A ceramic dielectric material, its preparation and use

Abstract

The application provides a ceramic dielectric material and a preparation method and application thereof, a main body material of the material is BaTiO3, doping materials include SiO2, CaO, V2O5, ZrO2 and oxides of rare earth elements; the oxides of the rare earth elements include at least two of Sc2O3, Sm2O3, Dy2O3 and Ho2O3; the addition amount of BaTiO3 is 93.5-95 mol% in terms of molar percentage; the total addition amount of the doping materials is 4.6-7 mol%. The application takes BaTiO3 as the main body material, takes sintering aids, metal oxides and rare earth elements as composite dopants, modifies a barium titanate ceramic base, adds sintering aids and doping materials to refine particles, controls defects and improves the uniformity of the grain size, and prepares fine-grain ceramic and multilayer ceramic capacitors with high reliability, stable capacitance characteristics and more easy lamination.

Description

TECHNICAL FIELD

[0001] The present application relates to a ceramic dielectric material, in particular to a ceramic dielectric material and a preparation method and application thereof. BACKGROUND

[0002] Multi-layer ceramic capacitor (MLCC) uses monolithic structure to achieve the effect of increasing capacity by parallel connection of multiple capacitors, and is widely used in communication basic equipment circuits in the fields of communication equipment, automobile electronics, industrial machines and medical machines due to its low cost, high capacity, stability and other characteristics. For example, it can be used as a power bypass capacitor, such as a liquid crystal module (liquid crystal drive voltage line), an LSI / IC / OP amplifier with high power voltage, or as a smoothing capacitor, such as a DC-DC converter (input and output), a switching power supply (secondary side), etc. In recent years, the miniaturization of mobile electronic devices has led to the development of MLCCs towards miniaturization and high capacity. Among them, barium titanate (BaTiO3) is the matrix material of type II capacitors in MLCCs, which has a relatively high dielectric constant. However, to obtain a barium titanate-based MLCC with high capacity, the number of stacked layers needs to be increased, which will lead to a significant decrease in the reliability of the MLCC. In addition, the temperature coefficient of the dielectric material of type II capacitors has X5R, X6R, X7R, etc. According to the capacitor specification of the Electronic Industries Association (EIA), the capacitance change rate of X5R is between +15% and -15% at temperatures between -55℃ and 85℃, relative to 25℃. The dielectric constant of barium titanate fluctuates greatly at -90℃, 0℃ and 125℃, which also limits the application range of barium titanate.

[0003] In order to overcome the above problems, it is urgent to modify and dope barium titanate materials, to prepare ultra-pure and ultra-fine powders with good dispersibility, so as to refine the grain size, improve the uniformity of grain size and distribution, and thus significantly improve the voltage resistance and reliability of the MLCC product. SUMMARY

[0004] The present application aims to overcome the shortcomings of the prior art and provides a ceramic dielectric material, a preparation method and application thereof. The present application mainly selects sintering aids, metal oxides and rare earth elements as composite dopants, modifies the barium titanate ceramic matrix, adds sintering aids and doping materials to refine the particles, controls defects and improves the uniformity of grain size, and prepares fine-grained ceramic and multi-layer ceramic capacitor with high reliability, stable capacitance characteristics and more easily stacked layers.

[0005] To achieve the above-mentioned purpose, the technical scheme adopted by the present application is as follows:

[0006] A ceramic dielectric material, a main body material of the material is BaTiO3, a doping material includes SiO2, CaO, V2O5, ZrO2 and oxide of rare earth element; the oxide of rare earth element includes at least two of Sc2O3, Sm2O3, Dy2O3, Ho2O3;The addition amount of BaTiO3 is 93.5-95mol% by mole percentage;The total addition amount of doping material is 4.6-7mol%.

[0007] The present application takes BaTiO3 as the main body material, and prepares co-doped barium titanate ceramic dielectric material with high breakdown strength and high reliability by optimizing the type, formula and proportion of doping material.SiO2 is added as a sintering aid to reduce and widen the sintering temperature, prevent the grain growth of ceramic particles in the sintering process;CaO and a small amount of Sc2O3 are added to refine the grain and promote the mass transfer process of BaTiO3 to improve the ceramic density; the combination of SiO2 and CaO produces liquid phase in the ceramic sintering process, which uniformly wraps each particle to prevent excessive growth of the particles; in addition, the liquid phase on the surface of the internal electrode can hinder the diffusion of metal elements to the dielectric layer, enhance the reliability of MLCC, and increase the superiority of the present application in the application field of MLCC; to prevent Ti 4+ ions from being reduced to Ti 3+ Oxygen vacancies are produced when sintering in a reducing atmosphere, and the addition of V2O5 allows the V element, which can change valence, to replace the Ti position in barium titanate (BT), thereby inhibiting the generation of oxygen vacancies and improving the residual polarization strength and high-temperature reliability; the addition of appropriate amount of ZrO2 can also improve the band gap and reduction enthalpy of Ti ions, thereby reducing the concentration of oxygen vacancies. In addition, the present application creatively selects rare earth oxide Dy2O3 mixed with a small amount of Sm2O3 or Ho2O3 as a co-doping material to form a "core-shell" structure in the ceramic grain, which makes up for the disadvantage of fixed rare earth element ion mobility that causes uneven concentration of shell elements, helps to achieve a uniform gradient of doping element concentration from the shell to the core of the grain, avoids complex defect morphology caused by poor uniformity to improve reliability, and thereby stabilizes the influence of temperature on capacitance.

[0008] As a preferred embodiment of the present application, the doping material includes SiO2 1.2-1.5mol%, CaO 1.6-2.0mol%, Sc2O3 0.4-0.6mol%, V2O5 0.6-0.9mol%, ZrO2 0.3-0.5mol%, Sm2O3 0-0.4mol%, Dy2O3 0.5-0.7mol%, Ho2O3 0-0.4mol%.

[0009] As a preferred embodiment of the present application, the oxide of rare earth element includes at least one of Dy2O3, Sc2O3 and Sm2O3, Ho2O3.

[0010] As a preferred embodiment of the present application, the doping material comprises SiO21.2-1.4mol%, CaO 1.6-2.0mol%, Sc2O30.4-0.6mol%, V2O50.6-0.9mol%, ZrO20.3-0.5mol%, Sm2O30.3-0.4mol%, Dy2O30.5-0.7mol%, Ho2O30.3-0.4mol%.

[0011] As a preferred embodiment of the present application, the grain size of the main body material BaTiO3 is 180-240nm.

[0012] The inventor has found through research that the commonly used solid phase method BaTiO3 powder material can reduce the complexity of the process and save costs. After the BaTiO3 nanoparticles are sintered to form a multilayer ceramic capacitor (MLCC), the grain size grows by 20%-35%, so the grain size of the main body BaTiO3 powder is controlled to be 180-240nm to obtain a final ceramic grain size of 200-320nm.

[0013] The present application also provides a preparation method of the above-mentioned ceramic dielectric material. The main body material BaTiO3 and the doping material are wet ball milled according to the formula amount, and the ceramic dielectric material can be obtained after drying.

[0014] As a preferred embodiment of the present application, the wet ball milling uses zirconium oxide balls as the ball milling medium and is carried out for 24h.

[0015] The present application also provides an application of the above-mentioned ceramic dielectric material in electronic components; the electronic components comprise a multilayer ceramic capacitor.

[0016] As a preferred embodiment of the present application, the ceramic dielectric material is sintered at 1200-1260℃ for 3-5h in a reducing atmosphere, and after annealing, the multilayer ceramic capacitor is obtained through cutting and end sealing treatment in sequence.

[0017] As a preferred embodiment of the present application, the grain size of the ceramic dielectric in the multilayer ceramic capacitor is 200-320nm.

[0018] As a preferred embodiment of the present application, the dielectric constant of the multilayer ceramic capacitor at 25℃ is 5000-5600.

[0019] As a preferred embodiment of the present application, the capacitance change rate of the multilayer ceramic capacitor at -55-85℃ is ±15%.

[0020] As a preferred embodiment of the present application, the average breakdown strength of the multilayer ceramic capacitor is 100-125 kV / mm.

[0021] As a preferred embodiment of the present application, the accelerated aging life test result is 2.3-2.7 h.

[0022] The multilayer ceramic capacitor MLCC prepared by co-doping barium titanate ceramic dielectric material and sintering in a reducing atmosphere has a breakdown strength of 100 kV / mm or more, delays the deterioration of insulation resistance at high temperature, and has an accelerated aging life test of 2.3 h or more. In addition, the dielectric constant is between 5000-5600, and can meet the X5R temperature characteristic requirement, i.e. the capacitance change rate is between +15% and -15% at a temperature of -55-85℃.

[0023] Compared with the prior art, the present application has the following beneficial effects:

[0024] (1) The multilayer ceramic capacitor prepared by co-doping barium titanate ceramic dielectric material and sintering in a reducing atmosphere has a breakdown strength of 100 kV / mm or more, an accelerated aging life test of 2.3 h or more, and a dielectric constant change that can meet the X5R requirement.

[0025] (2) The sintering aids used in the co-doped barium titanate ceramic dielectric material provided by the present application are all oxides, have many types and small amount, have low cost, and do not contain harmful elements such as lead and mercury.

[0026] (3) The multilayer ceramic capacitor prepared by the present application has fine and uniformly distributed crystal grains, and the ceramic layer matches well with the base metal internal electrode and the external electrode, and has few electrode holes and no stress cracks. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 FESEM image of the ceramic dielectric material of Example 1 of the present application.

[0028] Figure 2 FESEM image of the ceramic dielectric material of Example 2 of the present application.

[0029] Figure 3 FESEM image of the ceramic dielectric material of Example 3 of the present application.

[0030] Figure 4 FESEM image of the ceramic dielectric material of Example 4 of the present application.

[0031] Figure 5 FESEM image of the ceramic dielectric material of Example 1 according to Figure 1 FESEM image of the ceramic dielectric material of Example 1 according to

[0032] Figure 6 FESEM image of the ceramic dielectric material of Example 1 according toFigure 2 FESEM image statistics of ceramic grain size distribution of Example 2.

[0033] Figure 7 FESEM image statistics of ceramic grain size distribution of Example 3 according to the present application. Figure 3

[0034] Figure 8 FESEM image statistics of ceramic grain size distribution of Example 4 according to the present application. Figure 4

[0035] Figure 9 Capacitance constant change rate vs. temperature of MLCC sample prepared in Example 1 of the present application.

[0036] Figure 10 Capacitance constant change rate vs. temperature of MLCC sample prepared in Example 2 of the present application.

[0037] Figure 11 Capacitance constant change rate vs. temperature of MLCC sample prepared in Example 3 of the present application.

[0038] Figure 12 Capacitance constant change rate vs. temperature of MLCC sample prepared in Example 4 of the present application.

[0039] Figure 13 Weibull distribution result of breakdown strength of MLCC sample prepared in Example 1 of the present application.

[0040] Figure 14 Weibull distribution result of breakdown strength of MLCC sample prepared in Example 2 of the present application.

[0041] Figure 15 Weibull distribution result of breakdown strength of MLCC sample prepared in Example 3 of the present application.

[0042] Figure 16 Weibull distribution result of breakdown strength of MLCC sample prepared in Example 4 of the present application.

[0043] Figure 17 Accelerated aging test result of Example 1 of the present application.

[0044] Figure 18 Accelerated aging test result of Example 2 of the present application.

[0045] Figure 19 Accelerated aging test result of Example 3 of the present application.

[0046] Figure 20 Accelerated aging test result of Example 4 of the present application. ​​DETAILED DESCRIPTION

[0047] The present application aims to prepare a ceramic dielectric material, the main material of which is BaTiO3, the doping material including SiO2, CaO, V2O5, ZrO2 and oxides of rare earth elements; the oxides of rare earth elements including at least two of Sc2O3, Sm2O3, Dy2O3 and Ho2O3; the addition amount of BaTiO3 being 93.5-95 mol% in terms of molar percentage; the total addition amount of the doping material being 4.6-7 mol%. The particle size of the main material BaTiO3 is 180-240 nm.

[0048] In the following examples, the preparation process of the co-doped barium titanate ceramic dielectric material and the multilayer ceramic capacitor (MLCC) is as follows:

[0049] (1) High-purity BaTiO3 powder with a particle size of 180-240 nm is selected and mixed with various doping materials in proportion, zirconia balls are used as the ball milling medium, and wet ball milling is performed in a ball mill for 24 h. After ball milling, drying is performed to obtain ceramic dielectric material powder.

[0050] (2) Preparation of MLCC samples: The ceramic dielectric material powder obtained by the above method is made into a slurry, and a 1.5 μm film is cast. Electrode printing, lamination, pressing, and cutting are performed to form a green body with a certain shape and size. Nickel paste is used as the internal electrode, and the number of layers is 300. The green body is sintered at 1200-1260 °C in a reducing atmosphere (1.1% H2+98.9% N2) for 35 h, followed by re-oxidation degradation treatment at 900-1050 °C for 1.5 h, and then sintering is completed at 25 °C to form a monolithic ceramic body. Copper paste is then applied to the ends of the ceramic body by dipping, and sintering is performed to form copper electrodes firmly bonded to the ceramic body. A nickel layer is then electroplated on the surface of the copper electrodes, followed by a second electroplating of a tin layer to obtain the MLCC samples.

[0051] To better illustrate the purpose, technical solutions and advantages of the present application, the present application will be further described below in conjunction with specific examples.

[0052] Example 1

[0053] In this example, the particle size of the main material BaTiO3 powder is 180 nm, and Table 1 shows the formulation of each component in Example 1.

[0054] Table 1 Formulation table of Example 1

[0055]

[0056] Example 2

[0057] In this embodiment, the particle size of the BaTiO3 powder of the host material is 240 nm, and Table 2 is a formulation table of the components of Example 2.

[0058] Table 2 Formulation table of Example 2

[0059]

[0060] Example 3

[0061] In this embodiment, the particle size of the BaTiO3 powder of the host material is 240 nm, and Table 3 is a formulation table of the components of Example 3.

[0062] Table 3 Formulation table of Example 3

[0063]

[0064] Example 4

[0065] In this embodiment, the particle size of the BaTiO3 powder of the host material is 180 nm, and Table 3 is a formulation table of the components of Example 3.

[0066] Table 4 Formulation table of Example 4

[0067]

[0068] The FESEM characterization results of the preferred embodiments 1, 2 and 3, and the comparative example 4 are shown in Figure 1 , Figure 2 , Figure 3 and Figure 4 respectively, and the samples prepared in Examples 1, 2 and 3 have good density and no obvious pores.

[0069] The ceramic grain size distribution according to the SEM images is shown in Figure 5 , Figure 6 , Figure 7 , Figure 8 (wherein 157 grains are counted in Example 1, 165 grains are counted in Example 2, 154 grains are counted in Example 3, and 171 grains are counted in Example 4): the ceramic grain size distribution of the MLCCs prepared in Examples 1, 2 and 3 is more uniform, the average grain size is 240 nm, 310 nm and 320 nm respectively, and the average grain size of Example 4 is 200 nm, but a few grains abnormally grow to a size of more than 800 nm, and the uniformity is poor.

[0070] The relationship between the capacitance constant change rate and the temperature of the MLCC samples prepared in Examples 1, 2, 3 and 4 is compared, and the results are shown in Figure 9 , Figure 10 , Figure 11, Figure 12 As shown in the table, the capacitance change rate is between +15% and -15% at the temperature of 55-85℃, which basically meets the X5R requirement of EIA.

[0071] The Weibull distribution results of the breakdown strength of the MLCC samples prepared in the embodiments 1, 2, 3 and 4 of the present application are shown in the table below. Figure 13 Figure 14 Figure 15 Figure 16 As shown in the table, the samples prepared in the preferred embodiments 1, 2 and 3 of the present application have improved withstand voltage characteristics, and the average breakdown strength can reach more than 100kV / mm, while the breakdown strength of the comparative example 4 is less than 60kV / mm, which is about 2 times higher than that of the comparative example 4.

[0072] In order to expand the application field of the present application, the service life of the samples prepared in the embodiments 1, 2, 3 and 4 in the accelerated aging test at 150℃, starting from 2kV / mm, increasing the direct current voltage by 2kV / mm every 0.25h, is tested, and the results are shown in the table below. Figure 17 Figure 18 Figure 19 Figure 20 As shown in the table, the service life of the preferred embodiments 1, 2 and 3 in the aging test is also about 1.5 times higher than that of the comparative example 4.

[0073] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, but not to limit the protection scope of the present application. Although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present application can be modified or replaced by equivalents without departing from the essence and scope of the technical solutions of the present application.​​​​​​

Claims

1. A ceramic dielectric material, characterized by, The main material of the material is BaTiO3, and the doping material includes SiO2, CaO, V2O5, ZrO2 and oxide of rare earth elements; the oxide of rare earth elements includes Dy2O3, Sc2O3 and Sm2O3; the addition amount of BaTiO3 is 93.5-95 mol% in terms of molar percentage; the total addition amount of the doping material is 4.6-7 mol%; the doping material includes 1.2-1.4 mol% of SiO2, 1.6-2.0 mol% of CaO, 0.4-0.6 mol% of Sc2O3, 0.6-0.9 mol% of V2O5, 0.3-0.5 mol% of ZrO2, 0.3-0.4 mol% of Sm2O3 and 0.5-0.7 mol% of Dy2O3.

2. The ceramic dielectric material of claim 1, wherein, The grain size of the main material BaTiO3 is 180-240 nm.

3. A method of producing a ceramic dielectric material as claimed in any one of claims 1-2, characterized in that The main material BaTiO3 and the doping material are wet ball-milled according to the formula amount, and the ceramic dielectric material can be obtained after drying.

4. Application of the ceramic dielectric material according to any one of claims 1-2 in electronic components; the electronic components include multilayer ceramic capacitors.

5. Use of the ceramic dielectric material according to claim 4 in electronic components, characterized in that, The ceramic dielectric material is sintered in a reducing atmosphere at 1200-1260 ℃ for 3-5 h, and after annealing, the multilayer ceramic capacitor is obtained through cutting and end sealing in sequence.

6. Use of the ceramic dielectric material according to claim 5 in electronic components, characterized in that, The grain size of the ceramic dielectric material in the multilayer ceramic capacitor is 200-320 nm.

7. Use of the ceramic dielectric material according to claim 5 in electronic components, characterized in that, The dielectric constant of the multilayer ceramic capacitor at 25 ℃ is 5000-5600; the capacitance change rate of the multilayer ceramic capacitor at -55-85 ℃ is ±15%; and the average breakdown strength of the multilayer ceramic capacitor is 100-125 kV / mm.

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