeneous solution;

[0073] S4, wet mixing: the dry mix was transferred to a polyurethane ball mill, and the organic additive solution and 3 mm zirconia balls were added, with a ball-to-material ratio of 2:1. The mixture was ball-milled at 150 rpm for 18 hours in a sealed state to achieve nano-scale dispersion;

[0074] S5. Post-processing: The ball-milled slurry was filtered through a 100-mesh sieve, degassed at -0.08 MPa vacuum for 15 minutes, and finally allowed to stand for 24 hours to achieve rheological equilibrium, thereby obtaining a ceramic raw material for capacitors.

[0075] Example 3: A ceramic raw material for a capacitor, comprising the following raw materials in parts by weight:

[0076] Ba1- X Sr XTiO3 gradient layered particles 91 parts; rare earth oxide 2.6 parts; transition metal oxide 3.7 parts; alkaline earth metal oxide 4.6 parts; low melting point sintering agent 4.9 parts; organic processing aid 7.8 parts; solvent 34 parts;

[0077] Ba1- X Sr X The characteristics of TiO3 gradient layered particles are: the particles have a concentric layered structure, including an inner core layer, an intermediate transition layer and an outer shell layer, wherein the x value of the inner core layer is 0.08, the x value of the intermediate transition layer gradually increases from the inside to the outside along the radial direction, the x value of the outer shell layer is 0.28, and the thickness ratio of the inner core layer, the intermediate transition layer and the outer shell layer is 6.6:1.1:1.5; Ba1- X Sr X The average size of the TiO3 gradient layered particles is 0.7 μm.

[0078] Ba1- X Sr X The preparation of TiO3 gradient layered particles comprises the following steps:

[0079] A1. BaTiO3 precursor and SrTiO3 precursor were prepared by co-precipitation method. The detailed process was as follows: 11.2 parts of butyl titanate and 46.0 parts of anhydrous ethanol were weighed in parts by weight and stirred at 510 rpm for 13 min in an ice-water bath at 7°C to form a titanium source solution. At the same time, 8.1 parts of barium nitrate were dissolved in 28.0 parts of deionized water to prepare a barium source solution, and 6.6 parts of strontium nitrate were dissolved in 23.0 parts of deionized water to prepare a strontium source solution. Under continuous stirring, the barium source solution was slowly added to the titanium source solution at a drop rate of 4 mL / min. After reacting for 36 min, 26.8 parts of 27 wt% ammonia water was added to adjust the pH value to 10.6 to form a white BaTiO3 precursor suspension. The strontium source solution was added dropwise to another part of the titanium source solution using the same method to prepare a SrTiO3 precursor suspension. The two suspensions were aged at room temperature for 18 h, and then filtered and washed with deionized water 7 times until the pH value of the filtrate was 7.3. The filter cake was dried at 86 ° C for 14 h and ground through a 400 mesh sieve to obtain BaTiO3 precursor powder and SrTiO3 precursor powder, respectively.

[0080] A2. The BaTiO3 precursor was calcined at 830°C for 3 hours to obtain BaTiO3 core particles. The detailed process was as follows: the BaTiO3 precursor powder was placed in a high-purity alumina crucible, heated to 830°C in a tube furnace at a heating rate of 2.3°C / min, calcined at a constant temperature for 3 hours in an air atmosphere, and then cooled to room temperature at a cooling rate of 1.3°C / min. The calcined BaTiO3 powder was mixed with anhydrous ethanol in a weight ratio of 1:5, placed in a polyurethane-lined ball mill, and zirconia balls with a diameter of 4 mm were added as grinding media. The ball-to-material ratio was 5:1, and wet ball milling was carried out at a speed of 168 rpm for 45 hours. The suspension after ball milling was sieved through a 200-mesh sieve to remove large particles, filtered and washed with ethanol three times, and the filter cake was dried at 66°C in a vacuum environment for 11 hours to obtain an average particle size.

[0081] A3. Using the layer-by-layer deposition method, BaTiO3 core particles are used as the substrate, and Ba1- X Sr X TiO3 intermediate layer and Sr-rich Ba1- X Sr X TiO3 outer layer; the detailed process is: in parts by weight, three different Sr contents of Ba1- X Sr X TiO3 precursor solution, specifically: BaTiO3 precursor and SrTiO3 precursor are mixed in mass ratios of 9:1, 8:2 and 7:3, and a mixed solvent of anhydrous ethanol and glacial acetic acid with a volume ratio of 4:1 is added respectively, and the sol concentration is 0.13 mol / L; 9.2 parts of BaTiO3 core particles are dispersed in 112 parts of ethanol and ultrasonically treated for 18 minutes to form a uniform suspension; 33 parts of the first precursor solution are slowly added dropwise to the BaTiO3 core particle suspension at a rate of 3 mL / min at 41°C, the pH value is controlled at 10.1, and stirred for 78 minutes to allow the precursor to be uniformly deposited on the surface of the core particles; centrifuged at a centrifugal speed of 5600 rpm for 13 minutes, the precipitate is washed with ethanol 3 times, and dried at 60°C for 5 hours; the second and third precursor solutions are used in the same way for coating treatment; finally, the obtained particles are dispersed in ethanol, and 28 parts of Ba1- X Sr X A TiO3 precursor solution was prepared by mixing a BaTiO3 precursor and a SrTiO3 precursor in a mass ratio of 6:4 for outermost layer deposition, maintaining a pH value at 10.6, stirring for 5 hours, centrifuging, washing, and drying at 70°C for 9 hours to obtain composite particles with a multilayer structure.

[0082] A4. The resulting particles were calcined at 930 ° C for 4 hours and then lightly ground to obtain Ba1- X Sr X TiO3 gradient layered particles. The detailed process is as follows: in parts by weight, the multilayer composite particles obtained from A3 are placed in a high-purity alumina crucible, heated to 930°C in a tube furnace at a heating rate of 1.8°C / min, and calcined at a constant temperature for 4 hours in a nitrogen and oxygen mixed atmosphere with a volume ratio of 95:5 and a flow rate of 92 mL / min to promote the diffusion of elements between each layer to form a continuous gradient structure; after calcination, the temperature is cooled to 600°C at a cooling rate of 1.3°C / min, and then cooled to room temperature at a rate of 2.6°C / min; after light grinding, Ba1- X Sr X TiO3 gradient layered particles.

[0083] In this embodiment, the rare earth oxide is selected from Y2O3; the transition metal oxide is selected from CuO; the alkaline earth metal oxide is selected from Al2O3; and the low-melting-point sintering aid is selected from Bi2O3-ZnO-B2O3 composite oxide, with a mass ratio of 1.6:1.2:0.9.

[0084] The organic processing aids in this embodiment include a dispersant, a binder, a plasticizer, an antistatic agent and a defoaming agent, wherein the dispersant is 1.6 parts of ammonium polyacrylate, the binder is 3.2 parts of hydroxypropyl methylcellulose, the plasticizer is 2.4 parts of polyethylene glycol 600, the antistatic agent is 0.4 parts of sodium dodecylbenzene sulfonate, and the defoaming agent is 0.2 parts of polydimethylsiloxane.

[0085] The solvent in this embodiment is a mixture of deionized water, ethanol and acetone, with a volume ratio of 3.6:1:1.

[0086] A method for preparing a ceramic raw material for a capacitor according to this embodiment is characterized by comprising the following steps:

[0087] S1, dry material pretreatment: Ba1- X Sr X TiO3 gradient layered particles were dried at 90°C and -0.09 MPa in a vacuum environment for 16 hours. Rare earth oxides, transition metal oxides, alkaline earth metal oxides, and low-melting-point sintering aids were dried at 110°C for 6 hours. All dried powders were sieved through 400 mesh to remove agglomerates.

[0088] S2. Dry material mixing: Place the pretreated inorganic raw materials in a polytetrafluoroethylene mixer according to the proportion, and dry mix them at 40 rpm for 3 hours in a nitrogen atmosphere with 20% humidity to ensure uniform distribution of the components;

[0089] S3. Preparation of organic additive solution: First, prepare a deionized water / ethanol / acetone mixed solvent; directly dissolve the ammonium polyacrylate dispersant, dissolve the hydroxypropyl methylcellulose binder, polyethylene glycol 600 plasticizer, sodium dodecylbenzene sulfonate antistatic agent, and polydimethylsiloxane defoamer separately, then combine and stir at 550 rpm for 2 hours to form a homogeneous solution;

[0090] S4, wet mixing: the dry mix was transferred to a polyurethane ball mill, and the organic additive solution and 5 mm zirconia balls were added, with a ball-to-material ratio of 2:1. The mixture was ball-milled at 200 rpm for 24 hours in a sealed state to achieve nano-scale dispersion;

[0091] S5. Post-processing: The ball-milled slurry was filtered through a 100-mesh sieve, degassed at -0.09 MPa in a vacuum atmosphere for 20 minutes, and allowed to stand for 24 hours to achieve rheological equilibrium, thereby obtaining a ceramic raw material for capacitors.

[0092] Example 4: A ceramic raw material for a capacitor, comprising the following raw materials in parts by weight:

[0093] Ba1- X Sr X TiO3 gradient layered particles 95 parts; rare earth oxide 3.5 parts; transition metal oxide 4.9 parts; alkaline earth metal oxide 6.0 parts; low melting point sintering agent 6.5 parts; organic processing aid 9.8 parts; solvent 40 parts;

[0094] Ba1- X Sr X The characteristics of TiO3 gradient layered particles are: the particles have a concentric layered structure, including an inner core layer, an intermediate transition layer and an outer shell layer, wherein the x value of the inner core layer is 0.10, the x value of the intermediate transition layer gradually increases from the inside to the outside along the radial direction, the x value of the outer shell layer is 0.30, and the thickness ratio of the inner core layer, the intermediate transition layer and the outer shell layer is 7.0:1.2:1.6; Ba1- X Sr X The average size of the TiO3 gradient layered particles is 0.8 μm.

[0095] Ba1- X Sr X The preparation of TiO3 gradient layered particles comprises the following steps:

[0096] A1. BaTiO3 precursor and SrTiO3 precursor were prepared by co-precipitation method; the detailed process was as follows: 12.0 parts of butyl titanate and 50.0 parts of anhydrous ethanol were weighed in parts by weight, and stirred at 550 rpm for 15 min in an ice-water bath at 8°C to form a titanium source solution; at the same time, 8.5 parts of barium nitrate were dissolved in 30.0 parts of deionized water to prepare a barium source solution, and 7.0 parts of strontium nitrate were dissolved in 25.0 parts of deionized water to prepare a strontium source solution; under continuous stirring, the barium source solution was slowly added to the titanium source solution at a drop rate of 5 mL / min. After reacting for 40 min, 28.0 parts of 28 wt% ammonia water was added to adjust the pH value to 11.0 to form a white BaTiO3 precursor suspension; the strontium source solution was added dropwise to another part of the titanium source solution using the same method to prepare a SrTiO3 precursor suspension; the two suspensions were aged at room temperature for 20 h, and then filtered and washed 8 times with deionized water until the pH value of the filtrate was 7.5. The filter cake was dried at 90 °C for 16 h and ground through a 400-mesh sieve to obtain BaTiO3 precursor powder and SrTiO3 precursor powder, respectively.

[0097] A2. The BaTiO3 precursor was calcined at 850°C for 4 hours to obtain BaTiO3 core particles. The detailed process was as follows: the BaTiO3 precursor powder was placed in a high-purity alumina crucible, heated to 850°C in a tube furnace at a heating rate of 2.5°C / min, calcined at a constant temperature for 4 hours in an air atmosphere, and then cooled to room temperature at a cooling rate of 1.5°C / min. The calcined BaTiO3 powder was mixed with anhydrous ethanol in a weight ratio of 1:5, placed in a polyurethane-lined ball mill, and zirconia balls with a diameter of 5 mm were added as grinding media. The ball-to-material ratio was 5:1, and wet ball milling was carried out at a speed of 180 rpm for 48 hours. The suspension after ball milling was sieved through a 200-mesh sieve to remove large particles, filtered and washed with ethanol four times. The filter cake was dried in a vacuum environment at 70°C for 12 hours to obtain an average particle size.

[0098] A3. Using the layer-by-layer deposition method, BaTiO3 core particles are used as the substrate, and Ba1- X Sr X TiO3 intermediate layer and Sr-rich Ba1- X Sr X TiO3 outer layer; the detailed process is: in parts by weight, three different Sr contents of Ba1- X Sr XTiO3 precursor solution, specifically: BaTiO3 precursor and SrTiO3 precursor are mixed in mass ratios of 9:1, 8:2 and 7:3, and a mixed solvent of anhydrous ethanol and glacial acetic acid with a volume ratio of 4:1 is added respectively, and the sol concentration is 0.15 mol / L; 10.0 parts of BaTiO3 core particles are dispersed in 120 parts of ethanol and ultrasonically treated for 20 minutes to form a uniform suspension; at 45°C, 35 parts of the first precursor solution are slowly added dropwise to the BaTiO3 core particle suspension at a rate of 3 mL / min, the pH value is controlled at 10.5, and stirred for 90 minutes to allow the precursor to be uniformly deposited on the surface of the core particles; centrifuged at a centrifugal speed of 6000 rpm for 15 minutes, the precipitate is washed with ethanol 3 times, and dried at 60°C for 6 hours; the second and third precursor solutions are used in the same way for coating treatment; finally, the obtained particles are dispersed in ethanol, and 30 parts of Ba1- X Sr X A TiO3 precursor solution was prepared by mixing a BaTiO3 precursor and a SrTiO3 precursor in a mass ratio of 6:4 for outermost layer deposition, maintaining a pH value at 11.0, stirring for 6 hours, centrifuging, washing, and drying at 70°C for 10 hours to obtain composite particles with a multilayer structure.

[0099] A4. The resulting particles were calcined at 950 ° C for 5 hours and then lightly ground to obtain Ba1- X Sr X TiO3 gradient layered particles. The detailed process is as follows: in parts by weight, the multilayer composite particles obtained from A3 are placed in a high-purity alumina crucible, heated to 950°C in a tube furnace at a heating rate of 2.0°C / min, and calcined at a constant temperature for 5 hours in a nitrogen and oxygen mixed atmosphere with a volume ratio of 95:5 and a flow rate of 100 mL / min to promote the diffusion of elements between each layer to form a continuous gradient structure; after calcination, the temperature is cooled to 600°C at a cooling rate of 1.5°C / min, and then cooled to room temperature at a rate of 3.0°C / min; Ba1- X Sr X TiO3 gradient layered particles.

[0100] In this embodiment, the rare earth oxide is selected from La2O3; the transition metal oxide is selected from MnO2; the alkaline earth metal oxide is selected from CaO; and the low-melting-point sintering aid is selected from Bi2O3-ZnO-B2O3 composite oxide, with a mass ratio of 2.0:1.5:1.0.

[0101] The organic processing aids in this embodiment include a dispersant, a binder, a plasticizer, an antistatic agent and a defoaming agent, wherein the dispersant is 2.0 parts of ammonium polyacrylate, the binder is 4.0 parts of hydroxypropyl methylcellulose, the plasticizer is 3.0 parts of polyethylene glycol 600, the antistatic agent is 0.5 parts of sodium dodecylbenzene sulfonate, and the defoaming agent is 0.3 parts of polydimethylsiloxane.

[0102] The solvent in this embodiment is a mixture of deionized water, ethanol and acetone, with a volume ratio of 4.0:1:1.

[0103] This embodiment also provides a method for preparing a ceramic raw material for a capacitor, which is characterized by comprising the following steps:

[0104] S1, dry material pretreatment: Ba1- X Sr X TiO3 gradient layered particles were dried at 86°C and -0.09 MPa in a vacuum environment for 14 hours. Rare earth oxides, transition metal oxides, alkaline earth metal oxides, and low-melting-point sintering aids were dried at 108°C for 5 hours. All dried powders were sieved through 400 mesh to remove agglomerates.

[0105] S2. Dry material mixing: Place the pretreated inorganic raw materials according to the proportion in a polytetrafluoroethylene mixer and dry mix them at 36 rpm for 3 hours in a nitrogen atmosphere with 18% humidity to ensure uniform distribution of the components;

[0106] S3. Preparation of organic additive solution: First, prepare a deionized water / ethanol / acetone mixed solvent; directly dissolve the ammonium polyacrylate dispersant, dissolve the hydroxypropyl methylcellulose binder, polyethylene glycol 600 plasticizer, sodium dodecylbenzene sulfonate antistatic agent, and polydimethylsiloxane defoamer separately, then combine and stir at 510 rpm for 1.8 hours to form a homogeneous solution;

[0107] S4, wet mixing: the dry mix was transferred to a polyurethane ball mill, and the organic additive solution and 4 mm zirconia balls were added, with a ball-to-material ratio of 2:1. The mixture was sealed and ball milled at 180 rpm for 22 h to achieve nano-scale dispersion;

[0108] S5. Post-processing: The ball-milled slurry was filtered through a 100-mesh sieve, degassed at -0.09 MPa in vacuum for 18 minutes, and finally allowed to stand for 24 hours to achieve rheological equilibrium, thereby obtaining a ceramic raw material for capacitors.

[0109] Comparative Example 1

[0110] It is basically the same as Example 1, except that Ba1- X Sr X TiO3 particles are not gradient layered structures, but are uniform Ba 0.8 Sr0.2 TiO3 particles do not form a three-layer structure of inner core layer, middle transition layer and outer shell layer.

[0111] Comparative Example 2

[0112] The process is basically the same as Example 1, except that the calcination temperature of the BaTiO3 precursor in step A2 is 780°C, resulting in insufficient crystallinity of the core particles.

[0113] Comparative Example 3

[0114] The process is basically the same as Example 1, except that the final calcination temperature in step A4 is 980° C., which results in excessive sintering of the particles and partial homogenization of the Sr gradient structure.

[0115] Comparative Example 4

[0116] The same as Example 1, except that the layer-by-layer deposition method is not used in step A3, but three Ba1- X Sr X After the TiO3 precursor solutions were mixed at one time, they were simultaneously deposited on the surface of the BaTiO3 core particles without forming a clear transition structure with gradually increasing Sr content.

[0117] Comparative Example 5

[0118] It is basically the same as Example 1, except that no rare earth oxide is added (i.e., the rare earth oxide is 0 parts), and the regulating effect of La2O3, Gd2O3 or Y2O3 on the lattice structure is lacking.

[0119] Comparative Example 6

[0120] It is basically the same as Example 1, except that the low-melting-point sintering aid is a single Bi2O3 rather than a Bi2O3-ZnO-B2O3 composite oxide, which lacks the effect of the three components synergistically lowering the sintering temperature.

[0121] Comparative Example 7

[0122] It is basically the same as Example 1, except that in step A3, the mixing ratios of the BaTiO3 precursor and the SrTiO3 precursor are 9.5:0.5, 8.5:1.5 and 7.5:2.5, resulting in insufficient gradient change of the Sr content.

[0123] Performance testing:

[0124] The above capacitor ceramic raw materials were converted into testable ceramic dielectric materials through slurry preparation, molding, sintering and electrode preparation. The specific steps are as follows: first, the obtained ceramic raw material slurry was subjected to a secondary ball milling treatment. 3mm zirconia balls were added to a polyurethane ball mill with a ball-to-material ratio of 5:1. The slurry was ball milled at 180 rpm for 12 hours to ensure uniform dispersion. Then, a degassing treatment was performed under a vacuum environment of -0.09 MPa for 20 minutes to eliminate bubbles in the slurry. The tape casting method (tape casting) was used to form the slurry. The ceramic film was prepared by casting), and the slurry was evenly coated on a silicone oil-treated polyester film carrier using an automatic casting machine. The scraper height was set to 200 μm, the casting speed was 30 cm / min, and a green sheet with a thickness of about 100 μm was formed after drying at room temperature for 24 hours. The green sheet was cut into 25 mm × 25 mm square samples using a precision cutting machine, and 8 layers of green sheets were stacked using a lamination process. A composite green blank was formed by hot pressing at 80 ° C and 20 MPa for 10 minutes. The composite green blank was pre-sintered by heating to 400 ° C at a rate of 2 ° C / min in an oxygen atmosphere and holding for 2 hours to remove the organic binder. It was then sintered at high temperature by heating to 1250 ° C at a rate of 3 ° C / min in a mixed atmosphere of nitrogen and oxygen with a volume ratio of 95:5, holding for 2 hours, and then cooling at a rate of 2 ° C / min. The cooling rate was dropped to room temperature; both sides of the sintered ceramic wafer were surface polished using 1000, 2000, and 3000 grit metallographic sandpaper in sequence until the surface finish reached Ra ≤ 0.5 μm; electrodes were prepared on both sides of the ceramic wafer by magnetron sputtering, first sputtering a 20 nm thick Ti adhesion layer, then sputtering a 200 nm thick Pt electrode layer, and the electrode diameter was 10 mm; standard photolithography process was used with a mask to produce specific test patterns on the top electrode, including parallel plate capacitor structure, interdigital capacitor structure and microwave resonator structure; silver paste and fine gold wire were used to connect the electrode lead to the test fixture through ultrasonic pressure welding; the sample was dried in a 150 ° C oven for 2 hours to remove surface adsorbed moisture, and then packaged in a constant temperature and humidity environment (25 ° C, relative humidity <30%) test fixture for various electrical performance tests. The above process ensures that the prepared ceramic dielectric material has high density (relative density > 95%), uniform microstructure and good electrode adhesion, which can meet the requirements of various electrical tests.

[0125] Dielectric Temperature Characteristics: A Novocontrol Concept 80 broadband dielectric spectrometer was used to measure the temperature characteristics of ceramic dielectric materials over a temperature range of -60°C to 150°C at a test frequency of 100Hz-1MHz. Ceramic samples were equipped with Pt electrodes to form a parallel plate capacitor structure. The dielectric constant (εr), dielectric loss (tanδ), and temperature coefficient of capacitance (TCC) of the samples were measured at different temperatures. The rate of change of the dielectric constant with temperature (TCεr) was calculated, with particular attention paid to the dielectric peak morphology and diffusion phase transition characteristics near the Curie temperature (Tc). The temperature stability of the material was evaluated, and the mechanism by which the gradient layered structure suppresses the temperature sensitivity of dielectric properties was analyzed.

[0126] High-frequency dielectric performance testing: Using the Keysight N5242A PNA-X network analyzer combined with the split-post dielectric resonator method, the complex dielectric constant (ε' and ε") and microwave dielectric loss (tanδmw) of ceramic materials in the 1-20 GHz frequency range are measured. Samples are prepared as 1mm thick polished discs and placed in a dedicated test fixture for S-parameter measurement. Dielectric parameters are extracted using standard algorithms. The quality factor (Q×f) is calculated and its correlation with the material's microstructure is analyzed to evaluate the material's performance in high-frequency filter, antenna, and resonator applications.

[0127] Thermophysical Characterization: Thermal properties of ceramic samples were measured using a NETZSCH DIL 402C dilatometer and a DSC 404F3 differential scanning calorimeter. Measurements were performed in a nitrogen atmosphere over a temperature range of 30–800°C at a heating rate of 5°C / min. The coefficient of linear thermal expansion (CTE), specific heat capacity (Cp), and thermal conductivity (λ) were determined, and the phase transition temperature and latent heat were determined.

[0128] Mechanical Properties: Nanomechanical properties of ceramic samples were tested using an Agilent G200 nanoindenter. A Berkovich indenter was used, with a maximum load of 2 mN and a load-hold-unload time of 30 s, 10 s, and 30 s. The load-displacement curves were analyzed using the Oliver-Pharr method to determine the Young's modulus (E), hardness (H), fracture toughness (KIC), and elastic recovery.

[0129] The properties of the ceramic materials of Examples 1 to 4 and Comparative Examples 1 to 7 are summarized in Table 1. It can be seen from the table that Comparative Example 1 does not use Ba1- X Sr XTiO3 gradient layered structure, but uses uniform solid solution particles, resulting in insufficient regulation of the polarization response of the ceramic under temperature changes, manifested as a significant decrease in temperature stability, increased dielectric loss, low Curie temperature and reduced high-frequency quality factor, indicating that the gradient structure plays a key role in suppressing dielectric drift, reducing internal stress and enhancing frequency domain stability; in Example 2, the calcination temperature of the BaTiO3 precursor is low, resulting in insufficient crystallinity of the core particles, affecting the interface matching and lattice continuity of the subsequent deposited layers, and ultimately leading to a decrease in dielectric constant, increased loss and decreased mechanical properties; in Example 3, the final calcination temperature is too high, resulting in excessive sintering of the particle structure and homogenization of Sr diffusion, destroying the gradient design, resulting in deterioration of temperature stability and decreased dielectric properties, indicating that precise control of the sintering temperature is crucial to maintaining the integrity of the gradient structure; in Example 4, the layer-by-layer deposition method is not adopted but a one-time mixed deposition method, resulting in discontinuous Sr distribution and unclear structural gradient, thereby triggering dielectric response The unevenness and temperature drift are aggravated, and the loss increases, indicating that the deposition path directly affects the orderliness of the components and the degree of performance coordination; in Comparative Example 5, no rare earth oxides are added, and there is a lack of control over lattice distortion and grain boundary stability. Although the dielectric constant increases, the loss increases significantly, and the fracture toughness and mechanical properties decrease, indicating that the rare earth component makes an important contribution to improving structural stability and reducing dielectric loss; in Comparative Example 6, a single Bi2O3 is used as a sintering aid. Due to the lack of the synergistic effect of ZnO and B2O3, the sintering temperature window is narrow and the density is insufficient, which is manifested as a decrease in both dielectric and thermophysical properties, verifying the synergy of the ternary composite sintering aid system in improving sintering behavior; in Comparative Example 7, the gradient change amplitude of the mixing ratio of BaTiO3 and SrTiO3 is insufficient, and an obvious Sr concentration gradient cannot be formed, resulting in an overly uniform overall structure, decreased temperature stability, and deterioration of dielectric properties, indicating that the reasonable design of the gradient amplitude plays an important role in forming an effective polarization transition layer and regulating performance distribution.

[0130] Table 1 Summary of properties of ceramic materials of Examples 1 to 4 and Comparative Examples 1 to 7

[0131]

[0132] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that any equivalent structural transformations made within the scope of the present invention using the contents of the present invention's description and drawings should be included within the scope of protection of the claims of the present invention.

Claims

1. A ceramic raw material for a capacitor, characterized in that: The composition comprises the following raw materials in parts by weight: 85-95 parts of gradient layered particles; 1.3-3.5 parts of rare earth oxide; 2.0-4.9 parts of transition metal oxide; 2.5-6.0 parts of alkaline earth metal oxide; 2.5-6.5 parts of low melting point sintering aid; 4.8-9.8 parts of organic processing aid; 25-40 parts of solvent; described The gradient layered particles are characterized in that the particles present a concentric layered structure, including an inner core layer, an intermediate transition layer, and an outer shell layer, wherein the x value of the inner core layer is 0.05-0.10, the x value of the intermediate transition layer gradually increases radially from the inside to the outside, the x value of the outer shell layer is 0.25-0.30, and the thickness ratio of the inner core layer, the intermediate transition layer, and the outer shell layer is 6.0-7.0:1.0-1.2:1.4-1.6; The The average size of the gradient layered particles is 0.5~0.8 μm.

2. The ceramic raw material for capacitors according to claim 1, wherein: The The preparation of gradient layered particles comprises the following steps: A1. Preparation by co-precipitation method Precursors and Precursor; A2. The precursor is calcined at 800-850℃ for 2-4 hours to obtain core particles; A3. Using layer-by-layer deposition method, The core particles are the base, and the Sr content gradually increases. Intermediate layer and Sr-rich outer layer; A4. The obtained particles are calcined at 900-950℃ for 3-5 hours and then lightly ground to obtain Gradient layered particles.

3. The ceramic raw material for capacitors according to claim 2, characterized in that: The detailed process of A1 is as follows: 10.0-12.0 parts of butyl titanate and 40.0-50.0 parts of anhydrous ethanol are weighed in parts by weight, and stirred at 450-550 rpm for 10-15 min in an ice-water bath at 4-8°C to form a titanium source solution; at the same time, 7.5-8.5 parts of barium nitrate are dissolved in 25.0-30.0 parts of deionized water to prepare a barium source solution, and 6.0-7.0 parts of strontium nitrate are dissolved in 20.0-25.0 parts of deionized water to prepare a strontium source solution; under continuous stirring, the barium source solution is slowly added to the titanium source solution at a drop rate of 3-5 mL / min, and after reacting for 30-40 min, 25.0-28.0 parts of 25-28 wt% ammonia water are added to adjust the pH value to 10.0-11.0 to form a white Precursor suspension; using the same method, add the strontium source solution dropwise to another titanium source solution to prepare The two suspensions were aged at room temperature for 15-20 h, then filtered and washed with deionized water 6-8 times until the pH value of the filtrate was 7.0-7.

5. The filter cakes were dried at 80-90 ° C for 12-16 h and ground through a 400 mesh sieve to obtain Precursor powder and Precursor powder.

4. The ceramic raw material for capacitors according to claim 2, wherein: The detailed process of A2 is as follows: in parts by weight, The precursor powder was placed in a high-purity alumina crucible, heated to 800-850°C in a tube furnace at a heating rate of 2.0-2.5°C / min, calcined at a constant temperature for 2-4 h in an air atmosphere, and then cooled to room temperature at a cooling rate of 1.0-1.5°C / min. The powder was mixed with anhydrous ethanol in a weight ratio of 1:5 and placed in a polyurethane-lined ball mill. Zirconia balls with a diameter of 3 to 5 mm were added as grinding media, and the ball-to-material ratio was 5:

1. The mixture was wet ball milled at a speed of 150 to 180 rpm for 40 to 48 hours. The milled suspension was sieved through a 200-mesh sieve to remove large particles, filtered, and washed with ethanol 34 times. The filter cake was dried under vacuum at 60 to 70°C for 10 to 12 hours to obtain an average particle size.

5. The ceramic raw material for capacitors according to claim 2, characterized in that: The detailed process of A3 is as follows: three different Sr contents are prepared in parts by weight. Precursor solution, specifically: Precursors and The precursors were mixed in mass ratios of 9:1, 8:2 and 7:3, and a mixed solvent of anhydrous ethanol and glacial acetic acid in a volume ratio of 4:1 was added respectively, and the sol concentration was 0.10~0.15 mol / L; 8.0–10.0 parts of core particles were dispersed in 100–120 parts of ethanol and sonicated for 15–20 min to form a homogeneous suspension; At 35~45℃, slowly add 30~35 parts of the first precursor solution to the The pH value of the core particle suspension was controlled at 9.5-10.5, and the suspension was stirred for 60-90 min to allow the precursor to be evenly deposited on the surface of the core particles. The suspension was centrifuged at a speed of 5000-6000 rpm for 10-15 min, and the precipitate was washed with ethanol three times and dried at 60°C for 4-6 h. The second and third precursor solutions were used in the same manner for coating. Finally, the obtained particles were dispersed in ethanol and 25-30 parts of a solution with a higher Sr content were added. The precursor solution is prepared by Precursors and The precursors were mixed in a mass ratio of 6:4 for the outermost layer deposition, the pH value was maintained at 10.0-11.0, stirred for 4-6 h, centrifuged, washed, and dried at 70°C for 8-10 h to obtain composite particles with a multilayer structure.

6. The ceramic raw material for capacitors according to claim 2, wherein: The detailed process of A4 is as follows: the multilayer composite particles obtained in A3 are placed in a high-purity alumina crucible, heated to 900-950°C in a tube furnace at a heating rate of 1.5-2.0°C / min, and calcined at a constant temperature for 3-5 hours in a mixed atmosphere of nitrogen and oxygen with a volume ratio of 95:5 at a flow rate of 80-100 mL / min to promote the diffusion of elements between the layers to form a continuous gradient structure; after calcination, the temperature is cooled to 600°C at a cooling rate of 1.0-1.5°C / min, and then cooled to room temperature at a rate of 2.0-3.0°C / min; and the obtained product is obtained after light grinding. Gradient layered particles.

7. The ceramic raw material for capacitors according to claim 1, wherein: The rare earth oxide is selected from 、 and One or more of; The transition metal oxide is selected from 、 and CuO; The alkaline earth metal oxide is selected from one or more of MgO and CaO; The low melting point sintering aid is selected from Composite oxides, with a mass ratio of (1.0~2.0):(0.8~1.5):(0.7~1.0); The organic processing aid includes a dispersant, a binder, a plasticizer, an antistatic agent and a defoamer, wherein the dispersant is 1.0-2.0 parts of ammonium polyacrylate, the binder is 2.0-4.0 parts of hydroxypropyl methylcellulose, the plasticizer is 1.5-3.0 parts of polyethylene glycol 600, the antistatic agent is 0.2-0.5 parts of sodium dodecylbenzene sulfonate, and the defoamer is 0.1-0.3 parts of polydimethylsiloxane; The solvent is a mixture of deionized water, ethanol and acetone, with a volume ratio of (3.0-4.0):1:

1.

8. The method for preparing a ceramic raw material for a capacitor according to claim 1, wherein: The following steps are involved: S1. Dry material pretreatment: The gradient layered particles were dried at 80-90°C and -0.08-0.09 MPa in a vacuum environment for 12-16 hours. The rare earth oxides, transition metal oxides, alkaline earth metal oxides, and low-melting-point sintering aids were dried at 105-110°C for 4-6 hours. All dried powders were sieved through a 400-mesh sieve to remove agglomerates. S2. Dry material mixing: Place the pretreated inorganic raw materials in a polytetrafluoroethylene mixer according to the proportion, and dry mix them at 30-40 rpm for 2-3 hours in a nitrogen atmosphere with 15-20% humidity to ensure uniform distribution of the components; S3. Preparation of organic additive solution: First, prepare a deionized water / ethanol / acetone mixed solvent; directly dissolve the ammonium polyacrylate dispersant, dissolve the hydroxypropyl methylcellulose binder, polyethylene glycol 600 plasticizer, sodium dodecylbenzene sulfonate antistatic agent, and polydimethylsiloxane defoamer separately, then combine and stir at 450-550 rpm for 1.5-2 hours to form a homogeneous solution; S4. Wet mixing: Transfer the dry mix into a polyurethane ball mill, add the organic additive solution and 3-5 mm zirconia balls, set the ball-to-material ratio to 2:1, and ball mill at 150-200 rpm for 18-24 hours in a sealed state to achieve nano-scale dispersion; S5. Post-processing: The ball-milled slurry was filtered through a 100-mesh sieve, and then degassed at -0.08 to -0.09 MPa in a vacuum atmosphere for 15 to 20 minutes. The slurry was allowed to stand for 24 hours to achieve rheological equilibrium, thereby obtaining a ceramic raw material for capacitors.

9. Use of the ceramic raw material for capacitors according to claim 1 in dielectric constant ceramic capacitors, temperature compensation capacitors, radio frequency ceramic capacitors and high frequency filters.

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