High dielectric NP0 ceramic dielectric material and preparation method thereof

Abstract

The invention discloses a high-dielectric NP0 ceramic dielectric material and a preparation method thereof, and relates to the technical field of high-voltage ceramic dielectric materials. According to the high-dielectric NP0 ceramic dielectric material, the dielectric constant, the dielectric loss angle tangent value, the temperature characteristic and other core parameters of the NP0 ceramic dielectric material can be greatly superior to those of similar products, performance benchmarking imported materials are successfully achieved, and the high-dielectric NP0 ceramic dielectric material is ahead of the domestic level; meanwhile, the technical monopoly of Europe and America is broken, the market gap of domestic high-end NP0 materials is filled, the material cost is reduced, and the dual problems that domestic materials are insufficient in performance and high-end materials depend on import are solved.

Description

Technical Field

[0001] This invention relates to the field of high-voltage ceramic dielectric materials, and more specifically to a high-dielectric NPO ceramic dielectric material and its preparation method. Background Technology

[0002] NP0 (Negative-Positive-Zero) ceramic dielectric materials are ceramic dielectric materials made with neodymium, samarium, and rare oxides as the core, combined with multi-element oxides such as TiO2 and Sm2O3. Their core application is in the manufacture of ceramic capacitors. Due to their dielectric properties and temperature stability, they are widely used in high-frequency oscillation circuits, radio frequency coupling systems, and precision filtering networks. They are key basic materials supporting signal transmission and filtering functions in electronic devices, playing an irreplaceable role in the high-end electronics industry.

[0003] Existing NPO materials primarily use neodymium, samarium, and rare oxides as raw materials, resulting in a relatively simple composition. Preparation employs traditional ceramic processes, including basic steps such as mixing, pre-firing, ball milling, molding, and sintering. However, these processes lack precise optimization in details, such as uneven mixing and dispersion, coarse ball milling parameters, and imprecise control of pre-firing and sintering temperatures. In terms of performance, the dielectric constant is only 8–90, the dielectric loss tangent is less than or equal to 0.15%, and the temperature characteristic at -55℃ to 125℃ is less than or equal to 30 ppm, placing them at a low to mid-range level overall. In terms of market structure, high-end technologies are monopolized by Europe and the United States, while domestic companies rely on imported raw materials or technologies, resulting in weak product competitiveness and difficulty in meeting domestic high-end demand.

[0004] In summary, existing NPO materials suffer from the following problems: First, their performance indicators are relatively low, with insufficient dielectric constant and temperature stability, and high dielectric loss, making them unsuitable for the miniaturization and high stability requirements of high-end capacitors. Second, there is a significant contradiction between raw materials and costs, with reliance on imported high-end raw materials driving up costs, while domestically produced raw materials suffer from low utilization rates due to unreasonable formulations. Third, the preparation process is immature, with crude control of key parameters leading to poor powder uniformity and unstable main crystalline phases, affecting the overall performance of the material. Fourth, there are significant technological barriers, making it difficult for domestic companies to overcome core formulation and process bottlenecks, resulting in a large gap in domestically produced high-end products and a prominent supply-demand imbalance in the market. Summary of the Invention

[0005] This invention provides a high-dielectric NPO ceramic dielectric material and its preparation method, which can significantly improve the core parameters of the NPO ceramic dielectric material, such as dielectric constant, dielectric loss tangent, and temperature characteristics, compared with similar products. It successfully achieves performance comparable to imported materials and leads the domestic level. At the same time, it breaks the technological monopoly of Europe and the United States, fills the gap in the domestic high-end NPO material market, reduces material costs, and solves the dual problems of insufficient performance of domestic materials and reliance on imports for high-end materials.

[0006] This invention provides a high-dielectric NPO ceramic dielectric material, comprising:

[0007] 25%–35% TiO2;

[0008] 20%–30% Sm2O3;

[0009] 1%–8% La2O3;

[0010] 10%–30% BaCO3;

[0011] 1%–3% SiO2;

[0012] 10% to 30% Bi2O3.

[0013] This invention provides a method for preparing a high-dielectric NPO ceramic dielectric material, comprising:

[0014] The high dielectric NPO ceramic dielectric material, deionized water and zirconium balls in claim 1 are ball-milled in a ball mill in a 1:1:1 ratio to obtain the initial material after ball milling.

[0015] The initial material is filtered to remove water, resulting in a dehydrated material; the dehydrated material is then pre-calcined in a pre-calcination furnace at a temperature of 1100℃~1200℃ to obtain a pre-calcined material.

[0016] The pre-calcined material, deionized water and zirconium balls are ball-milled in a ball mill at a ratio of 1:1:1 to obtain the ball-milled material.

[0017] The ball milling material is mixed with 1% to 2% polyvinyl alcohol (PVA) and then spray-dried to obtain ceramic powder.

[0018] This invention provides a high-dielectric NPO ceramic dielectric material and its preparation method, which solves the problem of insufficient performance of domestically produced materials. By optimizing the formula, the dielectric constant of the NPO material made from domestic raw materials is increased to greater than or equal to 120, far exceeding the level of 8-90 of existing domestic and similar products. At the same time, the dielectric loss tangent is reduced to less than or equal to 0.05%, and the temperature characteristics are optimized to less than or equal to 15 ppm (-55℃ to 125℃), bridging the performance gap between domestic and imported materials and achieving performance comparable to imported products and leading the domestic level. It also solves the problem of high energy loss of existing materials by significantly reducing the dielectric loss tangent, reducing energy loss during circuit operation, and improving the energy efficiency and stability of capacitors and related electronic equipment that rely on this material. Furthermore, it solves the problem of insufficient temperature adaptability of the material by enhancing temperature stability through optimized formula, making the capacitance fluctuation of the material smaller in a wide temperature range of -55℃ to 125℃, meeting the stringent requirements of precision electronic equipment for stable performance under extreme temperature environments. Finally, it solves the problem of domestic reliance on imports and high costs for high-end materials. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a magnified microscopic diagram of the main crystalline phase BaTiO3 of the NPO ceramic dielectric material provided in an embodiment of the present invention.

[0021] Figure 2 This is a magnified microscopic diagram showing the formation of a dense structure in the NPO ceramic dielectric material provided in this embodiment of the invention after incorporating substances such as Bi2O3, Sm2O3, and SiO2. Detailed Implementation

[0022] 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 only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] To enable those skilled in the art to better understand the technical solutions of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0024] This invention provides a high dielectric NPO ceramic dielectric material, which mainly comprises 25%–35% TiO2; 20%–30% Sm2O3; 1%–8% La2O3; 10%–30% BaCO3 and 1%–3% SiO2.

[0025] The dielectric constant, loss tangent, and temperature characteristics of ceramic dielectric materials are interdependent. Generally, a higher dielectric constant results in a larger loss tangent and a greater rate of temperature change, while a lower dielectric constant results in a smaller loss tangent and a smaller rate of temperature change. Most existing materials only emphasize a single property, leading to relatively low overall performance. The NPO ceramic dielectric material provided in this invention balances the performance of each parameter through formula adjustments, thereby improving the overall performance of the NPO ceramic dielectric material. Furthermore, existing ceramic dielectric materials use neodymium, which is expensive. The NPO ceramic dielectric material provided in this invention uses inexpensive samarium, and all other materials are domestically produced, inexpensive industrial-grade materials, thus reducing the cost of the ceramic dielectric material.

[0026] To more clearly illustrate the high-dielectric NPO ceramic dielectric material provided in the embodiments of the present invention, the following embodiments strictly adhere to the core formulation ratio range (25%–35% TiO2, 20%–30% Sm2O3, 1%–8% La2O3, 10%–30% BaCO3, 1%–3% SiO2, and 10%–30% Bi2O3). The proportions of each component in the high-dielectric NPO ceramic dielectric material provided in the embodiments of the present invention are adjusted to suit different performance requirements (such as high dielectric constant, low loss, high temperature stability, low cost, and balanced performance). All embodiments are equipped with a unified standard process flow, and the final product performance meets the requirements of "dielectric constant greater than or equal to 120, dielectric loss tangent less than or equal to 0.05%, and temperature characteristic less than or equal to 15 ppm (-55℃ to 125℃)".

[0027] Example 1: High dielectric-focused formulation, its composition (total mass 100 parts).

[0028] Specifically, it comprises 35% TiO2, 22% Sm2O3, 5% La2O3, 20% BaCO3, 3% SiO2, and 15% Bi2O3.

[0029] In this embodiment, by increasing the proportion of TiO2 to the upper limit (35%), TiO2, as the core component for forming the main crystalline phase of BaTiO3, can significantly improve the dielectric constant; Bi2O3 (15%), as a flux, can lower the sintering temperature and promote uniform grain growth, synergistically enhancing the dielectric properties with TiO2. A high proportion of BaCO3 (20%) ensures sufficient reaction with TiO2 to form BaTiO3, further enhancing the dielectric properties; an appropriate amount of La2O3 (5%) optimizes the crystal structure and suppresses the increase in dielectric loss; SiO2 is taken at the upper limit (3%) to improve the sintering density of the ceramic and ensure high-temperature stability.

[0030] Furthermore, the high-dielectric NPO ceramic dielectric material obtained through this embodiment has a dielectric constant greater than or equal to 138, a dielectric loss tangent less than or equal to 0.04%, and a temperature characteristic less than or equal to 12 ppm, making it suitable for high-frequency oscillation circuit scenarios with extremely high dielectric constant requirements.

[0031] Example 2: Low-loss focused formulation, its composition (total mass 100 parts).

[0032] Specifically, it comprises 30% TiO2, 28% Sm2O3, 7% La2O3, 18% BaCO3, 2% SiO2, and 15% Bi2O3.

[0033] In this embodiment, by increasing the proportion of Sm2O3 (28%), Sm2O3 can refine ceramic grains, reduce grain boundary defects, and lower dielectric loss; increasing the content of La2O3 (7%), as a rare earth oxide, can optimize the lattice arrangement, improve the stability of dielectric properties, and further suppress loss; TiO2 is set at an intermediate value (30%) to balance the dielectric constant and loss, avoiding the increase in loss caused by excessive TiO2; Bi2O3 (15%), with its low melting point, can promote the densification of the ceramic body, reduce porosity defects, and further reduce loss. SiO2 is set at an intermediate value (2%) to achieve a balance between densification and dielectric properties.

[0034] Furthermore, the high-dielectric NPO ceramic dielectric material obtained through this embodiment has a dielectric constant greater than or equal to 130, a dielectric loss tangent less than or equal to 0.035%, and a temperature characteristic less than or equal to 10 ppm, making it suitable for precision filter networks with stringent loss requirements.

[0035] Example 3: High temperature stability formulation, its formulation composition (total mass 100 parts).

[0036] Specifically, it comprises 28% TiO2, 26% Sm2O3, 8% La2O3, 18% BaCO3, 2% SiO2, and 18% Bi2O3.

[0037] In this embodiment, La2O3 is taken at the upper limit (8%), as the rare earth element La can significantly reduce the temperature coefficient of the material and improve the performance stability over a wide temperature range; Sm2O3 is kept at a relatively high proportion (26%), which works synergistically with La2O3 to optimize the temperature adaptability of the crystal phase structure; BaCO3 is slightly higher (18%), which ensures the sufficient formation of the main crystal phase BaTiO3 and avoids crystal phase transformation caused by temperature changes; Bi2O3 (18%) can form a stable solid solution with other rare earth oxides, suppressing crystal phase transformation caused by temperature changes and improving temperature stability; TiO2 is taken at a relatively low value (28%) to reduce temperature characteristic fluctuations caused by excessive TiO2.

[0038] Furthermore, the high-dielectric NPO ceramic dielectric material obtained through this embodiment has a dielectric constant greater than or equal to 128, a dielectric loss tangent less than or equal to 0.04%, and a temperature characteristic less than or equal to 8 ppm, making it suitable for radio frequency coupling systems in a wide temperature range of -55℃ to 125℃.

[0039] Example 4: Low-cost and economical formula, its composition (total mass 100 parts).

[0040] Specifically, it comprises 25% TiO2, 30% Sm2O3, 1% La2O3, 23% BaCO3, 2% SiO2, and 20% Bi2O3.

[0041] In this embodiment, TiO2 is set at the lower limit (25%) to reduce the amount of high-cost titanium source used; La2O3 is set at the lower limit (1%) to reduce the amount of expensive rare earth oxides used, significantly reducing raw material costs; the proportion of Sm2O3 (30%) and BaCO3 (43%) is increased, as both are relatively inexpensive raw materials and can ensure the formation of the main crystal phase and basic dielectric properties; SiO2 is set at the lower limit (1%) to control the cost of auxiliary materials while meeting the basic sintering density requirements; Bi2O3 (18%) is cheaper than La2O3 and can replace some of the fluxing and crystal phase regulation functions of rare earth oxides, ensuring basic dielectric properties while controlling costs.

[0042] Furthermore, the high-dielectric NPO ceramic dielectric material obtained through this embodiment has a dielectric constant greater than or equal to 120, a dielectric loss tangent less than or equal to 0.05%, and a temperature characteristic less than or equal to 15 ppm, making it suitable for general-purpose ceramic capacitors that are cost-sensitive and have performance requirements as the basic standard.

[0043] Example 5: Balanced performance formulation, its formulation composition (total mass 100 parts).

[0044] Specifically, it comprises 32% TiO2, 25% Sm2O3, 4% La2O3, 17% BaCO3, 2% SiO2, and 20% Bi2O3.

[0045] In this embodiment, each component is taken as the middle value or close to the middle value of the formula range to avoid extreme values ​​of a single index and achieve balanced optimization of dielectric constant, loss and temperature stability; the ratio of TiO2 (32%) to BaCO3 (37%) is reasonable to ensure the full generation of the main crystal phase and to take into account both dielectric performance and reaction efficiency; Sm2O3 (25%) and La2O3 (4%) synergistically regulate the crystal phase structure to reduce loss and improve temperature stability; SiO2 (2%) ensures sintering quality and avoids product consistency problems caused by component fluctuations.

[0046] Furthermore, the high-dielectric NPO ceramic dielectric material obtained through this embodiment has a dielectric constant greater than or equal to 130, a dielectric loss tangent less than or equal to 0.04%, and a temperature characteristic less than or equal to 11 ppm, making it suitable for general-purpose electronic devices in multiple scenarios with medium to high requirements for various performance aspects.

[0047] The high-dielectric NPO ceramic dielectric material provided in the embodiments of the present invention, the formulation ratios provided in all embodiments can be scaled up or down according to the total mass requirements (e.g., 1kg, 10kg, 20kg) in actual production without affecting the performance stability.

[0048] This invention also provides a method for preparing high-dielectric NPO ceramic dielectric materials, specifically including:

[0049] Step 101: The high dielectric NPO ceramic dielectric material, deionized water and zirconium balls provided in the above example are ball-milled in a ball mill in a ratio of 1:1:1 to obtain the initial material after ball milling.

[0050] Step 102: The initial material is dehydrated by pressure filtration to obtain dehydrated material; the dehydrated material is pre-calcined in a pre-calcination furnace at a temperature of 1100℃~1200℃ to obtain pre-calcined material;

[0051] Step 103: The pre-calcined material, deionized water and zirconium balls are ball-milled in a ball mill at a ratio of 1:1:1 to obtain the ball-milled material.

[0052] Step 104: 1% to 2% polyvinyl alcohol (PVA) is added to the ball milling material, and the mixture is spray-dried to obtain ceramic powder.

[0053] In step 101, the raw material powder containing TiO2, Sm2O3, La2O3, BaCO3, Bi2O3 and SiO2 is weighed according to the proportion, and mixed with deionized water and zirconium balls in a 1:1:1 ratio. Then, it is placed in a ball mill for ball milling to obtain the initial material after ball milling.

[0054] In this embodiment of the invention, mechanical grinding within a ball mill can achieve uniform dispersion and initial particle size reduction of multi-component oxide raw materials, creating conditions for the formation of a uniform BaTiO3 main crystalline phase in the subsequent pre-calcination stage. The raw material powder is the core material for forming the ceramic phase. Deionized water reduces the agglomeration force between raw material powder particles, ensuring sufficient contact between particles during grinding; it also cools the heat generated during grinding, preventing localized overheating that could lead to raw material deterioration. A 1:1 ratio of raw material powder to zirconium balls ensures grinding efficiency. In practical applications, insufficient zirconium balls may result in insufficient grinding force and inadequate particle refinement; while excessive zirconium balls may increase the risk of raw material contamination.

[0055] In this embodiment of the invention, the ball mill can be a planetary ball mill or a horizontal ball mill, and there is no limitation thereto. Furthermore, the ball milling time can be set according to the initial particle size of the raw material. In this embodiment, ball milling for 6 hours can reduce the particle size of the raw material from the initial 10-20 μm to 2-5 μm, while simultaneously achieving uniform molecular-level mixing of the components. In practical applications, if the ball milling time is too short, uneven mixing will lead to localized abnormal crystal phases during subsequent pre-calcination; if the ball milling time is too long, it will cause excessive finening of the powder, which will increase the risk of agglomeration.

[0056] In step 102, since the initial material obtained after ball milling is a slurry, it is necessary to perform solid-liquid separation on the initial material of the slurry to remove excess water and obtain block dehydrated material with a water content of 15% to 20%, which facilitates the operation and heat transfer of the subsequent pre-calcination process.

[0057] Specifically, in the embodiments of the present invention, a plate and frame filter press or a chamber filter press is used. By applying a pressure of 0.5 to 1.5 MPa to the filter plate, the water in the slurry is allowed to seep out through the filter cloth (commonly polypropylene filter cloth with a pore size of 5 to 10 μm), thereby forming a cake-shaped dewatering material.

[0058] Compared with natural sun drying or centrifugal dehydration, pressure filtration has the following advantages: high dehydration efficiency; stable filter cake moisture content, ensuring uniform pre-firing temperature; and dense filter cake structure, reducing volume shrinkage differences during pre-firing.

[0059] In step 103, the synthesis of the main crystalline phase (BaCO3 reacts with TiO2 to generate BaTiO3) can be completed through high-temperature heat treatment; impurity removal (combustion of organic matter and decomposition of carbonates) can be achieved; and the powder can be initially sintered.

[0060] In practical applications, box-type resistance furnaces are suitable for pre-firing small batches of experimental samples due to their high temperature control accuracy (±5℃) and good temperature uniformity. The furnace lining material is mostly corundum, which is heat-resistant and does not chemically react with NPO ceramic raw materials, ensuring powder purity. Operation is convenient, with flexible settings for parameters such as heating rate and holding time. Therefore, box-type resistance furnaces can be used in experimental stages. Pusher kilns, on the other hand, are continuous heating devices. A pushing mechanism continuously feeds saggers containing pre-fired materials into the furnace lining, making them suitable for large-scale continuous production. The furnace lining can be segmented for temperature control, precisely controlling the heating, holding, and cooling stages of pre-firing to ensure consistent product performance across batches. They also have high thermal efficiency, being more energy-efficient than box-type resistance furnaces. Therefore, pusher kilns can be used for large-scale industrial production.

[0061] In this embodiment of the invention, at room temperature, the cake-shaped dewatering material is placed in a box-type resistance furnace or a pusher kiln. As the furnace slowly heats up, the moisture in the cake-shaped dewatering material gradually evaporates. If the cake-shaped dewatering material is placed directly into a furnace that has already been heated, the moisture in the cake-shaped dewatering material will evaporate and vaporize rapidly, causing the volume to expand sharply. This results in stress inside the filter cake, leading to problems such as cracking and pulverization.

[0062] Furthermore, when the pre-calcination temperature in the furnace is 1100℃~1200℃, the main crystalline phase synthesis reaction occurs: BaCO3+TiO2→BaTiO3+CO2↑. The initial temperature of this reaction is about 900℃, and the reaction rate is fastest at 1100℃~1200℃, with a conversion rate greater than 95%. In practical applications, if the furnace temperature is lower than 1100℃, BaTiO3 will not be fully formed, which will lead to a decrease in the dielectric constant. If the furnace temperature is higher than 1200℃, local over-calcination will occur, forming coarse grains and affecting the uniformity of dielectric properties.

[0063] Furthermore, during pre-firing in the pre-firing furnace, trace amounts of organic matter that may be contained in the raw materials (such as oil stains adsorbed on the surface of the powder) are completely burned at 600℃~800℃; carbonates such as BaCO3 and Sm2O3 decompose into oxides and CO2 at 900℃~1000℃, and CO2 is discharged through the filter cake pores.

[0064] After the pre-firing is completed, it is necessary to keep the filter cake warm in the pre-firing furnace for 2 to 3 hours. This warming process ensures that the internal temperature of the filter cake is uniform and avoids uneven distribution of crystal phases caused by external heat and internal cold.

[0065] In step 104, the dehydrated material forms agglomerated particles during pre-calcination due to high-temperature sintering, so the pre-calcined material obtained after pre-calcination is in the form of a cake. In this embodiment, the cake-shaped pre-calcined material needs to be crushed first to avoid clogging the ball mill jar. Then, the pre-calcined material, deionized water and zirconium balls are placed in a star ball mill in a 1:1:1 ratio and ball-milled for 6 hours to obtain a slurry-like ball milled material.

[0066] It should be noted that the amount of deionized water added during ball milling can be adjusted according to the moisture content of the filter cake. The particle hardness of the pre-calcined material is improved after pre-calcination, and a grinding time of 6 hours is required to ensure that the particle size meets the standard. If the grinding time is insufficient, the particles will be too coarse, resulting in poor flowability during subsequent spray granulation. If the grinding time is too long, too much fine powder will be generated, increasing the amount of binder used during granulation.

[0067] In this embodiment of the invention, the first ball milling is mainly for mixing and secondarily for refining, while the second milling is mainly for refining and secondarily for homogenization. Because the particles agglomerate and hardness increases after pre-firing, if only one ball milling is performed, it is impossible to simultaneously meet the dual requirements of uniform mixing and particle size compliance, which will lead to fluctuations in the dielectric properties of subsequent ceramic products.

[0068] In practical applications, PVA (polyvinyl alcohol) is used as an organic binder. After dissolving in water, it coats the powder particles and forms a binding film when drying, causing the fine powder to agglomerate into spherical particles. At the same time, it improves the mechanical strength of the granulated powder (compressive strength > 0.2 MPa) and avoids breakage during transportation and molding.

[0069] In step 105, 1%–2% polyvinyl alcohol (PVA) is added to the ball-milled material, stirred and dissolved, and then the ball-milled material is dried using a centrifugal spray drying tower to produce ceramic powder. In practical applications, when the PVA addition is less than 1%, the granulated powder has insufficient strength and is easily broken; when the addition is greater than 2%, a longer time is required to remove organic matter during subsequent sintering.

[0070] In this embodiment of the invention, a centrifugal spray drying tower is used, and the slurry can be atomized into ceramic powder with a diameter of 50 to 100 μm through a high-speed rotating atomizing disc;

[0071] In this embodiment of the invention, the key indicators of the granulated powder include: the flow rate of the ceramic powder is less than or equal to 15 s / 50 g, as measured by a Hall effect flow meter, meeting the requirements for dry pressing; and the loose packing density of the ceramic powder is 1.2–1.6 g / cm³. 3 This ensures uniform green body density during dry pressing; the sphericity of the ceramic powder is greater than 80%, reducing inter-particle friction during molding and preventing cracks in the green body. The high-dielectric NPO ceramic dielectric material preparation method provided in this invention produces a high-dielectric NPO ceramic dielectric material with a dielectric constant greater than or equal to 120°, a dielectric loss tangent less than or equal to 0.05%, and a temperature characteristic less than or equal to 15 ppm, providing a core raw material guarantee for the production of high-performance ceramic capacitors.

[0072] To more clearly illustrate the preparation method of high-dielectric NPO ceramic dielectric material provided in the embodiments of the present invention, the following embodiments strictly follow the core formula ratio range (25%–35% TiO2, 20%–30% Sm2O3, 1%–8% La2O3, 10%–30% BaCO3, 1%–3% SiO2, 10%–30% Bi2O3) and standard process flow design. By adjusting the formula ratio and process parameters (temperature, time, binder dosage, etc.) to adapt to different production scenarios (laboratory research and development, pilot production, low-cost production, etc.), NPO ceramic materials that meet the performance requirements can be prepared in all cases.

[0073] Example 6:

[0074] 601, Formula composition (total mass 1kg): TiO2 (35%): 350g; Sm2O3 (22%): 220g; La2O3 (5%): 50g; Bi2O3 (15%): 150g; BaCO3 (20%): 200g; SiO2 (3%): 30g.

[0075] 602, Process Flow Parameters:

[0076] 602-1, First ball milling: According to the ratio of raw material powder: deionized water: zirconium balls of 1:1:1, take 1 kg of raw material powder, 1 kg of deionized water and 1 kg of zirconium oxide grinding balls (5 mm in diameter), put them into a 5L planetary ball mill, rotate at 300 r / min and ball mill for 6 hours to obtain a uniform initial material, which is in the form of slurry.

[0077] 602-2, Filtration and dewatering: A small plate and frame filter press is used, a pressure of 0.8 MPa is applied, and the filter is pressed for 1.5 hours to obtain a pre-calcined material with a moisture content of 18%. The pre-calcined material is a block filter cake.

[0078] 602-3, Pre-firing: The blocky pre-firing material is broken into small pieces with a diameter of less than or equal to 1 cm, placed in a box-type resistance furnace, heated at a rate of 5℃ / min, raised to 1200℃, held for 3 hours, and naturally cooled to room temperature to obtain the pre-firing material, which is a block material.

[0079] 602-4, Second ball milling: After crushing the blocky pre-fired material, it is loaded into a ball mill at a ratio of 1:1:1 (pre-fired material: water: zirconium balls), rotated at 300 r / min, and milled for 6 hours to obtain the ball milled material. The slurry particle size of the ball milled material is D50 equal to 1.8 μm.

[0080] 602-5, Spray drying granulation: Add 2% (mass fraction, relative to dry powder) of PVA (degree of polymerization 1700) to the slurry-like ball milled material, stir and dissolve, and then send it into a small centrifugal spray dryer with an inlet temperature of 190℃, an outlet temperature of 85℃, and an atomizing disc speed of 12000r / min to obtain ceramic powder with a flowability of 12s / 50g.

[0081] The ceramic powder obtained through this embodiment has a dry-pressed green body density of 3.7 g / cm³. 3 The ceramic was sintered at 1310℃ for 4 hours and then infiltrated with silver paste. The results showed a dielectric constant of 135, a dielectric loss tangent of 0.04%, and a temperature characteristic (-55℃ to 125℃) of 12 ppm, meeting the requirements of high-end R&D.

[0082] Example 7:

[0083] 701, Formula composition (total mass 10kg): TiO2 (30%): 3kg; Sm2O3 (25%): 2.5kg; La2O3 (3%): 0.3kg; Bi2O3 (20%): 2kg; BaCO3 (19%): 1.9kg; SiO2 (2%): 0.2kg.

[0084] 702, Process Flow Parameters:

[0085] 702-1, First ball milling: According to the ratio of raw material powder: deionized water: zirconium balls of 1:1:1, take 10kg of raw material powder, 10kg of deionized water and 10kg of zirconium oxide grinding balls (diameter 8mm), put them into a 50L horizontal ball mill, rotate at 180r / min and ball mill for 6 hours to obtain initial material with no obvious particle agglomeration. The initial material is in slurry form.

[0086] 702-2, Filtration and dewatering: A chamber filter press is used, a pressure of 1.2 MPa is applied, and the filter is pressed for 2 hours to obtain a pre-calcined material with a moisture content of 16%. The pre-calcined material is a block filter cake with a dense and non-loose overall structure.

[0087] 702-3, Pre-calcination: After crushing the blocky pre-calcined material filter cake, it is loaded into a pusher kiln, heated at a rate of 8℃ / min, and heated to 1150℃. It is held for 2.5 hours, with continuous feeding and discharging. The conversion rate of pre-calcined blocks is greater than or equal to 96%, and the pre-calcined material is obtained. This pre-calcined material is a block material.

[0088] 702-4, Second ball milling: The pre-burnt material in pre-block form, water and zirconium balls are placed in a horizontal ball mill at a speed of 180 r / min for 6 hours to obtain the ball milled material. The slurry particle size of the ball milled material is D50 equal to 2.2 μm.

[0089] 702-5, Spray drying granulation: Add 1.5% PVA (degree of polymerization 1500) to the slurry-like ball milling material, stir evenly and then feed it into a medium-sized spray dryer. The inlet temperature is 185℃, the outlet temperature is 88℃, and the atomizing disc speed is 10000r / min. Ceramic powder with a flowability of 14s / 50g is obtained, with a yield of 8.5kg (yield 85%).

[0090] The ceramic powder obtained through this embodiment has a green body density of 3.6 g / cm³. 3 Sintering at 1305℃ for 3.5 hours yielded the following test results: dielectric constant 128, dielectric loss tangent 0.045%, and temperature characteristic 14 ppm, meeting the efficiency and quality requirements for pilot production.

[0091] Example 8:

[0092] 801, Formula composition (total mass 20kg): TiO2 (25%): 5kg; Sm2O3 (28%): 5.6kg; La2O3 (2%): 0.4kg; Bi2O3 (28%): 5.6kg; BaCO3 (16%): 3.2kg; SiO2 (1%): 0.2kg.

[0093] 802, Process Flow Parameters:

[0094] 802-1, First ball milling: According to the ratio of raw material powder: deionized water: zirconium balls equal to 1:1:1, 20kg of raw material, 20kg of deionized water, and 20kg of zirconium oxide grinding balls (diameter 10mm) are loaded into a 100L horizontal ball mill, with a rotation speed of 150r / min, and ball milled for 6 hours to produce initial material with no obvious impurities in the slurry.

[0095] 802-2, Filtration and Dewatering: A large plate and frame filter press is used, with a pressure of 1.0 MPa applied and filtration carried out for 2.5 hours to obtain a pre-fired material with a moisture content of 19%. This pre-fired material is a block filter cake, which meets the requirements for batch pre-fired production.

[0096] 802-3, Pre-firing: The block pre-firing material is heated in a pusher kiln at a rate of 10℃ / min to 1100℃ and held for 2 hours. The pre-firing blocks do not show signs of over-firing or under-firing.

[0097] 802-4, Second ball milling: The pre-fired material, water and zirconium balls are loaded into a horizontal ball mill at a ratio of 1:1:1. The ball mill is rotated at 150 r / min and milled for 6 hours to obtain the ball milled material. The slurry particle size of the ball milled material is D50 equal to 2.5 μm.

[0098] 802-5, Spray drying granulation: Add 1% PVA (degree of polymerization 1300) to the slurry-like ball milling material, stir to dissolve, and then send it to a large spray dryer with an inlet temperature of 180℃, an outlet temperature of 90℃, and an atomizing disc speed of 8000r / min to obtain ceramic powder with a flowability of 15s / 50g and a yield of 82%.

[0099] The ceramic powder obtained through this embodiment has a green body density of 3.5 g / cm³. 3 The sample was sintered at 1300℃ for 3 hours. Test results showed a dielectric constant of 122, a dielectric loss tangent of 0.05%, and a temperature characteristic of 15 ppm, which meets the requirements of basic application scenarios. The raw material cost was reduced by 18% compared with Example 1.

[0100] Example 9:

[0101] 901, Formula composition (total mass 5kg): TiO2 (32%): 1.6kg; Sm2O3 (24%): 1.2kg; La2O3 (6%): 0.3kg; Bi2O3 (18%): 0.9kg; BaCO3 (17%): 0.85kg; SiO2 (3%): 0.15kg.

[0102] 902, Process Flow Parameters

[0103] 902-1, First ball milling: Take 5 kg of raw material powder, 5 kg of deionized water, and 5 kg of zirconia grinding balls (diameter 6 mm) in a ratio of 1:1:1 and put them into a 5L planetary ball mill. The ball milling speed is 280 r / min and the milling time is 6 hours to obtain the initial material. The initial material is a slurry with a particle size of D50 equal to 2.0 μm.

[0104] 902-2, Filtration and dewatering: A small chamber filter press is used, with a pressure of 0.9 MPa applied and filtration carried out for 1.8 hours to obtain a pre-calcined material with a moisture content of 17%. This pre-calcined material is a block filter cake.

[0105] 902-3, Pre-firing: The block-shaped pre-firing material is placed in a box-type resistance furnace, the heating rate is 6℃ / min, the temperature is raised to 1120℃, held for 2.8 hours, and then naturally cooled to room temperature to obtain the pre-firing material. The pre-firing material has a uniform crystal phase.

[0106] 902-4, Second ball milling: Using the same parameters as the first ball milling, ball milling for 6 hours to obtain the ball milled material, which includes slurry particles with a d50 of 1.9 μm.

[0107] 902-5, Spray drying granulation: Add 1.8% PVA to the slurry-like ball milling material, stir to dissolve, and then send it into a small centrifugal spray dryer with an inlet temperature of 188℃, an outlet temperature of 86℃, and an atomizing disc speed of 11000r / min to obtain ceramic powder with a flowability of 13s / 50g.

[0108] The ceramic powder obtained through this embodiment has a green body density of 3.7 g / cm³. 3 Sintering at 1300℃ for 3 hours (10℃ lower than the conventional temperature) yielded the following test results: dielectric constant 130, dielectric loss tangent 0.042%, temperature characteristic 13 ppm. It is suitable for low-energy sintering equipment, reducing energy consumption by 12%.

[0109] Example 10:

[0110] 1001, Formula composition (total mass 8kg): TiO2 (28%): 2.24kg; Sm2O3 (26%): 2.08kg; La2O3 (7%): 0.56kg; Bi2O3 (14%): 1.12kg; BaCO3 (22%): 1.76kg; SiO2 (3%): 0.24kg.

[0111] 1002, Process Flow Parameters:

[0112] 1002-1, First ball milling: According to the ratio of raw material powder: water: zirconium balls equal to 1:1:1, take 8 kg of raw powder, 8 kg of deionized water, and 8 kg of zirconium oxide grinding balls (7 mm in diameter), load them into a 20L planetary ball mill, rotate at 250 r / min, and ball mill for 6 hours. The slurry mixing uniformity is greater than or equal to 98%, and a uniform initial material is obtained. This initial material is in slurry form.

[0113] 1002-2, Filtration and dewatering: A medium-sized plate and frame filter press was used, with a pressure of 1.1 MPa applied and filtration carried out for 2 hours to obtain a pre-calcined material with a moisture content of 16%. The pre-calcined material was a block filter cake.

[0114] 1002-3, Pre-firing: The block-shaped pre-firing material is placed in a box-type resistance furnace, the heating rate is 4℃ / min, the temperature is raised to 1180℃, held for 3 hours, and then naturally cooled to room temperature to obtain the pre-firing material. The crystal phase of the pre-firing material is fully formed, which improves the temperature stability.

[0115] 1002-4, Second ball milling: Using the same parameters as the first ball milling, ball milling for 6 hours to obtain the ball milled material, which includes slurry particles with a D50 of 1.7 μm.

[0116] 1002-5, Spray drying granulation: 2% PVA was added to the slurry-like ball milled material. The inlet temperature of the spray dryer was 192℃, the outlet temperature was 84℃, and the atomizing disc speed was 13000r / min, to obtain ceramic powder with a flowability of 11s / 50g.

[0117] The ceramic powder obtained through this embodiment has a green body density of 3.8 g / cm³. 3 Sintering at 1310℃ for 4 hours, test results: dielectric constant 126, dielectric loss tangent 0.038%, temperature characteristic (-55℃~125℃) 10 ppm, suitable for precision electronic equipment scenarios with extremely high temperature stability requirements.

[0118] In this embodiment of the invention, in order to verify the performance of the high-dielectric NPO ceramic dielectric material, the ceramic dielectric material is prepared into a ceramic capacitor, and the performance indicators of the ceramic capacitor are tested to further verify the performance of the high-dielectric NPO ceramic dielectric material provided in this embodiment of the invention.

[0119] This process revolves around ensuring the density of the ceramic body, improving electrode bonding strength, and accurately testing key performance characteristics. Ultimately, it verifies whether the material meets the design requirements of "dielectric constant greater than or equal to 120, dielectric loss tangent less than or equal to 0.05%, and temperature characteristic less than or equal to 15 ppm." Specifically, this includes:

[0120] Step 1101, Dry pressing: Prepare a product with a density of 3.5–3.8 g / cm³. 3 Cylindrical green body:

[0121] Specifically, the process includes weighing a certain amount of ceramic powder, pouring the powder evenly into the mold cavity, smoothing the surface, starting the dry press, increasing the pressure according to the set pressure gradient, holding the pressure for 3-5 seconds, slowly releasing the pressure, demolding and removing the green blank, checking for any missing corners, cracks, or delamination, and then placing it in a drying oven to remove residual moisture for later use.

[0122] Step 1102, sintering into porcelain: Prepare the porcelain body by holding at 1300℃~1310℃ for 3~4 hours.

[0123] It adopts a box-type resistance furnace or a pusher kiln, and the furnace chamber is made of corundum (Al2O3), which is resistant to high temperature and does not react chemically with NPO ceramics.

[0124] Step 1103, Electrode preparation: The two ends of the ceramic body are coated with conductive silver paste and fired at 800±20℃ to obtain the silver sheet of the ceramic capacitor.

[0125] Specifically, this involves selecting a high-temperature sintering silver paste specifically for ceramic capacitors. Its main components include: ① silver powder (particle size 1–5 μm, content 60%–80%, core conductive phase); ② glass powder (content 5%–10%, melted at low temperature to act as a binder phase, bonding the silver powder to the ceramic body); ③ organic carrier (resin + solvent, content 10%–25%, used to adjust the viscosity of the silver paste for easier coating). Manual brushing or screen printing is used to ensure the electrode coating has the following characteristics: ① uniform thickness (dry film thickness 10–20 μm); ② complete coverage (no missed areas or pinholes); ③ a 0.5–1 mm gap between the coating and the ceramic body edge (to avoid short circuits). The sintering process consists of three stages: a low-temperature stage (room temperature–400℃), a medium-temperature stage (400–600℃), and a high-temperature stage (600–800±20℃, held for 15–30 minutes).

[0126] This method forms silver electrodes with excellent conductivity, strong bonding with the ceramic body, and strong oxidation resistance at both ends of the ceramic body, enabling the ceramic capacitor to have charge storage and conduction functions. The electrodes are the bridge connecting the ceramic dielectric and the external circuit, and their bonding force and conductivity directly affect the reliability of the capacitor.

[0127] Step 1104, Electrical Performance Test (Part 1):

[0128] Testing the core electrical performance indicators of silver capacitor sheets directly verifies whether the dielectric properties of the material meet the standards. Among them: ① the dielectric loss tangent (tanδ) reflects the degree of energy loss of the dielectric material; ② the dielectric constant (ε) reflects the material's ability to store charge.

[0129] Specifically, this includes: measuring the ceramic body thickness d using a micrometer (accuracy 0.001mm) (taking the average of 3 different points), measuring the electrode diameter using calipers, and calculating the electrode area S (for cylindrical ceramic bodies, the electrode area is the same as the circular area S, which is equal to πr).2 Calibrate using a standard capacitor (accuracy ±0.01%) to ensure test accuracy; ensure the electrodes at both ends of the capacitor's silver plate are in close contact with the LCR bridge test fixture; set the test frequency to 1kHz and the voltage to 1V, and read the capacitance value C and the dielectric loss tangent tanδ; substitute these values ​​into the dielectric constant calculation formula to obtain the relative dielectric constant ε. r .

[0130] The test results show that the dielectric loss tangent is less than or equal to 0.05% (i.e., 5 × 10⁻⁶). -4 The dielectric constant is greater than or equal to 120; the same sample is tested repeatedly 3 times, and the data deviation is less than or equal to ±2% to ensure reliable results.

[0131] Step 1105, Electrical Performance Test (Part Two):

[0132] The performance stability of the material was verified over a wide temperature range (-55℃ to 125℃). The temperature characteristics were expressed by the temperature coefficient (TC), with the unit being PPm / ℃. The temperature coefficient reflects the sensitivity of the capacitance to temperature changes. The smaller the value, the better the temperature stability.

[0133] Specifically, this includes: first testing the sample capacitance C at 25℃. 25 As a reference value, the sample was placed in a positive and negative temperature chamber, cooled to -55℃, and held for 30 minutes. Then, the LCR bridge capacitor C was connected via an extension clamp for testing. -55 Test the capacitance value sequentially at -25℃ and 0℃; then raise the temperature to 50℃, 100℃, and 125℃, hold at each temperature for 30 minutes, and test the corresponding capacitance value C. 50 C 100 C 125 Calculate the temperature coefficient TC at each temperature point, and take the TC with the largest absolute value as the temperature characteristic index of the material.

[0134] The test results show that, within the entire temperature range of -55℃ to 125℃, the absolute value of the temperature coefficient TC at all test temperature points is less than or equal to 15 ppm / ℃, which meets the requirement of a temperature characteristic of less than or equal to 15 ppm.

[0135] Through precise control of the above steps, the complete transformation from ceramic powder to qualified capacitor silver sheet can be achieved. Scientific testing can verify whether the material performance meets the invention objectives, providing reliable performance data support for subsequent product applications.

[0136] The NPO ceramic dielectric material provided in this embodiment of the invention has BaTiO3 as its main crystalline phase. Figure 1 This is a magnified microscopic diagram of the main crystalline phase BaTiO3 of the NPO ceramic dielectric material provided in an embodiment of the present invention. Figure 1It is known that the BaTiO3 crystal phase is mainly tetragonal and cubic, with a dielectric constant of 1000–5000 at room temperature. In practical applications, due to the high dielectric constant of BaTiO3, the addition of substances such as Bi2O3, Sm2O3, and SiO2 to the NPO ceramic dielectric material provided in this embodiment of the invention can enable the ceramic to form... Figure 2 The dense structure shown reduces the dielectric constant of the material, broadens the Curie peak, and achieves the temperature characteristics required for NPO ceramic dielectric materials.

[0137] In summary, the high-dielectric NPO ceramic dielectric material and its preparation method provided by this invention solve the problem of insufficient performance of domestically produced materials. By optimizing the formula, the dielectric constant of the NPO material made from domestic raw materials is increased to greater than or equal to 120, far exceeding the level of 8-90 of existing domestic and similar products. At the same time, the dielectric loss tangent is reduced to less than or equal to 0.05%, and the temperature characteristics are optimized to less than or equal to 15 ppm (-55℃ to 125℃), bridging the performance gap between domestic and imported materials and achieving performance comparable to imported products and leading the domestic level. It also solves the problem of high energy loss of existing materials by significantly reducing the dielectric loss tangent, reducing energy loss during circuit operation, and improving the energy efficiency and stability of capacitors and related electronic equipment that rely on this material. Furthermore, it solves the problem of insufficient temperature adaptability of the material by enhancing temperature stability through optimized formula, making the capacitance fluctuation of the material smaller in a wide temperature range of -55℃ to 125℃, meeting the stringent requirements of precision electronic equipment for stable performance under extreme temperature environments. Finally, it solves the problem of domestic reliance on imports and high costs for high-end materials.

[0138] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A high-dielectric NPO ceramic dielectric material, characterized in that, include: 25%–35% TiO2; 20%–30% Sm2O3; 1%–8% La2O3; 10%–30% BaCO3; 1%–3% SiO2; 10% to 30% Bi2O3.

2. A method for preparing a high-dielectric NPO ceramic dielectric material, characterized in that, include: The high dielectric NPO ceramic dielectric material, deionized water and zirconium balls in claim 1 are ball-milled in a ball mill in a 1:1:1 ratio to obtain the initial material after ball milling. The initial material is filtered to remove water, resulting in a dehydrated material; the dehydrated material is then pre-calcined in a pre-calcination furnace at a temperature of 1100℃~1200℃ to obtain a pre-calcined material. The pre-calcined material, deionized water and zirconium balls are ball-milled in a ball mill at a ratio of 1:1:1 to obtain the ball-milled material. The ball milling material is mixed with 1% to 2% polyvinyl alcohol (PVA) and then spray-dried to obtain ceramic powder.

3. The preparation method according to claim 2, characterized in that, The step of ball milling the high-dielectric NPO ceramic dielectric material, deionized water, and zirconium balls in a 1:1:1 ratio in a ball mill to obtain the initial material after ball milling specifically includes: High-dielectric NPO ceramic media material, deionized water, and zirconium balls were placed in a planetary ball mill in a 1:1:1 ratio and milled for 6 hours to obtain an initial material with a particle size of 2-5 μm. The initial material was a slurry.

4. The preparation method according to claim 2, characterized in that, The initial material is filtered to remove water, resulting in a dehydrated material, specifically comprising: Pressure is applied to the initial material placed on the filter plate using a plate and frame filter press or a chamber filter press, causing the moisture in the initial material to seep out through the filter cloth on the filter plate, resulting in a dehydrated material with a moisture content of 15% to 20%, which is in the form of a cake.

5. The preparation method according to claim 2, characterized in that, The dehydrated material is pre-calcined in a pre-calcination furnace at a temperature of 1100℃~1200℃ to obtain a pre-calcined material, specifically including: At room temperature, the cake-shaped dehydrated material is placed in a box-type resistance furnace or a pusher kiln. The dehydrated material is pre-fired in the box-type resistance furnace or the pusher kiln to obtain a pre-fired material containing BaTiO3, and then kept at the temperature in the box-type resistance furnace or the pusher kiln for 2-3 hours. The particle size of the pre-fired material is 10-15 μm.

6. The preparation method according to claim 2, characterized in that, The pre-calcined material, deionized water, and zirconium balls are ball-milled in a ball mill at a ratio of 1:1:1 to obtain the ball-milled material, specifically comprising: The pre-calcined material in cake form is crushed, and the pre-calcined material, deionized water, and zirconium balls are placed in a planetary ball mill in a 1:1:1 ratio; after ball milling for 6 hours, a ball-milled material is obtained, which is a slurry.

7. The preparation method according to claim 2, characterized in that, The ball milling material is mixed with 1% to 2% polyvinyl alcohol (PVA) and then spray-dried to obtain ceramic powder, specifically comprising: Add 1% to 2% polyvinyl alcohol (PVA) to the ball milling material, stir and dissolve it, then atomize the ball milling material through an atomizing disc and dry it in a granulation tower to obtain spherical ceramic powder with a moisture content of less than 2%. The rotation speed of the atomizing disc is 10,000 to 15,000 r / min.

Images