Ceramic raw material for capacitor as well as preparation method and application of ceramic raw material

Abstract

The invention relates to the field of capacitor ceramic materials, provides a ceramic raw material for a capacitor and a preparation method of the ceramic raw material, and aims to solve the problem that high dielectric constant and temperature stability of a traditional ceramic material are difficult to consider at the same time. The ceramic raw material takes Ba1-XSrXTiO3 gradient layered particles as a main body, and is supplemented with a rare earth oxide, a transition metal oxide, an alkaline earth metal oxide, a low-melting-point sintering aid and an organic processing aid. The gradient particle has a concentric layer structure of core-middle layer-shell, and the x value is gradually increased along the radial direction to form continuous Curie temperature distribution. The preparation method comprises the steps of precursor coprecipitation, calcination, layer-by-layer deposition, secondary calcination and the like, and a high-uniformity ceramic raw material is obtained through wet ball milling and rheological regulation. The material has high dielectric property and wide temperature stability, is suitable for various capacitor devices, and has good application prospects.

Description

Technical Field

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

[0002] As a basic component in electronic information technology, capacitors are widely used in many key fields such as communication terminals, automotive electronics, power equipment, smart home appliances, and aerospace. Especially in high-performance products such as multilayer ceramic capacitors (MLCCs), temperature-compensating capacitors, and radio frequency filters, increasingly stringent performance requirements are imposed on the ceramic dielectric materials used therein. During the actual application process, capacitors need to work stably for a long time in frequently starting and stopping, electrothermal coupling, and wide-temperature environments, which pose double standards for the dielectric properties of ceramic materials: on the one hand, the material is required to have a high dielectric constant to achieve a larger capacitance density and device miniaturization; on the other hand, it is required to maintain good temperature stability in a wide temperature range such as -55°C to +125°C to ensure that the capacitance value change is controlled within the standard tolerance range. In addition, the ceramic material also needs to have excellent sintering densification, structural uniformity, and process adaptability to meet the requirements of modern electronic manufacturing processes for high reliability and batch consistency. Therefore, material design and structure regulation centered around these two key indicators of high dielectric constant and temperature stability are not only the core path to improving the comprehensive performance of capacitors but also the key support for promoting the localization and intelligent development of high-end electronic devices.

[0003] Currently, although BaTiO3-based ceramics have been widely studied as the mainstream dielectric material in recent years, there are still significant deficiencies in the prior art in simultaneously meeting high dielectric constant and temperature stability, which mainly stems from the insufficient understanding of the performance coupling mechanism between the two in material design, resulting in the sacrifice of one performance when improving the other. For example, Chinese Patent No. N105084891A discloses a medium-temperature sintered lead-free multilayer ceramic capacitor dielectric material and its use in multilayer ceramic capacitors. Although its dielectric constant has been improved, the capacitance fluctuates greatly in a wide temperature range and it is difficult to meet the temperature tolerance requirements of X7R or X8R type capacitors. Fundamentally, this is caused by uneven lattice distortion and unstable local polarization response due to disordered doping inside the material. On the other hand, some studies have also tried to use the solid solution regulation strategy to introduce SrTiO3 components to improve temperature stability, but they failed to achieve composition gradient regulation, and there are still obvious stress concentration and uneven thermal expansion problems inside the material, which limits the synergistic improvement of its overall performance. Therefore, there is an urgent need to adopt new structural design means to construct a multilayer ceramic particle structure with gradient distribution and achieve continuous composition transition and stress relief at the microscale, so as to essentially achieve the synergistic optimization of dielectric constant and temperature stability. Summary of the Invention

[0004] (1) Technical problems solved 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.

[0005] (2) Technical solution In order to achieve the above object, the present invention provides the following technical solutions: A ceramic raw material for capacitors, comprising the following raw materials in parts by weight: Ba1- X Sr X TiO3 gradient layered particles 85~95 parts; rare earth oxides 1.3~3.5 parts; transition metal oxides 2.0~4.9 parts; alkaline earth metal oxides 2.5~6.0 parts; low melting point sintering aids 2.5~6.5 parts; organic processing aids 4.8~9.8 parts; solvents 25~40 parts; The Ba1- X Sr X The characteristics of TiO3 gradient layered particles are as follows: 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 from the inside to the outside along the radial direction, 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 Ba1- X Sr X The average size of TiO3 gradient layered particles is 0.5~0.8 μm.

[0006] Further, the Ba1- X Sr X The preparation of TiO3 gradient layered particles comprises the following steps: A1. BaTiO3 precursor and SrTiO3 precursor were prepared by co-precipitation method; A2. calcining the BaTiO3 precursor at 800-850°C for 2-4 hours to obtain BaTiO3 core particles; A3. Using the layer-by-layer deposition method, BaTiO3 core particles are used as the substrate, and Ba1- X Sr X TiO3 interlayer and Sr-rich Ba1- X Sr X TiO3 outer layer; A4. The obtained particles were calcined at 900-950 ° C for 3 to 5 hours and lightly ground to obtain Ba1-X Sr X SrTiO3 gradient laminated particles.

[0007] Furthermore, the detailed process of A1 is as follows: By weight, 10.0 - 12.0 parts of tetrabutyl titanate and 40.0 - 50.0 parts of absolute ethanol are weighed, and stirred at a rate of 450 - 550 rpm for 10 - 15 min under an ice - water bath condition of 4 - 8 °C to form a titanium source solution; simultaneously, 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 dropping rate of 3 - 5 mL / min. After reacting for 30 - 40 min, 25.0 - 28.0 parts of ammonia water with a concentration of 25 - 28 wt% is added to adjust the pH value to 10.0 - 11.0 to form a white BaTiO3 precursor suspension; the strontium source solution is added dropwise to another portion of the titanium source solution in the same method to prepare a SrTiO3 precursor suspension; the two suspensions are aged at room temperature for 15 - 20 h respectively, then filtered by suction, washed 6 - 8 times with deionized water until the pH value of the filtrate is 7.0 - 7.5, and the obtained filter cake is dried at 80 - 90 °C for 12 - 16 h, ground through a 400 - mesh sieve to obtain BaTiO3 precursor powder and SrTiO3 precursor powder respectively.

[0008] Furthermore, the detailed process of A2 is as follows: By weight, the BaTiO3 precursor powder is placed in a high - purity alumina crucible, heated to 800 - 850 °C in a tubular furnace at a heating rate of 2.0 - 2.5 °C / min, and calcined at a constant temperature in an air atmosphere for 2 - 4 h, then cooled to room temperature at a cooling rate of 1.0 - 1.5 °C / min; the calcined BaTiO3 powder and absolute ethanol are mixed at a weight ratio of 1:5, placed in a polyurethane - lined ball - milling tank, 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 - milled at a rotation speed of 150 - 180 rpm for 40 - 48 h; the ball - milled suspension is passed through a 200 - mesh sieve to remove large particles, filtered by suction and washed 3 - 4 times with ethanol, and the obtained filter cake is dried in a vacuum environment at 60 - 70 °C for 10 - 12 h to obtain an average particle size.

[0009] Furthermore, the detailed process of A3 is as follows: By weight, three different Sr - content Ba1 - X Sr XTiO3 precursor solution, specifically: Mix BaTiO3 precursor and SrTiO3 precursor in a mass ratio of 9:1, 8:2, and 7:3, and add them to a mixed solvent of anhydrous ethanol and glacial acetic acid with a volume ratio of 4:1. The sol concentration is 0.10 - 0.15 mol / L; Disperse 8.0 - 10.0 parts of BaTiO3 core particles in 100 - 120 parts of ethanol, and ultrasonically treat for 15 - 20 min to form a uniform suspension; At 35 - 45 °C, slowly drip 30 - 35 parts of the first precursor solution at a rate of 2 - 3 mL / min into the BaTiO3 core particle suspension, control the pH value at 9.5 - 10.5, and stir for 60 - 90 min to uniformly deposit the precursor on the surface of the core particles; Centrifuge at a centrifugation rate of 5000 - 6000 rpm for 10 - 15 min, wash the precipitate with ethanol 3 times, and dry at 60 °C for 4 - 6 h; Using the same method, successively perform coating treatment with the second and third precursor solutions; Finally, disperse the obtained particles in ethanol, and add 25 - 30 parts of Ba1- X Sr X TiO3 precursor solution. This solution is prepared by mixing BaTiO3 precursor and SrTiO3 precursor in a mass ratio of 6:4 for the outermost layer deposition, maintaining the pH value at 10.0 - 11.0, stirring for 4 - 6 h, centrifuging, washing, and drying at 70 °C for 8 - 10 h to obtain composite particles with a multi-layer structure.

[0010] Furthermore, the detailed process of A4 is as follows: By weight, place the multi-layer composite particles obtained from A3 above in a high-purity alumina crucible, heat up to 900 - 950 °C in a tube furnace at a heating rate of 1.5 - 2.0 °C / min, and keep it at a constant temperature for 3 - 5 h in a mixed atmosphere of nitrogen and oxygen with a volume ratio of 95:5 and a flow rate of 80 - 100 mL / min to promote the element diffusion between layers to form a continuous gradient structure; After calcination, cool down to 600 °C at a cooling rate of 1.0 - 1.5 °C / min, and then cool down to room temperature at a rate of 2.0 - 3.0 °C / min; After gently grinding, obtain Ba1- X Sr X TiO3 gradient laminated particles.

[0011] The present invention uses Ba1- X Sr XThe design of TiO3 gradient laminated particles is mainly used to enhance the dielectric properties and temperature stability of ceramic raw materials in capacitor applications. By reasonably constructing a triple structure of a core layer, an intermediate transition layer, and a shell layer, the Sr element realizes a step-by-step transition distribution from the core to the shell inside the particles, 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 core layer in the gradient laminated structure is mainly composed of BaTiO3 with a low Sr content, maintaining a high dielectric response ability; the intermediate transition layer forms a buffer zone by moderately increasing the Sr ratio, reducing the lattice discontinuity caused by sudden composition changes; the shell layer is rich in Sr components, which helps to optimize the thermal response characteristics and temperature tolerance ability of the material. The above design precisely controls the composition of each layer through a layer-by-layer deposition process, and combines the calcination diffusion process to form a gradient structure with continuous transition and clear interfaces, avoiding the contradiction that it is difficult to balance the dielectric constant and temperature stability in single-component ceramics while improving the overall performance of the material. In addition, the gradient particles cooperate with components such as rare earth oxides, transition metal oxides, alkaline earth metal oxides, and low-melting-point sintering aids, further optimizing the structural uniformity and forming stability of the ceramic raw materials on the basis of ensuring the adaptability of the high-density sintering process. This technical solution shows significant advantages in material microstructure regulation, process adaptability, and performance synergistic integration, providing an effective solution path to meet the comprehensive performance requirements of high-reliability capacitors for dielectric materials.

[0012] Further, the rare earth oxide is selected from one or more of La2O3, Gd2O3, and Y2O3.

[0013] The transition metal oxide is selected from one or more of ZrO2, MnO2, and CuO.

[0014] The alkaline earth metal oxide is selected from one or more of MgO, CaO, and Al2O3.

[0015] The low-melting-point sintering aid is selected from the Bi2O3-ZnO-B2O3 composite oxide, and its mass ratio is (1.0~2.0):(0.8~1.5):(0.7~1.0).

[0016] The organic processing aids include a dispersant, a binder, a plasticizer, an antistatic agent, and a defoaming agent. Among them, 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 dodecylbenzenesulfonate, and the defoaming agent is 0.1~0.3 parts of polydimethylsiloxane.

[0017] The solvent is a mixture of deionized water, ethanol, and acetone, and its volume ratio is (3.0~4.0):1:1.

[0018] The present invention also provides a method for preparing a ceramic raw material for a capacitor, which is characterized by comprising the following steps: S1. Dry material pretreatment: placing Ba1- X Sr X TiO3 gradient layer particles in a vacuum environment at 80-90 °C and -0.08 to -0.09 MPa for drying for 12-16 hours; drying rare earth oxides, transition metal oxides, alkaline earth metal oxides, and low melting point sintering aids at 105-110 °C for 4-6 hours respectively; screening all dried powders through a 400-mesh sieve to remove agglomerates; S2. Dry material mixing: placing the pretreated inorganic raw materials in a polytetrafluoroethylene mixer according to the ratio, and dry mixing at a rotation speed of 30-40 rpm for 2-3 hours in a nitrogen atmosphere with a humidity of 15-20% to ensure uniform distribution of components; S3. Preparation of organic additive solution: first prepare a deionized water / ethanol / acetone mixed solvent; directly dissolve ammonium polyacrylate dispersant, and dissolve and combine hydroxypropyl methylcellulose binder, polyethylene glycol 600 plasticizer, sodium dodecylbenzenesulfonate antistatic agent, and polydimethylsiloxane defoamer respectively, and stir at 450-550 rpm for 1.5-2 hours to form a homogeneous solution; S4. Wet mixing: transferring the dry mixed material into a polyurethane ball milling tank, adding the organic additive solution and 3-5 mm zirconia balls, setting the ball-to-material ratio to 2:1, and ball milling at 150-200 rpm for 18-24 hours in a sealed state to achieve nanoscale dispersion; S5. Post-treatment: filtering the ball milled slurry through a 100-mesh sieve, vacuum degassing at -0.08 to -0.09 MPa for 15-20 minutes, and finally standing for 24 hours to reach rheological equilibrium to obtain a ceramic raw material for a capacitor.

[0019] The present invention also discloses the 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.

[0020] The present invention adopts the design of multi-component synergistic doping and multi-step composite dispersion, which is mainly used to enhance the comprehensive properties such as the forming stability, sintering adaptability and microstructure uniformity of ceramic raw materials in capacitor applications. By reasonably matching rare earth oxides, transition metal oxides, alkaline earth metal oxides and Bi2O3-ZnO-B2O3 composite low-melting-point sintering aids, a variety of functional ions are introduced to form a synergistic regulation effect on the lattice structure and sintering behavior of the ceramic matrix. Among them, rare earth oxides help to stabilize the crystal phase and regulate the dielectric response, transition metal oxides play a role in regulating the grain boundary activity and charge migration, and alkaline earth metal oxides improve the overall micro-uniformity by affecting the grain growth behavior during sintering. Together with the low-melting-point composite sintering aids, they jointly improve the densification process and interface bonding state of the material, effectively reducing the sintering temperature and enhancing the structural integrity. During the processing, by adopting a composite organic additive system composed of ammonium polyacrylate, hydroxypropyl methylcellulose, polyethylene glycol 600, sodium dodecylbenzenesulfonate and polydimethylsiloxane, the rheological stability and wettability of the slurry are improved on the basis of the complementary functions of various additives. Combined with a composite solvent environment constructed by deionized water, ethanol and acetone in a specific volume ratio, the distribution uniformity and interface wetting ability of the powder during mixing and dispersion are effectively improved. In the preparation process, the raw materials are initially homogenized by low-speed dry mixing, and then combined with steps such as wet ball milling, vacuum degassing and rheological static setting to ensure that the slurry has good fluidity and forming consistency in the nanoscale dispersion state. Various components not only complement each other in function, but also achieve a high degree of integration and synergy at the structural level, thus significantly improving the adaptability and practical application stability of ceramic raw materials in various capacitor products.

[0021] (3) Beneficial technical effects 1. Through the synergistic design of the Ba1- X Sr X TiO3 gradient structure and various functional oxides, the present invention realizes the simultaneous improvement of dielectric properties and temperature stability, and significantly enhances the structural uniformity and application stability of capacitor materials. Description of the drawings

[0022] Figure 1 This is the morphology diagram of the Ba1- X Sr X TiO3 gradient layered particles prepared in Example 1 of the present invention. Specific embodiments

[0023] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention.

[0024] Embodiment 1: A ceramic raw material for a capacitor, comprising the following raw materials in parts by weight: 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; 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.

[0025] Ba1- X Sr X The preparation of TiO3 gradient layered particles comprises the following steps: 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 by weight, 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 were 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 in the same way to prepare a SrTiO3 precursor suspension; the two suspensions were aged at room temperature for 15 h, 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, ground through a 400-mesh sieve to obtain BaTiO3 precursor powder and SrTiO3 precursor powder, respectively.

[0026] A2. The BaTiO3 precursor was calcined at 800 °C for 2 hours to obtain BaTiO3 core particles. The detailed process is as follows: By weight, the BaTiO3 precursor powder was placed in a high-purity alumina crucible and heated to 800 °C in a tube furnace at a heating rate of 2.0 °C / min. It was calcined at a constant temperature in an air atmosphere for 2 h, and then cooled to room temperature at a cooling rate of 1.0 °C / min. The calcined BaTiO3 powder was mixed with absolute ethanol at a weight ratio of 1:5, placed in a polyurethane-lined ball mill jar, 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 150 rpm for 40 h. The ball-milled suspension was passed through a 200-mesh sieve to remove large particles, filtered by suction and washed with ethanol 3 times. The obtained filter cake was dried in a vacuum environment at 60 °C for 10 h to obtain the average particles.

[0027] A3. Using the layer-by-layer deposition method, with the BaTiO3 core particles as the substrate, Ba1- X Sr X TiO3 intermediate layers and Sr-rich Ba1- X Sr X TiO3 outer layers were deposited in sequence. The detailed process is as follows: By weight, three different Sr-content Ba1- X Sr X TiO3 precursor solutions were prepared respectively. Specifically, the BaTiO3 precursor and the SrTiO3 precursor were mixed at a mass ratio of 9:1, 8:2, and 7:3, and a mixed solvent of absolute ethanol and glacial acetic acid with a volume ratio of 4:1 was added respectively. The sol concentration was 0.10 mol / L. 8.0 parts of the BaTiO3 core particles were dispersed in 100 parts of ethanol and ultrasonically treated for 15 min to form a uniform suspension. At 35 °C, 30 parts of the first precursor solution were slowly added dropwise to the BaTiO3 core particle suspension at a rate of 2 mL / min, and the pH value was controlled at 9.5. Stirring was carried out for 60 min to uniformly deposit the precursor on the surface of the core particles. Centrifugation was carried out at a centrifugal rate of 5000 rpm for 10 min, and the precipitate was washed with ethanol 3 times and dried at 60 °C for 4 h. In the same way, the second and third precursor solutions were used for coating treatment in sequence. Finally, the obtained particles were dispersed in ethanol, and 25 parts of a Ba1- X Sr X TiO3 precursor solution with a higher Sr content, which was prepared by mixing the BaTiO3 precursor and the SrTiO3 precursor at a mass ratio of 6:4, was used for the outermost layer deposition. The pH value was maintained at 10.0, stirring was carried out for 4 h, followed by centrifugal separation, washing, and drying at 70 °C for 8 h to obtain composite particles with a multi-layer structure.

[0028] A4. Calcinate the obtained particles at 900 °C for 3 hours, and through mild grinding treatment, obtain Ba1- X Sr X TiO3 gradient layered particles. The detailed process is as follows: By weight, place the multi-layer composite particles obtained in A3 above in a high-purity alumina crucible, heat it to 900 °C in a tube furnace at a heating rate of 1.5 °C / min, and under a mixed atmosphere of nitrogen and oxygen with a volume ratio of 95:5 and a flow rate of 80 mL / min, keep it at a constant temperature and calcine for 3 h to promote the elemental diffusion between layers to form a continuous gradient structure; after calcination, cool it to 600 °C at a cooling rate of 1.0 °C / min, and then cool it to room temperature at a rate of 2.0 °C / min; after mild grinding, obtain Ba1- X Sr X TiO3 gradient layered particles.

[0029] The rare earth oxide in this example is selected from La2O3; the transition metal oxide is selected from ZrO2; the alkaline earth metal oxide is selected from MgO; the low melting point sintering aid is selected from the Bi2O3-ZnO-B2O3 composite oxide, and its mass ratio is 1.0:0.8:0.7.

[0030] The organic processing aids in this example include a dispersant, a binder, a plasticizer, an antistatic agent, and an antifoaming agent. Among them, 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 part of sodium dodecylbenzenesulfonate, and the antifoaming agent is 0.1 part of polydimethylsiloxane.

[0031] The solvent in this example is a mixture of deionized water, ethanol, and acetone, and its volume ratio is 3.0:1:1.

[0032] A preparation method of a ceramic raw material for a capacitor in this example is characterized by including the following steps: S1. Dry material pretreatment: Place the Ba1- X Sr X TiO3 gradient layered particles in a vacuum environment at 83 °C and -0.08 MPa for 13 hours; the rare earth oxide, transition metal oxide, alkaline earth metal oxide, and low melting point sintering aid are dried at 107 °C for 5 hours respectively; all the dried powders are 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 ratio, and dry mix for 2 hours at a rotation speed of 33 rpm in a nitrogen atmosphere with a humidity of 17% to ensure uniform distribution of the components; S3. Preparation of organic auxiliary agent solution: First, prepare a mixed solvent of deionized water / ethanol / acetone; ammonium polyacrylate dispersant is directly dissolved, and hydroxypropyl methylcellulose binder, polyethylene glycol 600 plasticizer, sodium dodecylbenzenesulfonate antistatic agent, and polydimethylsiloxane defoamer are dissolved separately and then combined, and stirred at 480 rpm for 1.7 hours to form a homogeneous solution; S4. Wet mixing: Transfer the dry mixture into a polyurethane ball milling tank, add the organic auxiliary agent solution and 4 mm zirconia balls, set the ball-to-material ratio to 2:1, and mill at 165 rpm for 20 hours under a sealed state to achieve nanoscale dispersion; S5. Post-treatment: After the ball-milled slurry is filtered through a 100-mesh sieve, vacuum degassing is carried out at -0.08 MPa for 17 minutes, and finally left standing for 24 hours to reach rheological equilibrium, obtaining ceramic raw materials for capacitors.

[0033] Figure 1 Shows the typical morphological characteristics of the Ba1- X Sr X TiO3 gradient layered particles prepared in Example 1 of the present invention. It can be observed that the particles are spherical-like with uniform particle size, and a concentric layered structure composed of an inner core layer, an intermediate transition layer, and an outer shell layer can be clearly seen on the surface, indicating that the layer-by-layer deposition and controlled calcination process adopted can successfully construct a gradient structure with continuous composition transition, providing a structural basis for realizing the synergistic optimization of the dielectric properties and temperature stability of the material.

[0034] Example 2: A ceramic raw material for a capacitor, comprising the following raw materials in parts by weight: Ba1- X Sr X 88 parts of Ba1- Sr X TiO3 gradient layered particles; 2.0 parts of rare earth oxide; 2.9 parts of transition metal oxide; 3.6 parts of alkaline earth metal oxide; 3.7 parts of low melting point sintering aid; 6.3 parts of organic processing aid; 30 parts of solvent; X The Ba1- X Sr X TiO3 gradient layered particles are characterized in that: 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-

[0035] The Ba1- X Sr X Preparation of TiO3 gradient layered particles includes the following steps: A1. Prepare BaTiO3 precursor and SrTiO3 precursor by coprecipitation method; the detailed process is as follows: By weight, weigh 10.6 parts of tetrabutyl titanate and 43.0 parts of absolute ethanol, stir at a rate of 480 rpm for 12 min in a 5°C ice-water bath to form a titanium source solution; at the same time, dissolve 7.8 parts of barium nitrate in 26.5 parts of deionized water to prepare a barium source solution, and dissolve 6.3 parts of strontium nitrate in 21.5 parts of deionized water to prepare a strontium source solution; under continuous stirring, slowly add the barium source solution to the titanium source solution at a dropping rate of 4 mL / min, after reacting for 33 min, add 25.9 parts of ammonia water with a concentration of 26 wt% to adjust the pH value to 10.3 to form a white BaTiO3 precursor suspension; use the same method to drop the strontium source solution into another portion of the titanium source solution to prepare a SrTiO3 precursor suspension; age the two suspensions at room temperature for 17 h respectively, then filter by suction, wash with deionized water 7 times until the pH value of the filtrate is 7.2, and dry the obtained filter cake at 83°C for 13 h, grind it through a 400-mesh sieve to obtain BaTiO3 precursor powder and SrTiO3 precursor powder respectively.

[0036] A2. Calcinate the BaTiO3 precursor at 815°C for 3 hours to obtain BaTiO3 core particles; the detailed process is as follows: By weight, place the BaTiO3 precursor powder in a high-purity alumina crucible, heat it to 815°C in a tubular furnace at a heating rate of 2.2°C / min, keep it at a constant temperature and calcinate for 3 h in an air atmosphere, and then cool it to room temperature at a cooling rate of 1.2°C / min; mix the calcined BaTiO3 powder and absolute ethanol in a weight ratio of 1:5, place them in a polyurethane-lined ball milling tank, add zirconia balls with a diameter of 4 mm as grinding media, the ball-to-material ratio is 5:1, and wet ball mill at a rotation speed of 159 rpm for 42 h; pass the ball-milled suspension through a 200-mesh sieve to remove large particles, filter by suction and wash with ethanol 3 times, and dry the obtained filter cake in a vacuum environment at 63°C for 11 h to obtain an average particle size.

[0037] A3. Using the layer-by-layer deposition method, with BaTiO3 core particles as the substrate, sequentially deposit a Ba1- X Sr X TiO3 intermediate layer and a Sr-rich Ba1- X Sr X TiO3 outer layer; the detailed process is as follows: By weight, prepare three Ba1- X Sr XTiO3 precursor solution, specifically: Mix BaTiO3 precursor and SrTiO3 precursor in mass ratios of 9:1, 8:2, and 7:3, and respectively add a mixed solvent of absolute ethanol and glacial acetic acid with a volume ratio of 4:1. The sol concentration is 0.12 mol / L; Disperse 8.6 parts of BaTiO3 core particles in 106 parts of ethanol, and perform ultrasonic treatment for 17 min to form a uniform suspension; At 38 °C, slowly drop 32 parts of the first precursor solution into the BaTiO3 core particle suspension at a rate of 2 mL / min, control the pH value at 9.8, and stir for 69 min to uniformly deposit the precursor on the surface of the core particles; Centrifuge at a centrifugation rate of 5300 rpm for 12 min, wash the precipitate with ethanol 3 times, and dry at 60 °C for 5 h; In the same way, use the second and third precursor solutions for coating treatment in sequence; Finally, disperse the obtained particles in ethanol, and add 27 parts of Ba1- with a higher Sr content X Sr X TiO3 precursor solution. This solution is prepared by mixing BaTiO3 precursor and SrTiO3 precursor in a mass ratio of 6:4 for the outermost layer deposition. The pH value is maintained at 10.3, stirred for 5 h, centrifuged, washed, and dried at 70 °C for 9 h to obtain composite particles with a multi-layer structure.

[0038] A4. Calcinate the obtained particles at 915 °C for 4 hours, and through mild grinding treatment, obtain Ba1- X Sr X TiO3 gradient layered particles. The detailed process is as follows: By weight, place the multi-layer composite particles obtained in A3 above in a high-purity alumina crucible, heat up to 915 °C in a tube furnace at a heating rate of 1.7 °C / min, and under a mixed atmosphere of nitrogen and oxygen with a volume ratio of 95:5 and a flow rate of 86 mL / min, keep the temperature constant and calcine for 4 h to promote the elemental diffusion between layers to form a continuous gradient structure; After calcination, cool down to 600 °C at a cooling rate of 1.2 °C / min, and then cool down to room temperature at a rate of 2.3 °C / min; After mild grinding, obtain Ba1- X Sr X TiO3 gradient layered particles.

[0039] The rare earth oxide in this example is selected from Gd2O3; The transition metal oxide is selected from ZrO2; The alkaline earth metal oxide is selected from CaO; The low-melting-point sintering aid is selected from the Bi2O3-ZnO-B2O3 composite oxide, and its mass ratio is 1.3:1.0:0.8.

[0040] The organic processing aids in this embodiment include a dispersant, a binder, a plasticizer, an antistatic agent, and an antifoaming agent. Among them, 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 dodecylbenzenesulfonate, and the antifoaming agent is 0.2 parts of polydimethylsiloxane.

[0041] The solvent in this embodiment is a mixture of deionized water, ethanol, and acetone, and their volume ratio is 3.3:1:1.

[0042] A method for preparing a ceramic raw material for a capacitor in this embodiment is characterized by including the following steps: S1. Dry material pretreatment: Place the Ba1- X Sr X TiO3 gradient layer particles in a vacuum environment at 80 °C and -0.08 MPa for 12 hours; the rare earth oxide, transition metal oxide, alkaline earth metal oxide, and low melting point sintering aid are dried at 105 °C for 4 hours respectively; all dried powders are 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 ratio, and dry mix at a rotation speed of 30 rpm for 2 hours in a nitrogen atmosphere with 15% humidity to ensure uniform distribution of components; S3. Preparation of organic aid solution: First, prepare a deionized water / ethanol / acetone mixed solvent; the ammonium polyacrylate dispersant is directly dissolved, and the hydroxypropyl methylcellulose binder, polyethylene glycol 600 plasticizer, sodium dodecylbenzenesulfonate antistatic agent, and polydimethylsiloxane antifoaming agent are dissolved and then combined, and stirred at 450 rpm for 1.5 hours to form a homogeneous solution; S4. Wet mixing: Transfer the dry mixed material into a polyurethane ball mill tank, add the organic aid solution and 3-mm zirconia balls, set the ball-to-material ratio to 2:1, and mill at 150 rpm for 18 hours in a sealed state to achieve nanoscale dispersion; S5. Post-treatment: After filtering the ball-milled slurry through a 100-mesh sieve, carry out vacuum defoaming at -0.08 MPa for 15 minutes, and finally let it stand for 24 hours to reach rheological equilibrium, obtaining the ceramic raw material for the capacitor.

[0043] Example 3: A ceramic raw material for a capacitor includes the following raw materials in parts by weight: Ba1- X Sr X 91 parts of TiO3 gradient layer particles; 2.6 parts of rare earth oxide; 3.7 parts of transition metal oxide; 4.6 parts of alkaline earth metal oxide; 4.9 parts of low melting point sintering aid; 7.8 parts of organic processing aid; 34 parts of solvent; Ba1- X Sr XThe TiO3 gradient laminated particles are characterized in that: the particles have a concentric laminated structure, including a core layer, an intermediate transition layer and a shell layer, wherein the x value of the core layer is 0.08, the x value of the intermediate transition layer gradually increases from inside to outside along the radial direction, the x value of the shell layer is 0.28, and the thickness ratio of the core layer, the intermediate transition layer and the shell layer is 6.6:1.1:1.5; Ba1- X Sr X The average size of the TiO3 gradient laminated particles is 0.7 μm.

[0044] The Ba1- X Sr X preparation of TiO3 gradient laminated particles of this embodiment includes the following steps: A1. The BaTiO3 precursor and SrTiO3 precursor are prepared by the co-precipitation method; the detailed process is as follows: by weight, 11.2 parts of tetrabutyl titanate and 46.0 parts of absolute ethanol are weighed, and stirred at a rate of 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 are dissolved in 28.0 parts of deionized water to prepare a barium source solution, and 6.6 parts of strontium nitrate are dissolved in 23.0 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 dropping rate of 4 mL / min. After reacting for 36 min, 26.8 parts of ammonia water with a concentration of 27 wt% is added to adjust the pH value to 10.6 to form a white BaTiO3 precursor suspension; the strontium source solution is added dropwise to another portion of the titanium source solution in the same way to prepare a SrTiO3 precursor suspension; the two suspensions are aged at room temperature for 18 h, then filtered by suction, washed 7 times with deionized water until the pH value of the filtrate is 7.3, and the obtained filter cake is dried at 86 °C for 14 h and ground through a 400-mesh sieve to obtain BaTiO3 precursor powder and SrTiO3 precursor powder respectively.

[0045] A2. The BaTiO3 precursor is calcined at 830 °C for 3 hours to obtain BaTiO3 core particles; the detailed process is as follows: by weight, the BaTiO3 precursor powder is placed in a high-purity alumina crucible, heated to 830 °C in a tube furnace at a heating rate of 2.3 °C / min, and calcined at a constant temperature in an air atmosphere for 3 h, and then cooled to room temperature at a cooling rate of 1.3 °C / min; the calcined BaTiO3 powder and absolute ethanol are mixed at a weight ratio of 1:5, placed in a polyurethane-lined ball mill jar, and zirconia balls with a diameter of 4 mm are added as grinding media, and the ball-to-material ratio is 5:1. Wet ball milling is carried out at a rotation speed of 168 rpm for 45 h; the ball-milled suspension is passed through a 200-mesh sieve to remove large particles, filtered by suction and washed 3 times with ethanol, and the obtained filter cake is dried in a vacuum environment at 66 °C for 11 h to obtain an average particle.

[0046] A3. Using the layer-by-layer deposition method, with BaTiO3 core particles as the substrate, successively deposit a Ba1- X Sr X TiO3 intermediate layer and a Sr-rich Ba1- X Sr X TiO3 outer layer; the detailed process is as follows: By weight, prepare three different Sr-content Ba1- X Sr X TiO3 precursor solutions. Specifically, mix the BaTiO3 precursor and the SrTiO3 precursor in a mass ratio of 9:1, 8:2, and 7:3, and respectively add a mixed solvent of anhydrous ethanol and glacial acetic acid with a volume ratio of 4:1. The sol concentration is 0.13 mol / L; Disperse 9.2 parts of BaTiO3 core particles in 112 parts of ethanol, and ultrasonically treat for 18 min to form a uniform suspension; At 41 °C, slowly drip 33 parts of the first precursor solution at a rate of 3 mL / min into the BaTiO3 core particle suspension, control the pH value at 10.1, and stir for 78 min to uniformly deposit the precursor on the surface of the core particles; Centrifuge at a centrifugation rate of 5600 rpm for 13 min, wash the precipitate with ethanol 3 times, and dry at 60 °C for 5 h; In the same way, successively use the second and third precursor solutions for coating treatment; Finally, disperse the obtained particles in ethanol, add 28 parts of a Ba1- X Sr X TiO3 precursor solution with a higher Sr content. This solution is prepared by mixing the BaTiO3 precursor and the SrTiO3 precursor in a mass ratio of 6:4 for the outermost layer deposition. Maintain the pH value at 10.6, stir for 5 h, centrifuge and separate, wash, and dry at 70 °C for 9 h to obtain composite particles with a multi-layer structure.

[0047] A4. Calcinate the obtained particles at 930 °C for 4 hours, and through mild grinding treatment, obtain Ba1- X Sr X TiO3 gradient layered particles. The detailed process is as follows: By weight, place the multi-layer composite particles obtained in A3 above in a high-purity alumina crucible, heat up to 930 °C in a tube furnace at a heating rate of 1.8 °C / min, and under a mixed atmosphere of nitrogen and oxygen with a volume ratio of 95:5 and a flow rate of 92 mL / min, keep the temperature constant and calcine for 4 h to promote the element diffusion between layers to form a continuous gradient structure; After calcination, cool down to 600 °C at a cooling rate of 1.3 °C / min, and then cool down to room temperature at a rate of 2.6 °C / min; After mild grinding, obtain Ba1- X Sr X TiO3 gradient layered particles.

[0048] The rare earth oxide in this embodiment is selected from Y2O3; the transition metal oxide is selected from CuO; the alkaline earth metal oxide is selected from Al2O3; the low melting point sintering aid is selected from the Bi2O3-ZnO-B2O3 composite oxide, and its mass ratio is 1.6:1.2:0.9.

[0049] The organic processing aids in this embodiment include a dispersant, a binder, a plasticizer, an antistatic agent, and an antifoaming agent. Among them, 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 dodecylbenzenesulfonate, and the antifoaming agent is 0.2 parts of polydimethylsiloxane.

[0050] The solvent in this embodiment is a mixture of deionized water, ethanol, and acetone, and their volume ratio is 3.6:1:1.

[0051] A method for preparing a ceramic raw material for a capacitor in this embodiment is characterized by including the following steps: S1. Dry material pretreatment: Place the Ba1- X Sr X TiO3 gradient layer particles in a vacuum environment at 90 °C and -0.09 MPa for 16 hours; the rare earth oxide, transition metal oxide, alkaline earth metal oxide, and low melting point sintering aid are dried at 110 °C for 6 hours respectively; all dried powders are 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 ratio, and dry mix at a rotation speed of 40 rpm for 3 hours in a nitrogen atmosphere with 20% humidity to ensure uniform distribution of components; S3. Preparation of organic aid solution: First, prepare a mixed solvent of deionized water / ethanol / acetone; the ammonium polyacrylate dispersant is directly dissolved, and the hydroxypropyl methylcellulose binder, polyethylene glycol 600 plasticizer, sodium dodecylbenzenesulfonate antistatic agent, and polydimethylsiloxane antifoaming agent are dissolved and then combined, and stirred at 550 rpm for 2 hours to form a homogeneous solution; S4. Wet mixing: Transfer the dry mixture into a polyurethane ball mill tank, add the organic aid solution and 5-mm zirconia balls, set the ball-to-material ratio to 2:1, and mill at 200 rpm for 24 hours in a sealed state to achieve nanoscale dispersion; S5. Post-treatment: After the ball-milled slurry is filtered through a 100-mesh sieve, it is vacuum degassed at -0.09 MPa for 20 minutes, and finally left standing for 24 hours to reach rheological equilibrium, obtaining the ceramic raw material for the capacitor.

[0052] Example 4: A ceramic raw material for a capacitor, including the following raw materials in parts by weight: Ba1- X Sr X95 parts of TiO3 gradient laminated particles; 3.5 parts of rare earth oxide; 4.9 parts of transition metal oxide; 6.0 parts of alkaline earth metal oxide; 6.5 parts of low melting point sintering aid; 9.8 parts of organic processing aid; 40 parts of solvent; Ba1- X Sr X The TiO3 gradient laminated particles are characterized in that: the particles have a concentric laminated structure, including a core layer, an intermediate transition layer and a shell layer, wherein the x value of the core layer is 0.10, the x value of the intermediate transition layer gradually increases from inside to outside along the radial direction, the x value of the shell layer is 0.30, and the thickness ratio of the core layer, the intermediate transition layer and the shell layer is 7.0:1.2:1.6; Ba1- X Sr X The average size of the TiO3 gradient laminated particles is 0.8 μm.

[0053] The Ba1- X Sr X preparation of TiO3 gradient laminated particles in this example includes the following steps: A1. Prepare BaTiO3 precursor and SrTiO3 precursor by coprecipitation method; the detailed process is as follows: in terms of weight parts, weigh 12.0 parts of tetrabutyl titanate and 50.0 parts of absolute ethanol, stir at a rate of 550 rpm for 15 min in an 8°C ice-water bath to form a titanium source solution; at the same time, dissolve 8.5 parts of barium nitrate in 30.0 parts of deionized water to prepare a barium source solution, and dissolve 7.0 parts of strontium nitrate in 25.0 parts of deionized water to prepare a strontium source solution; under continuous stirring, slowly add the barium source solution to the titanium source solution at a dropping rate of 5 mL / min, after reacting for 40 min, add 28.0 parts of 28 wt% ammonia water to adjust the pH value to 11.0 to form a white BaTiO3 precursor suspension; use the same method to drop the strontium source solution into another portion of the titanium source solution to prepare a SrTiO3 precursor suspension; age the two suspensions at room temperature for 20 h respectively, then filter by suction, wash with deionized water 8 times until the pH value of the filtrate is 7.5, and dry the obtained filter cake at 90°C for 16 h, and grind it through a 400-mesh sieve to obtain BaTiO3 precursor powder and SrTiO3 precursor powder respectively.

[0054] A2. The BaTiO3 precursor was calcined at 850 °C for 4 hours to obtain BaTiO3 core particles. The detailed process is as follows: By weight, the BaTiO3 precursor powder was placed in a high-purity alumina crucible and heated to 850 °C in a tube furnace at a heating rate of 2.5 °C / min, and then calcined at a constant temperature in an air atmosphere for 4 h. Subsequently, it was cooled to room temperature at a cooling rate of 1.5 °C / min. The calcined BaTiO3 powder was mixed with absolute ethanol at a weight ratio of 1:5, placed in a polyurethane-lined ball milling tank, and zirconia balls with a diameter of 5 mm were added as the grinding medium. The ball-to-material ratio was 5:1, and wet ball milling was carried out at a rotation speed of 180 rpm for 48 h. The ball-milled suspension was passed through a 200-mesh sieve to remove large particles, filtered by suction and washed with ethanol 4 times. The obtained filter cake was dried in a vacuum environment at 70 °C for 12 h to obtain the average particles.

[0055] A3. Using the layer-by-layer deposition method, with the BaTiO3 core particles as the substrate, a Ba1- X Sr X TiO3 intermediate layer and a Sr-rich Ba1- X Sr X TiO3 outer layer were sequentially deposited. The detailed process is as follows: By weight, three different Sr-content Ba1- X Sr X TiO3 precursor solutions were prepared respectively. Specifically, the BaTiO3 precursor and the SrTiO3 precursor were mixed at a mass ratio of 9:1, 8:2, and 7:3, and then a mixed solvent of absolute ethanol and glacial acetic acid with a volume ratio of 4:1 was added, and the sol concentration was 0.15 mol / L. 10.0 parts of the BaTiO3 core particles were dispersed in 120 parts of ethanol and ultrasonically treated for 20 min to form a uniform suspension. At 45 °C, 35 parts of the first precursor solution were slowly added dropwise to the BaTiO3 core particle suspension at a rate of 3 mL / min, and the pH value was controlled at 10.5. Stirring was carried out for 90 min to uniformly deposit the precursor on the surface of the core particles. Centrifugation was carried out at a centrifugal rate of 6000 rpm for 15 min, and the precipitate was washed with ethanol 3 times and dried at 60 °C for 6 h. In the same way, the second and third precursor solutions were used for coating treatment in turn. Finally, the obtained particles were dispersed in ethanol, and 30 parts of a Ba1- X Sr X TiO3 precursor solution with a higher Sr content, which was prepared by mixing the BaTiO3 precursor and the SrTiO3 precursor at a mass ratio of 6:4, was used for the outermost layer deposition. The pH value was maintained at 11.0, stirring was carried out for 6 h, followed by centrifugal separation, washing, and drying at 70 °C for 10 h to obtain composite particles with a multi-layer structure.

[0056] A4. The obtained particles are calcined at 950 °C for 5 hours, and through mild grinding treatment, Ba1- X Sr X TiO3 gradient laminated particles are obtained. The detailed process is as follows: By weight, the multi-layer composite particles obtained in A3 above are placed in a high-purity alumina crucible, and the temperature is raised to 950 °C in a tube furnace at a heating rate of 2.0 °C / min. In a mixed atmosphere of nitrogen and oxygen with a volume ratio of 95:5 and a flow rate of 100 mL / min, it is calcined at a constant temperature for 5 h to promote the elemental diffusion between layers to form a continuous gradient structure; after calcination, it 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; after mild grinding, Ba1- X Sr X TiO3 gradient laminated particles are obtained.

[0057] In this example, 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; the low-melting-point sintering aid is selected from the Bi2O3-ZnO-B2O3 composite oxide, and its mass ratio is 2.0:1.5:1.0.

[0058] The organic processing aids in this example include a dispersant, a binder, a plasticizer, an antistatic agent, and a defoaming agent. Among them, 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 dodecylbenzenesulfonate, and the defoaming agent is 0.3 parts of polydimethylsiloxane.

[0059] The solvent in this example is a mixture of deionized water, ethanol, and acetone, and their volume ratio is 4.0:1:1.

[0060] This example also provides a preparation method for ceramic raw materials for capacitors, which is characterized by including the following steps: S1. Dry material pretreatment: Ba1- X Sr X TiO3 gradient laminated particles are placed in a vacuum environment at 86 °C and -0.09 MPa for 14 hours for drying; the rare earth oxide, transition metal oxide, alkaline earth metal oxide, and low-melting-point sintering aid are dried at 108 °C for 5 hours respectively; all dried powders are sieved through a 400-mesh screen to remove agglomerates; S2. Dry material mixing: The pretreated inorganic raw materials are placed in a polytetrafluoroethylene mixer according to the ratio, and dry-mixed at a rotation speed of 36 rpm for 3 hours in a nitrogen atmosphere with a humidity of 18% to ensure uniform distribution of the components; S3, preparation of organic additive solution: first prepare a mixed solvent of deionized water / ethanol / acetone; directly dissolve the ammonium polyacrylate dispersant, dissolve the hydroxypropyl methylcellulose binder, polyethylene glycol 600 plasticizer, sodium dodecylbenzene sulfonate antistatic agent and polydimethylsiloxane defoamer respectively, then combine and stir at 510 rpm for 1.8 hours to form a homogeneous solution; S4, wet mixing: the dry mixture was transferred into a polyurethane ball mill, and the organic additive solution and 4 mm zirconium oxide balls were added, the ball-to-material ratio was set to 2:1, and the mixture was ball milled at 180 rpm for 22 hours in a sealed state to achieve nano-scale dispersion; S5. Post-treatment: The ball-milled slurry was filtered through a 100-mesh sieve, and then degassed at -0.09 MPa for 18 minutes. Finally, it was allowed to stand for 24 hours to achieve rheological equilibrium, thereby obtaining a ceramic raw material for capacitors.

[0061] Comparative Example 1 It is basically the same as Example 1, except that Ba1- X Sr X TiO3 particles are not gradient layered structures, but uniform Ba 0.8 Sr 0.2 TiO3 particles do not form a three-layer structure of inner core layer, intermediate transition layer and outer shell layer.

[0062] Comparative Example 2 It 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.

[0063] Comparative Example 3 It is basically the same as Example 1, except that the final calcination temperature in step A4 is 980°C, which leads to excessive sintering of the particles and partial homogenization of the Sr gradient structure.

[0064] Comparative Example 4 The same as Example 1, except that in step A3, the layer-by-layer deposition method is not used, 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.

[0065] Comparative Example 5 It is basically the same as Example 1, except that no rare earth oxide is added (ie, the rare earth oxide is 0 parts), and the regulating effect of La2O3, Gd2O3 or Y2O3 on the lattice structure is lacking.

[0066] Comparative Example 6 Basically the same as Example 1, except that the low-melting-point sintering aid used is a single Bi2O3 instead of the Bi2O3-ZnO-B2O3 composite oxide, lacking the effect of the three components synergistically reducing the sintering temperature.

[0067] Comparative Example 7 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 Sr content gradient change.

[0068] Performance test: The aforementioned capacitor ceramic raw materials are transformed into testable ceramic dielectric materials through slurry preparation, forming, sintering, and electrode preparation. The specific steps are as follows: First, the obtained ceramic raw material slurry is subjected to secondary ball milling. 3mm zirconia balls are added to a polyurethane ball milling tank, with a ball-to-material ratio of 5:1, and ball milled at a speed of 180 rpm for 12 hours to ensure uniform dispersion of the slurry. Subsequently, degassing treatment is carried out, degassing for 20 minutes in a vacuum environment of -0.09 MPa to eliminate the bubbles in the slurry. The ceramic film is prepared by the tape casting method. The slurry is evenly coated on a polyester film carrier treated with silicone oil using an automatic tape casting machine. The height of the doctor blade is set at 200μm, the tape casting speed is 30 cm / min, and it is dried at room temperature for 24 hours to form a green sheet with a thickness of approximately 100μm. The green sheet is cut into 25mm×25mm square samples using a precision cutting machine, and 8 layers of green sheets are laminated using the lamination process, and hot pressed at 80°C and 20 MPa for 10 minutes to form a composite green blank. The composite green blank is subjected to pre-sintering treatment, heated to 400°C at a rate of 2°C / min in an oxygen atmosphere and held for 2 hours to remove the organic binder. Subsequently, high-temperature sintering is carried out. In a mixed atmosphere of nitrogen and oxygen with a volume ratio of 95:5, it is heated to 1250°C at a heating rate of 3°C / min and held for 2 hours, and then cooled to room temperature at a cooling rate of 2°C / min. The two sides of the sintered ceramic sheet are subjected to surface polishing treatment, polished successively with 1000, 2000, and 3000 mesh metallographic sandpapers until the surface finish reaches Ra≤0.5μm. Electrodes are prepared on both sides of the ceramic sheet by magnetron sputtering. First, a 20nm thick Ti adhesion layer is sputtered, and then a 200nm thick Pt electrode layer is sputtered, with an electrode diameter of 10mm. Specific test patterns, including parallel plate capacitor structures, interdigital capacitor structures, and microwave resonator structures, are fabricated on the top electrode using standard photolithography technology in cooperation with a mask. The electrode leads are connected to the test fixture using silver paste and fine gold wire through ultrasonic wire bonding. After the sample is dried in an oven at 150°C for 2 hours to remove surface adsorbed moisture, it is encapsulated in a test fixture in a constant temperature and humidity environment (25°C, relative humidity <30%) for various electrical property tests. The above process ensures that the prepared ceramic dielectric material has high density (relative density >95%), uniform microstructure, and good electrode adhesion, and can meet the requirements of various electrical tests.

[0069] Temperature Characteristics Test of Dielectric Properties: The temperature characteristics of ceramic dielectric materials were measured using a Novocontrol Concept 80 broadband dielectric spectrometer. The temperature range was -60°C to 150°C, and the test frequency was 100 Hz - 1 MHz. The ceramic sample was equipped with Pt electrodes to form a parallel-plate capacitor structure, and the dielectric constant (εr), dielectric loss (tanδ), and temperature coefficient of capacitance (TCC) of the sample were measured at different temperatures. The rate of change of the dielectric constant with temperature (TCεr) was calculated, and special attention was paid to the dielectric peak shape and diffusive phase transition characteristics near the Curie temperature (Tc) to evaluate the temperature stability of the material and analyze the mechanism of the gradient laminated structure in suppressing the temperature sensitivity of dielectric properties.

[0070] High-Frequency Dielectric Property Test: The complex dielectric constants (ε' and ε") and microwave dielectric loss (tanδmw) of ceramic materials were measured in the frequency range of 1 - 20 GHz using a Keysight N5242A PNA-X network analyzer combined with the split-post dielectric resonator method. The sample was prepared as a polished wafer with a thickness of 1 mm and placed in a special test fixture for S-parameter measurement. The dielectric parameters were extracted through standard algorithms. The quality factor (Q×f) value was calculated, and its correlation with the microstructure of the material was analyzed to evaluate the performance of the material in high-frequency filter, antenna, and resonator applications.

[0071] Characterization of Thermophysical Properties: The thermal properties of ceramic samples were measured using a NETZSCH DIL 402C thermomechanical analyzer and a DSC 404F3 differential scanning calorimeter. The measurement temperature range was 30 - 800°C, and the heating rate was 5°C / min under a nitrogen protection atmosphere. The linear thermal expansion coefficient (CTE), specific heat capacity (Cp), and thermal conductivity (λ) of the material were obtained, and the phase transition temperature and latent heat were determined.

[0072] Mechanical Property Test: The nano-mechanical properties of ceramic samples were tested using an Agilent G200 nanoindenter. A Berkovich indenter was used, with a maximum load of 2 mN, and the loading-holding-unloading time was 30 s - 10 s - 30 s. The load-displacement curve was analyzed by the Oliver-Pharr method to obtain the Young's modulus (E), hardness (H), fracture toughness (KIC), and elastic recovery rate of the material.

[0073] The properties of the ceramic materials in Examples 1 - 4 and Comparative Examples 1 - 7 are summarized in Table 1. It can be seen from the table that Comparative Example 1 did not use Ba1- X Sr XTiO3 gradient layered structure is not used, but uniform solid solution particles are used, resulting in insufficient regulation of the polarization response of the ceramic under temperature changes, which is 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 the dielectric constant, increased losses 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; Example 4 does not adopt a layer-by-layer deposition method but a one-time mixed deposition, resulting in discontinuous Sr distribution and unclear structural gradient, thereby triggering a 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 coordination of the performance; in Example 5, no rare earth oxides are added, and there is a lack of the ability to regulate the 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 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 properties and thermal properties, verifying the synergy of the ternary composite sintering aid system in improving sintering behavior; in Example 7, the gradient change 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 deteriorated 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.

[0074] Table 1 Performance of ceramic materials of Examples 1 to 4 and Comparative Examples 1 to 7

[0075] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that all equivalent structural changes made under the concept of the present invention and using the contents of the present invention specification and drawings should be covered within the scope of protection of the claims of the present invention.

Claims

1. A ceramic raw material for a capacitor, characterized in that, Comprising the following raw materials in parts by weight: Ba1- X Sr X 85 - 95 parts of Ba1 - X Sr X TiO3 gradient - layer 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; The Ba1- X Sr X TiO3 gradient layered particles are characterized in that the particles have a concentric layered structure, including a core layer, an intermediate transition layer, and a shell layer, wherein the x value of the core layer is 0.05 to 0.10, the x value of the intermediate transition layer gradually increases from inside to outside along the radial direction, the x value of the shell layer is 0.25 to 0.30, and the thickness ratio of the core layer, the intermediate transition layer, and the shell layer is 6.0 to 7.0:1.0 to 1.2:1.4 to 1.6; The described Ba1- X Sr X The average size of the TiO3 gradient laminated particles is 0.5 - 0.8 μm.

2. The ceramic raw material for a capacitor according to claim 1, characterized in that, The described preparation of Ba1- X Sr X TiO3 gradient layer particles comprises the following steps: A1. Prepare BaTiO3 precursor and SrTiO3 precursor by coprecipitation method; A2. Calcinate the BaTiO3 precursor at 800 - 850 °C for 2 - 4 hours to obtain BaTiO3 core particles; A3. Using the layer-by-layer deposition method, with BaTiO3 core particles as the substrate, successively deposit a Ba1- X Sr X TiO3 intermediate layer and a Sr-rich Ba1- X Sr X TiO3 outer layer; A4. The obtained particles are calcined at 900 - 950 °C for 3 - 5 hours, and through mild grinding treatment, Ba1- X Sr X TiO3 gradient layered particles are obtained.

3. The ceramic raw material for a capacitor according to claim 2, characterized in that, The detailed process of A1 is as follows: In parts by weight, weigh 10.0 - 12.0 parts of tetrabutyl titanate and 40.0 - 50.0 parts of absolute ethanol, and stir 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; simultaneously, dissolve 7.5 - 8.5 parts of barium nitrate in 25.0 - 30.0 parts of deionized water to prepare a barium source solution, and dissolve 6.0 - 7.0 parts of strontium nitrate in 20.0 - 25.0 parts of deionized water to prepare a strontium source solution; under continuous stirring, slowly add the barium source solution to the titanium source solution at a dropping rate of 3 - 5 mL / min, after reacting for 30 - 40 min, add 25.0 - 28.0 parts of ammonia water with a concentration of 25 - 28 wt% to adjust the pH value to 10.0 - 11.0 to form a white BaTiO3 precursor suspension; use the same method to drop the strontium source solution into another portion of the titanium source solution to prepare a SrTiO3 precursor suspension; age the two suspensions at room temperature for 15 - 20 h respectively, then filter by suction, wash with deionized water 6 - 8 times until the pH value of the filtrate is 7.0 - 7.5, and dry the obtained filter cake at 80 - 90 °C for 12 - 16 h, grind it through a 400 - mesh sieve to obtain BaTiO3 precursor powder and SrTiO3 precursor powder respectively.

4. A ceramic raw material for a capacitor according to claim 2, characterized in that, The detailed process of A2 is as follows: In parts by weight, place the BaTiO3 precursor powder in a high - purity alumina crucible, heat it to 800 - 850 °C in a tubular furnace at a heating rate of 2.0 - 2.5 °C / min, keep it at a constant temperature and calcine in air atmosphere for 2 - 4 h, then cool it to room temperature at a cooling rate of 1.0 - 1.5 °C / min; mix the calcined BaTiO3 powder and absolute ethanol according to a weight ratio of 1:5, place it in a polyurethane - lined ball - milling tank, add zirconia balls with a diameter of 3 - 5 mm as grinding media, the ball - to - material ratio is 5:1, and wet - mill at a rotation speed of 150 - 180 rpm for 40 - 48 h; pass the ball - milled suspension through a 200 - mesh sieve to remove large particles, filter by suction and wash with ethanol 3 - 4 times, and dry the obtained filter cake in a vacuum environment at 60 - 70 °C for 10 - 12 h to obtain an average particle size.

5. A ceramic raw material for a capacitor according to claim 2, characterized in that, The detailed process of A3 is as follows: by weight, prepare three different Sr-content Ba1- X Sr X TiO3 precursor solutions, specifically: mix BaTiO3 precursor and SrTiO3 precursor in a mass ratio of 9:1, 8:2, and 7:3, respectively, add a mixed solvent of absolute ethanol and glacial acetic acid with a volume ratio of 4:1, and the sol concentration is 0.10 - 0.15 mol / L; disperse 8.0 - 10.0 parts of BaTiO3 core particles in 100 - 120 parts of ethanol, and ultrasonically treat for 15 - 20 min to form a uniform suspension; Under the condition of 35 - 45 °C, 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, the pH value is controlled at 9.5 - 10.5, and stirred for 60 - 90 min to uniformly deposit the precursor on the surface of the core particles; centrifuged at a centrifugal rate of 5000 - 6000 rpm for 10 - 15 min, the precipitate is washed 3 times with ethanol and dried at 60 °C for 4 - 6 h; in the same way, the second and third precursor solutions are used for coating treatment in turn; finally, the obtained particles are dispersed in ethanol, and 25 - 30 parts of a Ba1- X Sr X TiO3 precursor solution, which is prepared by mixing BaTiO3 precursor and SrTiO3 precursor in a mass ratio of 6:4, is used for the outermost layer deposition, the pH value is 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 multi-layer structure.

6. The ceramic raw material for a capacitor according to claim 2, wherein, The detailed process of A4 is as follows: by weight, the multi-layer composite particles obtained from A3 above are placed in a high-purity alumina crucible, and heated in a tube furnace at a heating rate of 1.5 - 2.0 °C / min to 900 - 950 °C, and isothermally calcined for 3 - 5 h in a mixed atmosphere of nitrogen and oxygen with a volume ratio of 95:5 and a flow rate of 80 - 100 mL / min to promote the elemental diffusion between layers to form a continuous gradient structure; after calcination, it 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; after mild grinding, Ba1- X Sr X TiO3 gradient laminated particles are obtained.

7. A ceramic raw material for a capacitor according to claim 1, characterized in that, The rare - earth oxide is selected from one or more of La2O3, Gd2O3 and Y2O3; The transition - metal oxide is selected from one or more of ZrO2, MnO2 and CuO; The alkaline - earth metal oxide is selected from one or more of MgO, CaO and Al2O3; The low - melting - point sintering aid is selected from Bi2O3 - ZnO - B2O3 composite oxide, and its mass ratio is (1.0 - 2.0):(0.8 - 1.5):(0.7 - 1.0); The organic processing aids include a dispersant, a binder, a plasticizer, an antistatic agent, and an antifoaming agent. Among them, 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 dodecylbenzenesulfonate, and the antifoaming agent is 0.1 - 0.3 parts of polydimethylsiloxane; The solvent is a mixture of deionized water, ethanol, and acetone, and their volume ratio is (3.0 - 4.0):1:

1.

8. The preparation method of a ceramic raw material for a capacitor according to claim 1, characterized in that, It includes the following steps: S1. Pretreatment of dry materials: Place the Ba1- X Sr X TiO3 gradient laminated particles in a vacuum environment at 80 - 90 °C and -0.08 - 0.09 MPa for drying for 12 - 16 hours; dry the rare earth oxide, transition metal oxide, alkaline earth metal oxide and low melting point sintering aid at 105 - 110 °C for 4 - 6 hours respectively; screen all the dried powders through a 400-mesh sieve to remove agglomerates; S2. Dry mixing: Place the pretreated inorganic raw materials in a polytetrafluoroethylene mixer according to the ratio, and dry mix for 2 - 3 hours at a rotation speed of 30 - 40 rpm in a nitrogen atmosphere with a humidity of 15 - 20% to ensure uniform distribution of the components; S3. Preparation of the organic aid solution: First, prepare a mixed solvent of deionized water / ethanol / acetone; the ammonium polyacrylate dispersant is directly dissolved, and the hydroxypropyl methylcellulose binder, polyethylene glycol 600 plasticizer, sodium dodecylbenzenesulfonate antistatic agent, and polydimethylsiloxane antifoaming agent are dissolved separately and then combined, and stirred at 450 - 550 rpm for 1.5 - 2 hours to form a homogeneous solution; S4. Wet mixing: Transfer the dry mixture into a polyurethane ball milling tank, add the organic aid 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-level dispersion; S5. Post-treatment: After the ball-milled slurry is filtered through a 100-mesh sieve, vacuum degassing is carried out at -0.08 - 0.09 MPa for 15 - 20 minutes, and finally left to stand for 24 hours to reach rheological equilibrium, obtaining the ceramic raw material for capacitors.

9. The application of a ceramic raw material for a capacitor as described in claim 1 in a dielectric constant ceramic capacitor, a temperature compensation capacitor, a radio frequency ceramic capacitor, and a high-frequency filter.

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