X7R type anti-reduction BaTiO3-based dielectric ceramic material as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of functional ceramics, and particularly relates to an X7R type anti-reduction BaTiO3-based dielectric ceramic material as well as a preparation method and application thereof. The BaTiO3-based dielectric ceramic material comprises a main body material and a doping material, the main body material is BaTiO3, and the doping materials comprise MgO, CaCO3, Y2O3 and MnCO3; the molar ratio of the BaTiO3 to the MgO to the CaCO3 to the Y2O3 to the MnCO3 is 100 to (0.5 to 2.2) to (0.5 to 2.2) to (0.5 to 2.2) to (0.4 to 1.5). The dielectric constant, the reduction resistance, the service life and the temperature stability of the dielectric material for the MLCC are improved by controlling the dosage of each component, especially the molar ratio of MgO, CaCO3, Y2O3 and MnCO3.

Description

Technical Field

[0001] The invention belongs to the technical field of functional ceramics, and in particular relates to an X7R type anti-reduction BaTiO3-based dielectric ceramic material and a preparation method and application thereof. Background Art

[0002] In the modern electronics industry, capacitors, as key passive components, occupy a major share of passive electronic components. As an indispensable component of the circuit, capacitors play an important role in energy storage, signal filtering, bypass and coupling. Among them, the rapid development of multilayer ceramic capacitor (MLCC) technology has promoted the evolution of electronic components towards miniaturization, large capacity and high withstand voltage. However, with the continuous improvement of MLCC performance, its stability issues in high temperature environments have become increasingly prominent. At present, X7R type MLCC (operating temperature -55℃ to 125℃, ΔC / C in the range of ±15%), barium titanate (BaTiO3) has become the main raw material for high-capacity ceramic capacitors due to its high dielectric constant, low sintering temperature and economy. In order to improve the application performance of BaTiO3-based materials in X7RMLCC, researchers mainly adopted the following strategies: by adding high Curie temperature materials (such as PbTiO3, Na 0.5 Bi 0.5 TiO3, etc.) to adjust the Curie temperature; introduce Bi-containing composite oxides (such as Bi(Li 0.5 Nb 0.5 )O3, etc.) to obtain stable dielectric properties over a wide temperature range. Although the existing technology has made certain progress, it still faces the following challenges: the volatility of bismuth-containing compounds at high temperatures and their reactivity with electrodes will affect the manufacturing process and performance of MLCC, and lead will cause pollution to the human body and the environment. At the same time, with the continuous fierce market competition, the price of MLCC continues to decline. The use of traditional precious metal silver as the internal electrode to manufacture X7R-MLCC is costly, which greatly weakens the market competitiveness of the product. Therefore, it is necessary to develop a method for manufacturing X7R MLCC using base metal nickel as the internal electrode. The key to developing nickel electrode MLCC is to develop MLCC materials that are resistant to reduction.

[0003] Considering that the preparation of MLCC casting film will reach below 1 micron, and each layer of casting film must be composed of at least 5 grains to ensure the quality of the casting film. Therefore, the grain size of BaTiO3 should be maintained below 200 nanometers, preferably reaching 100 nm. However, according to the size effect of BaTiO3, the dielectric constant of BaTiO3 with grain size of 100 - 200 nm should theoretically be between 900 - 1900. In today's context of further miniaturization of capacitors, a larger dielectric constant is required to ensure a high capacitance. How to combine the grain size of BaTiO3 (100 - 150 nm), the dielectric properties of BaTiO3 (optimal dielectric constant > 1500, loss < 0.02), the rate of change of the capacitance temperature coefficient of BaTiO3 within the working temperature range (-55°C to 125°C), with a change rate within the range of ±15%, and excellent anti-reduction property, and co-firing matching with nickel electrodes has become a research difficulty. Among them, forming a uniform core-shell structure is one of the keys to achieving the above difficulties. Regarding how to uniformly coat the matrix ceramic particles of 100 - 150 nm with 10 - 30 nm fine particles, nano-powders are extremely prone to agglomeration in air and liquid due to mutual forces such as van der Waals force, electrostatic force, and liquid bridge force. The smaller the particle size, the more severe the agglomeration. Some researchers have proposed using chemical coating methods, which can uniformly coat nano-particles on the surface of the matrix, but it is difficult and costly in large-scale production. Summary of the Invention

[0004] The purpose of the present invention is to provide an X7R type anti-reduction BaTiO3-based dielectric ceramic material, its preparation method and application, by controlling the dosage of each component of the doping material, to improve the dielectric constant, anti-reduction property, service life and temperature stability of the dielectric material for MLCC.

[0005] To achieve the above purpose, the first aspect of the present invention provides a BaTiO3-based dielectric ceramic material, including a main material and a doping material; the main material is BaTiO3, and the doping material includes MgO, CaCO3, Y2O3, and MnCO3; the molar ratio of BaTiO3, MgO, CaCO3, Y2O3, and MnCO3 is 100:(0.5 - 2.2):(0.5 - 2.2):(0.5 - 2.2):(0.4 - 1.5).

[0006] Further, the molar ratio of BaTiO3, MgO, CaCO3, Y2O3, and MnCO3 is 100:(1 - 2):(1 - 2):(1 - 2):(0.5 - 1); the grain size of the BaTiO3-based dielectric ceramic material is 100 - 200 nm.

[0007] The second aspect of the present invention provides a preparation method of a BaTiO3-based dielectric ceramic material, including the following steps:

[0008] (1) Mix BaTiO3, MgO, CaCO3, Y2O3 and MnCO3 according to a preset molar ratio, then add deionized water and a dispersant, ball mill and dry to obtain ceramic powder;

[0009] (2) Mix the ceramic powder and a binder, granulate, screen and press into a shape to obtain a ceramic green body; heat the ceramic green body to remove the binder, and then continue to heat and sinter in a reducing atmosphere to obtain a BaTiO3-based dielectric ceramic material.

[0010] Further, the particle size of the BaTiO3 is 100-150 nm, and the particle sizes of the MgO, CaCO3, Y2O3 and MnCO3 are 10-30 nm;

[0011] The ceramic powder has a core-shell structure with BaTiO3 as the core and a doping material as the shell layer;

[0012] The grain size of the BaTiO3-based dielectric ceramic material is 100-200 nm.

[0013] Further, in step (1), the volume ratio of the deionized water to the dispersant is (8-15):1, preferably (10-12):1;

[0014] The mass ratio of the sum of the mass of the deionized water and the dispersant to the mass of BaTiO3 is (1-3):1.

[0015] Further, in step (2), the addition amount of the binder is 5%-25% of the mass of the ceramic powder; and / or, the binder is polyvinyl alcohol or polyvinyl butyral.

[0016] Further, in step (2), the temperature for removing the binder is 500-600 °C, and the heat preservation time is 1-3 h;

[0017] The sintering is to first heat to 750-850 °C and keep warm for 0.5-2 h, then heat to 1130 °C-1250 °C and keep warm for 1-3 h;

[0018] The reducing atmosphere is composed of an inert gas (such as nitrogen, argon) and hydrogen with a volume ratio of 1000:(1-8).

[0019] The third aspect of the present invention provides a method for preparing a ceramic dielectric layer, sintering the BaTiO3-based dielectric ceramic material obtained by the above-mentioned preparation method and a nickel electrode in a reducing atmosphere to obtain.

[0020] Further, nickel electrodes are screen-printed on the surface of the BaTiO3-based dielectric ceramic material, and then sintered at 1050-1250 °C for 1-2 h in a mixed atmosphere of nitrogen and hydrogen with a volume ratio of 1000:(1-8) to obtain the ceramic dielectric layer.

[0021] The fourth aspect of the present invention provides a multilayer ceramic capacitor, including the ceramic dielectric layer obtained by the above-mentioned preparation method;

[0022] The multilayer ceramic capacitor is preferably an X7R type multilayer ceramic capacitor.

[0023] Generally speaking, compared with the prior art by the above technical solutions conceived by the present invention, the following technical advantages are mainly possessed:

[0024] (1) The BaTiO3-based dielectric ceramic material provided by the present invention uses BaTiO3 powder as the matrix and MgO, CaCO3, Y2O3 and MnCO3 as dopants. By controlling the dosage of each component, the dielectric constant, anti-reduction property, service life and temperature stability of the BaTiO3-based dielectric ceramic material are improved.

[0025] (2) The preparation method of the BaTiO3-based dielectric ceramic material provided by the present invention uses BaTiO3 powder (particle size of 100-150 nm) as the matrix and MgO, CaCO3, Y2O3 and MnCO3 with a particle size of 10-30 nm as dopants. The ultrasonic method and the ball milling method with a dispersant are combined, so that the 10-30 nm dispersant is uniformly coated on the surface of the BaTiO3 matrix, thereby forming a uniform core-shell structure. Compared with the chemical coating method, this method has a simple process, is conducive to large-scale production and has a low cost. And the specific surface area of the final powder is less than or equal to 20 m 2 / g.

[0026] (3) The X7R type anti-reduction BaTiO3 matrix provided by the present invention has a high dielectric constant, which can reach 900-1900 at room temperature; the dielectric loss is low, less than 1% at room temperature; the material described in the present invention satisfies the capacitance temperature change rate ≤ ±15% at -55 °C to 125 °C; it has good anti-reduction property and can be co-fired with nickel electrodes in a reducing atmosphere.

[0027] (4) The particle size of the BaTiO3 nano matrix material described in the present invention is preferably <200 nm, which is suitable for miniaturized and high-capacity MLCCs of models such as 0805.

[0028] (5) The BaTiO3 nano matrix material described in the present invention does not contain lead, is environmentally friendly, and does not contain bismuth at the same time. It can be co-fired with nickel electrodes in a reducing atmosphere; the preparation process is simple and is conducive to large-scale production. Description of the Drawings

[0029] Figure 1 SEM image of the ceramic powder obtained in step (1) of Example 8.

[0030] Figure 2 SEM and energy spectrum images of the ceramic powder obtained in step (1) of Example 8.

[0031] Figure 3 Dispersion effect diagrams of different parts of the ceramic powder obtained in step (1) of Example 8, with the scale bar being 200 nm for all.

[0032] Figure 4 Particle size distribution diagram of the ceramic powder obtained in step (1) of Example 8. Detailed implementation manners

[0033] In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0034] The present invention discloses a reducing-resistant BaTiO3-based dielectric ceramic material for MLCC, the raw materials of which include a main material and a doping material; the main material is nano-tetragonal BaTiO3 with a particle size of 100 - 150 nm; the doping material is a mixture of MgO, CaCO3, Y2O3 and MnCO3 with a particle size of 10 - 30 nm. The molar ratio of MgO to BaTiO3 is 0.5% - 2%, the molar ratio of CaCO3 to BaTiO3 is 0.5% - 2%, the molar ratio of Y2O3 to BaTiO3 is 0.5% - 2%, and the molar ratio of MnCO3 to BaTiO3 is 0.5% - 1.5%.

[0035] The preparation method of the X7R type reducing-resistant BaTiO3-based dielectric ceramic material includes:

[0036] (1) Mix BaTiO3 powder with MgO, CaCO3, Y2O3, and MnCO3 in a molar ratio of 100:(0.5 - 2):(0.5 - 2):(0.5 - 2):(0.5 - 1.5), add a solution of deionized water and dispersant BYK (volume ratio of 8 - 11:1) for ultrasonic dispersion, ball milling, and then drying to obtain ceramic powder.

[0037] (2) Add a binder to the ceramic powder, then granulate, screen, form, and degrease. Subsequently, sinter and hold the temperature in a mixed atmosphere of nitrogen and reducing gas to obtain a ceramic sample, and co-fire it with a nickel electrode in a weakly reducing atmosphere to obtain the BaTiO3-based ceramic material for X7R MLCC.

[0038] As a preferred embodiment of the above technical solution, in step (1), the ultrasonic time is 1 to 2 hours, the ball milling time is 12 to 24 hours, and the ball milling speed is 250 r / min to 360 r / min. The specific surface area of ​​the final powder is ≤20m 2 / g.

[0039] As a preferred embodiment of the above technical solution, the binder is PVA or PVB, and the added amount of the binder is 5% to 25% of the mass of the ceramic powder, so that the sintering shrinkage curve thereof can be adjusted.

[0040] As a preferred embodiment of the above technical solution, the sintering in step (2) is divided into two steps. First, the temperature is raised to 800°C at 5°C / min and the holding time is 1 hour to allow MnCO3 and CaCO3 to fully react. Then the temperature is raised to 1130°C to 1250°C and the holding time is 2 hours. The ratio of nitrogen to hydrogen in the weak reducing atmosphere is 1000:5.

[0041] As a preferred embodiment of the above technical solution, the purity of the raw materials for preparation is greater than 99%.

[0042] In some specific embodiments, the preparation method of the X7R type anti-reduction BaTiO3-based dielectric ceramic material includes:

[0043] (1) 100-150nm tetragonal BaTiO3 powder was fully mixed with 10-30nm MgO, CaCO3, Y2O3 and MnCO3 dopants, BaTiO3-based nano-ceramic powder was mixed with deionized water at a mass ratio of 1:1.5, and then BYK dispersant was added at a volume ratio of 1:11 to deionized water. After ultrasonic dispersion for 1h-2h, the mixture was ball-milled at 250r / min for 12-24h, dried in an oven, and sieved to obtain ceramic powder.

[0044] (2) Add 5% PVA binder by mass to the ceramic powder, granulate and shape it to obtain ceramic bodies with different solid contents and sintering shrinkage curves; debind the ceramic bodies at a debinding temperature of 550°C, a heating rate of 5°C / min, and keep it warm for 2 hours; then heat it to 800°C at a heating rate of 5°C / min and keep it warm for 1 hour to fully decompose the nano MnCO3 and CaCO3. Finally, heat it to 1130°C-1250°C and keep it warm for 2 hours to obtain a tetragonal BaTiO3-based dielectric ceramic material with a particle size of 100-150nm; the BaTiO3-based dielectric ceramic material has a core-shell structure, a dielectric constant between 1000 and 2000, ΔC / C <±15% in the range of -55°C-125°C, and a loss <0.02, and has different sintering shrinkage curves, and can be co-fired with nickel electrodes in a reducing atmosphere.

[0045] The present invention improves the dielectric constant, anti-reduction property, service life and temperature stability of the dielectric material for MLCC by controlling the dosages of various components, especially the molar ratios of MgO, CaCO3, Y2O3 and MnCO3. By regulating the addition amount of BYK dispersant and ultrasonic ball milling, the dopants with a size of 10 - 30 nm are uniformly coated on barium titanate with a size of 100 - 150 nm. By adding different mass fractions of PVA to regulate the solid content of barium titanate, and through screening, granulation and tabletting, a ceramic green body is obtained.

[0046] The anti-reduction BaTiO3-based dielectric ceramic material provided by the present invention has the following beneficial effects:

[0047] (1) It combines the grain size of BaTiO3 (100 - 200 nm), the dielectric properties of BaTiO3 (dielectric constant 900 - 1900, loss < 0.02), and the change rate of the BaTiO3 capacitance temperature coefficient within the range of ±15%. It flattens its Curie peak, and the dielectric temperature stability meets the X7R requirement. At the same time, on the premise of ensuring that the grain size is 100 - 200 nm, it has a relatively high dielectric constant.

[0048] (2) It solves the problem of forming a uniform core-shell structure on the surface of barium titanate with a size of 100 - 150 nm in large-scale production. By using a non-chemical coating method, the dopants with a size of 10 - 30 nm before sintering are uniformly coated on the surface of the 100 - 150 nm barium titanate matrix. A uniform core-shell structure is formed during the sintering process.

[0049] (3) Donor and acceptor doping are carried out simultaneously. By adjusting the addition amount of PVA, its shrinkage curve is adjusted. While ensuring good anti-reduction performance, it is co-fired with nickel electrodes in a reducing atmosphere. It has the advantages of environmental friendliness, low electrode cost and easy industrial production.

[0050] The present invention uses nano-tetragonal BaTiO3 powder (particle size 100 - 150 nm) as the matrix, and then adds MgO, CaCO3, Y2O3 and MnCO3 with a size of 10 - 30 nm as dopants. By using a method combining ultrasonic dispersion and ball milling with the addition of dispersant BYK, the dopants are uniformly coated on the surface of nano-BaTiO3. Compared with the chemical coating method, this method has low cost and simple process, which is mainly due to:

[0051] (1) MgO can first form a coating layer on BaTiO3 at low temperature, inhibiting the penetration of dopants with faster diffusion, thereby forming a preliminary "shell" structure on the surface of BaTiO3. The wrapping of the core layer also has the effect of refining grains and preventing excessive crystal growth. It ensures that the size of grain growth is controllable, so as to obtain a BaTiO3 nano-matrix with particle size anti-reduction property.

[0052] (2) CaCO3 plays a role in refining grains, and at the same time can carry out acceptor compensation to enhance the anti-reduction property of the BaTiO3 nanomatrix.

[0053] (3) Y2O3 can carry out both donor and acceptor compensations to enhance the anti-reduction property of the BaTiO3 nanomatrix.

[0054] (4) MnCO3 carries out acceptor compensation to reduce losses.

[0055] (5) The method of combining ultrasonic dispersion and low-speed ball milling with the dispersant BYK can uniformly coat 10 - 30 nm of MgO, CaCO3, Y2O3, and MnCO3 on the surface of BaTiO3. The method is simple and can be used for large-scale production.

[0056] These five aspects ensure that the 100 - 150 nm tetragonal BaTiO3 matrix can form a uniform "core-shell" structure with 10 - 30 nm dopants before sintering, ensuring its good anti-reduction property, low losses, etc. after sintering, inhibiting grain growth during the sintering process, and thus obtaining a BaTiO3 nanoceramic material (<200 nm) with anti-reduction and low losses that can be mass-produced and is suitable for miniaturized and high-capacity MLCCs such as the 0805 model.

[0057] Example 1

[0058] A preparation method of an X7R-type anti-reduction BaTiO3-based dielectric ceramic material, and its specific steps are as follows:

[0059] (1) Mix BaTiO3 powder with MgO, CaCO3, Y2O3, and MnCO3 in a molar ratio of 100:1:2:2:0.5, and mix deionized water and the dispersant BYK in a volume ratio of 11:1 to obtain a solution. Mix the BaTiO3 powder and the solution in a mass ratio of 1:1.5, carry out ultrasonic dispersion for 1 h, ball mill for 24 h at a rotation speed of 250 r / min, and then dry to obtain ceramic powder.

[0060] (2) Add PVA with a mass of 5 wt% of the ceramic powder obtained in step 1, then granulate, sieve, and mold to obtain a ceramic green body with a diameter of 12 mm and a thickness of 2 mm. The ceramic green body is degummed at 550 °C for 2 h in an air atmosphere, and then heated to 800 °C at a rate of 1000:5 in a weakly reducing atmosphere of nitrogen and hydrogen, held for 1 h, and then heated to 1150 °C and held for 2 h.

[0061] (3) Coat nickel electrodes on both sides of the obtained single-layer ceramic green body by screen printing, and carry out co-sintering in a weakly reducing atmosphere of nitrogen and hydrogen with a volume ratio of 1000:5. Obtain a BaTiO3 nanoceramic matrix with anti-reduction property.

[0062] Example 2

[0063] A preparation method of an X7R-type anti-reducing BaTiO3-based dielectric ceramic material, and the specific steps are as follows:

[0064] (1) Mix BaTiO3 powder with MgO, CaCO3, Y2O3, and MnCO3 in a molar ratio of 100:1:2:2:0.5, and mix ionized water and dispersant BYK in a volume ratio of 11:1 to obtain a solution. Mix the BaTiO3 powder and the solution in a mass ratio of 1:1.5, perform ultrasonic dispersion for 1 h, ball mill for 24 h at a rotation speed of 250 r / min, and then dry to obtain ceramic powder.

[0065] (2) Add 5 wt% PVA to the ceramic powder obtained in step (1), then granulate, sieve, and mold to obtain a ceramic green body with a diameter of 12 mm and a thickness of 2 mm. The ceramic green body is degummed at 550 °C for 2 h, and then heated to 800 °C in a weakly reducing atmosphere with a nitrogen-to-hydrogen ratio of 1000:5, held for 1 h, and then heated to 1170 °C and held for 2 h.

[0066] (3) Apply nickel electrodes on both sides of the obtained single-layer ceramic green body by screen printing, and perform co-firing in a weakly reducing atmosphere with a nitrogen-to-hydrogen volume ratio of 1000:5. Obtain an anti-reducing BaTiO3 nanoceramic matrix.

[0067] Example 3

[0068] A preparation method of an X7R-type anti-reducing BaTiO3-based dielectric ceramic material, and the specific steps are as follows:

[0069] (1) Mix BaTiO3 powder with MgO, CaCO3, Y2O3, and MnCO3 in a molar ratio of 100:1.5:2:2:0.5, and mix ionized water and dispersant BYK in a volume ratio of 11:1 to obtain a solution. Mix the BaTiO3 powder and the solution in a mass ratio of 1:1.5, perform ultrasonic dispersion for 1 h, ball mill for 24 h at a rotation speed of 250 r / min, and then dry to obtain ceramic powder.

[0070] (2) Add 5 wt% PVA to the ceramic powder obtained in step (1), then granulate, sieve, and mold to obtain a ceramic green body with a diameter of 12 mm and a thickness of 2 mm. The ceramic green body is degummed at 550 °C for 2 h, and then heated to 800 °C in a weakly reducing atmosphere with a nitrogen-to-hydrogen ratio of 1000:5, held for 1 h, and then heated to 1170 °C and held for 2 h.

[0071] (3) The obtained single-layer ceramic blank is coated with nickel electrodes on both sides of the blank by screen printing, and co-fired in a weakly reducing atmosphere with a volume ratio of nitrogen to hydrogen of 1000:5. A BaTiO3 nanoceramic matrix with anti-reducing properties is obtained.

[0072] Example 4

[0073] A preparation method of an X7R-type anti-reducing BaTiO3-based dielectric ceramic material, and the specific steps are as follows:

[0074] (1) Mix BaTiO3 powder with MgO, CaCO3, Y2O3, and MnCO3 in a molar ratio of 100:1.5:2:2:0.5, and mix ionized water and dispersant BYK in a volume ratio of 11:1 to obtain a solution. The mass ratio of BaTiO3 powder to the solution is 1:1.5, ultrasonically disperse for 1 h, ball mill for 24 h at a rotation speed of 250 r / min, and then dry to obtain ceramic powder.

[0075] (2) Add 5 wt% PVA to the ceramic powder obtained in step (1), then granulate, sieve, and mold to obtain a ceramic blank with a diameter of 12 mm and a thickness of 2 mm. The ceramic blank is degummed at 550 °C for 2 h, then heated to 800 °C in a weakly reducing atmosphere with a ratio of nitrogen to hydrogen of 1000:5, held for 1 h, and then heated to 1210 °C and held for 2 h.

[0076] (3) The obtained single-layer ceramic blank is coated with nickel electrodes on both sides of the blank by screen printing, and co-fired in a weakly reducing atmosphere with a volume ratio of nitrogen to hydrogen of 1000:5. A BaTiO3 nanoceramic matrix with anti-reducing properties is obtained.

[0077] Example 5

[0078] A preparation method of an X7R-type anti-reducing BaTiO3-based dielectric ceramic material, and the specific steps are as follows:

[0079] (1) Mix BaTiO3 powder with MgO, CaCO3, Y2O3, and MnCO3 in a molar ratio of 100:2:2:2:0.5, and mix ionized water and dispersant BYK in a volume ratio of 11:1 to obtain a solution. The mass ratio of BaTiO3 powder to the solution is 1:1.5, ultrasonically disperse for 1 h, ball mill for 24 h at a rotation speed of 250 r / min, and then dry to obtain ceramic powder.

[0080] (2) Add 5 wt% PVA to the ceramic powder obtained in step (1), then granulate, screen, and form it to obtain a ceramic green body with a diameter of 12 mm and a thickness of 2 mm. The ceramic green body is debinded at 550 °C for 2 h, and then heated to 800 °C in a weakly reducing atmosphere with a nitrogen-to-hydrogen ratio of 1000:5, held for 1 h, and then heated to 1170 °C and held for 2 h.

[0081] (3) Coat nickel electrodes on both sides of the obtained single-layer ceramic green body by screen printing method, and co-fire it in a weakly reducing atmosphere with a nitrogen-to-hydrogen volume ratio of 1000:5. A BaTiO3 nano-ceramic matrix with anti-reducing property is obtained.

[0082] Example 6

[0083] A preparation method of an X7R type anti-reducing BaTiO3-based dielectric ceramic material, the specific steps are as follows:

[0084] (1) Mix BaTiO3 powder with MgO, CaCO3, Y2O3, and MnCO3 in a molar ratio of 100:2:2:2:0.5, and mix ionized water and dispersant BYK in a volume ratio of 11:1 to obtain a solution. Mix the BaTiO3 powder and the solution in a mass ratio of 1:1.5, ultrasonically disperse for 1 h, ball mill for 24 h at a rotation speed of 250 r / min, and then dry to obtain ceramic powder.

[0085] (2) Add 5 wt% PVA to the ceramic powder obtained in step (1), then granulate, screen, and form it to obtain a ceramic green body with a diameter of 12 mm and a thickness of 2 mm. The ceramic green body is debinded at 550 °C for 2 h, and then heated to 800 °C in a weakly reducing atmosphere with a nitrogen-to-hydrogen ratio of 1000:5, held for 1 h, and then heated to 1190 °C and held for 2 h.

[0086] (3) Coat nickel electrodes on both sides of the obtained single-layer ceramic green body by screen printing method, and co-fire it in a weakly reducing atmosphere with a nitrogen-to-hydrogen volume ratio of 1000:5. A BaTiO3 nano-ceramic matrix with anti-reducing property is obtained.

[0087] Example 7

[0088] A preparation method of an X7R type anti-reducing BaTiO3-based dielectric ceramic material, the specific steps are as follows:

[0089] (1) Mix BaTiO3 powder with MgO, CaCO3, Y2O3, and MnCO3 in a molar ratio of 100:2:2:2:0.5. Mix ionized water and dispersant BYK in a volume ratio of 11:1 to obtain a solution. Mix the BaTiO3 powder and the solution in a mass ratio of 1:1.5, ultrasonically disperse for 1 h, ball mill for 24 h at a rotation speed of 250 r / min, and then dry to obtain ceramic powder.

[0090] (2) Add 5 wt% PVA to the ceramic powder obtained in step (1), then granulate, screen, and mold to obtain a ceramic green body with a diameter of 12 mm and a thickness of 2 mm. Debind the ceramic green body at 550 °C for 2 h, then heat it to 800 °C in a weakly reducing atmosphere with a nitrogen-to-hydrogen ratio of 1000:5, hold for 1 h, then heat it to 1210 °C and hold for 2 h.

[0091] (3) Coat nickel electrodes on both sides of the obtained single-layer ceramic green body by screen printing, and co-fire in a weakly reducing atmosphere with a nitrogen-to-hydrogen volume ratio of 1000:5. Obtain a BaTiO3 nanoceramic matrix with anti-reduction property.

[0092] Example 8

[0093] A preparation method of an X7R-type anti-reduction BaTiO3-based dielectric ceramic material, and its specific steps are as follows:

[0094] (1) Mix BaTiO3 powder with MgO, CaCO3, Y2O3, and MnCO3 in a molar ratio of 100:2:2:2:0.5. Mix ionized water and dispersant BYK in a volume ratio of 11:1 to obtain a solution. Mix the BaTiO3 powder and the solution in a mass ratio of 1:1.5, ultrasonically disperse for 1 h, ball mill for 24 h at a rotation speed of 250 r / min, and then dry to obtain ceramic powder.

[0095] (2) Add 5 wt% PVA to the ceramic powder obtained in step (1), then granulate, screen, and mold to obtain a ceramic green body with a diameter of 12 mm and a thickness of 2 mm. Debind the ceramic green body at 550 °C for 2 h, then heat it to 800 °C in a weakly reducing atmosphere with a nitrogen-to-hydrogen ratio of 1000:5, hold for 1 h, then heat it to 1230 °C and hold for 2 h.

[0096] (3) Coat nickel electrodes on both sides of the obtained single-layer ceramic green body by screen printing, and co-fire in a weakly reducing atmosphere with a nitrogen-to-hydrogen volume ratio of 1000:5. Obtain a BaTiO3 nanoceramic matrix with anti-reduction property.

[0097] As Figure 1As shown, it can be seen that the ceramic powder has achieved a uniform coating of 10 - 30 nm dopants on the BaTiO₃ nano - matrix, forming a core - shell structure, and its specific surface area is 14.92 m 2 / g. Figure 2 It shows that the obtained ceramic powder contains the elements contained in each raw material. From Figure 3 any Figure 4 it can be seen that there are fewer agglomeration sites in the ceramic powder, and the particle size is mainly distributed in the range of 100 - 200 nm.

[0098] Comparative Example 1

[0099] A preparation method of a BaTiO₃ ceramic material, and its specific steps are as follows:

[0100] Add 5% by mass of PVA binder to pure BaTiO₃ powder, granulate and form it to obtain a ceramic green body with a diameter of 12 mm and a thickness of 2 mm. The ceramic green body is heated in air at a heating rate of 5 °C / min to 550 °C and kept warm for 2 h for debinding, then heated to 1230 °C and kept warm for 2 h. After silver plating, it is co - fired with silver electrodes in air to obtain a BaTiO₃ ceramic matrix material.

[0101] Comparative Example 2

[0102] A preparation method of a BaTiO₃ ceramic material, and its specific steps are as follows:

[0103] Add 5% by mass of PVA binder to pure BaTiO₃ powder, granulate and form it to obtain a ceramic green body with a diameter of 12 mm and a thickness of 2 mm. The ceramic green body is heated to 550 °C in air and kept warm for 2 h for debinding, then heated in a weakly reducing atmosphere with a nitrogen - to - hydrogen ratio of 1000:5 at a heating rate of 5 °C / min to 800 °C, kept warm for 1 h, and finally heated to 1230 °C and kept warm for 2 h. A BaTiO₃ ceramic matrix material with serious semi - conductivity is obtained.

[0104] Table 1 Performance test results of the BaTiO₃ nano - ceramic matrix obtained from the examples and comparative examples

[0105]

[0106]

[0107] As can be seen from Table 1, Examples 1 to 8 all meet the application standards of X7R. With a relatively small grain size, the dielectric constant ranges from 900 to 1850, and the variation amplitude of the maximum dielectric constant (Max|TCC|) is 14.4%. The loss varies with temperature and is less than 2% from -55°C to 125°C. Among them, Preferred Examples 4 and 8 have good anti-reduction properties after co-sintering in a reducing atmosphere with a nitrogen:hydrogen ratio of 1000:5, and their dielectric constants are 1643±243 and 1801±260 respectively. Compared with Comparative Examples 1 and 2, Examples 1 to 8 form a stable core-shell structure, have high temperature stability and good anti-reduction properties, and can be co-fired with electrodes such as nickel electrodes in a reducing atmosphere and applied to BME-MLCC.

[0108] In summary, the present invention uses nano-tetragonal BaTiO3 powder (particle size of 100 - 150 nm) as the matrix, and MgO, CaCO3, Y2O3, and MnCO3 with a particle size of 10 - 30 nm as dopants. By combining the ultrasonic method and the ball milling method with a dispersant, the 10 - 30 nm dispersant is uniformly coated on the surface of the BaTiO3 matrix, so that a uniform core-shell structure can be formed, the ceramic grain size < 200 nm, and the dielectric constant of the co-fired single dielectric layer remains at a relatively high level.

[0109] It is easy for those skilled in the art to understand that the above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A BaTiO3-based dielectric ceramic material, characterized in that: It includes a main material and a doping material; the main material is BaTiO3, and the doping material includes MgO, CaCO3, Y2O3 and MnCO3; the molar ratio of BaTiO3, MgO, CaCO3, Y2O3 and MnCO3 is 100: (0.5-2.2): (0.5-2.2): (0.5-2.2): (0.4-1.5).

2. The BaTiO3-based dielectric ceramic material according to claim 1, characterized in that: The molar ratio of BaTiO3, MgO, CaCO3, Y2O3 and MnCO3 is 100:(1-2):(1-2):(1-2):(0.5-1); The grain size of the BaTiO3-based dielectric ceramic material is 100-200 nm.

3. A method for preparing the BaTiO3-based dielectric ceramic material according to claim 1 or 2, characterized in that: The following steps are involved: (1) BaTiO3, MgO, CaCO3, Y2O3 and MnCO3 are mixed according to a preset molar ratio, deionized water and a dispersant are added, and the mixture is ball-milled and then dried to obtain a ceramic powder; (2) The ceramic powder and the binder are mixed, granulated, sieved, and pressed to obtain a ceramic body; the ceramic body is heated to remove the binder, and then the temperature is further increased and sintered in a reducing atmosphere to obtain a BaTiO3-based dielectric ceramic material.

4. The method for preparing the BaTiO3-based dielectric ceramic material according to claim 3, characterized in that: The particle size of the BaTiO3 is 100-150 nm, and the particle sizes of the MgO, CaCO3, Y2O3 and MnCO3 are 10-30 nm; The ceramic powder has a core-shell structure with BaTiO3 as the core and the doping material as the shell; The grain size of the BaTiO3-based dielectric ceramic material is 100-200 nm.

5. The method for preparing the BaTiO3-based dielectric ceramic material according to claim 3, characterized in that: In step (1), the volume ratio of deionized water to dispersant is (8-15):1, preferably (10-12):1; The mass ratio of the sum of the mass of the deionized water and the dispersant to the mass of BaTiO3 is (1-3):

1.

6. The method for preparing the BaTiO3-based dielectric ceramic material according to claim 3, characterized in that: In step (2), the amount of the binder added is 5% to 25% of the mass of the ceramic powder; And / or, the binder is polyvinyl alcohol or polyvinyl butyral.

7. The method for preparing the BaTiO3-based dielectric ceramic material according to claim 3, characterized in that: In step (2), the debinding temperature is 500-600° C. and the holding time is 1-3 hours; The sintering is firstly heated to 750-850°C and kept at this temperature for 0.5-2h, then heated to 1130-1250°C and kept at this temperature for 1-3h; The reducing atmosphere is composed of an inert gas and hydrogen in a volume ratio of 1000:(1-8).

8. A method for preparing a ceramic dielectric layer, characterized in that: Sintering the BaTiO3-based dielectric ceramic material according to claim 1 or 2 and a nickel electrode in a reducing atmosphere to obtain a ceramic dielectric layer; Preferably, a nickel electrode is screen-printed on the surface of the BaTiO3-based dielectric ceramic material, and then the temperature is raised to 1050-1250° C. and sintered for 1-2 hours in a mixed atmosphere of nitrogen and hydrogen in a volume ratio of 1000:(1-8) to obtain the ceramic dielectric layer.

9. A ceramic dielectric layer obtained by the preparation method according to claim 8.

10. A multilayer ceramic capacitor, characterized in that: comprising the ceramic dielectric layer of claim 9; The multilayer ceramic capacitor is preferably an X7R type multilayer ceramic capacitor.

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