Medium material, method for preparing the same and use thereof

Abstract

The application discloses a dielectric material and a preparation method and application thereof. The dielectric material comprises a core, a first coating layer coated on the surface of the core, and a second coating layer coated on the surface of the first coating layer. The core comprises BaTiO3. The first coating layer comprises MgO, M1, and M2. The second coating layer comprises (Ca (1‑x‑y) Ba x Sr y )ZrO3 and R2O3. In the (Ca (1‑x‑y) Ba x Sr y )ZrO3, 0<=x<=1 and 0<=y<=1. The dielectric material has high dielectric strength, high dielectric constant, and excellent dielectric-temperature characteristics, and can be used for manufacturing high-voltage and high-capacity chip multilayer ceramic capacitors.

Description

Technical Field

[0001] This invention belongs to the field of ceramic materials, specifically relating to a dielectric material, its preparation method, and its application. Background Technology

[0002] Multilayer ceramic chip capacitors (MLCCs) are one of the representatives of ceramic electronic components. Due to their high reliability and low cost, they are widely used in various electronic devices. Especially for thin and small electronic devices, multilayer ceramic chip capacitors need to be developed towards miniaturization, high capacitance, high performance and thinness to meet the increasingly advanced usage requirements.

[0003] Currently, BaTiO3-based compounds are the primary dielectric materials used in manufacturing small-size, high-capacity MLCCs. The dielectric layer formed from BaTiO3 (BT) materials exhibits a high dielectric constant. However, BaTiO3 is a typical ferroelectric material at room temperature, but it transforms from a tetragonal ferroelectric phase to a cubic paraelectric phase at high temperatures (around 120°C). This transformation causes a sharp change in the dielectric constant, with a rapid initial increase followed by a sharp decrease with increasing temperature. This results in poor performance stability of MLCCs made from BaTiO3 materials under high-temperature or high-pressure operating conditions. Furthermore, BaTiO3 exhibits significant polarization, leading to low breakdown field strength in MLCCs made from it, making it difficult to meet the requirements of high-capacitance, high-pressure applications. (BaCaSr)ZrO3-based materials obtained through A-site doping are non-ferroelectric materials with a flat dielectric-temperature characteristic curve and good dielectric stability at high temperatures. However, their very low dielectric constant makes them unsuitable for high-capacitance products. Therefore, there is an urgent need to develop a ceramic dielectric material capable of producing MLCCs with high voltage resistance, high temperature stability, and a high dielectric constant. Summary of the Invention

[0004] In order to overcome the problems existing in the prior art, one of the objectives of the present invention is to provide a medium material.

[0005] The second objective of this invention is to provide a method for preparing a dielectric material.

[0006] The third objective of this invention is to provide a chip-type multilayer ceramic capacitor.

[0007] The fourth objective of this invention is to provide the application of the above-mentioned dielectric materials and / or multilayer ceramic chip capacitors in electronic devices.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0009] A first aspect of the present invention provides a dielectric material comprising a core, a first coating layer covering the surface of the core, and a second coating layer covering the surface of the first coating layer; the core comprising BaTiO3; the first coating layer comprising MgO, M1, and M2; and the second coating layer comprising (Ca... (1-x-y) Ba x Sr y ZrO3 and R2O3;

[0010] The (Ca) (1-x-y) Ba x Sr y In ZrO3, 0 ≤ x ≤ 1, 0 ≤ y ≤ 1;

[0011] M1 is an oxide selected from at least one of Mn, Fe, Co, Cr, Ni, Mo, W, and V;

[0012] M2 is an oxide selected from at least one of Si, Al, B, and Li;

[0013] The R is selected from at least one of La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and Y.

[0014] In the dielectric material of this invention, the core is BaTiO3, which possesses ferroelectric properties and a high dielectric constant, enabling the dielectric material to have a high dielectric constant, thereby giving the chip multilayer ceramic capacitor made of this dielectric material a high capacitance characteristic; the first coating layer contains MgO, M1, and M2, and the second coating layer contains (Ca... (1-x-y) Ba x Sr y ZrO3 and R2O3, being paraelectric phases, give MLCC products prepared from dielectric materials excellent stability under high temperature and high pressure. Furthermore, the (Ca) in the second coating layer... (1-x-y) Ba x Sr y ZrO3 possesses high breakdown field strength and highly stable dielectric-temperature properties, which can increase the activation energy for oxygen vacancy migration in dielectric materials, thereby reducing the capacitance change rate of MLCCs made from dielectric materials at different temperatures and extending the material's service life.

[0015] The first and second coating layers in this invention can improve the reliability, dielectric strength, and temperature stability of MLCC products prepared from dielectric materials.

[0016] Preferably, the BaTiO3 is tetragonal. Tetragonal BaTiO3 possesses excellent ferroelectric properties and a high dielectric constant.

[0017] Preferably, based on a BaTiO3 molar percentage of 100%, the molar percentage of MgO is 0.5-10%, the molar percentage of M1 is 0.1-5%, the molar percentage of M2 is 0.1-10%, and the molar percentage of (Ca) is... (1-x-y) Ba x Sr y The molar percentage of ZrO3 is 0.5-15%, and the molar percentage of R2O3 is 0.1-5%.

[0018] In this invention, the molar percentage of MgO is 0.5% to 10%, for example, the molar percentage of MgO can be selected from 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5%, and 10%; more preferably, the molar percentage of MgO is 1% to 6%. In this invention, MgO can act as a barrier to (Ca) (1-x-y) Ba x Sr y ZrO3 diffuses into the core and dissolves in BaTiO3, preventing the formation of a homogeneous compound in the (CaBaSr)(TiZr)O3 system, thus hindering the formation of a second coating layer. When the MgO content is too high (e.g., greater than 10%), the sinterability of the material decreases, hindering the solid solution of elements, thinning the first coating layer, and reducing the activation energy for oxygen vacancy migration in the dielectric material, thereby degrading the reliability of the MLCC product prepared from the dielectric material. When the MgO content is too low (e.g., less than 0.5%), the hindering effect of Mg is weakened, and (CaBaSr)ZrO3 easily dissolves in the BaTiO3 core, even forming a homogeneous phase, preventing the formation of a second coating layer, resulting in poor voltage withstand capability and high-temperature capacity stability of the MLCC product prepared from the dielectric material.

[0019] In this invention, the (Ca) (1-x-y) Ba x Sr y The molar percentage of ZrO3 is 0.5-15%, for example, the (Ca) (1-x-y) Ba x Sr y The molar percentage of ZrO3 can be selected from 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5%, 10%, 10.5%, 11%, 11.5%, 12%, 12.5%, 13%, 13.5%, 14%, 14.5%, and 15%; more preferably, the (Ca) (1-x-y) Ba x Sry The molar percentage of ZrO3 is 1-10%. In this invention, when (Ca... (1-x-y) Ba x Sr y When the ZrO3 content is too high (e.g., exceeding 15%), the proportion of the second coating layer is too high, resulting in a low dielectric constant of the second coating layer and a significant decrease in the overall dielectric constant of the MLCC product prepared from the dielectric material; when (Ca... (1-x-y) Ba x Sr y When the ZrO3 content is too low (e.g., below 0.5%), the thickness of the second coating layer is too thin, resulting in poor breakdown field strength and dielectric-temperature characteristics of the MLCC products prepared from the dielectric material.

[0020] In this invention, (Ca) (1-x-y) Ba x Sr y In ZrO3, 0 ≤ x ≤ 1, 0 ≤ y ≤ 1; for example, x can be selected from 0, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.12, 0.14, 0.16, 0.18, 0.2, 0.22, 0.24, 0.26, 0.28, 0.3, 0.32, 0.34, 0.36, ... 0.38, 0.4, 0.42, 0.44, 0.46, 0.48, 0.5, 0.52, 0.54, 0.56, 0.58, 0.6, 0.62, 0.64, 0.66, 0.68, 0.7, 0.72, 0.74, 0.76, 0.78, 0.8, 0.82, 0.84, 0.86, 0.88, 0.9, 0.92, 0.94, 0 0.96, 0.98, 1; y can be selected from 0, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.12, 0.14, 0.16, 0.18, 0.2, 0.22, 0.24, 0.26, 0.28, 0.3, 0.32, 0.34, 0.36, 0.38, 0.4, 0. 42, 0.44, 0.46, 0.48, 0.5, 0.52, 0.54, 0.56, 0.58, 0.6, 0.62, 0.64, 0.66, 0.68, 0.7, 0.72, 0.74, 0.76, 0.78, 0.8, 0.82, 0.84, 0.86, 0.88, 0.9, 0.92, 0.94, 0.96, 0.98, 1. Preferably, the (Ca) (1-x-y) Ba x Sr y ZrO3 is selected from (Ca 0.5 Ba 0.2 Sr0.3 ZrO3, (Ca 0.1 Ba 0.1 Sr 0.8 ZrO3, (Ca 0.1 Ba 0.2 Sr 0.7 ZrO3, (Ca 0.3 Ba 0.3 Sr 0.4 ZrO3, (Ca 0.1 Ba 0.4 Sr 0.5 ZrO3, (Ca 0.2 Ba 0.5 Sr 0.3 ZrO3, (Ca 0.2 Ba 0.6 Sr 0.2 ZrO3, (Ca 0.1 Ba 0.6 Sr 0.3 ZrO3, (Ca 0.2 Ba 0.7 Sr 0.1 ZrO3, (Ca 0.1 Ba 0.8 Sr 0.1 ZrO3, (Ca 0.05 Ba 0.9 Sr 0.05 ZrO3, (Ca 0.7 Ba 0.2 Sr 0.1 ZrO3, (Ca 0.8 Ba 0.1 Sr 0.1 ZrO3, (Ca 0.9 Ba 0.05 Sr 0.05 ZrO3, (Ca 0.05 Ba 0.05 Sr 0.9 )ZrO3, CaZrO3, SrZrO3, BaZrO3, (Ca 0.5 Ba 0.5 ZrO3 or (Ca 0.5 Sr 0.5 ZrO3. The above (Ca) (1-x-y) Ba x Sr y ZrO3 possesses high breakdown field strength and highly stable dielectric-temperature properties, which can improve the activation energy of oxygen vacancy migration in dielectric materials, thereby reducing the capacitance change rate of MLCCs made from dielectric materials at different temperatures and extending the material's service life.

[0021] In this invention, the molar percentage of R2O3 is 0.1% to 5%, for example, the molar percentage of R2O3 can be selected from 0.1%, 0.2%, 0.4%, 0.6%, 0.8%, 1%, 1.2%, 1.4%, 1.6%, 1.8%, 2%, 2.2%, 2.4%, 2.6%, 2.8%, 3%, 3.2%, 3.4%, 3.6%, 3.8%, 4%, 4.2%, 4.4%, 4.6%, 4.8%, and 5%. In this invention, when the R2O3 content is too high (e.g., greater than 5%), after sintering into MLCC products, the rare earth element R is dissolved in too much solid solution, the first coating layer becomes thicker, the core ratio becomes smaller, and the dielectric constant of the MLCC products prepared by the dielectric material decreases at room temperature. When the R2O3 content is too low (e.g., less than 0.1%), the first coating layer is difficult to form, which leads to the deterioration of the insulation resistance of the MLCC products prepared by the dielectric material at high temperature, a shorter service life, and a deterioration of temperature characteristics.

[0022] In this invention, the molar percentage of M1 is 0.1% to 5%, for example, the molar percentage of M1 can be selected from 0.1%, 0.2%, 0.4%, 0.6%, 0.8%, 1%, 1.2%, 1.4%, 1.6%, 1.8%, 2%, 2.2%, 2.4%, 2.6%, 2.8%, 3%, 3.2%, 3.4%, 3.6%, 3.8%, 4%, 4.2%, 4.4%, 4.6%, 4.8%, and 5%. In this invention, when the M1 content is too high (e.g., greater than 5%), semiconducting is easily caused, leading to a decrease in the insulation resistance of the MLCC product prepared from the dielectric material, and poor aging rate and DC bias characteristics; when the M1 content is too low (e.g., less than 0.1%), the reduction resistance decreases, leading to Ti… 4+ The reduction of dielectric materials leads to a significant deterioration in the high-temperature and high-voltage insulation resistance performance of MLCC products prepared from dielectric materials.

[0023] In this invention, the molar percentage of M2 is 0.1% to 10%, for example, the molar percentage of M2 can be selected from 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5%, and 10%. In this invention, when the content of M2 is too high (e.g., greater than 10%), there is too much liquid phase during sintering into MLCC products, the grains are prone to grow, and the life characteristics deteriorate significantly; when the content is too low (e.g., less than 0.1%), the sinterability decreases, higher sintering temperature is required, and the insulation resistance of the MLCC products prepared from the dielectric material decreases.

[0024] The second aspect of the present invention provides a method for preparing the dielectric material provided in the first aspect of the present invention, comprising the following steps:

[0025] S1: Add magnesium salt, salt of M1, and salt of M2 to a suspension of barium titanate, mix, dry, and then pre-fire to obtain ceramic powder with a first coating layer.

[0026] S2: The ceramic powder with the first coating layer, (Ca) (1-x-y) Ba x Sr y ZrO3 and R2O3 are mixed, ground, and then calcined to obtain the medium powder.

[0027] During the preparation of dielectric powder, MgO can begin to dissolve into the BaTiO3 core at relatively low temperatures. However, due to the slow diffusion rate of Mg within the BaTiO3 grains, its solubility is low, mainly concentrated in the outer region of BaTiO3, and then dispersed into R2O3 and (Ca). (1-x-y) Ba x Sr y When ZrO3 begins to dissolve, MgO has not yet diffused sufficiently, thus hindering the dissolution of both. Furthermore, the dissolution rate of rare earth element R is faster than that of Ca. (1-x-y) Ba x Sr y ZrO3, thus forming R2O3 and (Ca) (1-x-y) Ba x Sr y The second coating layer of ZrO3 composite improves the performance of MLCC products prepared from dielectric materials under high temperature and high pressure.

[0028] Preferably, the preparation method of the barium titanate suspension is as follows: barium titanate powder is mixed with a solvent selected from at least one of water, ethanol, and glacial acetic acid, and then ground to obtain the suspension.

[0029] Preferably, the barium titanate powder is prepared by a method selected from solid-phase method, co-precipitation method, hydrothermal method or oxalate method.

[0030] Preferably, the magnesium salt is selected from at least one of magnesium nitrate, magnesium carbonate, and magnesium acetate.

[0031] Preferably, the salt of M1 is selected from at least one of the nitrate, carbonate, and acetate of M1.

[0032] Preferably, the salt of M2 is selected from at least one of the nitrate, carbonate, and acetate of M2.

[0033] Preferably, the drying temperature in step S1 is 100-300℃, for example, it can be selected from 100℃, 120℃, 140℃, 160℃, 180℃, 200℃, 220℃, 240℃, 260℃, 280℃, 300℃, 320℃, 340℃, 360℃, 380℃, 400℃; more preferably, the drying temperature in step S1 is 120-200℃.

[0034] Preferably, the drying time in step S1 is 2 to 10 hours, for example, it can be selected from 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, or 10 hours; more preferably, the drying time in step S1 is 4 to 8 hours.

[0035] Preferably, the pre-firing temperature in step S1 is 400-800℃, for example, it can be selected from 400℃, 420℃, 440℃, 460℃, 480℃, 500℃, 520℃, 540℃, 560℃, 580℃, 600℃, 620℃, 640℃, 660℃, 680℃, 700℃, 720℃, 740℃, 760℃, 780℃, 800℃; more preferably, the pre-firing temperature in step S1 is 500-700℃.

[0036] Preferably, the pre-firing time in step S1 is 0.5 to 3 hours, for example, it can be selected from 0.5 hours, 0.8 hours, 1 hour, 1.2 hours, 1.5 hours, 1.8 hours, 2 hours, 2.2 hours, 2.5 hours, 2.8 hours, and 3 hours; more preferably, the pre-firing time in step S1 is 1 to 2.5 hours.

[0037] Preferably, the calcination temperature in step S2 is 500–1000°C, for example, it can be selected from 500°C, 550°C, 600°C, 650°C, 700°C, 750°C, 800°C, 850°C, 900°C, 950°C, and 1000°C; more preferably, the calcination temperature in step S2 is 600–900°C.

[0038] Preferably, the calcination time in step S2 is 1 to 4 hours, for example, it can be selected from 1 hour, 1.2 hours, 1.5 hours, 1.8 hours, 2 hours, 2.2 hours, 2.5 hours, 2.8 hours, 3 hours, 3.2 hours, 3.5 hours, 3.8 hours, and 4 hours; more preferably, the calcination time in step S2 is 1 to 3 hours.

[0039] Preferably, step S2 is: mixing the ceramic powder with the first coating layer and (Ca) (1-x-y) Ba x Sr y ZrO3 and R2O3 are mixed and ground, wet-milled and dried, and then calcined to obtain the medium powder.

[0040] Preferably, the wet pulverization time in step S2 is 4 to 12 hours, for example, it can be selected from 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, 11 hours, or 12 hours.

[0041] Preferably, the drying temperature in step S2 is 100 to 400°C, for example, it can be selected from 100°C, 200°C, 300°C, or 400°C.

[0042] Preferably, the drying time in step S2 is 150 to 300 min, for example, it can be selected from 150 min, 170 min, 190 min, 200 min, 220 min, 240 min, 260 min, 280 min, or 300 min.

[0043] Preferably, the grinding step in step S2 is ball milling.

[0044] In the preparation of the dielectric material of this invention, the elements in the raw materials diffuse and dissolve in BaTiO3 (i.e., BT). Mg ions begin to dissolve at low temperatures, but their diffusion rate in BT is low, hindering the diffusion of rare earth ions R and (Ca). (1-x-y) Ba x Sr y The diffusion of ZrO3 forms a double-shell structure.

[0045] A third aspect of the present invention provides a chip-type multilayer ceramic capacitor, including a dielectric layer, wherein the dielectric layer is made of the dielectric material described in the first aspect of the present invention.

[0046] Preferably, the chip multilayer ceramic capacitor includes a laminate, which comprises a dielectric layer and an inner electrode layer stacked sequentially.

[0047] Preferably, each of the two ends of the laminate is provided with an external electrode, which is electrically connected to the inner electrode layer.

[0048] Preferably, the surface of the outer electrode layer is provided with a plating layer.

[0049] Preferably, the plating layer includes a first plating layer disposed on the surface of the outer electrode and a second plating layer disposed on the surface of the first plating layer.

[0050] Preferably, the method for manufacturing the chip multilayer ceramic capacitor includes the following steps:

[0051] A ceramic slurry containing the aforementioned medium material is formed into a film to obtain a ceramic green sheet;

[0052] A conductive film is formed on the ceramic green sheet, stacked, heat-treated, and sintered to obtain the laminate.

[0053] External electrodes are formed at both ends of the laminate, and a coating film is formed on the surface of the external electrodes to obtain the chip multilayer ceramic capacitor.

[0054] Preferably, the ceramic slurry comprises a medium material, an organic binder, and an organic solvent in a mass ratio of 100:(7-10):(40-60).

[0055] Preferably, the step of forming a film from the ceramic slurry containing the medium material specifically involves forming a film from the ceramic slurry using any one of the methods selected from lip coating and blade coating.

[0056] Preferably, the heat treatment temperature is 250–350°C.

[0057] Preferably, the sintering atmosphere is a strong reducing atmosphere; more preferably, the sintering atmosphere is a strong reducing atmosphere with a hydrogen to nitrogen volume ratio of (0.1-2):100.

[0058] Preferably, the sintering temperature is 1100–1300°C.

[0059] Preferably, the sintering time is 2 to 4 hours.

[0060] Preferably, the step of forming external electrodes at both ends of the laminate is as follows: coating external electrode paste at both ends of the laminate, and then baking at a temperature of 600-900°C for 2-4 hours.

[0061] The fourth aspect of the present invention provides the application of the dielectric material described in the first aspect of the present invention and / or the chip multilayer ceramic capacitor described in the third aspect of the present invention in electronic devices.

[0062] The beneficial effects of this invention are as follows: The dielectric material in this invention uses barium titanate as the core. Barium titanate possesses ferroelectric properties and a high dielectric constant, which allows the dielectric material to maintain a high dielectric constant. Using MgO or similar materials as the first coating layer can prevent the reaction of R₂O₃ and (Ca)₂O₃. (1-x-y) Ba x Sr y The infiltration of ZrO3 into the core prevents the formation of a double-shell structure. Therefore, R2O3-doped (Ca) alloys are used instead. (1-x-y) Ba x Sr y ZrO3 material is used as the second coating layer. It has a paraelectric phase structure, which enables the MLCC products prepared by the dielectric material to have excellent stability under high temperature and high pressure. Therefore, the dielectric material in this invention has high dielectric strength, high dielectric constant and excellent dielectric-temperature characteristics, and can be used to make high voltage and high capacitance chip multilayer ceramic capacitors. Attached Figure Description

[0063] Figure 1 The image shows the TEM-EDS diagram of the chip multilayer ceramic capacitor prepared using the dielectric material in Comparative Example 1.

[0064] Figure 2 The image shows a TEM-EDS image of a chip multilayer ceramic capacitor prepared using the dielectric material described in Example 1. Detailed Implementation

[0065] The specific implementation of the present invention will be further described in detail below with reference to the accompanying drawings and examples, but the implementation and protection of the present invention are not limited thereto. It should be noted that any processes not specifically described in detail below are those that can be implemented or understood by those skilled in the art by referring to the prior art. Reagents or instruments used without specified manufacturers are all conventional products that can be purchased commercially.

[0066] In the dielectric material of the present invention, when the materials in the first coating layer and the second coating layer meet the following requirements, such as: the molar percentage of MgO is 0.5-10%; (Ca (1-x-y) Ba x Sr y In ZrO3, 0≤x≤1, 0≤y≤1, and the molar percentage is 0.5~15%; M1 is selected from at least one oxide of Mn, Fe, Co, Cr, Ni, Mo, W, V, and the molar percentage is 0.1~5%; M2 is selected from at least one oxide of Si, Al, B, Li, and the molar percentage is 0.1~10%; R is selected from at least one of La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Y, and the molar percentage of R2O3 is 0.1~5%. All of these conditions allow multilayer chip capacitors using this dielectric material as the dielectric layer to simultaneously meet the following requirements: dielectric constant ≥2500, breakdown field strength ≥40V / μm, 50% mean time to failure (MTTF) ≥3h, and TCC within ±15%. For ease of explanation of the technical solutions in this invention, only (Ca) oxides are selected in the following examples and comparative examples. (1-x-y) Ba x Sr y ZrO3 is (Ca 0.5 Ba 0.2 Sr 0.3 )ZrO3, CaZrO3, SrZrO3, BaZrO3, (Ca 0.5 Ba 0.5 ZrO3, (Ca 0.5 Sr 0.5 ZrO3, (Ca 0.1 Ba 0.4 Sr 0.5Several specific embodiments of ZrO3, M1 being MnO2, M2 being SiO2, and R2O3 being Dy2O3.

[0067] This invention uses ICP, XRF and other detection methods to detect the elemental composition and content of the sintered products in the following examples and comparative examples, and uses TEM to test the core-double shell structure of the sintered products in the examples and comparative examples.

[0068] Example 1

[0069] This example provides a dielectric material, including a core, a first coating layer, and a second coating layer;

[0070] A first coating layer covers the surface of the core, and a second coating layer covers the surface of the first coating layer; the core is BaTiO3, the first coating layer is a composite oxide layer of MgO, MnO2, and SiO2, and the second coating layer is (Ca... 0.5 Ba 0.2 Sr 0.3 A composite oxide layer of ZrO3 and Dy2O3.

[0071] With the core BaTiO3 molar percentage as 100%, the molar percentage of MgO is 4%, the molar percentage of MnO2 (i.e., M1) is 1%, the molar percentage of SiO2 (i.e., M2) is 4%, the molar percentage of Dy2O3 (i.e., R2O3) is 3%, and (Ca... 0.5 Ba 0.2 Sr 0.3 The molar percentage of ZrO3 is 6%, as shown in Table 1.

[0072] The dielectric material in this example was prepared using a method including the following steps:

[0073] 1) Place BaTiO3 powder in pure water, stir, grind and disperse to obtain a suspension;

[0074] 2) Taking BaTiO3 as 100 mol%, add 4 mol% magnesium acetate, 1 mol% manganese acetate and 4 mol% silicon acetate to the above suspension, stir and disperse to obtain a mixed solution containing the core and the first coating layer material.

[0075] 3) The mixed solution obtained in step 2) is dried and pre-fired to obtain BaTiO3 ceramic powder coated with MgO, MnO2 and SiO2, that is, ceramic powder with the first coating layer; the drying temperature is 200℃ and the drying time is 6h, the pre-fired temperature is 600℃ and the pre-fired time is 2h.

[0076] 4) Taking BaTiO3 as 100 mol%, 6 mol% (Ca) 0.5 Ba0.2 Sr 0.3 ZrO3 and 3 mol% Dy2O3 powders are mixed with ceramic powder with the first coating layer obtained in step 3), wet-milled for 6 hours, dried at 200°C for 200 minutes, and calcined at 750°C for 2 hours to obtain the medium material in this example.

[0077] Examples 2-6

[0078] The only difference between the medium materials in Examples 2 to 6 and those in Example 1 is that the molar percentage of MgO in the first coating layer is different, as shown in Table 1.

[0079] Examples 7-8

[0080] The only difference between the medium materials in Examples 7 and 8 and those in Example 1 is that the molar percentage of MnO2 in the first coating layer is different, as shown in Table 1.

[0081] Examples 9-10

[0082] The only difference between the dielectric materials in Examples 9 and 10 and those in Example 1 is that the molar percentage of SiO2 in the first coating layer is different, as shown in Table 1.

[0083] Examples 11-13

[0084] The only difference between the medium materials in Examples 11-13 and those in Example 1 is that the molar percentage of Dy2O3 in the second coating layer is different, as shown in Table 1.

[0085] Examples 14-19

[0086] The only difference between the dielectric materials in Examples 14-19 and those in Example 1 is that in the second coating layer (Ca 0.5 Ba 0.2 Sr 0.3 The molar percentage of ZrO3 varies, as shown in Table 1.

[0087] Comparative Examples 1-3

[0088] The only difference between the media materials in Comparative Examples 1 to 3 and those in Example 1 is that the molar percentage of MgO in the first coating layer is different, as shown in Table 1.

[0089] Comparative Examples 4-5

[0090] The only difference between the media materials in Comparative Examples 4 and 5 and those in Example 1 is that the molar percentage of Dy2O3 in the second coating layer is different, as shown in Table 1.

[0091] Comparative Examples 6-8

[0092] The only difference between the dielectric materials in Comparative Examples 6-8 and Example 1 is that in the second coating layer (Ca 0.5 Ba 0.2 Sr 0.3 The molar percentage of ZrO3 varies, as shown in Table 1.

[0093] The dielectric materials in Examples 2-19 and Comparative Examples 1-8 were all prepared according to the preparation method in Example 1.

[0094] Table 1. Composition ratios of dielectric materials in Examples 1-19 and Comparative Examples 1-8

[0095]

[0096] Examples 20-23

[0097] The only difference between the preparation methods of the dielectric materials in Examples 20-23 and Example 1 is that the pre-firing temperature in step 3) is different, as shown in Table 2.

[0098] Examples 24-27

[0099] The only difference between the preparation methods of the dielectric materials in Examples 24-27 and Example 1 is that the pre-firing time in step 3) is different, as shown in Table 2.

[0100] Examples 28-31

[0101] The only difference between the preparation methods of the dielectric materials in Examples 28-31 and Example 1 is that the calcination temperature in step 4) is different, as shown in Table 2.

[0102] Examples 32-35

[0103] The only difference between the preparation methods of the medium materials in Examples 32-35 and Example 1 is that the calcination time in step 4) is different, as shown in Table 2.

[0104] Comparative Examples 9-10

[0105] The only difference between the preparation methods of the dielectric materials in Comparative Examples 9 and 10 and those in Example 1 is that the pre-firing temperature in step 3) is different, as shown in Table 2.

[0106] Comparative Examples 11-12

[0107] The only difference between the preparation methods of the dielectric materials in Comparative Examples 11 and 12 and those in Example 1 is that the pre-firing time in step 3) is different, as shown in Table 2.

[0108] Comparative Examples 13-14

[0109] The only difference between the preparation methods of the media materials in Comparative Examples 13-14 and Example 1 is that the calcination temperature in step 4) is different, as shown in Table 2.

[0110] Comparative Examples 15-16

[0111] The only difference between the preparation methods of the media materials in Comparative Examples 15-16 and Example 1 is that the calcination time in step 4) is different, as shown in Table 2.

[0112] The dielectric materials in Examples 20-35 and Comparative Examples 9-16 have the same structure and composition ratio as the dielectric material in Example 1.

[0113] Table 2. Preparation parameters of the dielectric materials in Examples 20-35 and Comparative Examples 9-16

[0114]

[0115]

[0116] Examples 36-41

[0117] The only difference between the dielectric materials in Examples 36-41 and those in Example 1 is that Examples 36-41 use equimolar percentages of CaZrO3, SrZrO3, BaZrO3, and (CaZrO3). 0.5 Ba 0.5 ZrO3, (Ca 0.5 Sr 0.5 ZrO3, (Ca 0.1 Ba 0.4 Sr 0.5 ZrO3 replaces (Ca) in Example 1 0.5 Ba 0.2 Sr 0.3 ZrO3, as shown in Table 3.

[0118] Table 3. Composition ratio of the dielectric material in Examples 36-41

[0119]

[0120] Fabrication of multilayer ceramic chip capacitors:

[0121] (1) The media materials in Examples 1 to 41 and Comparative Examples 1 to 16, together with polyvinyl butyral (PVB) and ethanol, were added to a sand mill in a mass ratio of 100:10:50. The mixture was then wet-mixed to produce a ceramic media slurry. The ceramic media slurry was then processed by a lip coating method to produce a ceramic media green sheet.

[0122] (2) Then prepare a conductive paste for internal electrodes with base metal materials such as Ni as the main component, and use the conductive paste for internal electrodes to perform screen printing on the ceramic dielectric green sheet to form a conductive film with a given pattern on the surface of the ceramic dielectric green sheet.

[0123] (3) Multiple ceramic dielectric green sheets with conductive films are stacked in a given direction, with the ceramic dielectric green sheets without conductive films placed on the top layer and pressed together. The layers are then cut to a given size to produce a ceramic laminate. The ceramic laminate is then heat-treated at 300°C in an atmospheric atmosphere to decompose and remove the binder. Finally, it is sintered at 1200°C for 2 hours in a strongly reducing atmosphere composed of a gas with a H2:N2 volume ratio of 0.005:1 to obtain a sintered ceramic body.

[0124] (4) Apply conductive paste for external electrodes (mainly composed of Ag) to both ends of the ceramic sintered body and bake at 750°C for 2 hours to form external electrodes. In addition, although there are no particular limitations on the conductive material contained in the conductive paste for external electrodes, from the point of view of cost reduction, it is preferable to use Ag, Cu, or materials with alloys of them as the main components.

[0125] In addition, as a common method for preparing external electrodes, conductive paste for external electrodes can be applied to both ends of the ceramic laminate and then fired together with the ceramic laminate.

[0126] (5) Finally, electroplating is performed to form a first plating film composed of Ni, Cu, Ni-Cu alloy, etc. on the surface of the external electrode. Then, a second plating film composed of solder, tin, etc. is formed on the surface of the first plating film to obtain a chip multilayer ceramic capacitor.

[0127] Then, the dielectric constant, breakdown field strength, accelerated life test, and TCC performance of the multilayer ceramic capacitors made of the dielectric materials in Examples 1-41 and Comparative Examples 1-16 were tested respectively. The specific test methods are shown in Table 4 below.

[0128] Table 4 Performance Test Items, Test Conditions, Standards and Requirements

[0129]

[0130] The performance data of the multilayer ceramic capacitors made of the dielectric materials of Examples 1-19 and Comparative Examples 1-8, measured according to the above test method, are shown in Table 5 below. The performance data of the multilayer ceramic capacitors made of the dielectric materials of Examples 20-35 and Comparative Examples 9-16, measured according to the above test method, are shown in Table 6 below. The performance data of the multilayer ceramic capacitors made of the dielectric materials of Examples 36-41, measured according to the above test method, are shown in Table 7 below.

[0131] Table 5 Performance data of multilayer ceramic capacitors in Examples 1-19 and Comparative Examples 1-8

[0132]

[0133]

[0134] As shown in Table 5, compared with Comparative Examples 1-8, Examples 1-19 of the present invention, by adjusting the content of MgO, MnO2, and SiO2 in the first coating layer, and the content of (CaO, MnO2, and SiO2) in the second coating layer, respectively... 0.5 Ba 0.2 Sr 0.3 The ZrO3 and Dy2O3 content determines the dielectric constant of the fabricated multilayer ceramic capacitor, which is ≥2500, breakdown field strength ≥40V / μm, 50% mean time to failure (MTTF) ≥3h, and TCC ≤±15%, thus meeting the requirements for high-capacity, high-voltage MLCCs. A detailed analysis follows:

[0135] Comparing Examples 1-6 and Comparative Examples 1-3, it can be seen that because the first coating layer of BaTiO3 contains MgO, Mg ions can dissolve and enter BaTiO3 at a lower temperature when the dielectric material is sintered into the dielectric layer of MLCC products. However, its diffusion rate in BaTiO3 is slow, which affects the rare earth ions and (Ca) in the original second coating layer. 0.5 Ba 0.2 Sr 0.3 The solid solution and diffusion of ZrO3 have an inhibitory effect, thus maintaining the core-double-shell structure after sintering. In particular, the rare-earth-doped calcium barium strontium zirconate material in the second coating layer improves the withstand voltage and dielectric-temperature characteristics of the MLCC products prepared by the dielectric material of this invention. Therefore, appropriately increasing the MgO content in the first coating layer of the dielectric material helps in the formation of the second coating layer, which is beneficial to improving the withstand voltage, temperature characteristics, and service life of the MLCC products. However, when the MgO content is too low (e.g., Comparative Example 1 does not contain MgO), the core-double-shell structure cannot be formed, reducing the temperature stability, breakdown field strength, and service life of the MLCC products made from this dielectric material. Transmission electron microscopy was used to perform EDS energy dispersive spectroscopy analysis on the multilayer ceramic chip capacitors prepared from the dielectric materials of Comparative Example 1 and Example 1 to confirm the elemental distribution. The specific test results are as follows: Figure 1 and Figure 2 As shown. By Figure 1 and Figure 2 It can be seen that the rare earth Dy elements all formed a shell structure, and the Mg and Mn elements were uniformly distributed; in Example 1, the Ca, Sr and Zr elements in each grain overlapped and were wrapped around the outer layer of Ba and Ti elements, indicating that a (Ca)-containing structure was formed.(1-x-y) Ba x Sr y The second coating layer of ZrO3 in Comparative Example 1 shows a double-shell structure with rare earth elements in the inner shell. In contrast, in Comparative Example 1, Ca, Sr, Zr, Ba, and Ti are uniformly distributed, and no Ca, Sr, or Zr shells were found, meaning a double-shell grain structure could not be formed. In Comparative Example 1, the hindering effect of MgO was absent, and the (Ca) in the second coating layer... 0.5 Ba 0.2 Sr 0.3 ZrO3 diffuses into the core layer and forms a homogeneous phase with BaTiO3; while in Example 1, a phase containing (Ca) was formed. 0.5 Ba 0.2 Sr 0.3 The second coating layer of ZrO3; however, when the MgO content is too high, Mg ions excessively hinder the diffusion of other elements, the solid solubility of rare earth ions in BaTiO3 decreases, the sinterability of the material decreases, and grain growth is inhibited, resulting in a decrease in the dielectric constant and lifetime of MLCC products.

[0136] Comparative Examples 11-13 and 4-5 show that rare earth element Dy can be dissolved in the perovskite structure of ABO3, modifying the ABO3 perovskite material and forming a core-double-shell structure, which helps improve the dielectric-temperature stability and service life of MLCC products. When the rare earth element Dy doping is too low, the first coating layer of the material is difficult to form, resulting in a shorter lifespan. At the same time, the temperature characteristics deteriorate due to the increased proportion of barium titanate core. When the rare earth element Dy doping is too high, the proportion of the first and second coating layer regions is too high, the barium titanate core with high dielectric constant is reduced, and the room temperature dielectric constant of the MLCC product prepared by the dielectric material is reduced.

[0137] By comparing Examples 14-19 and Examples 6-8, it can be seen that (Ca) 0.5 Ba 0.2 Sr 0.3 The use of ZrO3 allows the dielectric material to form a second coating layer, which helps to improve the withstand voltage of the resulting MLCC products; when (Ca... 0.5 Ba 0.2 Sr 0.3 When the ZrO3 content is too low, the proportion of the second coating layer is small, resulting in a decrease in the breakdown field strength of the MLCC product prepared from the dielectric material; when (Ca... 0.5 Ba 0.2 Sr 0.3 When the ZrO3 content is too high, the proportion of the second coating layer is high, the proportion of the paraelectric phase increases, and the dielectric constant of the MLCC product prepared by the dielectric material is reduced.

[0138] Table 6 Performance data of multilayer ceramic capacitors in Examples 20-35 and Comparative Examples 9-16

[0139]

[0140]

[0141] As shown in Table 6, Examples 20-35 of the present invention can improve the dielectric constant and breakdown field strength of the prepared multilayer ceramic capacitors, prolong the MTTF time, and reduce the TCC by adjusting the pre-firing temperature and time. The specific analysis is as follows:

[0142] Comparative examples 20-23 and 9-10 show that the pre-calcination temperature affects the coating of the first coating layer containing MgO, influencing the solid solution effect and uniform distribution of Mg ions, and thus affecting the formation of the core-double-shell structure. When the pre-calcination temperature is too low or too high, the MgO coating effect is poor or it dissolves prematurely, affecting the rare earth elements and (Ca) (1-x-y) Ba x Sr y The solid solution barrier effect of ZrO3 is insufficient, which affects the formation of the core-double shell structure and reduces the breakdown field strength of MLCC products prepared from dielectric materials.

[0143] Comparative Examples 24-27 and Comparative Examples 11-12 show that the pre-firing time affects the formation and stability of the first coating layer containing MgO. When the pre-firing time is too short, the MgO coating is uneven, and some of it may even fail to form the first coating layer and remain in a free state, affecting the uniformity of the shell phase formation and reducing the breakdown field strength of the MLCC product prepared by the dielectric material. When the pre-firing time is too long, Mg ions dissolve prematurely, and the sintering activity of the powder decreases, resulting in poor compactness of the dielectric material and a decrease in the breakdown field strength of the MLCC product prepared by the dielectric material.

[0144] Comparative Examples 28-31 and Comparative Examples 13-14 show that calcination temperature has an effect on (Ca) 0.5 Ba 0.2 Sr 0.3 The formation and uniformity of the ZrO3 layer are affected by the fact that when the calcination temperature is too low, the second coating layer is not uniform, which affects the uniformity of the second coating layer and reduces the breakdown field strength of the MLCC product prepared by the dielectric material. When the calcination temperature is too high, the sintering activity of the powder becomes worse, the density of the dielectric material decreases, and the porosity is high, which also reduces the breakdown field strength of the MLCC product prepared by the dielectric material.

[0145] Comparative examples 32-35 and 15-16 show that the calcination time has an effect on (Ca). 0.5 Ba 0.2 Sr 0.3The formation and uniformity of the ZrO3 layer are affected by insufficient calcination time, resulting in poor formation of the second coating layer and impacting its uniformity. This leads to the presence of some (Ca) inclusions. 0.5 Ba 0.2 Sr 0.3 The single enriched phase of ZrO3 reduces the breakdown field strength of MLCC products prepared from dielectric materials; when the calcination time is too long, the sintering activity of the powder deteriorates, the material density decreases, and the porosity increases, which in turn reduces the breakdown field strength of MLCC products prepared from dielectric materials.

[0146] Table 7 Performance data of multilayer ceramic capacitors in Examples 36-41

[0147]

[0148] As shown in Table 7, the second coating layer of the dielectric material uses (Ca) (1-x-y) Ba x Sr y When ZrO3 is used for coating, as long as x and y satisfy the following conditions: 0≤x≤1, 0≤y≤1, the dielectric constant and breakdown field strength of the multilayer ceramic capacitor made of this dielectric material can be increased, the MTTF time can be extended and the TCC can be reduced.

[0149] In summary, the dielectric material in this invention is constructed by coating a BaTiO3 core with a first coating layer containing MgO, M1, and M2, followed by a coating layer containing Ca. (1-x-y) Ba x Sr y The composite oxide layers of ZrO3 and R2O3 ultimately form a dielectric material with a double-shell-core structure. During calcination, the highly tetragonal barium titanate core endows the dielectric material with a high dielectric constant, while the double-shell structure is a non-ferroelectric phase, especially (Ca... (1-x-y) Ba x Sr y The second coating layer of ZrO3 significantly enhances the activation energy for oxygen vacancy migration in the dielectric material, giving it a high breakdown field strength and excellent dielectric-temperature characteristics, thus resulting in a dielectric material for MLCCs with high voltage resistance, high capacity, and high reliability.

[0150] The embodiments of the present invention have been described in detail above. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention. Furthermore, the embodiments of the present invention and the features thereof can be combined with each other unless otherwise specified.

Claims

1. A dielectric material, characterized in that: The system includes a core, a first coating layer covering the surface of the core, and a second coating layer covering the surface of the first coating layer; the core comprises BaTiO3; the first coating layer comprises MgO, M1, and M2; and the second coating layer comprises (Ca... (1-x-y) Ba x Sr y ZrO3 and R2O3; The (Ca) (1-x-y) Ba x Sr y In ZrO3, 0 ≤ x ≤ 1, 0 ≤ y ≤ 1; M1 is an oxide selected from at least one of Mn, Fe, Co, Cr, Ni, Mo, W, and V; M2 is an oxide selected from at least one of Si, Al, B, and Li; The R is selected from at least one of La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and Y.

2. The dielectric material according to claim 1, characterized in that: Based on a BaTiO3 molar percentage of 100%, the molar percentage of MgO is 0.5-10%, the molar percentage of M1 is 0.1-5%, the molar percentage of M2 is 0.1-10%, and the molar percentage of (Ca... (1-x-y) Ba x Sr y The molar percentage of ZrO3 is 0.5-15%, and the molar percentage of R2O3 is 0.1-5%.

3. The dielectric material according to claim 2, characterized in that: The molar percentage of MgO is 1-6%; And / or, the (Ca) (1-x-y) Ba x Sr y The molar percentage of ZrO3 is 1~10%.

4. The method for preparing the dielectric material according to any one of claims 1 to 3, characterized in that: Includes the following steps: S1: Add magnesium salt, salt of M1, and salt of M2 to a suspension of barium titanate, mix, dry, and then pre-fire to obtain ceramic powder with a first coating layer. S2: The ceramic powder with the first coating layer, (Ca) (1-x-y) Ba x Sr y ZrO3 and R2O3 are mixed, ground, and then calcined to obtain the medium powder.

5. The method for preparing the dielectric material according to claim 4, characterized in that: The drying temperature in step S1 is 100~300℃; And / or, the drying time in step S1 is 2~10h; And / or, the pre-firing temperature in step S1 is 400~800℃; And / or, the pre-firing time in step S1 is 0.5~3h; And / or, the calcination temperature in step S2 is 500~1000℃; And / or, the calcination time in step S2 is 1~4h.

6. The method for preparing the dielectric material according to claim 4, characterized in that: The drying temperature in step S1 is 120~200℃; And / or, the drying time in step S1 is 4~8 hours; And / or, the pre-firing temperature in step S1 is 500~700℃; And / or, the pre-firing time in step S1 is 1~2.5h; And / or, the calcination temperature in step S2 is 600~900℃; And / or, the calcination time in step S2 is 1~3h.

7. The method for preparing the dielectric material according to claim 4, characterized in that: Step S2 is as follows: The ceramic powder with the first coating layer, (Ca...) (1-x-y) Ba x Sr y ZrO3 and R2O3 are mixed and ground, wet-milled and dried, and then calcined to obtain the medium powder.

8. The method for preparing the dielectric material according to claim 7, characterized in that: The wet pulverization time in step S2 is 4~12 hours; And / or, the drying temperature in step S2 is 100~400℃; And / or, the drying time in step S2 is 150~300 min.

9. A multilayer ceramic chip capacitor, comprising a dielectric layer, characterized in that: The dielectric layer is prepared using the dielectric material described in any one of claims 1 to 3.

10. The application of the dielectric material according to any one of claims 1 to 3 and / or the chip multilayer ceramic capacitor according to claim 9 in electronic devices.

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