A wide temperature stable MLCC dielectric material and a preparation method thereof

Abstract

The application discloses a wide-temperature stable MLCC dielectric material and a preparation method thereof. The MLCC dielectric material is composed of Ba 1‑x Ce x Ti 1‑y Ce y O3 ceramic, wherein 0 < x <= 0.005 and 0.1 <= y <= 0.3. The preparation method comprises the following steps of batching, ball milling, drying, pre-sintering after sieving, secondary ball milling, drying, pressing a green body after granulation, and sintering to obtain the MLCC dielectric material. The dielectric temperature characteristic of the MLCC dielectric material meets the EIA X7R standard, has a high dielectric constant epsilon r > 1800 in a temperature range of -55 to 125 DEG C, low dielectric loss, and excellent insulation performance. The preparation method has the advantages of simple process, short preparation period, low cost and excellent performance of the prepared MLCC dielectric material.

Description

Technical Field

[0001] This application relates to the field of electronic ceramic materials technology, and in particular to a wide temperature stability MLCC dielectric material and its preparation method. Background Technology

[0002] Multilayer ceramic capacitors (MLCCs) are typical capacitor components that have kept pace with the development of electronic technology. They have become one of the most important categories of passive electronic components, widely used in consumer electronics and industrial electronic equipment, and are hailed as the "rice of the electronics industry." MLCCs are produced by alternately layering internal electrode materials and ceramic dielectric materials in multiple layers, co-firing them into a single unit, and then sealing external electrodes at both ends, resulting in a ceramic element with a monolithic structure. They can provide various functions, including energy storage, filtering, and decoupling. Due to their small size, high capacitance, low cost, and high reliability, MLCCs have become the most in-demand surface-mount passive devices in the modern electronics industry.

[0003] The dielectric material of MLCCs is fundamental to MLCC devices. The demand for small-size, high-performance, low-cost, and high-reliability electronic components requires MLCC dielectric materials to have high dielectric constants and low dielectric losses. Especially in aerospace, oil drilling, and industrial control fields, MLCCs are required to maintain stable performance at high operating temperatures and over a wide temperature range. Generally, wide-temperature stable MLCCs are required to meet the EIA X7R standard, meaning that the dielectric constant must satisfy ΔΔε within a temperature range of -55 to 125°C. r / ε r25℃ ≤±15%.

[0004] BaTiO3-based dielectric materials possess advantages such as high dielectric constant, low dielectric loss, low cost, and environmental friendliness, making them ideal materials for the fabrication of MLCCs. However, pure BaTiO3 is a typical ferroelectric material, and its dielectric constant undergoes a sudden change near the Curie temperature (approximately 120°C), resulting in unstable dielectric properties over a wide temperature range. Therefore, methods such as doping modification are often used to optimize the dielectric temperature characteristics of BaTiO3 to meet the requirements of wide-temperature stable MLCC dielectric materials. However, existing methods often require multi-element synergistic doping to achieve relatively stable dielectric temperature characteristics and necessitate the combined use of hydrothermal methods, sol-gel methods, and solid-state sintering methods, which have drawbacks such as long production cycles, low batch yields, and high production costs.

[0005] Rare earth element doping can effectively affect the physicochemical properties of ceramics, so its modification effect on the dielectric properties of BaTiO3 has attracted researchers' attention. A patent application (publication number: CN101328061A) filed by Jilin Chemical Engineering Institute introduces two different rare earth elements from La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Yb, and Lu into the Ba site (A site) of BaTiO3, with the addition amount being 1-5 mol% of the total A site content; simultaneously, Ce element is introduced into the Ti site (B site), with the addition amount being 3-5 mol% of the total B site content. The resulting material has a room temperature dielectric constant greater than 10000, but its dielectric properties only meet the EIA Y5V standard (dielectric constant meets Δε within the temperature range of -30 to 85℃). r / ε r25℃ (≤±22%), which cannot meet the requirements of wide-temperature stable MLCC for the dielectric material's temperature stability. Summary of the Invention

[0006] This invention provides a wide-temperature-stable MLCC dielectric material and its preparation method, which overcomes the shortcomings of existing technologies such as long production time, low batch yield, and high production cost. The provided MLCC dielectric material has the characteristics of achieving EIA X7R standard dielectric temperature stability, high dielectric constant, low dielectric loss, and excellent insulation performance.

[0007] To achieve the above objectives, this invention proposes a wide-temperature-stability MLCC dielectric material, the composition of which is Ba. 1- x Ce x Ti 1-y Ce y O3 ceramics, where 0 < x ≤ 0.005, 0.1 ≤ y ≤ 0.3.

[0008] This invention also provides a method for preparing the above-mentioned wide-temperature-stability MLCC dielectric material, comprising the following steps:

[0009] S1: According to Ba 1-x Ce x Ti 1-y Ce y The values ​​of x and y in the composition of O3 ceramic are taken, and BaCO3, TiO2 and CeO2 are weighed out by molar percentage. The mixture is ball-milled, dried, sieved, heated and kept at a certain temperature to obtain pre-fired ceramic powder.

[0010] S2: The pre-fired ceramic powder is ball-milled and dried to obtain ceramic raw material powder;

[0011] S3: Ceramic raw material powder is mixed with polyvinyl alcohol solution, granulated, and pressed into shape to obtain green body;

[0012] S4: Place the green compact in an air atmosphere, heat and hold it at that temperature, and then cool it to obtain a wide temperature stability MLCC dielectric material.

[0013] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0014] 1. The wide temperature stability MLCC dielectric material provided by this invention is made of Ba. 1-x Ce x Ti 1-y Ce y BaTiO3 ceramics are composed of a single Ce element doped with O3, wherein the Ce element can be used as Ce during doping. 3+ With Ce 4+ Ce doping simultaneously enters the Ba (A-site) and Ti (B-site) sites of BaTiO3 ceramics, thereby simultaneously regulating the position, height, and width of the dielectric peaks. This effect is significantly stronger than elemental doping acting only on a single site. First, the significantly higher concentration of Ce doping at the B-site primarily suppresses and broadens the dielectric peaks of BaTiO3, resulting in a slower change in the dielectric temperature curve. Second, the introduction of a small amount of Ce doping at the A-site shifts the dielectric peaks of BaTiO3 towards lower temperatures, improving the dielectric stability of the ceramic in the low-temperature region. Third, during sintering, some Ce is reduced from +4 to +3 valence, introducing additional chemical defects into the BaTiO3 ceramic. This, combined with the effects of low-concentration Ce doping at the A-site and high-concentration Ce doping at the B-site, induces micro-regions with different dielectric properties within the ceramic, resulting in dual dielectric peaks on the dielectric temperature curve and further widening the dielectric stability temperature range of the ceramic. In particular, the appearance of dual dielectric peaks significantly distinguishes the dielectric temperature characteristics of the material provided by this invention from those of existing technologies, and this difference is the main reason for the excellent dielectric temperature stability of the material provided by this invention. Therefore, the wide-temperature-stability MLCC dielectric material provided by this invention has the outstanding advantages of simple composition design and excellent overall performance.

[0015] 2. The wide-temperature-stable MLCC dielectric material provided by this invention uses BaCO3, TiO2, and CeO2 as raw materials, and is obtained through ball milling, drying, sieving, heating, heat preservation, secondary ball milling and drying, granulation, pressing into green blanks, and heating, heat preservation, and cooling. Because it uses the carbonates and simple oxides of each element as raw materials to directly synthesize BaCO3... 1-x Ce x Ti 1-y Ce yInstead of first synthesizing pure BaTiO3 and then introducing Ce doping, this method uses O3 ceramics, resulting in a more uniform distribution of Ce in the ceramic. The doping concentration of Ce at different sites can also be controlled by adjusting the Ba / Ti ratio in BaTiO3, thus ensuring the controllability of the material's performance. Furthermore, this preparation method does not use complex equipment or high-value chemical raw materials; it is simple, has a short preparation cycle, low cost, and produces MLCC dielectric materials with excellent performance.

[0016] 3. The wide temperature stability MLCC dielectric material provided by this invention has the inherent advantages of BaTiO3-based ceramic materials. Therefore, the various properties of this material can be further adjusted by adding additional doping elements and sintering aids, thereby giving the material good designability, adjustable performance and process parameters, and broad prospects for commercial application. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0018] Figure 1 The flowchart illustrates the method for preparing wide-temperature-stable MLCC dielectric materials provided by this invention.

[0019] Figure 2 The dielectric temperature spectrum of the sample in Example 1 was measured after being subjected to a silver electrode.

[0020] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0021] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] Furthermore, the technical solutions of the various embodiments of the present invention can be combined with each other, but only if they are feasible for those skilled in the art. If the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by the present invention.

[0023] Unless otherwise specified, all medicines / reagents used are commercially available.

[0024] This invention proposes a wide-temperature-stability MLCC dielectric material, the composition of which is Ba. 1- x Ce x Ti 1-y Ce y O3 ceramics, where 0 < x ≤ 0.005, 0.1 ≤ y ≤ 0.3.

[0025] The dielectric properties of the above-mentioned MLCC dielectric materials conform to the EIA X7R standard, that is, Δε within the temperature range of -55 to 125℃. r / ε r25℃ ≤±15%, dielectric constant 1800~2300, dielectric loss ≤0.02, resistivity ≥10 11 Ω·cm.

[0026] The MLCC dielectric material provided by this invention has the characteristics of simple composition, excellent performance, and strong designability. The technical concept of this invention lies in utilizing the variable valence and multi-site doping capability of Ce, that is, it can be doped with Ce... 3+ The form of the electrode material enters the Ba site (A site) of BaTiO3, causing a rapid decrease in the Curie temperature of BaTiO3, while the dielectric peak is enhanced and narrowed, and it can also be converted into Ce. 4+ The doping of Ce at Ti sites (B sites) causes the dielectric peak of BaTiO3 to shift towards room temperature while simultaneously experiencing significant suppression and broadening. This invention utilizes the variable valence property of Ce to simultaneously dope both the A and B sites of BaTiO3 ceramics with a single Ce element, thereby simultaneously controlling the position, height, and width of the dielectric peak of BaTiO3 ceramics. The effect is significantly stronger than elemental doping acting only on a single site, resulting in a dielectric material that possesses a wide dielectric stability temperature range, high dielectric constant, low dielectric loss, and excellent insulation properties.

[0027] This invention also proposes a method for preparing a wide-temperature-stability MLCC dielectric material, such as... Figure 1 As shown, it includes the following steps:

[0028] S1: According to Ba 1-x Ce x Ti 1-y Ce y The values ​​of x and y in the composition of O3 ceramic are taken. BaCO3, TiO2 and CeO2 are weighed out by molar percentage, ball milled, dried, sieved, heated and kept at a certain temperature to obtain pre-fired ceramic powder.

[0029] Among them, Ba 1-x Ce x Ti 1-y Cey The values ​​of x and y in the O3 ceramic composition correspond to the molar percentages of each component in the ceramic powder formula as follows: 49.75–50 mol% BaCO3, 35–45 mol% TiO2, and 5–15.25 mol% CeO2.

[0030] S2: The pre-fired ceramic powder is ball-milled and dried to obtain ceramic raw material powder.

[0031] The ceramic raw material powder is ball-milled to promote mixing, thereby ensuring that the obtained pre-fired ceramic powder is a completely and uniformly mixed powder before pre-firing.

[0032] S3: Ceramic raw material powder is mixed with polyvinyl alcohol solution, granulated, and pressed into shape to obtain green body.

[0033] Polyvinyl alcohol solution is used as a binder for granulating raw material powder. After granulation, the molding properties of the powder are significantly improved, and it can be pressed into green bodies of various sizes and shapes, such as round green bodies with a diameter of 10 mm and a thickness of 1 mm.

[0034] S4: Place the green compact in an air atmosphere, heat and hold it at that temperature, and then cool it to obtain a wide temperature stability MLCC dielectric material.

[0035] Preferably, in step S1, the ball milling speed is 300-500 rpm and the ball milling time is 12-18 h.

[0036] Preferably, in step S1, the drying temperature is 100-110°C.

[0037] This invention synthesizes pre-fired ceramic powder via a solid-state reaction method. Preferably, in step S1, the heating and holding process specifically involves heating from room temperature to 900–1000°C at a heating rate of 5–10°C / min, and holding at the corresponding temperature for 2–4 hours.

[0038] Preferably, in step S2, the ball milling speed is 1000–1200 rpm, and the ball milling time is 10–15 h. The ball milling speed and time are controlled to ensure that the particle size of the obtained ceramic powder is within the ideal range.

[0039] Preferably, in step S2, the drying temperature is 100-110°C.

[0040] Preferably, in step S3, the ratio of raw material powder to polyvinyl alcohol solution is (8-10) g: 1 mL; the mass fraction of polyvinyl alcohol in the polyvinyl alcohol solution is 5 wt%.

[0041] Preferably, step S4 specifically includes:

[0042] The green compact is placed in a silicon molybdenum rod furnace and heated from room temperature to 450–480°C in air at a rate of 3–5°C / min, and held at that temperature for 1–2 hours. Then, the temperature is further increased to 1450–1550°C at a rate of 3–5°C / min, and held at that temperature for 2–4 hours. The furnace is then cooled to obtain a wide-temperature-stable MLCC dielectric material. The purpose of continuing to heat and hold is to ensure the solid-phase reaction proceeds fully and to promote grain boundary migration and pore removal, thereby achieving ceramic densification.

[0043] This process introduces a staged heating process, which involves holding the material at a lower temperature for an extended period to fully eliminate added polyvinyl alcohol and other organic residues, thereby ensuring that the sintering process at higher temperatures is not affected by organic residues.

[0044] Example 1

[0045] This embodiment provides a method for preparing a wide-temperature-stability MLCC dielectric material, including:

[0046] S1: According to Ba 1-x Ce x Ti 1-y Ce y The values ​​of x = 0.001 and y = 0.20 in the O3 ceramic composition were determined. The raw materials were weighed by molar percentage: 49.95 mol% BaCO3, 40 mol% TiO2 and 10.05 mol% CeO2. The mixture was ball-milled at 500 rpm for 12 h, dried at 110 °C and sieved. The mixture was then heated from room temperature to 1000 °C in an alumina crucible at a heating rate of 10 °C / min and held at 1000 °C for 2 h to obtain pre-fired ceramic powder.

[0047] S2: The pre-fired ceramic powder is mixed with agate balls and anhydrous ethanol in a weight ratio of 1:5:3, and then ball-milled in a ball mill at 1000 rpm for 12 hours and dried at 110℃ to obtain ceramic raw material powder.

[0048] S3: The ceramic raw material powder is mixed with a polyvinyl alcohol solution (polyvinyl alcohol mass fraction is 5wt%) at a ratio of 10:1 and then granulated. The granulated raw material powder is pressed into a round green body with a diameter of 10mm and a thickness of 1mm under a uniaxial pressure of 30MPa.

[0049] S4: Place the green billet into a silicon molybdenum rod furnace, heat it from room temperature to 450°C in air at a heating rate of 5°C / min, and hold it at 450°C for 2 hours.

[0050] Then, the temperature was increased from 450℃ to 1450℃ at a rate of 5℃ / min, and held at the corresponding temperature for 2 hours. The material was then cooled in the furnace to obtain a wide-temperature-stable MLCC dielectric material.

[0051] Example 2

[0052] This embodiment provides a method for preparing a wide-temperature-stable MLCC dielectric material. Compared with Example 1, the final sintering temperature in step S4 of this embodiment is 1500℃, and the other preparation processes are the same as in Example 1.

[0053] Example 3

[0054] This embodiment provides a method for preparing a wide-temperature-stable MLCC dielectric material. Compared with Example 1, the final sintering temperature in step S4 of this embodiment is 1550℃, and the other preparation processes are the same as in Example 1.

[0055] Example 4

[0056] This embodiment provides a method for preparing a wide-temperature-stable MLCC dielectric material. Compared with Embodiment 1, the values ​​of x and y in step S1 of this embodiment are x = 0.002 and y = 0.2, respectively, and the other preparation processes are the same as in Embodiment 1.

[0057] Example 5

[0058] This embodiment provides a method for preparing a wide-temperature-stable MLCC dielectric material. Compared with Embodiment 1, the values ​​of x and y in step S1 of this embodiment are x = 0.002 and y = 0.25, respectively, and the other preparation processes are the same as in Embodiment 1.

[0059] After silver electrodes were applied to both sides of the wide-temperature-stable MLCC dielectric materials (disc-shaped samples) prepared in Examples 1-5, the dielectric constant ε of the samples at -100 to 250 °C was measured using a Wayne-Kerr 6500B precision impedance analyzer equipped with a BALAB DMS-2000 high and low temperature dielectric temperature spectrometer. r The dielectric loss tanδ was measured using a Keithley 6517B high-resistivity meter, and the resistivity ρ of the sample was also measured. v The results are shown in Table 1. Figure 2 The dielectric temperature spectrum of the sample from Example 1 after being subjected to a silver electrode is given.

[0060] Table 1. Performance Comparison of MLCC Dielectric Materials Prepared in Examples 1-5

[0061]

[0062] The various embodiments of the present invention have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A wide-temperature-stability MLCC dielectric material, characterized in that, The MLCC dielectric material is composed of Ba. 1- x Ce x Ti 1-y Ce y O3 ceramics, where 0 < x ≤0.005, 0.1≤ y ≤0.3; The dielectric properties of the MLCC dielectric material conform to the EIA X7R standard, i.e., within a temperature range of -55~125℃, Δ ε r / ε r25℃ ≤±15%, dielectric constant 1800~2300, dielectric loss ≤0.02, resistivity ≥10 11 Ω·cm; The above-mentioned method for preparing a wide-temperature-stability MLCC dielectric material includes the following steps: S1: According to Ba 1-x Ce x Ti 1-y Ce y O3 ceramic composition x and y The values ​​of BaCO3, TiO2 and CeO2 are weighed out as a percentage, ball-milled, dried, sieved, heated and kept warm to obtain pre-fired ceramic powder; The heating and heat preservation specifically refer to: The temperature is increased from room temperature to 900-1000℃ at a heating rate of 5-10℃ / min, and held at the corresponding temperature for 2-4 hours. S2: The pre-fired ceramic powder is ball-milled and dried to obtain ceramic raw material powder; S3: The ceramic raw material powder is mixed with a polyvinyl alcohol solution and then granulated and pressed into a green body; the ratio of the raw material powder to the polyvinyl alcohol solution is (8~10) g: 1 mL; the mass fraction of polyvinyl alcohol in the polyvinyl alcohol solution is 5 wt%. S4: Place the green billet into a silicon molybdenum rod furnace, heat it from room temperature to 450-480°C in an air atmosphere at a heating rate of 3-5°C / min, and hold it at the corresponding temperature for 1-2 hours; Then, the temperature is increased to 1450-1550℃ at a heating rate of 3-5℃ / min, and held at the corresponding temperature for 2-4 hours. The material is then cooled with the furnace to obtain a wide-temperature-stable MLCC dielectric material.

2. The wide temperature stability MLCC dielectric material according to claim 1, characterized in that, In step S1, the ball milling speed is 300~500 rpm and the ball milling time is 12~18h.

3. The wide temperature stability MLCC dielectric material according to claim 1, characterized in that, In step S1, the drying temperature is 100~110℃.

4. The wide temperature stability MLCC dielectric material according to claim 1, characterized in that, In step S2, the ball milling speed is 1000~1200 rpm and the ball milling time is 10~15 h.

5. The wide temperature stability MLCC dielectric material according to claim 1, characterized in that, In step S2, the drying temperature is 100~110℃.

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