X8R type high-reliability ceramic dielectric material with double-shell design as well as preparation method and application of X8R type high-reliability ceramic dielectric material

Abstract

The invention discloses an X8R type high-reliability ceramic dielectric material with a double-shell design and a preparation method and application thereof, and belongs to the technical field of electronic ceramic materials. According to the ceramic dielectric material, barium titanate is used as a main body material, at least one of Y2O3 and Dy2O3 is used as a first dopant, and at least one of MgO and MnO2 is used as a second dopant. The preparation method comprises the following steps: pre-sintering BaTiO3 and a first doping agent at a high temperature; and then adding a second doping agent for secondary mixing and high-temperature sintering. According to the method, a double-shell structure of a tetragonal phase crystal nucleus, a rare earth-rich inner shell layer and an Mg / Mn-rich outer shell layer is constructed in ceramic crystal grains. The high dielectric property of the BaTiO3 crystal nucleus is reserved, the rare earth-rich inner shell layer is used for inhibiting oxygen vacancy long-range migration, the Mg / Mn-rich outer shell layer is used for optimizing temperature stability, synergistic improvement of the high dielectric constant (epsilon r gt, 2200), X8R wide-temperature stability (delta C / C 25 DEG C is smaller than or equal to + / -15%, minus 55-150 DEG C) and high breakdown field strength (larger than or equal to 6.7 kV / mm) is achieved, and the high-dielectric-temperature-stability high-voltage-resistant MLCC is suitable for manufacturing the high-dielectric-temperature-stability high-voltage-resistant MLCC.

Description

Technical Field

[0001] This invention relates to the field of electronic ceramic materials technology, and in particular to an X8R type high-reliability ceramic dielectric material with a double-shell design, its preparation method, and its application. Background Technology

[0002] Multilayer ceramic capacitors (MLCCs) are widely used in consumer electronics, automotive electronics, and communication equipment. Barium titanate (BaTiO3)-based ceramics are the most common dielectric material in MLCCs. However, pure barium titanate ceramics exhibit a sharp dielectric constant peak near the Curie temperature (approximately 120 °C), resulting in poor temperature stability and making it difficult to meet the requirements of X7R or X8R (-55~150 °C, ΔC / CT). 25℃ High-end application standards such as ≤ ±15% are required. Furthermore, with the development of electronic systems such as 5G communications, high-end servers, and electric vehicles towards high frequency, high speed, and high power density, MLCC dielectric materials face more stringent application conditions in terms of operating temperature, operating electric field, and reliability. The stability and reliability of the BaTiO3 system under high temperature and strong electric field have become key bottlenecks limiting the overall performance and service life of MLCC devices: on the one hand, the inherent abrupt change in dielectric constant near the Curie point makes it difficult to meet the requirements for wide-temperature range use; on the other hand, the long-range migration of oxygen vacancies leads to a decrease in insulation resistance, accelerated dielectric aging, and a decrease in breakdown strength.

[0003] While core-shell structure design and multi-element synergistic doping strategies have significantly improved the performance of MLCC dielectric materials, their control mechanisms still have inherent limitations, making it difficult to synergistically optimize the three key indicators of "high dielectric constant, wide temperature range stability, and high reliability." Although traditional core-shell strategies leverage the thermal stability of the cubic phase of the outer shell to mitigate temperature variations in the dielectric constant, the discrete or discontinuous transition of the shell composition leads to insufficient lattice distortion control, making it difficult to construct effective compositional gradients and stress fields at the interface. Simultaneously, while multi-element doping can reduce oxygen vacancy concentration through valence state compensation, it is constrained by doping site competition, solid solubility differences, and diffusion kinetics, easily leading to local element enrichment or even new defects at grain boundaries or in the shell. This not only weakens the dielectric's insulation capacity and increases interfacial conductive channels but may also induce premature breakdown under high electric fields. Furthermore, existing methods are mostly limited to local optimization at the level of a single structure or defect, lacking a systematic control of the global correlation between dielectric response, temperature stability, and electric field reliability.

[0004] Therefore, there is an urgent need to develop a comprehensive strategy that can synergistically regulate composition distribution, lattice strain, and defect chemistry at the macroscopic to lattice scale in order to break through existing performance bottlenecks and achieve an overall leap in the dielectric properties and reliability of MLCC dielectric materials. Summary of the Invention

[0005] To address the challenges of synergistically optimizing the dielectric constant, wide-temperature-range X8R stability, and high breakdown field strength of existing materials, as well as the insufficient reliability caused by uneven doping and oxygen vacancy migration, this invention aims to provide a high-reliability X8R-type ceramic dielectric material with a double-shell compositional gradient and its preparation method. This invention utilizes a unique two-step "pre-sintering" process to construct a special double-shell structure of "tetragonal core-inner shell-outer shell," and leverages compositional gradient design and defect engineering to synergistically improve dielectric properties and reliability.

[0006] To achieve this objective, the present invention adopts the following technical solution: In a first aspect, the present invention provides an X8R type high-reliability ceramic dielectric material with a double-shell design, the raw material of which is composed of a host material and a doping modifier, wherein the host material is barium titanate (BaTiO3); the doping modifier includes a first dopant, a second dopant, and a sintering aid; the first dopant is at least one of rare earth element oxides Y2O3 and Dy2O3; the second dopant includes at least one of MgO and MnO2; and the sintering aid is at least one of SiO2 and Cr2O3.

[0007] The content of the main material is 90.5~92.9 mol% based on the total molar amount of the ceramic dielectric material, and the total amount of the dopant modifier is 7.1~9.5 mol% based on the total molar amount of the ceramic dielectric material. The ceramic dielectric material has a core-double-shell structure, consisting of a tetragonal barium titanate core, an inner shell layer rich in a first dopant, and an outer shell layer rich in a second dopant, arranged from the inside out.

[0008] In some specific implementations, based on the X8R type high-reliability ceramic dielectric material: Based on the total molar amount of the co-doped BaTiO3 ceramic dielectric material being 100%, the amount of the main material added is 90.5~92.9 mol%, for example, it can be 90.5 mol%, 90.7 mol%, 90.9 mol%, 91.1 mol%, 91.3 mol%, 91.5 mol%, 91.7 mol%, 91.9 mol%, 92.1 mol%, 92.3 mol%, 92.5 mol%, 92.7 mol%, or 92.9 mol%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0009] The total addition amount of the first dopant, the second dopant, and the sintering aid is 7.1~9.5 mol%, for example, it can be 7.1 mol%, 7.3 mol%, 7.5 mol%, 7.7 mol%, 7.9 mol%, 8.1 mol%, 8.3 mol%, 8.5 mol%, 8.7 mol%, 8.9 mol%, 9.1 mol%, 9.3 mol%, or 9.5 mol%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0010] The total amount of the first dopant added is 0.2~1.1 mol%, for example, it can be 0.2 mol%, 0.4 mol%, 0.6 mol%, 0.8 mol%, 1.0 mol%, or 1.1 mol%, used to form a rare earth-rich inner shell layer to play a defect isolation role.

[0011] The total amount of the second dopant added is 5.1~7.4 mol%, for example, it can be 5.1 mol%, 5.3 mol%, 5.5 mol%, 5.7 mol%, 5.9 mol%, 6.1 mol%, 6.3 mol%, 6.5 mol%, 6.7 mol%, 6.9 mol%, 7.1 mol%, 7.3 mol%, or 7.4 mol%, used to form the outer shell layer and synergistically optimize temperature stability and insulation performance.

[0012] The total amount of the sintering aid is 1.3~2.5 mol%, for example, it can be 1.3 mol%, 1.5 mol%, 1.7 mol%, 1.9 mol%, 2.1 mol%, 2.3 mol%, or 2.5 mol%, used to promote the sintering densification of the material.

[0013] The values ​​for each addition are not limited to the specific values ​​listed above; other unlisted values ​​within the corresponding range also apply.

[0014] In a preferred embodiment, the content of each component in the first dopant is based on the X8R type high-reliability ceramic dielectric material: The content of Y₂O₃ is 0.1~1 mol%, and the content of Dy₂O₃ is 0~0.5 mol%. For example, the content of Y₂O₃ can be: 0.1 mol%, 0.2 mol%, 0.4 mol%, 0.6 mol%, 0.8 mol%, 1.0 mol%. The content of Dy₂O₃ can be: 0 mol%, 0.1 mol%, 0.2 mol%, 0.3 mol%, 0.4 mol%, 0.5 mol%.

[0015] In a preferred embodiment, the content of each component in the second dopant is based on the X8R type high-reliability ceramic dielectric material: The content of MgO is 1~5 mol%, and the content of MnO2 is 0~3 mol%. For example, the content of MgO can be: 1.0 mol%, 1.5 mol%, 2.0 mol%, 2.5 mol%, 3.0 mol%, 3.5 mol%, 4.0 mol%, 4.5 mol%, 5.0 mol%. The content of MnO2 can be: 0 mol%, 0.5 mol%, 1.0 mol%, 1.5 mol%, 2.0 mol%, 2.5 mol%, 3.0 mol%.

[0016] In a preferred embodiment, the content of each component in the sintering aid is based on the X8R type high-reliability ceramic dielectric material: The SiO2 content is 0~2.5 mol%, and the Cr2O3 content is 0~2.5 mol%. The SiO2 content can be, for example: 0 mol%, 0.5 mol%, 1.0 mol%, 1.5 mol%, 2.0 mol%, 2.5 mol%. The Cr2O3 content can be, for example: 0 mol%, 0.5 mol%, 1.0 mol%, 1.5 mol%, 2.0 mol%, 2.5 mol%.

[0017] In the technical solution of the present invention, when the contents of each component of the first dopant, the second dopant, and the sintering aid are different, their respective maximum values ​​are taken to ensure that the total molar amount of each component meets the defined range.

[0018] Furthermore, the particle size of each component of the first dopant, the second dopant, and the sintering aid does not exceed 100 nm.

[0019] Furthermore, the average grain size of the ceramic dielectric material is 180~250 nm.

[0020] Furthermore, the ceramic dielectric material satisfies at least two of the following performance indicators: (a) The rate of change of capacitance ΔC / C over a temperature range of -55 to 150 °C 25℃ ≤ ±15%; (b) Room temperature dielectric constant ε r >2200; (c) Breakdown field strength ≥ 6.7 kV / mm.

[0021] Secondly, this invention provides an X8R-type high-reliability ceramic dielectric material with a double-shell design. This invention employs a unique "two-step sintering method," where an inner shell is built through pre-sintering, followed by secondary mixing and sintering to form a complete double-shell structure. The preparation method includes the following steps: (1) Preparation of pre-sintering powder: The main material BaTiO3 and the first dopant were mixed in a certain proportion, wet ball milled and dried, and then pre-sintered at 800~1000℃ in air to obtain pre-sintered powder. The pre-sintering holding time was 2 hours. During the pre-sintering process, Y 3+ Ions preferentially occupy the A sites of the BaTiO3 lattice, forming a Y-rich defect inner shell (Shell I) on the grain surface, i.e., forming an inner shell rich in the first dopant.

[0022] (2) Secondary mixing: The pre-fired powder obtained in step (1) is mixed with the second dopant and sintering aid in proportion, and then subjected to secondary wet ball milling and drying to obtain ceramic dielectric material powder, so that the second dopant is uniformly coated on the surface of the pre-fired powder. (3) Forming and sintering: The powder obtained in step (2) is granulated, pressed into shape, and sintered at high temperature of 1100~1300℃ under a reducing atmosphere. After holding at this temperature for 2~4 hours, it is cooled in the furnace to obtain the ceramic dielectric material. In this process, the pre-formed inner shell layer acts as an "isolation wall" to prevent the subsequent dopants from diffusing into the core, causing them to accumulate in the outer shell layer (Shell II), thereby forming a clear double-shell composition gradient structure.

[0023] Furthermore, in step (3), the reducing atmosphere is a mixture of H2 and N2.

[0024] The preparation method of the above-mentioned ceramic dielectric material constructs a composition gradient through a pre-sintering process, and uses a Y-rich inner shell to block the excessive diffusion of the second dopant (Mg, Mn) into the grain core, while restricting the migration of oxygen vacancies to the grain boundaries.

[0025] Thirdly, the present invention provides a multilayer ceramic capacitor, wherein the dielectric layer comprises the above-mentioned X8R type high reliability ceramic dielectric material, and the multilayer ceramic capacitor has high dielectric constant, high temperature stability X8R and high withstand voltage.

[0026] Fourthly, the present invention provides the use of the X8R type high-reliability ceramic dielectric material in the fabrication of electronic components, wherein the electronic components are multilayer ceramic capacitors.

[0027] Furthermore, the multilayer ceramic capacitor possesses high dielectric constant, X8R temperature characteristics, and high withstand voltage characteristics.

[0028] Compared with the prior art, the present invention has the following significant advantages: 1. Enhanced Reliability Through Double-Shell Structure: The rare-earth-rich inner shell formed by pre-sintering acts as a defect isolation barrier, effectively pinning defects and suppressing the excessive diffusion of subsequent second dopants (Mg, Mn) into the depths of the grain nucleus. It also hinders the long-range migration of oxygen vacancies under high temperature and high electric field conditions, creating a compositional gradient and reducing grain boundary defects. Microstructural analysis confirms that this gradient structure significantly suppresses the long-range migration of oxygen vacancies, increases the activation energy of grain boundaries and the shell, thereby raising the breakdown strength to ≥ 6.7 kV / mm, significantly improving the material's insulation performance and reliability.

[0029] 2. Synergistic Improvement of Dielectric Properties: This invention, through a double-shell composition gradient design, prepares an X8R-type high-reliability ceramic dielectric material. The structure retains the high tetragonality of the BaTiO3 crystal nucleus, enabling the material to meet the wide-temperature stability characteristics of X8R (-55℃~150℃, ΔC / C). 25℃ While maintaining a high dielectric constant (≤ ±15%), it also achieved a high dielectric constant. ε r >2200).

[0030] 3. Nanoscale microdomain engineering: Pre-sintering and composite doping induce the formation of nanoscale polar microdomains, which optimizes the temperature stability of the capacitor.

[0031] 4. Strong process controllability: The two-step sintering process is simple and easy to implement, effectively solving the problem of uneven doping in the traditional one-step process, and is suitable for large-scale industrial production. Attached Figure Description

[0032] Figure 1 The pre-firing process flow diagram for preparing X8R type high-reliability ceramic dielectric material is shown in the embodiment of the present invention.

[0033] Figure 2 This is a SEM image of the ceramic dielectric material prepared in Example 1 of the present invention.

[0034] Figure 3 This is a SEM image of the ceramic dielectric material prepared in Example 2 of the present invention.

[0035] Figure 4This is a SEM image of the ceramic dielectric material prepared in Comparative Example 1 of the present invention.

[0036] Figure 5 This is a SEM image of the ceramic dielectric material prepared in Comparative Example 2 of this invention.

[0037] Figure 6 This is a grain distribution diagram of the ceramic dielectric material prepared in Example 1 of the present invention.

[0038] Figure 7 This is a grain distribution diagram of the ceramic dielectric material prepared in Example 2 of the present invention.

[0039] Figure 8 This is a grain distribution diagram of the ceramic dielectric material prepared in Comparative Example 1 of the present invention.

[0040] Figure 9 This is a grain distribution diagram of the ceramic dielectric material prepared in Comparative Example 2 of the present invention.

[0041] Figure 10 The dielectric temperature spectra of the ceramic dielectric material samples prepared in the embodiments and comparative examples of this invention are shown.

[0042] Figure 11 The dielectric constant as a function of temperature (TCC) is shown for the ceramic dielectric material samples prepared in the embodiments and comparative examples of this invention.

[0043] Figure 12 The breakdown strength Weibull distribution diagrams of the ceramic dielectric materials prepared in the embodiments and comparative examples of the present invention are shown. Detailed Implementation

[0044] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments. However, the following examples are merely simplified examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention is determined by the claims.

[0045] In the following examples, unless otherwise specified, all reagents and consumables were purchased from conventional reagent manufacturers in the art; unless otherwise specified, the experimental methods and techniques used are conventional methods and techniques in the art.

[0046] The following is a flowchart of the core process for preparing ceramic dielectric materials in the embodiments. Figure 1As shown, the pre-firing process involves three steps: First, BaTiO3 powder is mixed with a first dopant (such as at least one of Y2O3 and Dy2O3). Second, the mixed material is fed into the pre-firing furnace shown in the attached diagram for high-temperature pre-firing to form a shell-coated structure. Third, the pre-firing mixed powder is taken out and mixed with a second dopant (such as at least one of MgO and MnO2) and a sintering aid (such as at least one of SiO2 and Cr2O3), pressed into sheets, and then sent to an atmosphere furnace (such as a reducing atmosphere furnace with a mixture of H2 and N2) shown in the attached diagram for sintering into ceramic. Finally, a ceramic dielectric material is obtained, which constructs a "tetragonal phase nucleus-rare earth-rich inner shell-Mg / Mn-rich outer shell" structure, i.e., a "core-shell" double-shell structure, within the ceramic grains. Unless otherwise specified, the process flow used in each embodiment is the same as the above-mentioned pre-firing process.

[0047] Example 1 This embodiment provides a co-doped BaTiO3 ceramic dielectric material, based on a total molar amount of 100% for the ceramic dielectric material: wherein the co-doped BaTiO3 ceramic dielectric material comprises 92.4 mol% BaTiO3 particles with an average particle size of 200 nm, 0.1 mol% Y2O3, 4 mol% MgO, 2 mol% MnO2, and 1.5 mol% SiO2.

[0048] The specific preparation method is as follows: (1) Preparation of pre-sintered powder: According to the above formula, weigh the main material BaTiO3 (92.4 mol%) with an average particle size of 200 nm and the first dopant Y2O3 (0.1 mol%). Place the mixed powder in a ball mill jar, use anhydrous ethanol as the medium and zirconia balls as the grinding balls, and perform wet ball milling for 24 hours. After ball milling, the slurry is dried, sieved, and placed in a muffle furnace for high-temperature pre-sintering treatment in an air atmosphere. The pre-sintering temperature is 900 ℃, the holding time is 2 hours, and the pre-sintered powder is obtained after cooling with the furnace. During this process, Y 3+Ions preferentially diffuse and occupy the A sites on the surface of the BaTiO3 lattice, forming a Y-rich inner shell layer. (2) Secondary mixing: The pre-calcined powder obtained in step (1) is mixed with the second dopant MgO (4 mol%), MnO2 (2 mol%) and sintering aid SiO2 (1.5 mol%) in proportion. Anhydrous ethanol and zirconium oxide balls are added again for secondary wet ball milling for 24 hours to make the second dopant uniformly coat the surface of the pre-calcined powder particles. The slurry is dried and sieved to obtain ceramic dielectric material powder. (3) Molding and sintering: Polyvinyl alcohol (PVA) binder is added to the powder obtained in step (2) for granulation, and it is pressed into a disc sample with a diameter of 10 mm and a thickness of 1 mm (for material performance testing), or a green tape is prepared by tape casting process (for MLCC preparation). The formed green body was sintered at high temperature in a reducing atmosphere (a mixture of H2 and N2, with an H2 concentration of 1.5%) at 1230 °C for 2 hours. After sintering, it was cooled to room temperature in the furnace to obtain a ceramic dielectric material with a double-shell design.

[0049] Example 2 This embodiment provides a co-doped BaTiO3 ceramic dielectric material, based on a total molar amount of 100% for the ceramic dielectric material: wherein the co-doped BaTiO3 ceramic dielectric material comprises 92.2 mol% BaTiO3 particles with an average particle size of 200 nm, 0.3 mol% Y2O3, 4 mol% MgO, 2 mol% MnO2, and 1.5 mol% SiO2.

[0050] The specific preparation method is as follows: (1) Preparation of pre-sintered powder: According to the above formula, weigh the main material BaTiO3 (92.4 mol%) with an average particle size of 200 nm and the first dopant Y2O3 (0.3 mol%). Place the mixed powder in a ball mill jar, use anhydrous ethanol as the medium and zirconia balls as the grinding balls, and perform wet ball milling for 24 hours. After ball milling, the slurry is dried, sieved, and placed in a muffle furnace for high-temperature pre-sintering treatment in an air atmosphere. The pre-sintering temperature is 900 ℃, the holding time is 2 hours, and the pre-sintered powder is obtained after cooling with the furnace. During this process, Y 3+Ions preferentially diffuse and occupy the A sites on the surface of the BaTiO3 lattice, forming a Y-rich inner shell layer. (2) Secondary mixing: The pre-calcined powder obtained in step (1) is mixed with the second dopant MgO (4 mol%), MnO2 (2 mol%) and sintering aid SiO2 (1.5 mol%) in proportion. Anhydrous ethanol and zirconium oxide balls are added again for secondary wet ball milling for 24 hours to make the second dopant uniformly coat the surface of the pre-calcined powder particles. The slurry is dried and sieved to obtain ceramic dielectric material powder. (3) Molding and sintering: Polyvinyl alcohol (PVA) binder is added to the powder obtained in step (2) for granulation, and it is pressed into a disc sample with a diameter of 10 mm and a thickness of 1 mm (for material performance testing), or a green tape is prepared by tape casting process (for MLCC preparation). The formed green body was sintered at high temperature in a reducing atmosphere (a mixture of H2 and N2, with an H2 concentration of 1.5%) at 1230 °C for 2 hours. After sintering, it was cooled to room temperature in the furnace to obtain a ceramic dielectric material with a double-shell design.

[0051] Comparative Example 1 This embodiment provides a co-doped BaTiO3 ceramic dielectric material, based on a total molar amount of 100% for the ceramic dielectric material: wherein the co-doped BaTiO3 ceramic dielectric material comprises 92.2 mol% BaTiO3 particles with an average particle size of 200 nm, 0.3 mol% Y2O3, 4 mol% MgO, 2 mol% MnO2, and 1.5 mol% SiO2.

[0052] The specific preparation method is as follows: (1) Preparation of pre-sintered powder: According to the above formula, weigh the main material BaTiO3 (92.4 mol%) with an average particle size of 200 nm and the first dopant Y2O3 (0.3 mol%). Place the mixed powder in a ball mill jar, use anhydrous ethanol as the medium and zirconia balls as the grinding balls, and perform wet ball milling for 24 hours. After ball milling, the slurry is dried, sieved, and placed in a muffle furnace for high-temperature pre-sintering treatment in an air atmosphere. The pre-sintering temperature is 800 ℃, the holding time is 2 hours, and the pre-sintered powder is obtained after cooling with the furnace. During this process, Y 3+Ions preferentially diffuse and occupy the A sites on the surface of the BaTiO3 lattice, forming a Y-rich inner shell layer. (2) Secondary mixing: The pre-calcined powder obtained in step (1) is mixed with the second dopant MgO (4 mol%), MnO2 (2 mol%) and sintering aid SiO2 (1.5 mol%) in proportion. Anhydrous ethanol and zirconium oxide balls are added again for secondary wet ball milling for 24 hours to make the second dopant uniformly coat the surface of the pre-calcined powder particles. The slurry is dried and sieved to obtain ceramic dielectric material powder. (3) Molding and sintering: Polyvinyl alcohol (PVA) binder is added to the powder obtained in step (2) for granulation, and it is pressed into a disc sample with a diameter of 10 mm and a thickness of 1 mm (for material performance testing), or a green tape is prepared by tape casting process (for MLCC preparation). The formed green body was sintered at high temperature in a reducing atmosphere (a mixture of H2 and N2, with an H2 concentration of 1.5%) at 1230 °C for 2 hours. After sintering, it was cooled to room temperature in the furnace to obtain a ceramic dielectric material with a double-shell design.

[0053] Comparative Example 2 This embodiment provides a co-doped BaTiO3 ceramic dielectric material, based on a total molar amount of 100% for the ceramic dielectric material: wherein the co-doped BaTiO3 ceramic dielectric material comprises 92.2 mol% BaTiO3 particles with an average particle size of 200 nm, 0.3 mol% Y2O3, 4 mol% MgO, 2 mol% MnO2, and 1.5 mol% SiO2.

[0054] Preparation method (one-step sintering method): No pre-sintering step processing is performed. The specific steps are as follows: BaTiO3, the first dopant Y2O3, the second dopant (MgO, MnO2), and the sintering aid (SiO2) are all added to a ball mill jar at once and wet-milled for 24 hours. After drying, a binder is added for granulation and pressing. Subsequently, sintering is performed in the same reducing atmosphere and at 1230 °C as in Example 1.

[0055] Test method: 1. The microstructure of the sample cross section was observed using a Thermo Fisher Apreo 2 field emission scanning electron microscope.

[0056] II. The method for testing the dielectric constant is as follows: using the Alpha-A wideband dielectric tester from Novocontrol Technologies, Germany, with a driving field of 1 V, the capacitance and loss at different frequencies at each 2℃ interval between -60 and 200℃ are measured.

[0057] Figure 2-5The SEM images of the ceramic dielectric materials prepared in the examples and comparative examples are shown below. The corresponding grain distribution diagrams after summarizing the observed grain distribution data are as follows: Figure 6-9 As shown.

[0058] The test results of the ceramic dielectric material samples prepared in Examples 1-2 and Comparative Examples 1-2 are shown in Table 1 below.

[0059] Table 1

[0060] Analysis of the test results, through the test results of the examples and comparative examples, shows that: (1) Regarding grain size and microstructure: A comparison between Example 1 (226 nm) and Comparative Example 1 (195 nm) shows that the 900 ℃ pre-sintering process of the present invention can promote moderate grain growth and form a well-developed microstructure. Due to the lower pre-sintering temperature (800 ℃) in Comparative Example 1, the grain development is relatively incomplete and the size is smaller. The grain size of Example 2 (219 nm) is close to that of Example 1, indicating that adjusting the Y2O3 content within a certain range has little effect on the grain size. Comparative Example 2 (237 nm) uses a one-step sintering method, and the grain size is slightly larger. This may be due to the lack of an effective inhibition of grain boundary migration by the inner shell formed by pre-sintering, resulting in slightly faster grain growth.

[0061] (2) Regarding temperature stability (X8R characteristics): such as Figure 11 As shown, the capacitance change rates of Example 1 at -55 °C and +150 °C are -14% and 5%, respectively, which fully meet the X8R standard (ΔC / C). 25℃ ≤ ±15%). Example 2 also performed excellently, with -11% and -6% respectively, demonstrating good wide-temperature stability. In contrast, although Comparative Example 1 met the requirements at the low temperature end, its capacitance change rate reached -19% at the high temperature end (+150 °C), exceeding the standard range, indicating that the 800 °C low-temperature pre-sintering failed to form a sufficiently dense and effective shell structure to stabilize the high-temperature dielectric properties. Comparative Example 2 also reached -15% at the high temperature end, which is on the edge, and its performance at the low temperature end was not as stable as that of the examples, indicating that the one-step method is difficult to precisely control the shell structure to achieve wide-temperature stability.

[0062] (3) Regarding dielectric properties: such as Figure 10As shown, Examples 1 and 2 maintained high room temperature dielectric constants (2080 and 2250, respectively) and low dielectric losses (0.98% and 0.75%, respectively). Example 2, in particular, achieved a good balance between high dielectric constant and low loss by optimizing the Y₂O₃ content to 0.3 mol%. The lower dielectric constant of Comparative Example 1 (1920) is likely due to insufficient grain development and an imperfect shell structure. While Comparative Example 2 has a higher dielectric constant (2259), its temperature stability is poor, failing to simultaneously meet the high-performance requirements.

[0063] (4) Regarding reliability: such as Figure 12 As shown, Example 2 and Comparative Example 1 were compared in terms of breakdown strength. Example 2 showed a high breakdown strength of 6.707 kV / mm, which was greater than the 5.198 kV / mm of the unburned sample in Comparative Example 1.

[0064] In summary, this invention constructs a double-shell structure of "tetragonal core-inner shell-outer shell" through a unique pre-sintering process. While ensuring a high dielectric constant, it significantly improves the temperature stability of the material, enabling it to meet the stringent X8R standard and exhibit excellent reliability.

[0065] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A high-reliability ceramic dielectric material of type X8R with a double-shell design, characterized in that, It is composed of a main material and a doping modifier, wherein the main material is BaTiO3; the doping modifier includes a first dopant, a second dopant, and a sintering aid; the first dopant is at least one of rare earth element oxides Y2O3 and Dy2O3; the second dopant includes at least one of MgO and MnO2; and the sintering aid is at least one of SiO2 and Cr2O3. The content of the main material is 90.5~92.9 mol% based on the total molar amount of the ceramic dielectric material, and the total amount of the dopant modifier is 7.1~9.5 mol% based on the total molar amount of the ceramic dielectric material. The ceramic dielectric material has a core-double-shell structure, consisting of a tetragonal barium titanate core, an inner shell layer rich in a first dopant, and an outer shell layer rich in a second dopant, arranged from the inside out.

2. The X8R type high-reliability ceramic dielectric material according to claim 1, characterized in that, Based on the total molar amount of the ceramic dielectric material: The total amount of the first dopant is 0.2~1.1 mol%, and the content of Y2O3 in the first dopant is 0.1~1 mol%, and / or the content of Dy2O3 is 0~0.5 mol%; The total amount of the second dopant is 5.1~7.4 mol%, and the content of MgO in the second dopant is 1~5 mol%, and / or the content of MnO2 is 0~3 mol%. The total amount of the sintering aid is 1.3~2.5 mol%, and the content of SiO2 in the sintering aid is 0~2.5 mol%, and / or the content of Cr2O3 is 0~2.5 mol%.

3. The X8R type high-reliability ceramic dielectric material according to claim 1, characterized in that, The particle size of each component of the first dopant, the second dopant, and the sintering aid does not exceed 100 nm.

4. The X8R type high-reliability ceramic dielectric material according to claim 1, characterized in that, The average grain size of the ceramic dielectric material is 180~250 nm.

5. The X8R type high-reliability ceramic dielectric material according to claim 1, characterized in that, The ceramic dielectric material satisfies at least two of the following performance indicators: (a) The rate of change of capacitance ΔC / C over a temperature range of -55 to 150 °C 25℃ ≤ ±15%; (b) Room temperature dielectric constant ε r > 2200; (c) Breakdown field strength ≥ 6.7 kV / mm.

6. The method for preparing the X8R type high-reliability ceramic dielectric material with a double-shell design according to any one of claims 1 to 5, characterized in that, Includes the following steps: (1) Preparation of pre-sintered powder: The main material BaTiO3 and the first dopant are mixed in proportion, wet ball milled and dried, and then pre-sintered at 800~1000℃ in air atmosphere. After holding at the temperature for 2 hours, the pre-sintered powder is obtained. (2) Secondary mixing: The pre-calcined powder obtained in step (1) is mixed with the second dopant and sintering aid in proportion, and then subjected to secondary wet ball milling and drying to obtain ceramic dielectric material powder; (3) Molding and sintering: The powder obtained in step (2) is granulated and pressed into shape, and then sintered at high temperature at 1100~1300℃ in a reducing atmosphere. After holding at the temperature for 2~4 hours, it is cooled in the furnace to obtain the ceramic medium material.

7. The preparation method according to claim 6, characterized in that, In step (3), the reducing atmosphere is H. 2 With N 2 A mixture of gases.

8. A multilayer ceramic capacitor, characterized in that, Its dielectric layer comprises the X8R type high reliability ceramic dielectric material as described in any one of claims 1 to 5, and the multilayer ceramic capacitor has high dielectric constant, high temperature stability X8R and high withstand voltage.

9. The use of the X8R type high-reliability ceramic dielectric material according to any one of claims 1 to 6 in the fabrication of electronic components, characterized in that, The electronic component is a multilayer ceramic capacitor.

10. The use according to claim 9, characterized in that, The multilayer ceramic capacitor has a high dielectric constant, X8R temperature characteristics, and high withstand voltage characteristics.

Images