A dielectric ceramic material for chip capacitors with high dielectric strength, low loss, and high temperature stability, its preparation method, and its application.

Abstract

This invention discloses a dielectric ceramic material for chip capacitors with high dielectric constant, low loss, and high temperature stability, as well as its preparation method and application. It relates to the technical field of dielectric materials for capacitors, their preparation methods, and applications. The material includes a core layer and a shell layer. The ceramic material is composed of a BaTiO3 main crystalline phase and dopants, with the BaTiO3 main crystalline phase located in the core layer. The dopants include shell dopants and core dopants, with the melting point of the shell dopants being lower than that of the core dopants. The BaTiO3-based 2B1-332 dielectric ceramic material for chip capacitors provided by this invention must meet the following performance requirements: dielectric constant of approximately 3300, dielectric loss less than 2.0%@1kHz, dielectric loss less than 3.0%@1MHz, and capacitance change rate with temperature (-55℃ to +125℃) of 0±10%.

Description

Technical Field

[0001] This invention relates to the technical field of dielectric materials for capacitors, their preparation methods, and applications, specifically to a high dielectric, low loss, and high temperature stability dielectric ceramic material for chip capacitors, its preparation method, and applications. Background Technology

[0002] In recent years, with the rapid development of science and technology, my country's electronics field has also developed rapidly. These series of highly reliable chip-type ceramic capacitors are needed in fields such as aerospace, microwave communication, power amplifiers, and radar. This places higher demands on dielectric ceramic materials: while ensuring a high dielectric constant, further reducing dielectric loss, and simultaneously achieving higher temperature stability. Currently, these products are almost entirely imported (from companies like DLI and ATC in the US), which are not only expensive but also have fluctuating performance. Crucially, foreign countries frequently impose embargoes on these components. Therefore, developing the basic materials for high-performance chip capacitors and gradually completing the research and manufacturing of series-type chip capacitors is of great significance for breaking foreign embargoes and improving my country's modern electronic information technology capabilities. Summary of the Invention

[0003] To address the problem of high high-frequency loss in high-dielectric, high-temperature-stable low-frequency ceramic materials, this invention provides a dielectric ceramic material for chip capacitors with high dielectric properties, low loss, and high temperature stability, as well as its preparation method.

[0004] This invention is achieved through the following technical solution:

[0005] This application proposes a dielectric ceramic material for chip capacitors with high dielectric strength, low loss, and high temperature stability, comprising a core layer and a shell layer. The ceramic material is composed of a BaTiO3 main crystal phase and dopants, wherein the BaTiO3 main crystal is located in the core layer.

[0006] The dopant includes a shell dopant and a core dopant, wherein the melting point of the shell dopant is lower than that of the core dopant.

[0007] Preferably, the dopant comprises substance A, substance B, and substance C, wherein,

[0008] Substance A contains at least one of La2O3 and Nd2O3;

[0009] Substance B contains at least one of Co2O3, Nb2O5, ZnO, MgO, and MnCO3;

[0010] The C substance contains at least one of Al2O3, SrTiO3, CaZrO3, and ZrO2.

[0011] Preferably, the doping amount of substance A is 0.34–0.86 wt%, the doping amount of substance B is 1.44–1.78 wt%, and the doping amount of substance C is 0.2–0.44 wt%.

[0012] Preferably, substance A comprises La2O3 and Nd2O3.

[0013] Preferably, the dopant contains trivalent rare earth ions, which account for 0.01–0.9 wt% of the main BaTiO3 phase, and the trivalent rare earth ions include La. 3+ 、Nd 3+ Dy 3+ 、Sm 3+ Ho 3+ Y 3+ A mixture of one or more of them.

[0014] Preferably, the dopant comprises the following substances in weight fractions: 0.15 wt% La2O3, 0.42 wt% Nd2O3, 0.16 wt% Co2O3, 1.2 wt% Nb2O5, 0.23 wt% ZnO, 0.1 wt% MnCO3, 0.12 wt% Al2O3, and 0.16 wt% CaZrO3.

[0015] To achieve the above objectives, this application also proposes a method for preparing a dielectric ceramic material for chip capacitors with high dielectric strength, low loss, and high temperature stability, comprising the following steps:

[0016] S1: Weigh the main crystalline phase and dopants, mix and grind them, and then dry them;

[0017] S2: Add a binder to the dried material, then granulate, sieve, and dry press to obtain a ceramic green body;

[0018] S3: After removing the binder from the ceramic green body, sinter it to obtain a ceramic material.

[0019] Preferably, the grinding method in S1 is vibratory ball milling, the vibratory ball milling time is 30 to 40 hours, the weight ratio of material balls is 1:5 to 7, and the drying temperature is 100 to 140°C.

[0020] Preferably, the binder in S2 is paraffin wax, the weight fraction of which is 8-10 wt%, and the dry pressing process includes a pressure of 10-14 MPa and a holding pressure of 15-25 seconds; the binder removal process in S3 includes raising the temperature from room temperature to 500-600°C at a rate of 0.8-1.2°C / min and holding it for 1.5-2.5 hours; the sintering process in S3 includes raising the temperature from 500-600°C to the sintering temperature at a rate of 2-3°C / min and holding it for 1.5-2.5 hours, followed by furnace cooling, and the sintering temperature is 1220-1260°C.

[0021] The application of a ceramic material prepared by a method for preparing a high-dielectric-weight, low-loss, and high-temperature-stability dielectric ceramic material for chip capacitors, wherein the ceramic material is used in the preparation of capacitors.

[0022] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0023] (1) The BaTiO3-based chip capacitor provided by the invention uses 2B1-332 dielectric ceramic material, and its performance indicators must meet the following requirements: dielectric constant of about 3300, dielectric loss of less than 2.0%@1kHz, dielectric loss of less than 3.0%@1MHz, and capacitance change rate with temperature (-55℃~+125℃) of 0±10%, which meets the needs of modern electronic information technology.

[0024] (2) This invention uses barium titanate powder synthesized by hydrothermal method as the main crystalline phase. Other substances in the example, such as La2O3, Nd2O3, Co2O3, Nb2O5, ZnO, MgO, MnCO3, Al2O3, SrTiO3, CaZrO3, and ZrO2, are used as trace dopants. The various substances are mixed uniformly using a vibratory ball milling process, ensuring that the dopants are evenly distributed around the barium titanate main crystalline phase. During sintering, donor and acceptor dopant ions enter the A-site or B-site of the barium titanate main crystalline phase, achieving substitution modification or grinding to a certain particle size, resulting in a powder material with a specific particle size. This powder material is a mixture of barium titanate and other dopants. Then, a ceramic sample is obtained through molding and sintering processes, and its dielectric properties are characterized after being silvered on both sides. Attached Figure Description

[0025] 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:

[0026] Figure 1This is a SEM image of the surface of the dielectric ceramic material in Embodiment 3 of the present invention;

[0027] Figure 2 This is a SEM image of the cross-section of the dielectric ceramic material in Embodiment 3 of the present invention;

[0028] Figure 3 This is a diagram of the "core-shell" structure provided in an embodiment of the present invention. Detailed Implementation

[0029] 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.

[0030] 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.

[0031] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0032] This invention provides a method for preparing a dielectric ceramic material for chip capacitors with high dielectric strength, low loss, and high temperature stability, wherein the preparation method includes the following steps:

[0033] S1: Weigh the main crystalline phase and dopants, mix and grind them, and then dry them. The grinding method is vibratory ball milling. The vibratory ball milling time is 30 to 40 hours, and the weight ratio of the material to the ball is 1:5 to 7. The drying temperature is 100 to 140°C.

[0034] S2: A binder is added to the dried material for granulation, sieving, and dry pressing to obtain a ceramic green body. The binder is paraffin wax, and the weight fraction of the paraffin wax is 8-10 wt%. The dry pressing process includes a pressure of 10-14 MPa and a holding pressure of 15-25 seconds.

[0035] S3: The ceramic green body is sintered after removing the binder to obtain the ceramic material. The process of removing the binder includes heating from room temperature to 500-600℃ at a rate of 0.8-1.2℃ / min and holding for 1.5-2.5 hours. The sintering process includes heating from 500-600℃ to the sintering temperature at a rate of 2-3℃ / min and holding for 1.5-2.5 hours, followed by cooling in the furnace. The sintering temperature is 1220-1260℃.

[0036] The dopant comprises substances A, B, and C, wherein...

[0037] Substance A contains at least one of La2O3 and Nd2O3;

[0038] Substance B contains at least one of Co2O3, Nb2O5, ZnO, MgO, and MnCO3;

[0039] The C substance contains at least one of Al2O3, SrTiO3, CaZrO3, and ZrO2.

[0040] The doping amount of substance A is 0.34–0.86 wt%, the doping amount of substance B is 1.44–1.78 wt%, and the doping amount of substance C is 0.2–0.44 wt%.

[0041] Substance A contains La2O3 and Nd2O3;

[0042] The dopant contains trivalent rare earth ions, which account for 0.01–0.9 wt% of the main BaTiO3 phase. These trivalent rare earth ions include La. 3+ 、Nd 3+ Dy 3+ 、Sm 3+ Ho 3+ Y 3+ A mixture of one or more of them.

[0043] Example 1

[0044] This invention provides a method for preparing a dielectric ceramic material for chip capacitors with high dielectric strength, low loss, and high temperature stability, wherein the preparation method includes the following steps:

[0045] S1: Weigh the main crystalline phase and dopants, mix and grind them, and then dry them. The grinding method is vibratory ball milling, and the vibratory ball milling time is 35 hours. The weight ratio of the material to the ball is 1:6, and the drying temperature is 120℃.

[0046] S2: A binder is added to the dried material for granulation, sieving, and dry pressing to obtain a ceramic green body. The binder is paraffin wax with a weight fraction of 9 wt%. The dry pressing process includes a pressure of 12 MPa and a holding pressure of 20 seconds.

[0047] S3: After removing the binder from the ceramic green body, a ceramic material is obtained. The process of removing the binder includes heating from room temperature to 550°C at a rate of 1°C / min and holding for 2 hours. The sintering process includes heating from 550°C to the sintering temperature at a rate of 2.5°C / min and holding for 2 hours, followed by cooling in the furnace. The sintering temperature is 1240°C.

[0048] The dopant comprises the following substances in weight fractions: 0 wt% La2O3, 0.57 wt% Nd2O3, 0.16 wt% Co2O3, 1.2 wt% Nd2O5, 0.23 wt% ZnO, 0.1 wt% MnCO3, 0.12 wt% Al2O3, and 0.16 wt% CaZrO3.

[0049] The difference between Examples 2-15 and Example 1 is the sintering temperature and the type and amount of dopant. The types of dopant and corresponding doping amounts of Examples 1-15 and Comparative Examples 1-9 are shown in Table 1 below:

[0050] Table 1. Ceramic material formulation (main crystalline phase is BaTiO3)

[0051]

[0052]

[0053] Experimental results

[0054] Figure 1 The image shows a SEM image of the ceramic material surface prepared in Example 3. As can be seen from the image, the BaTiO3 grains are basically tetragonal, with uniform grain distribution and a size of about 0.7 μm. Some individual grains grow to 1 μm, which is the guarantee for the high dielectric constant of BaTiO3-based dielectric ceramics.

[0055] Figure 2 The image shows a cross-sectional SEM image of the ceramic material prepared in Example 3. As can be seen from the image, the ceramic body has a dense cross-section without voids, which ensures the low dielectric loss, high insulation, and high reliability of BaTiO3-based dielectric ceramics and chip capacitor products.

[0056] The ceramic materials prepared in Examples 1-15 and Comparative Examples 1-9 were partially fabricated into chip capacitors. The ceramic materials and chip capacitors were tested. The testing methods and preparation methods of the samples were in accordance with GB-T 5596-1996. The results are shown in Table 2.

[0057] Table 2 Dielectric Properties

[0058]

[0059]

[0060] This experiment uses BaTiO3 as the main crystalline phase and constructs a "core-shell" structure to achieve high dielectric constant and high stability temperature characteristics. Figure 3 As shown, the "core" is tetragonal BaTiO3 and trace amounts of Nd2O3. 3+ Mg 2+ Mn 2+ The tetragonal-like BaTiO3 doped with various materials forms the core, which ensures a high dielectric constant. The shell consists of low-melting-point materials such as Nb2O5, ZnO, and Al2O3, which form a liquid phase around the core during sintering to stabilize the temperature and volume characteristics.

[0061] Furthermore, dielectric loss is also a crucial indicator for evaluating the quality of dielectric ceramics. In BaTiO3 systems at high frequencies, the long polarization times of orientation polarization and space charge polarization cannot be completed in time. Structurally, this manifests as repeated orientation movements of the domains along the electric field direction, constantly overcoming internal stresses and friction between domains, consuming a large amount of energy, leading to a sharp increase in dielectric loss at high frequencies in the BaTiO3 system. To address this phenomenon, compensating ions (trivalent rare earth ions, such as La) are used. 3+ 、Nd 3+ Dy 3+ 、Sm 3+ Ho 3+ Y 3+ Doping measures (such as reducing impurities, pores, grain boundary defects, and domain wall movements that cause orientation polarization) reduce the loss of BaTiO3-based dielectric ceramic materials at high frequencies.

[0062] Low-frequency high-dielectric ceramics generally suffer from low insulation resistance and insulation strength, which significantly affects the practical value of dielectric materials, thus hindering material development from reaching the laboratory stage and preventing their commercial application. This invention employs two measures to improve the insulation performance of dielectric materials.

[0063] (1) Doping with appropriate amounts of substances with high insulation strength and high insulation resistance, such as Al2O3, ZrO2, SrTiO3, CaZrO3, etc.

[0064] (2) Introduce fine-graining materials to refine the grains on the one hand and prevent abnormal grain growth on the other hand, so as to improve the insulation resistance and insulation strength, such as MnCO3, Nb2O5, MgO, ZnO, etc.

[0065] Through comparison of multiple embodiments, it can be seen that when the doping amount of substance A is 0.34-0.86 wt%, the doping amount of substance B is 1.44-1.78 wt%, and the doping amount of substance C is 0.2-0.44 wt%, the prepared ceramic material has better performance. At the same time, comparing Example 1, Example 3 and Example 5, Example 3 has better results. It can be seen that when the total amount of substance A is the same, co-doping of La and Nd in substance A helps to obtain better performance. As can be seen from Comparative Example 3 or Comparative Example 4, when at least one of substance A and substance B is missing in the dopant, ceramic cannot be formed.

[0066] The performance of the ceramic materials prepared in the embodiments of the present invention was compared with that of imported standard products, and the results are shown in Table 3 below:

[0067] Table 3

[0068]

[0069] Overall, the ceramic materials obtained in the embodiments of this invention can be used as the basic materials for manufacturing high-performance chip-type ceramic capacitors, thereby gradually completing the research and manufacturing of a series of chip capacitors. This is of great significance for breaking foreign embargoes and improving my country's modern electronic information technology capabilities.

[0070] 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 dielectric ceramic material for chip capacitors with high dielectric strength, low loss, and high temperature stability, characterized in that... The ceramic material comprises a core layer and a shell layer, and is composed of a BaTiO3 main crystal phase and dopants, wherein the BaTiO3 main crystal is located in the core layer. The dopant includes a shell dopant and a core dopant, wherein the melting point of the shell dopant is lower than that of the core dopant; The dopant comprises substances A, B, and C, wherein, Substance A contains La2O3 and / or Nd2O3; Substance B contains Co2O3, Nb2O5, ZnO, and MnCO3; The C substance contains Al2O3 and CaZrO3; The doping amount of substance A is 0.34~0.86 wt%, the doping amount of substance B is 1.44~1.78 wt%, and the doping amount of substance C is 0.2~0.44 wt%.

2. The dielectric ceramic material for chip capacitors with high dielectric strength, low loss, and high temperature stability according to claim 1, characterized in that, Substance A contains La2O3 and Nd2O3.

3. The dielectric ceramic material for chip capacitors with high dielectric strength, low loss, and high temperature stability according to claim 2, characterized in that, The dopant comprises the following substances in weight fractions: 0.15wt%La2O3, 0.42wt%Nd2O3, 0.16wt%Co2O3, 1.2wt%Nb2O5, 0.23wt%ZnO, 0.1wt%MnCO3, 0.12wt%Al2O3, and 0.16wt%CaZrO3.

4. A method for preparing a dielectric ceramic material for chip capacitors with high dielectric strength, low loss, and high temperature stability as described in any one of claims 1-3, characterized in that... Includes the following steps: S1: Weigh the main crystalline phase and dopants, mix and grind them, and then dry them; S2: Add a binder to the dried material, then granulate, sieve, and dry press to obtain a ceramic green body; S3: After removing the binder from the ceramic green body, sinter it to obtain a ceramic material.

5. The method for preparing a high-dielectric-value, low-loss, and high-temperature-stability dielectric ceramic material for chip capacitors according to claim 4, characterized in that, The grinding method in S1 is vibratory ball milling, the vibratory ball milling time is 30 to 40 hours, the weight ratio of material balls is 1:5 to 7, and the drying temperature is 100 to 140°C.

6. The method for preparing a dielectric ceramic material for chip capacitors with high dielectric strength, low loss, and high temperature stability according to claim 5, characterized in that, The binder mentioned in S2 is paraffin wax, and the weight fraction of the paraffin wax is 8~10wt%. The dry pressing process includes a pressure of 10~14Mpa and a holding time of 15~25 seconds. The process for removing the binder described in S3 includes raising the temperature from room temperature to 500-600°C at a rate of 0.8-1.2°C / min and holding it therefore for 1.5-2.5 hours. The sintering process described in S3 includes raising the temperature from 500 to 600°C at a rate of 2 to 3°C / min to the sintering temperature, holding it at that temperature for 1.5 to 2.5 hours, and then cooling it in the furnace. The sintering temperature is 1220 to 1260°C.

7. The application of the ceramic material prepared by the method for preparing a high-dielectric-weight, low-loss, and high-temperature-stability dielectric ceramic material for chip capacitors according to any one of claims 4-6, characterized in that, The ceramic material is used in the fabrication of chip capacitors.

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