Mg-mo synergistic anti-reduction x7r barium titanate ceramic and preparation method thereof

Abstract

The application discloses a Mg-Mo synergistic anti-reduction X7R barium titanate ceramic material, and belongs to the technical field of electronic ceramics and multilayer ceramic capacitors. The ceramic material takes BaTiO3 as a main material, and contains MgCO3, MnCO3, SiO2, rare earth oxides and MoO3, wherein the mass ratio of MgCO3 to MoO3 is 4.5:1-6.5:1. After the raw materials are subjected to wet ball milling, drying, granulation and forming, sintering is carried out at 1280-1300 DEG C in a 1%-2% H2-N2 reducing atmosphere, and re-oxidation is carried out in a N2 atmosphere containing 10-200 ppm O2. The Mg-Mo synergistic regulation controls the BaTiO3 grain shell layer proportion and defect compensation, inhibits oxygen vacancy migration, so that the material meets the X7R temperature characteristic, and has a higher dielectric constant, a lower dielectric loss and a higher insulation resistivity, and is suitable for BME-MLCC.

Description

Technical Field

[0001] This invention belongs to the technical field of electronic ceramic materials and multilayer ceramic capacitors. Specifically, it relates to a reduction-resistant X7R barium titanate-based dielectric ceramic material and its preparation method for multilayer ceramic capacitors with nickel or nickel alloy base metal internal electrodes. In particular, it relates to a ceramic material that controls the shell ratio and defect compensation state of BaTiO3 grain core-shell structure by controlling the mass ratio of MgCO3 to MoO3. Background Technology

[0002] Multilayer ceramic capacitors (MLCCs) are characterized by their small size, high specific capacitance, and high reliability, and are widely used in consumer electronics, industrial control, and automotive electronics. Based on the temperature characteristics of the dielectric material, MLCCs can be classified into Class I and Class II ceramic capacitors. The X7R belongs to the Class II ceramic capacitor temperature characteristic class, with an operating temperature range of -55℃ to 125℃. Using the capacitance at 25℃ as a reference, the capacitance change rate should be controlled within ±15%.

[0003] Base metal internal electrode multilayer ceramic capacitors (BME-MLCCs) using nickel or nickel alloys as internal electrodes require sintering in a reducing atmosphere with low oxygen partial pressure to prevent oxidation of the internal electrodes. When BaTiO3-based ceramics are sintered in a reducing atmosphere, some Ti... 4+ Easily reduced to Ti 3+ This, along with the generation of oxygen vacancies and electron carriers, may lead to semiconducting dielectric layers, increased dielectric loss, decreased insulation resistivity, and reduced long-term reliability.

[0004] Existing technologies typically employ Mg, Mn, rare earth elements, SiO2, and high- or variable-valence oxides to modify BaTiO3-based ceramics. Mg can suppress aberrant grain growth and promote core-shell structure formation; Mn can act as an acceptor-type compensating component; rare earth elements such as Y, Dy, and Ho exhibit amphoteric A-site / B-site occupancy characteristics; and SiO2 can promote sintering densification and regulate grain boundary states. However, the proportions of these additives simultaneously affect the shell ratio, dielectric constant, temperature stability, and reduction resistance; increasing the content of a single additive can easily lead to performance imbalances.

[0005] The disclosed technologies related to this invention include: US Patent 7821770B2 discloses a dielectric ceramic composition with BaTiO3 as the main component and containing Mg, V / Cr / Mn oxides, rare earth oxides and SiO2; Chinese authorized patent CN112174658B discloses a technical solution for obtaining core-shell structured BaTiO3-based ceramic dielectric materials through coating modification; and international publication WO2024203277A1 discloses a BaTiO3-based dielectric ceramic composition containing different grain compositions, and involves the distribution of elements such as Mg in the grains.

[0006] The aforementioned disclosed technologies focus on multi-component co-doping, coated core-shell structures, or the control of different grain compositions. However, a clear solution is still lacking for the mass ratio window of MgCO3 to MoO3 and its synergistic control over the proportion of BaTiO3 grain shells, defect compensation, and reduction resistance. Therefore, it is necessary to provide a barium titanate-based ceramic material whose composition and processing are suitable for BME-MLCC production and which can balance the temperature characteristics of X7R with insulation reliability. Summary of the Invention

[0007] The purpose of this invention is to provide a Mg-Mo synergistic anti-reduction X7R barium titanate ceramic and its preparation method. The ceramic material is mainly composed of BaTiO3, and the mass ratio of MgCO3 to MoO3 is controlled at 4.5:1 to 6.5:1 to achieve the desired Mg-Mo synergistic anti-reduction effect. 2+ with Mo 6+ Synergistic defect compensation is formed during reduction sintering and re-oxidation, and element diffusion and shell formation on the surface of BaTiO3 grains are regulated, thereby inhibiting oxygen vacancy migration and improving the temperature stability and insulation reliability of the material.

[0008] To achieve the above objectives, the ceramic material comprises, by mass percentage, 97.60–98.10 wt% BaTiO3, 0.50–1.00 wt% MgCO3, 0.30–0.40 wt% MnCO3, 0.30–0.50 wt% SiO2, 0.30–0.30 wt% Y2O3, 0.30–0.30 wt% Dy2O3, 0.10–0.30 wt% Ho2O3, and 0.10–0.20 wt% MoO3, with the sum of the mass percentages of all components being 100 wt%. The mass ratio of MgCO3 to MoO3 is 4.5:1 to 6.5:1, preferably 5:1 to 6:1.

[0009] The Y₂O₃, Dy₂O₃, and Ho₂O₃ constitute the rare earth oxide component, and the total content of the rare earth oxide component is preferably 0.30–0.80 wt%. 3+ Dy 3+ and Ho 3+It can regulate the site occupancy and charge balance in the BaTiO3 lattice and improve the grain boundary insulation state together with Mg-Mo synergistic defect compensation.

[0010] After sintering, the ceramic material forms BaTiO3 core-shell structure grains. The core of the BaTiO3 core-shell structure grains is dominated by tetragonal BaTiO3, while the shell and grain boundary regions are enriched with Mg, Mo, Mn, and rare earth elements relative to the core. Preferably, the shell thickness accounts for 18% to 35% of the grain radius, or the shell area accounts for 35% to 60% of the cross-sectional area of ​​a single grain. The shell ratio can be determined by transmission electron microscopy, scanning transmission electron microscopy energy dispersive spectroscopy, or electron probe microanalysis.

[0011] The present invention also provides a method for preparing the ceramic material, comprising the following steps: weighing BaTiO3, MgCO3, MnCO3, SiO2, Y2O3, Dy2O3, Ho2O3 and MoO3 according to the above mass percentages; subjecting each component to wet ball milling, drying, granulation and pressing to obtain a shaped green body; placing the shaped green body in a H2-N2 reducing atmosphere and sintering at 1280-1300 °C for 2-4 h to obtain a sintered body; placing the sintered body in an N2 atmosphere containing 10-200 ppm O2 and re-oxidizing at 900 °C for 2 h.

[0012] Preferably, during wet ball milling, the mass ratio of deionized water, zirconium balls, and powder is 2:1:1, the milling speed is 280 r / min, and the milling time is 3–16 h; the pressing pressure is 10–15 MPa. The reducing atmosphere is 1% H2–99% N2 or 2% H2–98% N2, the gas flow rate is 50–70 sccm, the heating rate is 3 °C / min, and the cooling rate is 4 °C / min.

[0013] Beneficial effects of the present invention

[0014] 1. This invention limits the mass ratio of MgCO3 to MoO3 to 4.5:1 to 6.5:1, so that the Mg-induced shell expansion and MoO3... 6+ The high-price compensation provided is conducive to increasing the shell ratio in the core-shell structure while maintaining a high dielectric constant.

[0015] 2. Mg 2+ with Mo 6+ In the BaTiO3 lattice, charge compensation correlations represented by MgTi″-MoTi•• are formed, which, together with Mn acceptor compensation and rare earth amphoteric occupancy, help to reduce the effective mobility of oxygen vacancies and improve the grain boundary insulation state.

[0016] 3. In this invention, the amount of MoO3 added is 0.10 to 0.20 wt%. Within the range shown in the examples, no significant deterioration of dielectric properties due to excessive Mo components was observed, which is beneficial for balancing temperature stability and insulation performance.

[0017] 4. This invention employs wet ball milling, conventional molding, reducing atmosphere sintering, and re-oxidation treatment, without requiring complex coating processes or pre-synthesized composite additives, and has good compatibility with conventional BME-MLCC dielectric ceramic preparation processes.

[0018] 5. The ceramic material prepared in the examples has a dielectric constant of 2510–3090 at 25 °C and 1 kHz, a dielectric loss tanδ of no more than 1.5%, and an insulation resistivity of no less than 1.5 × 10⁻⁶. 12 Ω·cm, and meets the X7R temperature characteristics in the range of -55 ℃ to 125 ℃. Attached Figure Description

[0019] Figure 1 This is a schematic flowchart of the preparation method of the reduction-resistant high-performance X7R type ceramic material of the present invention;

[0020] Figure 2 These are characteristic curves showing the change of dielectric constant as a function of temperature for the samples in Examples 1-8 of this invention.

[0021] Figure 3 These are characteristic curves showing the change of dielectric constant as a function of temperature for the samples in Examples 1-8 of this invention. Detailed Implementation

[0022] Examples 1-8

[0023] Step S1, Ingredients: Weigh BaTiO3, MgCO3, MnCO3, SiO2, Y2O3, Dy2O3, Ho2O3, and MoO3 according to the mass percentages listed in Table 1. "—" in Table 1 indicates no addition, and the corresponding content is considered as 0. In each embodiment, the mass ratio of MgCO3 to MoO3 is within the range of 4.5:1 to 6.5:1.

[0024] Step S2, ball milling: Add the components weighed in step S1 into a ball mill jar and mix them according to the mass ratio of deionized water, zirconium balls and powder of 2:1:1. Wet ball mill at 280 r / min for 10 h to make the added components uniformly dispersed in BaTiO3 powder.

[0025] Step S3, drying, granulation and molding: The slurry obtained in step S2 is dried in an oven at 100 ℃, and polyvinyl alcohol accounting for 15% of the mass of the dried powder is added for granulation. The granulation particle size is controlled to be 80-250 mesh. The granulated blank is pressed into a molded body with a diameter of about 10 mm and a thickness of about 1 mm under a pressure of 12 MPa.

[0026] Step S4, reduction sintering: The shaped blank obtained in step S3 is placed in a 1% H2-99% N2 atmosphere or a 2% H2-98% N2 atmosphere, heated to 1280-1300 ℃ at a heating rate of 3 ℃ / min, held at that temperature for 2 h, and then cooled at a cooling rate of 4 ℃ / min; the gas flow rate of the reducing atmosphere is 50-70 sccm.

[0027] Step S5, re-oxidation: The sintered body obtained in step S4 is placed in an N2 atmosphere containing 10-200 ppm O2 and re-oxidized at 900℃ for 2 h to obtain Mg-Mo synergistic anti-reduction X7R barium titanate ceramic material. The specific ingredients, process parameters and performance test results of each embodiment are shown in Tables 1, 2 and 3, respectively.

[0028] Table 1. Ingredients (wt%) of Mg-Mo synergistic anti-reduction X7R barium titanate ceramic materials in Examples 1-8

[0029]

[0030] Table 2 Process parameters of Mg-Mo synergistic anti-reduction X7R barium titanate ceramic materials in Examples 1-8

[0031]

[0032] Table 3 Performance of Mg-Mo synergistic anti-reduction X7R barium titanate ceramic materials in Examples 1-8

[0033] .

Claims

1. A Mg-Mo synergistic anti-reduction X7R barium titanate ceramic material, characterized in that, The ceramic material comprises the following components by mass percentage: BaTiO3 97.60–98.10 wt%, MgCO3 0.50–1.00 wt%, MnCO3 0.30–0.40 wt%, SiO2 0.30–0.50 wt%, Y2O3 0–0.30 wt%, Dy2O3 0–0.30 wt%, Ho2O3 0.10–0.30 wt%, and MoO3 0.10–0.20 wt%, with the sum of the mass percentages of each component being 100 wt%; the mass ratio of MgCO3 to MoO3 is 4.5:1 to 6.5:

1.

2. The Mg-Mo synergistic anti-reduction X7R barium titanate ceramic material according to claim 1, characterized in that, The Y2O3, Dy2O3 and Ho2O3 constitute a rare earth oxide component, and the total content of the rare earth oxide component is 0.30 to 0.80 wt%.

3. The Mg-Mo synergistic anti-reduction X7R barium titanate ceramic material according to claim 1 or 2, characterized in that, The mass ratio of MgCO3 to MoO3 is 5:1 to 6:

1.

4. The Mg-Mo synergistic anti-reduction X7R barium titanate ceramic material according to any one of claims 1 to 3, characterized in that, After sintering, the ceramic material forms BaTiO3 core-shell structure grains. The core of the BaTiO3 core-shell structure grains is mainly composed of tetragonal BaTiO3, while the shell and grain boundary regions are enriched with Mg, Mo, Mn and rare earth elements relative to the core. The thickness of the shell accounts for 18% to 35% of the radius of the BaTiO3 core-shell structure grain, or the area of ​​the shell accounts for 35% to 60% of the cross-sectional area of ​​a single BaTiO3 core-shell structure grain.

5. The Mg-Mo synergistic anti-reduction X7R barium titanate ceramic material according to any one of claims 1 to 4, characterized in that, The ceramic material has a dielectric constant of 2510–3090 at 25 °C and 1 kHz, a dielectric loss tanδ of no more than 1.5%, and an insulation resistivity of no less than 1.5 × 10⁻⁶. 12 Ω·cm; with the capacitance at 25 °C as a reference, the capacitance change rate of the ceramic material in the range of -55 °C to 125 °C does not exceed ±15%.

6. A method for preparing a Mg-Mo synergistic anti-reduction X7R barium titanate ceramic material, characterized in that, Includes the following steps: Step S1: Weigh out the following components by mass percentage: BaTiO3 97.60–98.10 wt%, MgCO3 0.50–1.00 wt%, MnCO3 0.30–0.40 wt%, SiO2 0.30–0.50 wt%, Y2O3 0–0.30 wt%, Dy2O3 0–0.30 wt%, Ho2O3 0.10–0.30 wt%, and MoO3 0.10–0.20 wt%, so that the sum of the mass percentages of each component is 100 wt%, and the mass ratio of MgCO3 to MoO3 is 4.5:1–6.5:

1. Step S2: Perform wet ball milling, drying, granulation, and pressing of the components weighed in Step S1 to obtain a shaped green body. Step S3: Place the shaped green body in a H2-N2 reducing atmosphere and sinter at 1280–1300℃ for 2–4 days. h, to obtain a sintered body; step S4, place the sintered body in an N2 atmosphere containing 10-200 ppm O2, and re-oxidize it at 900 °C for 2 h to obtain the Mg-Mo synergistic anti-reduction X7R barium titanate ceramic material.

7. The preparation method of the Mg-Mo synergistic anti-reduction X7R barium titanate ceramic material according to claim 6, characterized in that, The wet ball milling in step S2 includes: mixing deionized water, zirconium balls, and the total mass of the components weighed in step S1 in a mass ratio of 2:1:1, and ball milling at 280 r / min for 3 to 16 h; the pressing pressure in step S2 is 10 to 15 MPa.

8. A method for preparing a Mg-Mo synergistic anti-reduction X7R barium titanate ceramic material according to claim 6 or 7, characterized in that, The H2-N2 reducing atmosphere in step S3 is either 1% H2-99% N2 or 2% H2-98% N2, with a gas flow rate of 50-70 sccm, a heating rate of 3 ℃ / min, and a cooling rate of 4 ℃ / min.

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