A temperature-stable capacitor ceramic powder with a core-shell structure after sintering, its preparation method and application.

Abstract

This invention discloses a temperature-stable capacitor ceramic powder with a core-shell structure, its preparation method, and its application. It relates to the field of ceramic materials and their manufacturing technology. The main component is BaTiO3, which is doped with modifiers and glass powder. The modifiers include TiO2, NaCO3, and Nb2O5; the glass powders include Li-B-Si glass compounds and Bi-B glass compounds. By adding appropriate amounts of dopants in the formulation design, residual doped modified materials adhere to the surface of the grain shell when the dielectric layer is thick. When the dielectric layer becomes thinner, the weakened core-shell structure concentration gradient is compensated, maintaining a stable capacitance temperature change rate and low dielectric loss. This solves the problem of unstable capacitance temperature change rate and increased loss in current Pb-Ag internal electrode MLCCs with X7R characteristics sintered at medium and low temperatures for MLCCs with small size and large capacity.

Description

Technical Field

[0001] This invention relates to the field of ceramic materials and their manufacturing technology, specifically to a temperature-stable capacitor ceramic powder with a core-shell structure after sintering, its preparation method, and its application. Background Technology

[0002] Multilayer ceramic chip capacitors (MLCCs), characterized by temperature stability and large capacitance, are suitable for use in circuits such as switching power supplies, power amplifiers, and transmitters, serving functions such as bypassing, low-frequency coupling, power supply filtering, and DC blocking. They have wide applications in aerospace, marine, automotive, communications, satellite, and military equipment. With the iterative upgrading of electronic technology and the increasing demand year by year, MLCCs are developing towards larger capacitance, higher stability, higher reliability, and lower cost, while the thickness of the single-layer ceramic film dielectric is trending towards thinner layers.

[0003] Currently, barium titanate-based ceramic materials with X7R properties are the main materials for preparing this type of capacitor and have been extensively studied. Most are used in MLCC capacitors. These ceramic materials are mostly doped with barium titanate by rare earth oxides, alkaline earth metal oxides, carbonates, or transition metal oxides to form a core-shell microstructure, achieving capacitance temperature stability. The degree of temperature stability is determined by the grain core-shell structure concentration gradient of the barium titanate main crystalline phase. This core-shell structure concentration gradient is formed through doping and is affected by the type and quantity of dopants, the size of the main crystalline phase particles, and the sintering process. The same doping amount can form different core-shell microstructure concentration gradients under different preparation and sintering processes, resulting in different capacitance temperature change rates. During the preparation of MLCCs, the grinding process, ceramic film thickness, internal electrode composition, and sintering curve all weaken the core-shell microstructure concentration gradient to varying degrees, affecting the proportion of the material forming a "core-shell" structure, leading to a deterioration in the capacitance temperature change rate and increased losses. This phenomenon is more pronounced in the preparation of small-size, high-capacity MLCCs due to the thinning of the dielectric layer, and this problem restricts the development of MLCCs towards smaller sizes and larger capacities.

[0004] In the prior art, patent ZL201611170717.6 proposes a dielectric material for medium- and high-voltage X7R characteristic multilayer ceramic capacitors, patent ZL201010530760.5 proposes a reduction-resistant multilayer ceramic capacitor dielectric material, and patent ZL201710922478.3 proposes a ceramic dielectric material and its preparation method for high-voltage MLCCs. None of these patents mention the application of thin dielectric layer MLCCs. Patent CN 114999817 A, "A Dielectric Material for Thin Dielectric X7R Characteristic MLCCs and Its Preparation Method," describes a dielectric material suitable for manufacturing MLCC products with a dielectric thickness of 4μm or more and an operating voltage of 25V or higher. It uses base metal nickel or nickel alloy as the internal electrode and is sintered in a nitrogen-hydrogen reducing atmosphere at a sintering temperature of 1220–1260℃.

[0005] Currently, research and application of barium titanate-based ceramic materials with X7R characteristics sintered at medium and low temperatures for Pb-Ag internal electrode MLCCs mainly focus on formulation systems and doping modifications. Although the content of doping modifiers is precisely controlled, the process is not precisely controlled, resulting in unstable capacity temperature change rate and increased loss in small-size, large-capacity MLCC applications. Summary of the Invention

[0006] The technical problem this invention aims to solve is that current barium titanate-based ceramic materials with X7R characteristics sintered at medium and low temperatures for Pb-Ag internal electrode MLCCs are difficult to precisely control in terms of core-shell structure during processing, and suffer from unstable capacitance temperature change rate and increased loss in small-size, high-capacity MLCC applications. The purpose is to provide a temperature-stable capacitor ceramic powder with a core-shell structure after sintering, along with its preparation method and applications. This solves the problems of current barium titanate-based ceramic materials with X7R characteristics sintered at medium and low temperatures for Pb-Ag internal electrode MLCCs, which suffer from unstable capacitance temperature change rate and increased loss in small-size, high-capacity MLCC applications.

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

[0008] In a first aspect, this application provides a temperature-stable capacitor ceramic powder with a core-shell structure after sintering, the main component of which is BaTiO3, wherein the BaTiO3 is doped with a modifier and glass powder; the modifier comprises TiO2, NaCO3 and Nb2O5; and the glass powder comprises Li-B-Si glass compound and Bi-B glass compound.

[0009] In the fabrication of multilayer ceramic chip capacitors (MLCCs), the mixture of ceramic powder and organic solvent needs to be ground to ensure thorough mixing. This process further reduces the particle size of the ceramic powder, weakening the core-shell concentration gradient after sintering. This results in unstable capacitance temperature gradient. Simultaneously, the internal electrode slurry partially diffuses into the ceramic body during co-firing, acting as a flux to lower the sintering temperature. In the design of small-size, large-capacity MLCCs, the dielectric layer thickness tends to be thinner, exacerbating the fluxing effect of the internal electrode and further weakening the core-shell concentration gradient. These two factors contribute to a deteriorated capacitance temperature gradient and increased dielectric loss in small-size, large-capacity MLCCs.

[0010] The temperature-stable capacitor ceramic powder with a core-shell structure of this invention incorporates an appropriate amount of dopant in its formulation design. When the dielectric layer is thick, residual dopant-modified substances adhere to the shell surface. When the dielectric layer becomes thinner, the weakened concentration gradient of the core-shell structure is compensated, maintaining a stable capacitance temperature change rate and low dielectric loss. This solves the problem of unstable capacitance temperature change rate and increased loss in barium titanate-based ceramic materials with X7R characteristics sintered at medium and low temperatures for Pb-Ag internal electrode MLCCs in small-size, high-capacity MLCC applications. It maintains a stable capacitance temperature change rate while preserving low dielectric loss and high withstand voltage.

[0011] The temperature-stable capacitor ceramic powder with a core-shell structure in this invention has a distinct core-shell structure. After sintering, residual doped modified materials are attached to the surface of the shell layer, which have not yet completely dissolved with the shell layer of the main crystalline phase. At the positive temperature end of 25℃~125℃, the dielectric constant increases with the increase of temperature, with an increase of 8% to 15%.

[0012] Furthermore, the amount of TiO2 in the modifier is 2-10 wt% of the amount of the main component BaTiO3, the amount of NaCO3 is 0.5-2 wt% of the amount of the main component BaTiO3, and the amount of Nb2O5 is 1-2 wt% of the amount of the main component BaTiO3.

[0013] Furthermore, the modifier also includes any one or more of Nd2O3, ZnO, Bi2O3, SrCO3, Al2O3, MnCO3, and Co2O3.

[0014] Furthermore, the amount of Nd2O3 used is 0~0.8wt% of the amount of the main component BaTiO3; the amount of ZnO used is 0~1.2wt% of the amount of the main component BaTiO3; the amount of Bi2O3 used is 0~2wt% of the amount of the main component BaTiO3; the amount of SrCO3 used is 0~2wt% of the amount of the main component BaTiO3; the amount of Al2O3 used is 0.2~1wt% of the amount of the main component BaTiO3; the amount of MnCO3 used is 0~0.5wt% of the amount of the main component BaTiO3; and the amount of Co2O3 used is 0~0.3wt% of the amount of the main component BaTiO3.

[0015] Furthermore, the glass powder is a cooling agent, the amount of the Li-B-Si glass compound is 0.05~0.3wt% of the amount of the main component BaTiO3; the amount of the Bi-B glass compound is 0.05~0.3wt% of the amount of the main component BaTiO3; and the mass ratio of Li:B:Si in the Li-B-Si glass compound is 31:46:23.

[0016] Furthermore, the preparation method of the Li-B-Si glass compound is as follows:

[0017] 1) Weigh out LiCO3 powder, B2O3 powder and SiO2 powder according to the proportion, add them to the ball mill jar, and mix them evenly using wet ball milling.

[0018] 2) Dry the anhydrous ethanol on the uniformly mixed powder, and then send the powder into a heating furnace for calcination. After calcination, the glass material is sequentially subjected to wet ball milling and drying to obtain Li-B-Si glass powder.

[0019] Furthermore, the preparation method of the Bi-B glass compound is as follows:

[0020] 1) Weigh out Bi2O3 powder and B2O3 powder according to the proportion, add them to the ball mill jar, and mix them evenly using wet ball milling.

[0021] 2) Dry the anhydrous ethanol on the uniformly mixed powder, and then send the powder into a heating furnace for calcination. After calcination, the glass material is sequentially subjected to wet ball milling and drying to obtain Bi-B glass powder.

[0022] Furthermore, the mass ratio of Bi to B in the Bi-B glass compound is 89:11.

[0023] Secondly, this application provides a method for preparing temperature-stable capacitor ceramic powder with a core-shell structure, comprising the following steps:

[0024] Step 1: Weigh the main crystalline phase BaTiO3 powder according to the required ratio, and grind it using a wet vibratory ball mill until the particle size D is reached. 50 When the particle size reaches 700–800 μm, slurry A is obtained;

[0025] Step 2: Weigh the modifier according to the dosage ratio and grind it using a wet vibratory ball mill until the particle size D is reached. 50 When the particle size reaches 200–300 μm, slurry B is obtained;

[0026] Step 3: Weigh the glass powder according to the specified ratio and grind it using a wet vibratory ball mill until the particle size D is reached. 50 When the particle size reaches 200–300 μm, slurry C is obtained;

[0027] Step 4: Mix slurry B and slurry C, add slurry A after vibratory ball milling, and continue vibratory ball milling to obtain ceramic slurry. Then, dry and sieve the ceramic slurry in sequence to obtain temperature-stable capacitor ceramic powder with core-shell structure.

[0028] The preparation method of this invention, by strictly controlling the particle size of the main components, dopant modifiers and glass compounds, and through abrasive and mixing processes, stably controls the particle size and activity of the main crystalline phase material and the dopant modifier material, reduces the instability of the core-shell microstructure concentration gradient caused by the abrasive process, solves the problem of the difficulty in accurately controlling the core-shell structure of barium titanate-based ceramic materials with X7R characteristics sintered at medium and low temperatures for Pb-Ag internal electrode MLCCs, and improves the consistency of capacity temperature change rate.

[0029] Thirdly, this application provides a capacitor prepared using temperature-stable capacitor ceramic powder with a core-shell structure prepared by the above-described method or by the preparation method of temperature-stable capacitor ceramic powder with a core-shell structure.

[0030] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0031] (1) The temperature-stable capacitor ceramic powder with core-shell structure of the present invention adds an appropriate amount of dopant during the formulation design, so that when the dielectric is thick, residual doped modified material is attached to the surface of the shell layer. When the dielectric layer becomes thin, the weakened core-shell structure concentration gradient is compensated, maintaining a stable capacitance temperature change rate and a small dielectric loss. It solves the problem of unstable capacitance temperature change rate and increased loss of barium titanate-based ceramic material with X7R characteristics sintered at medium and low temperature in Pb-Ag internal electrode MLCCs in small-size and large-capacity MLCC applications, so that the capacitance temperature change rate is kept stable, and the dielectric loss and high withstand voltage are maintained.

[0032] (2) The temperature-stable capacitor ceramic powder with core-shell structure in this invention has an obvious core-shell structure. After sintering, residual doped modified materials are attached to the surface of the shell layer, which have not yet completely dissolved with the shell layer of the main crystal phase. At the positive temperature end of 25℃~125℃, the dielectric constant increases with the increase of temperature, by about 8%~15%.

[0033] (3) The preparation method of the present invention strictly controls the particle size of the main component, dopant and glass compound, and stabilizes the particle size and activity of the main crystalline phase material and the dopant and modified material through abrasive process and mixing process. It reduces the instability of the core-shell microstructure concentration gradient caused by abrasive process, solves the problem of difficulty in accurately controlling the core-shell structure of barium titanate-based ceramic material with X7R characteristics sintered at medium and low temperature for Pb-Ag internal electrode MLCC, and improves the consistency of capacity temperature change rate. Attached Figure Description

[0034] To more clearly illustrate the technical solutions of the exemplary embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of the present invention and should not be considered as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort. In the drawings:

[0035] Figure 1 SEM image of a circular sample prepared using the method of Example 1 of this invention;

[0036] Figure 2 SEM images of MLCC samples prepared using the method of Example 1 of this invention;

[0037] Figure 3 SEM image of a circular sample prepared using the method of Example 3 of this invention;

[0038] Figure 4 SEM images of MLCC samples prepared using the method of Example 3 of this invention;

[0039] Figure 5 SEM image of a circular sample prepared using the method of Example 6 of this invention;

[0040] Figure 6 SEM images of MLCC samples prepared using the method of Example 6 of this invention;

[0041] Figure 7 SEM image of a circular sample prepared using the method of Example 8 of this invention;

[0042] Figure 8SEM images of MLCC samples prepared using the method of Example 8 of this invention;

[0043] Figure 9 SEM image of the disc sample prepared using the method of Example 9 of this invention;

[0044] Figure 10 The image shows a SEM image of an MLCC sample prepared using the method described in Example 9 of this invention. Detailed Implementation

[0045] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments.

[0046] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0047] Example 1

[0048] This embodiment provides a method for preparing temperature-stable capacitor ceramic powder with a core-shell structure after sintering. The formula and dosage are as follows: 100g BaTiO3, 4g TiO2, 1.2g NaCO3, 1g Nb2O5, 0.8g Nd2O3, 0.32g ZnO, 0.2g Al2O3, 0.3g Li-B-Si glass compound, and 0.1g Bi-B glass compound.

[0049] The preparation method of the Li-B-Si glass compound is as follows:

[0050] 1) Weigh 31g of LiCO3 powder, 46g of B2O3 powder, and 23g of SiO2 powder, add them to a ball mill jar, and mix them evenly using wet ball milling; wherein, the total mass of LiCO3 powder, B2O3 powder, and SiO2 powder: ball milling media: anhydrous ethanol = 1:5:1;

[0051] 2) Dry the anhydrous ethanol on the uniformly mixed powder. After drying, send the powder into a heating furnace and calcine it at 800℃ for 2.5 hours. After calcination, the glass material is sequentially subjected to wet ball milling and drying to obtain Li-B-Si glass powder.

[0052] The preparation method of the Bi-B glass compound is as follows:

[0053] 1) Weigh 89g of Bi2O3 powder and 11g of B2O3 powder, add them to a ball mill jar, and mix them evenly using wet ball milling; wherein, the total weight of Bi2O3 powder and B2O3 powder: ball milling media: anhydrous ethanol = 1:5:1;

[0054] 2) Dry the anhydrous ethanol on the uniformly mixed powder. After drying, send the powder into a heating furnace and calcine it at 600℃ for 2.5 hours. After calcination, the glass material is sequentially subjected to wet ball milling and drying to obtain Bi-B glass powder.

[0055] The preparation method of temperature-stable capacitor ceramic powder with a core-shell structure after sintering is as follows:

[0056] S1: Weigh 100g of the main crystalline phase BaTiO3 powder and perform wet vibratory ball milling according to the weight ratio of BaTiO3 powder: milling media: deionized water = 1:5:1.4. During the ball milling process, check the particle size until the particle size D is reached. 50 Achieving a thickness of 750 μm yields slurry A;

[0057] S2: Weigh 4g TiO2, 1.2g NaCO3, 1g Nb2O5, 0.8g Nd2O3, 0.32g ZnO, and 0.2g Al2O3. Perform wet vibratory ball milling according to the weight ratio of total mass of TiO2, NaCO3, Nb2O5, Nd2O3, ZnO, and Al2O3: milling media: deionized water = 1:5:1.4. During the ball milling process, monitor the particle size down to particle size D. 50 Reaching 250μm, slurry B is obtained;

[0058] S3: Weigh 0.3g of Li-B-Si glass compound and 0.1g of Bi-B glass compound, and perform wet vibratory ball milling according to the weight ratio of total mass of Li-B-Si glass compound and Bi-B glass compound: milling media: deionized water = 1:5:1. During the ball milling process, the particle size is measured until the particle size D is reached. 50 Reaching 250 μm, slurry C is obtained;

[0059] S4: Mix slurry B and slurry C, add slurry A after vibratory ball milling, and continue vibratory ball milling for 0.5 hours to obtain ceramic slurry. Then, dry and sieve the ceramic slurry in sequence to obtain temperature-stable capacitor ceramic powder with core-shell structure.

[0060] The milling media used in S1 to S4 are all zirconium balls.

[0061] Example 2

[0062] Based on Example 1, this example provides a method for preparing temperature-stable capacitor ceramic powder with a core-shell structure after sintering. The difference from Example 1 is that the formulation and dosage used in this example are: 100g BaTiO3, 4g TiO2, 1.2g NaCO3, 2g Nb2O5, 0.6g Nd2O3, 0.32g ZnO, 0.2g Al2O3, 0.02g MnCO3, 0.3g Li-B-Si glass compound, and 0.1g Bi-B glass compound. Other technical features are completely identical to those in Example 1.

[0063] Example 3

[0064] Based on Example 1, this example provides a method for preparing temperature-stable capacitor ceramic powder with a core-shell structure after sintering. The difference from Example 1 is that the formula and dosage used in this example are: 100g BaTiO3, 4g TiO2, 1.2g NaCO3, 2g Nb2O5, 0.6g Nd2O3, 0.32g ZnO, 0.2g Al2O3, 0.02g MnCO3, 0.1g Co2O3, 0.3g Li-B-Si glass compound, and 0.1g Bi-B glass compound. Other technical features are completely identical to those in Example 1.

[0065] Example 4

[0066] Based on Example 1, this example provides a method for preparing temperature-stable capacitor ceramic powder with a core-shell structure after sintering. The difference from Example 1 is that the formula and dosage used in this example are: 100g BaTiO3, 7g TiO2, 2g NaCO3, 1.5g Nb2O5, 1.2g ZnO, 2g Bi2O3, 2g SrCO3, 1g Al2O3, 0.3g Co2O3, 0.1g Li-B-Si glass compound, and 0.05g Bi-B glass compound. Other technical features are completely identical to those in Example 1.

[0067] Example 5

[0068] Based on Example 1, this example provides a method for preparing temperature-stable capacitor ceramic powder with a core-shell structure after sintering. The difference from Example 1 is that the formulation and dosage used in this example are: 100g BaTiO3, 7g TiO2, 2g NaCO3, 2g Nb2O5, 0.2g Nd2O3, 1.2g ZnO, 2g Bi2O3, 2g SrCO3, 1g Al2O3, 0.02g MnCO3, 0.3g Co2O3, 0.1g Li-B-Si glass compound, and 0.05g Bi-B glass compound. Other technical features are completely identical to those in Example 1.

[0069] Example 6

[0070] Based on Example 1, this example provides a method for preparing temperature-stable capacitor ceramic powder with a core-shell structure after sintering. The difference from Example 1 is that the formula and dosage used in this example are: 100g BaTiO3, 6g TiO2, 1.4g NaCO3, 1.5g Nb2O5, 0.4g Nd2O3, 1g ZnO, 1g Bi2O3, 1g SrCO3, 0.5g Al2O3, 0.02g MnCO3, 0.2g Co2O3, 0.15g Li-B-Si glass compound, and 0.05g Bi-B glass compound. Other technical features are completely identical to those in Example 1.

[0071] Example 7

[0072] Based on Example 1, this example provides a method for preparing temperature-stable capacitor ceramic powder with a core-shell structure after sintering. The difference from Example 1 is that the formula and dosage used in this example are: 100g BaTiO3, 2g TiO2, 0.5g NaCO3, 1.5g Nb2O5, 0.5g Nd2O3, 0.5g Bi2O3, 1g Al2O3, 0.5g MnCO3, 0.1g Co2O3, 0.05g Li-B-Si glass compound, and 0.3g Bi-B glass compound. Other technical features are completely identical to those in Example 1.

[0073] Example 8

[0074] Based on Example 1, this example provides a method for preparing temperature-stable capacitor ceramic powder with a core-shell structure after sintering. The difference from Example 1 is that, in this example, when preparing temperature-stable capacitor ceramic powder with a core-shell structure, the particle size D of slurry A is... 50 The thickness is 700 μm. Other technical features are exactly the same as in Example 1.

[0075] Example 9

[0076] Based on Example 1, this example provides a method for preparing temperature-stable capacitor ceramic powder with a core-shell structure after sintering. The difference from Example 1 is that, in this example, when preparing temperature-stable capacitor ceramic powder with a core-shell structure, the particle size D of slurry A is... 50 It is 800 μm. Other technical features are exactly the same as in Example 1.

[0077] Example 10

[0078] Based on Example 1, this example provides a method for preparing temperature-stable capacitor ceramic powder with a core-shell structure after sintering. The difference from Example 1 is that, in this example, when preparing temperature-stable capacitor ceramic powder with a core-shell structure, the particle size D of slurry B is... 50 It is 200 μm. Other technical features are exactly the same as in Example 1.

[0079] Example 11

[0080] Based on Example 1, this example provides a method for preparing temperature-stable capacitor ceramic powder with a core-shell structure after sintering. The difference from Example 1 is that, in this example, when preparing temperature-stable capacitor ceramic powder with a core-shell structure, the particle size D of slurry B is... 50 The thickness is 300 μm. Other technical features are exactly the same as in Example 1.

[0081] Example 12

[0082] Based on Example 1, this example provides a method for preparing temperature-stable capacitor ceramic powder with a core-shell structure after sintering. The difference from Example 1 is that, in this example, the particle size D of the slurry C is [not specified in the original text]. 50 It is 200 μm. Other technical features are exactly the same as in Example 1.

[0083] Example 13

[0084] Based on Example 1, this example provides a method for preparing temperature-stable capacitor ceramic powder with a core-shell structure after sintering. The difference from Example 1 is that, in this example, the particle size D of the slurry C is [not specified in the original text]. 50 The thickness is 300 μm. Other technical features are exactly the same as in Example 1.

[0085] The temperature-stable capacitor ceramic powder with a core-shell structure prepared by the methods of Examples 1 to 13 was used to prepare test samples for performance testing.

[0086] (1) Preparation of disc samples: 8 wt% paraffin was added to the prepared ceramic powder for granulation, and the powder was pressed into discs using a hydraulic press. Then, the temperature was raised to 450°C at a rate of 2°C / min to remove the adhesive. After that, the temperature was raised to 1160°C at a rate of 3°C / min. After sintering for 3 hours, the temperature was cooled with the furnace to obtain disc test samples.

[0087] (2) MLCC sample preparation: The prepared ceramic powder was ball-milled with zirconia balls, toluene, ethanol, etc. in a ratio of 1:5:1.5. After 2 hours, 8wt% of binder was added and ball-milled for 28 hours to make a ceramic slurry. The ceramic slurry was cast into a film strip on a spray casting machine. The film strip was printed with internal electrode paste and dried on a printing machine. The film strip with internal electrode and the blank film strip were stacked according to the design of sheet-like (2.3±0.20)mm×(1.6±0.20)mm, one series of internal electrodes, and no less than 20 layers of internal electrodes to make a green block. The block was further pressed and compacted by a warm isostatic press. The green block was cut on a cutting machine to form a capacitor green block. Then, the temperature was raised to 550℃ at a rate of 1℃ / min to discharge the adhesive. Then, the temperature was raised to 1140℃ at a rate of 1.5℃ / min. After sintering for 3 hours, the temperature was cooled with the furnace to obtain the MLCC test sample. The test results are shown in the table below.

[0088] Table 1. Performance List of Porcelain Powder Disc Samples

[0089]

[0090] Table 2 Performance List of MLCC Capacitor Samples

[0091]

[0092] As shown in Table 1, Examples 1-13 of this invention achieved temperature-stable capacitor ceramic powder formulations with X7R characteristics by doping BaTiO3 with modifiers and glass powder. The main modifiers TiO2, NaCO3, and Nb2O5 form the basis for the core-shell structure of the ceramic grains. The composite doping of Nd2O3, ZnO, and Bi2O3... 、 SrCO3 and Al2O3 promote the chemical reaction of the shell structure material, increase the shell structure concentration, and further optimize and stabilize the capacity temperature characteristics. Trace doping with MnCO3 and Co2O3 optimizes dielectric loss and insulation performance. The addition of Li-B-Si glass compounds and Bi-B glass compounds forms a glass liquid phase, which accelerates the chemical reaction, promotes sintering, and reduces the sintering temperature for ceramic formation.

[0093] In Examples 1-13 of this invention, the particle size of the main component, dopant modifier, and glass compound were strictly controlled during the abrasive process. In Examples 1, 8, and 9, under the premise that other technical conditions remained unchanged, the particle size D of the main component A in slurry was... 50 The particle size D of the slurry B doped with the modifier is controlled at 750μm, 700μm, and 800μm. Examples 1, 10, and 11, under the premise that other technical conditions remain unchanged, are also considered. 50The particle size D of the glass compound in slurry C was controlled at 250μm, 200μm, and 300μm. Examples 1, 12, and 13, with other technical conditions remaining unchanged, were also discussed. 50 The particle sizes were controlled at 250μm, 200μm, and 300μm. As shown in Table 1, the particle size D of the main component A and the doped modifier in slurry B were... 50 The effect of the capacity-temperature change rate is significant; the particle size of the main component D in slurry A is also significant. 50 Increase or increase the particle size D of the slurry B doped with the modifier. 50 As the volume decreases, the temperature change gradually increases. The slurry C, a glass compound, promotes sintering; particle size D... 50 The insulation resistance and insulation strength are reduced.

[0094] As shown in Table 2, after the temperature-stable capacitor ceramic powder with core-shell structure of Examples 1-13 of the present invention was prepared into MLCC samples, compared with the electrical performance of the wafer samples, the sintering temperature was lower, the insulation resistance was lower, the dielectric loss was higher, and the capacitance temperature change rate fluctuated significantly. In particular, the capacitance change rate of the MLCC sample with a dielectric thickness of 10 μm decreased by about 10% compared with the wafer sample after the temperature was raised from 25℃ to 125℃. These changes in electrical properties are due to the grinding of the ceramic powder and organic solvent mixture during MLCC fabrication to ensure thorough mixing. This process further reduces the particle size of the ceramic powder, weakening the core-shell concentration gradient of the ceramic grains after sintering. Consequently, the electrical properties change, particularly the capacity-temperature change rate. Simultaneously, the internal electrode metal paste partially diffuses into the ceramic body during co-firing, acting as a flux to lower the sintering temperature. The thinner the single-layer ceramic film, the more pronounced the diffusion and fluxing effect of the internal electrode metal, resulting in a weaker core-shell concentration gradient and a greater change in the electrical properties of the MLCC.

[0095] In response to the trend of thinner dielectric films in MLCCs, this invention fully considers the increased dielectric loss and significant decrease in capacitance temperature change rate when the MLCC temperature rises from 25°C to 125°C after the ceramic powder formulation is designed. This invention provides a temperature-stable capacitor ceramic powder with a core-shell structure. Through the design of the ceramic powder formulation, the ceramic grains exhibit a core-shell structure after sintering, with residual doped modified substances adhering to the shell surface, which are not yet fully miscible with the main crystalline phase. At the positive temperature range of 25°C to 125°C, the dielectric constant increases with increasing temperature, with the increase controlled within the range of 8% to 15%. Simultaneously, it exhibits low dielectric loss. The electrical performance obtained by this ceramic powder formulation design, after being fabricated into a thin-layer MLCC, can still maintain a capacitance temperature change rate within ±15% at the positive temperature range of 25°C to 125°C, while also exhibiting low dielectric loss and high voltage withstand capability.

[0096] Based on precise control of the ceramic powder formulation, this invention strictly controls the particle size of the main components, dopant modifiers, and glass compounds through certain abrasive and mixing processes. This reduces the fluctuation of the core-shell structure concentration gradient caused by the abrasive process and improves the stability of the capacity temperature change rate of Pb-Ag internal electrode MLCCs prepared from barium titanate-based ceramic materials with X7R characteristics.

[0097] Microscopic examination of disc samples and MLCC samples made from temperature-stable capacitor powder with a core-shell structure, prepared according to the methods of Examples 1, 3, 6, 8, and 9, was performed using electron microscopy. The electron micrographs are shown below. Figures 1 to 10 As shown.

[0098] Depend on Figures 1 to 5 It can be seen that the disc samples made of temperature-stable capacitor ceramic powder with core-shell structure prepared by the methods of Examples 1, 3, 6, 8 and 9 have a large amount of residual doped modified material attached to the surface of the grain shell. Among them, the grain shell surface of Example 6 has the most residual doped modified material, and its capacity changes with temperature at the highest rate of +14.33% when the temperature rises from 25℃ to 125℃. Conversely, the grain shell surface of Example 8 has less residual doped modified material, and its capacity changes with temperature at a relatively small rate when the temperature rises from 25℃ to 125℃.

[0099] After the temperature-stable capacitor ceramic powder with a core-shell structure prepared using the methods of Examples 1, 3, 6, 8, and 9 was used to prepare MLCCs, the ceramic powder was further ground during the MLCC preparation process, resulting in a further reduction in particle size and an increase in specific surface area. This made it easier for the doped and modified substances to react during sintering and diffuse into the lattice of the main crystalline phase grains. Figures 6 to 10 It can be seen that the residual doping modification material on the surface of the grain shell is significantly reduced compared with the wafer sample, which weakens the concentration gradient of the core-shell structure. Therefore, the capacity change rate with temperature is significantly reduced compared with the wafer sample when the temperature is increased from 25℃ to 125℃.

[0100] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A temperature-stable capacitor ceramic powder with a core-shell structure after sintering, characterized in that, The main component is BaTiO3, which is doped with a modifier and glass powder; the modifier includes TiO2, NaCO3 and Nb2O5; the glass powder includes Li-B-Si glass compound and Bi-B glass compound. The modifier contains TiO2 at a rate of 2-10 wt% of the main component BaTiO3, NaCO3 at a rate of 0.5-2 wt% of the main component BaTiO3, and Nb2O5 at a rate of 1-2 wt% of the main component BaTiO3. The glass powder is a cooling agent, and the amount of the Li-B-Si glass compound used is 0.05~0.3wt% of the amount of the main component BaTiO3. The amount of the Bi-B glass compound used is 0.05~0.3 wt% of the amount of the main component BaTiO3; The mass ratio of Li:B:Si in the Li-B-Si glass compound is 31:46:23; The temperature-stable capacitor ceramic powder with a core-shell structure after sintering is prepared through the following steps: Step 1: Weigh the main crystalline phase BaTiO3 powder according to the required ratio, and grind it using a wet vibratory ball mill until the particle size D is reached. 50 When the particle size reaches 700–800 μm, slurry A is obtained; Step 2: Weigh the modifier according to the dosage ratio and grind it using a wet vibratory ball mill until the particle size D is reached. 50 When the particle size reaches 200–300 μm, slurry B is obtained; Step 3: Weigh the glass powder according to the specified ratio and grind it using a wet vibratory ball mill until the particle size D is reached. 50 When the particle size reaches 200–300 μm, slurry C is obtained; Step 4: Mix slurry B and slurry C, add slurry A after vibratory ball milling, and continue vibratory ball milling to obtain ceramic slurry. Then, dry and sieve the ceramic slurry in sequence to obtain temperature-stable capacitor ceramic powder with core-shell structure after sintering.

2. The temperature-stable capacitor ceramic powder with a core-shell structure after sintering according to claim 1, characterized in that, The modifier also includes any one or more of Nd2O3, ZnO, Bi2O3, SrCO3, Al2O3, MnCO3, and Co2O3.

3. The temperature-stable capacitor ceramic powder with a core-shell structure after sintering according to claim 2, characterized in that, The amount of Nd2O3 is 0~0.8wt% of the main component BaTiO3; the amount of ZnO is 0~1.2wt% of the main component BaTiO3; the amount of Bi2O3 is 0~2wt% of the main component BaTiO3; the amount of SrCO3 is 0~2wt% of the main component BaTiO3; the amount of Al2O3 is 0.2~1wt% of the main component BaTiO3; the amount of MnCO3 is 0~0.5wt% of the main component BaTiO3; and the amount of Co2O3 is 0~0.3wt% of the main component BaTiO3.

4. The temperature-stable capacitor ceramic powder with a core-shell structure after sintering according to claim 1, characterized in that, The preparation method of the Li-B-Si glass compound is as follows: 1) Weigh out LiCO3 powder, B2O3 powder and SiO2 powder according to the proportion, add them to the ball mill jar, and mix them evenly using wet ball milling. 2) Dry the anhydrous ethanol on the uniformly mixed powder, and then send the powder into a heating furnace for calcination. After calcination, the glass material is sequentially subjected to wet ball milling and drying to obtain Li-B-Si glass powder.

5. The temperature-stable capacitor ceramic powder with a core-shell structure after sintering according to claim 1, characterized in that, The preparation method of the Bi-B glass compound is as follows: 1) Weigh out Bi2O3 powder and B2O3 powder according to the proportion, add them to the ball mill jar, and mix them evenly using wet ball milling. 2) Dry the anhydrous ethanol on the uniformly mixed powder, and then send the powder into a heating furnace for calcination. After calcination, the glass material is sequentially subjected to wet ball milling and drying to obtain Bi-B glass powder.

6. The temperature-stable capacitor ceramic powder with a core-shell structure after sintering according to claim 1, characterized in that, The mass ratio of Bi to B in the Bi-B glass compound is 89:

11.

7. A temperature-stable capacitor ceramic powder having a core-shell structure after sintering, as described in any one of claims 1 to 6, is used to prepare a capacitor.

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