Nickel-coated barium titanate composite powder, preparation method thereof, slurry and multilayer ceramic capacitor

Abstract

The application provides a nickel-coated barium titanate composite powder, a preparation method thereof, a slurry and a multilayer ceramic capacitor. The composite powder comprises core-shell particles, the core-shell particles comprise a barium titanate core and a nickel shell layer covering the barium titanate core, and the mass ratio of the barium titanate core to the nickel shell layer in the core-shell particles is 1:(17-20). The raw material of the slurry comprises the composite powder. The inner electrode of the multilayer ceramic capacitor is prepared from the composite powder and / or the slurry. The composite powder can improve the anti-shrinkage of the inner electrode of the multilayer ceramic capacitor, the matching between the inner electrode and the ceramic dielectric layer, the uniformity of the distribution of nickel and barium titanate, and the overall performance and reliability of the multilayer ceramic capacitor.

Description

Technical Field

[0001] This invention relates to the field of multilayer ceramic capacitors, specifically to a nickel-coated barium titanate composite powder, its preparation method, slurry, and multilayer ceramic capacitor. Background Technology

[0002] In the prior art, the internal electrodes of multilayer ceramic capacitors are generally made of nickel powder. However, during the sintering process, there is a large difference in shrinkage properties between the nickel powder and the ceramic dielectric layer (whose main component is barium titanate), which makes the capacitor prone to cracking and delamination after sintering. This seriously weakens the performance, reliability and yield of the capacitor.

[0003] Therefore, how to improve the shrinkage of the internal electrode in the sintering process of multilayer ceramic capacitors and how to improve the matching between the internal electrode and the ceramic dielectric of multilayer capacitors in order to improve the overall performance of multilayer ceramic capacitors are problems that urgently need to be solved in this field. Summary of the Invention

[0004] The purpose of this invention is to provide a nickel-coated barium titanate composite powder and its preparation method, slurry, and multilayer ceramic capacitor, which can improve the shrinkage of the internal electrode in the multilayer ceramic capacitor during the sintering process, improve the matching between the internal electrode and the ceramic dielectric, and enhance the overall performance of the multilayer ceramic capacitor.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] A composite powder comprising core-shell particles, wherein the core-shell particles comprise a barium titanate core and a nickel shell layer covering the core;

[0007] The mass ratio of the barium titanate core to the nickel shell in the core-shell particles is 1:(17-20).

[0008] In some embodiments of the present invention, the barium titanate comprises tetragonal barium titanate and / or cubic barium titanate. Preferably, the barium titanate comprises at least 30 wt.% tetragonal barium titanate.

[0009] In some embodiments of the present invention, the D50 of the composite powder is 270–800 nm;

[0010] And / or, the tap density of the composite powder is 4-6 g / cm³. 3 .

[0011] In some embodiments of the present invention, the D50 of the barium titanate core is 70–200 nm.

[0012] In some embodiments of the present invention, the thickness of the nickel layer is 100–300 nm;

[0013] And / or, the oxygen content of the nickel layer is less than 0.3 wt.%.

[0014] In some embodiments of the present invention, the crystallinity of the nickel shell layer of the composite powder is greater than 95%.

[0015] To achieve the above objectives, the present invention also provides the following technical solutions:

[0016] A method for preparing the above-mentioned nickel-coated barium titanate composite powder, the method comprising the following steps:

[0017] S1 provides barium titanate particles;

[0018] S2, optionally, the barium titanate particles are subjected to surface treatment;

[0019] S3, to prepare a nickel ion solution;

[0020] S4, mix and react the nickel ion solution obtained in step S3, the barium titanate particles obtained in step S2, and the precipitant.

[0021] S5. The reaction product obtained in step S4 is post-processed to obtain the nickel-coated barium titanate composite powder.

[0022] Some embodiments of the present invention include at least one of the following features:

[0023] In step S1, the barium titanate particles include tetragonal barium titanate. Preferably, the mass percentage of tetragonal barium titanate in the barium titanate particles is at least 30 wt.%.

[0024] And / or, in step S1, the D50 of the barium titanate particles is 70-200 nm;

[0025] And / or, in step S1, the specific surface area of ​​the barium titanate particles is 13–21 m². 2 / g.

[0026] In some embodiments of the present invention, in step S2, the surface treatment is ultrasonic cleaning;

[0027] Preferably, alcohol is used as the medium for ultrasonic cleaning;

[0028] Preferably, the ultrasonic cleaning power is 35-40 kHz and the cleaning time is 30-60 min;

[0029] Preferably, in step S2, after ultrasonic cleaning, the sample is centrifuged at 3000-4000 rpm for 5-10 minutes.

[0030] In some embodiments of the present invention, at least one of the following features is included: in step S3, the molar concentration of nickel ions in the nickel ion solution is 0.1 to 3 mol / L;

[0031] The nickel ion solution is selected from at least one of nickel chloride, nickel nitrate, nickel acetate, nickel sulfate, and nickel ammonium sulfate (NiSO4·(NH4)2SO4) solutions;

[0032] The nickel ion solution contains a dispersant;

[0033] The dispersant is at least one of polyethylene glycol, polyoxyethylene, and fatty acid polyethylene glycol ester, preferably, the molecular weight of the polyethylene glycol is 5000 to 7000;

[0034] And / or, the dispersant is used in an amount of 0.1-2 wt% relative to the nickel ion solution;

[0035] And / or, when mixing the nickel ion solution with the dispersant, the stirring speed is 2000-2500 rpm and the stirring time is 30-60 min.

[0036] In some embodiments of the present invention, in step S4, the nickel ion solution is mixed with barium titanate particles by stirring or ultrasonic mixing. Preferably, the mixing speed is 3500-4000 rpm and the mixing time is 1-2 hours.

[0037] And / or, the precipitant is used at a molar ratio of (0.5 to 2):1 relative to nickel ions in the nickel ion solution;

[0038] And / or, the precipitant is oxalic acid.

[0039] In some embodiments of the present invention, in step S5, the post-processing includes separating, washing, drying and dehydrating, and sintering the reaction products;

[0040] Preferably, the sintering temperature is 600–900°C, and the sintering apparatus is a vacuum atmosphere furnace.

[0041] To achieve the above objectives, the present invention also provides the following technical solutions:

[0042] A paste for preparing internal electrodes of multilayer ceramic capacitors, the raw materials of the paste comprising:

[0043] The nickel-coated barium titanate composite powder described above, or the nickel-coated barium titanate composite powder prepared by the method described above; and

[0044] Adhesives, primary solvents.

[0045] In some embodiments of the present invention, the first solvent is at least one of terpineol, butyl carbitol, dodecyl alcohol ester, hydrogenated terpineol, dihydroacetic acid terpineol, alkane mixture, and diethylene glycol ethyl ether acetate;

[0046] And / or, in the raw materials of the slurry, the mass ratio of the nickel-coated barium titanate composite powder, the binder, and the first solvent is (49.5-50.5):(39-41):(9-11.5).

[0047] In some embodiments of the present invention, the adhesive is a mixture of resin and a second solvent, preferably, the mass ratio of the resin and the second solvent is (5-10):(90-95);

[0048] The resin is at least one of ethyl cellulose resin, acrylic resin, and PVB resin, or the second solvent is at least one of terpineol, butyl carbitol, dodecyl alcohol ester, hydrogenated terpineol, dihydroacetic acid terpineol, alkane mixture, and diethylene glycol ethyl ether acetate.

[0049] To achieve the above objectives, the present invention also provides the following solutions:

[0050] A multilayer ceramic capacitor includes an inner electrode, a dielectric layer, and an outer electrode. The inner electrode is disposed on the dielectric layer, and the two ends of the inner electrode are connected to the outer electrode through a spacer.

[0051] The internal electrode of the multilayer ceramic capacitor is made from the above-mentioned nickel-coated barium titanate composite powder, or from the nickel-coated barium titanate composite powder obtained by the above-mentioned method, or from the above-mentioned slurry.

[0052] Other applicable areas will become apparent from the description provided in this disclosure.

[0053] The descriptions and specific examples in the invention summary are intended to be illustrative only and are not intended to limit the scope of this disclosure.

[0054] Compared with the prior art, the technical solution provided by the present invention has the following beneficial effects:

[0055] This invention provides a nickel-coated barium titanate composite powder, its preparation method, slurry, and a multilayer ceramic capacitor. The composite powder comprises core-shell particles, each comprising a barium titanate core and a nickel shell layer coating the barium titanate core, wherein the mass ratio of the barium titanate core to the nickel shell layer in the core-shell particles is 1:(17-20). The slurry is made from the aforementioned nickel-coated barium titanate composite powder. The internal electrode of the multilayer ceramic capacitor is prepared from the aforementioned composite powder and / or slurry.

[0056] The composite powder provided by this invention can improve the shrinkage resistance of the internal electrode of multilayer ceramic capacitors and its compatibility with the ceramic dielectric layer. It can also improve the uniformity of nickel and barium titanate distribution, thereby improving the overall performance and reliability of multilayer ceramic capacitors. When the composite powder provided by this invention is applied to the nickel paste of multilayer ceramic capacitors, it can prevent the phase separation phenomenon between barium titanate powder and nickel powder, and improve the storage stability and performance consistency of the nickel internal electrode paste. Attached Figure Description

[0057] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0058] Figure 1 This is a flowchart of a method for preparing nickel-coated barium titanate composite powder according to the first embodiment of the present invention.

[0059] Figure 2 Transmission electron microscope image of nickel-coated barium titanate composite powder provided in the second embodiment of the present invention;

[0060] Figure 3 This is a schematic diagram of the structure of a multilayer ceramic capacitor provided in the fourth embodiment of the present invention.

[0061] Explanation of icon numbers

[0062] 1-Inner electrode; 2-Dielectric layer; 3-Outer electrode. Detailed Implementation

[0063] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. 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. It should be understood that the specific embodiments described herein are only for illustration and explanation of the present invention and are not intended to limit the present invention.

[0064] Any specific numerical values ​​disclosed herein (including the endpoints of numerical ranges) are not limited to their exact values, but should be understood to also include values ​​close to the exact value, such as all possible values ​​within ±5% of the exact value. Furthermore, with respect to the disclosed numerical ranges, one or more new numerical ranges can be obtained by arbitrarily combining the endpoint values ​​of the range, the endpoint values ​​with specific point values ​​within the range, and the specific point values ​​themselves; these new numerical ranges should also be considered as specifically disclosed herein.

[0065] The terminology used in this disclosure is for the purpose of describing particular exemplary embodiments only and is not intended to be limiting. Unless the context clearly indicates otherwise, the singular forms “a,” “an,” and “the” as used in this disclosure are intended to include the plural forms as well. The terms “comprising,” “including,” “containing,” and “having” are inclusive and thus describe the presence of said features, elements, compositions, steps, integers, operations, and / or components, but do not exclude the presence or inclusion of one or more other features, integers, steps, operations, elements, components, and / or sets thereof. Although the open-ended term “comprising” should be understood as a non-limiting term used to describe and claim the various embodiments described in this disclosure, in some aspects it may instead be understood as a more restrictive and limiting term, such as “consisting of” or “substantially consisting of.” Thus, for any given embodiment describing a composition, material, component, element, feature, integer, operation, and / or process step, this disclosure also particularly includes embodiments consisting of or substantially consisting of such compositions, materials, components, elements, features, integers, operations, and / or process steps. In the case of “consisting of…”, the alternative embodiments exclude any additional compositions, materials, components, elements, features, integers, operations and / or process steps. In the case of “essentially composed of…”, any additional compositions, materials, components, elements, features, integers, operations and / or process steps that substantially affect the essential and novel characteristics are excluded from such embodiments. However, any compositions, materials, components, elements, features, integers, operations and / or process steps that do not substantially affect the essential and novel characteristics may be included in the embodiments.

[0066] Any method steps, processes, and operations described in this disclosure should not be construed as necessarily requiring them to be performed in a particular order as discussed or shown, unless explicitly specified. It should also be understood that additional or alternative steps may be used unless otherwise stated.

[0067] In this application, except where expressly stated, any matters or issues not mentioned are directly applicable to those known in the art without any modification. Furthermore, any implementation described in this disclosure may be freely combined with one or more other implementations described in this disclosure, and the resulting technical solutions or concepts shall be considered part of the original disclosure or original record of this application, and should not be regarded as new content not disclosed or anticipated in this disclosure, unless those skilled in the art consider the combination to be clearly unreasonable.

[0068] Unless otherwise stated, the terms used herein have the same meaning as commonly understood by those skilled in the art, and if a term is defined herein and its definition differs from the common understanding in the art, the definition herein shall prevail.

[0069] Unless otherwise stated, when % is mentioned in this document, it means wt.%.

[0070] First aspect

[0071] The present invention provides a composite powder comprising core-shell particles, wherein the core-shell particles comprise a barium titanate core and a nickel shell layer covering the barium titanate core; wherein the mass ratio of the barium titanate core to the nickel shell layer in the core-shell particles is 1:(17-20).

[0072] For example, the mass ratio of the barium titanate core to the nickel shell can be 1:18 or 1:19.

[0073] It is worth noting that, compared to simply mixing barium titanate powder into nickel powder to prepare MLCC nickel paste, nickel-coated barium titanate powder can prevent the 2.7 g / cm³ density difference between barium titanate powder and nickel powder from causing problems. 3 The phase separation caused by the 6-10 times difference in particle size (in order to improve the dispersibility of barium titanate to control shrinkage in MLCC nickel paste, the barium titanate powder has a smaller particle size) improves the storage stability and performance consistency of the nickel internal electrode paste.

[0074] It is worth noting that, compared to barium titanate-coated nickel composite powder, using nickel-coated barium titanate composite powder significantly reduces the sintering temperature by 200°C. Barium titanate has a melting temperature of approximately 1618°C, while nickel powder has a melting temperature of approximately 1453°C. This results in energy savings and improved density of the nickel electrode. Furthermore, using nickel-coated barium titanate composite powder, compared to barium titanate-coated nickel composite powder, avoids the process of removing barium titanate when the slurry is applied to MLCCs.

[0075] According to one embodiment, the barium titanate comprises tetragonal barium titanate. Preferably, the barium titanate comprises at least 30 wt.% tetragonal barium titanate.

[0076] It is worth noting that the tetragonal barium titanate has better electrical properties, a higher dielectric constant, and better temperature stability. Its application in multilayer ceramic capacitors can result in multilayer ceramic capacitors with better performance.

[0077] The composite powder provided by this invention can improve the shrinkage resistance of the internal electrode of multilayer ceramic capacitors and its compatibility with the ceramic dielectric layer. It can also improve the uniformity of nickel and barium titanate distribution, thereby improving the overall performance and reliability of multilayer ceramic capacitors. When the composite powder provided by this invention is applied to the nickel paste of multilayer ceramic capacitors, it can prevent the phase separation phenomenon between barium titanate powder and nickel powder, and improve the storage stability and performance consistency of the nickel internal electrode paste.

[0078] In some embodiments of the present invention, the mass percentage of tetragonal barium titanate in the barium carbonate core can be any one of 40 wt.%, 45 wt.%, 50 wt.%, 55 wt.%, 60 wt.%, 65 wt.%, 70 wt.%, 75 wt.%, 80 wt.%, 85 wt.%, or 90 wt.%, or a range consisting of any two of the above values ​​and any one of the values ​​within that range.

[0079] According to one embodiment, the barium titanate comprises tetragonal barium titanate and cubic barium titanate.

[0080] According to one embodiment, the barium titanate comprises cubic phase barium titanate.

[0081] In some embodiments of the present invention, the cubic phase barium titanate in the barium carbonate core can be any one of 40 wt.%, 45 wt.%, 50 wt.%, 55 wt.%, 60 wt.%, 65 wt.%, 70 wt.%, 75 wt.%, 80 wt.%, 85 wt.%, or 90 wt.%, or a range consisting of any two of the above values ​​and any one of the values ​​within that range.

[0082] In some embodiments of the present invention, the D50 of the composite powder is 270–800 nm, preferably 300–750 nm. Exemplarily, the D50 of the composite powder can be any value selected from 300 nm, 350 nm, 400 nm, 450 nm, 500 nm, 550 nm, 600 nm, 650 nm, 700 nm, or 750 nm, or a range consisting of any two of the above values, or any value within that range.

[0083] In the context of this invention, D50 refers to the particle size at which the cumulative particle size distribution percentage of a sample reaches 50%. According to one embodiment of the invention, D50 is measured using a laser particle size analyzer. In the context of this invention, D50 is measured after the ceramic powder has undergone a grinding step.

[0084] In some embodiments of the present invention, the tap density of the composite powder is 4-6 g / cm³. 3 The preferred concentration is 4.5–6 g / cm³. 3 For example, 4.5 g / cm³ 3 5g / cm 3 Or 5.5g / cm 3 Any one of the values ​​in, or any range formed by any two of the above values ​​and any one of the values ​​within that range.

[0085] In the context of this invention, tapped density is the mass per unit volume of powder in a container after it has been tapped under specified conditions, expressed in g / cm³. 3 .

[0086] In some embodiments of the present invention, the D50 of the barium titanate core is 70–200 nm, preferably 80–180 nm. Exemplarily, the D50 of the barium titanate core can be any value selected from 80 nm, 100 nm, 125 nm, 150 nm, or 180 nm, or a range consisting of any two of the above values, or any value within that range. It is worth noting that the barium titanate core within the above range has better electrical properties because the nickel metal layer is thicker and has better conductivity.

[0087] In some embodiments of the present invention, the thickness of the nickel layer is 100–300 nm. Exemplarily, the thickness of the nickel layer can be any value selected from 130 nm, 150 nm, 175 nm, 200 nm, 220 nm, 250 nm, or 285 nm, or a range consisting of any two of the above values, or any value within that range. It is worth noting that a nickel shell layer with the above thickness has better electrical properties because a thicker nickel metal layer results in better conductivity.

[0088] In some embodiments of the present invention, the oxygen content of the nickel layer is less than 0.3 wt.%, preferably less than 0.25 wt.%. Exemplarily, the oxygen content of the nickel layer can be any one of 0.28 wt.%, 0.25 wt.%, 0.225 wt.%, 0.2 wt.%, 0.18 wt.%, 0.15 wt.%, 0.125 wt.%, 0.1 wt.%, 0.08 wt.%, 0.065 wt.%, 0.05 wt.%, or 0.03 wt.%, or a range consisting of any two of the above values ​​and any value within that range.

[0089] In some embodiments of the present invention, the crystallinity of the nickel shell layer of the composite powder is greater than 95%. Exemplarily, the crystallinity of the nickel layer of the composite powder can be any one of 96%, 97%, 98%, and 99%, or a range consisting of any two of the above values ​​and any one of the values ​​within that range.

[0090] It is worth noting that the composite powder provided by the present invention has a high tap density, and the nickel layer in the composite powder also has a high degree of crystallinity. Therefore, the expansion of the nickel layer during sintering is relatively lower, which helps to reduce the shrinkage of nickel during sintering and improve the oxidation resistance of nickel, so as to obtain a multilayer ceramic capacitor with better performance and higher yield after sintering.

[0091] Second aspect

[0092] This invention provides a method for preparing the above-mentioned composite powder, the method comprising the following steps: S1, providing barium titanate particles; S2, optionally, performing surface treatment on the barium titanate particles; S3, preparing a nickel ion solution; S4, mixing and reacting the nickel ion solution obtained in step S3, the barium titanate particles obtained in step S2, and a precipitant; S5, performing post-treatment on the reaction product obtained in step S4 to obtain the composite powder.

[0093] In some embodiments of the present invention, in step S1, the barium titanate particles comprise tetragonal barium titanate.

[0094] In some embodiments of the present invention, the mass percentage of the tetragonal barium titanate in the barium titanate particles is at least 30 wt.%. Exemplarily, the mass percentage of the tetragonal barium titanate can be any one of 40 wt.%, 45 wt.%, 50 wt.%, 55 wt.%, 60 wt.%, 65 wt.%, 70 wt.%, 75 wt.%, 80 wt.%, 85 wt.%, or 90 wt.%, or a range consisting of any two of the above values ​​and any value within that range.

[0095] In some embodiments of the present invention, in step S1, the D50 of the barium titanate particles is 70-200 nm. Exemplarily, the D50 of the barium titanate particles can be any value selected from 80 nm, 90 nm, 100 nm, 120 nm, 140 nm, 160 nm, 180 nm, or 200 nm, or a range consisting of any two of the above values ​​and any value within that range.

[0096] In some embodiments of the present invention, in step S1, the specific surface area of ​​the barium titanate particles is 13–21 m². 2 / g. For example, the specific surface area of ​​the barium titanate may be 13.5m². 2 / g、14m 2 / g or 14.5m 2 Any value in / g, or any range consisting of any two of the above values ​​and any value within that range.

[0097] In the context of this invention, specific surface area is BET specific surface area.

[0098] In some embodiments of the present invention, in step S1, the barium titanate particles are prepared by a solid-state method. It is worth noting that the barium titanate particles prepared by the solid-state method have the advantages of high tetragonal phase content, low particle size, and high dispersibility.

[0099] In some embodiments of the present invention, in step S2, the surface treatment is ultrasonic cleaning.

[0100] In some embodiments of the present invention, alcohol is used as the medium for ultrasonic cleaning.

[0101] In some embodiments of the present invention, the ultrasonic cleaning power is 35–40 kHz, and the cleaning duration is 30–60 min. Exemplarily, the ultrasonic power can be any value selected from 36 kHz, 37 kHz, 38 kHz, or 39 kHz, or any range formed by any two of the above values, or any value within that range; the cleaning duration can be any value selected from 35 min, 40 min, 45 min, 50 min, or 55 min, or any range formed by any two of the above values, or any value within that range.

[0102] In some embodiments of the present invention, in step S2, after the ultrasonic cleaning is completed, centrifugation is performed at a speed of 3000-4000 rpm for 5-10 minutes. Exemplarily, the centrifugation speed can be any value among 3200 rpm, 3500 rpm, or 3800 rpm, or any range of two of the above values ​​plus any value within that range; the centrifugation time can be any value among 6 minutes, 7 minutes, 8 minutes, or 9 minutes, or any range of two of the above values ​​plus any value within that range.

[0103] In some embodiments of the present invention, in step S3, the molar concentration of nickel ions in the nickel ion solution is 0.1–3 mol / L. Exemplarily, the molar concentration of nickel ions in the nickel ion solution can be any one of 0.5 mol / L, 0.85 mol / L, 1 mol / L, 1.2 mol / L, 1.5 mol / L, 1.75 mol / L, 2 mol / L, 2.25 mol / L, 2.5 mol / L, or 2.75 mol / L, or a range consisting of any two of the above values, or any value within that range.

[0104] In some embodiments of the present invention, the nickel ion solution further comprises a dispersant, wherein the dispersant is at least one selected from polyethylene glycol, polyoxyethylene, and fatty acid polyethylene glycol esters.

[0105] In some embodiments of the present invention, the dispersant, preferably polyethylene glycol, has a molecular weight of 5000 to 7000. Exemplarily, the molecular weight of the polyethylene glycol can be any one of 5300, 5500, 5800, 6000, 6300, 6500, or 6800, or a range consisting of any two of the above values, or any value within that range.

[0106] In some embodiments of the present invention, the dispersant is used in an amount of 0.1-2 wt% relative to the nickel ion solution. Exemplarily, the amount of dispersant used can be any one of 0.3 wt%, 0.5 wt%, 0.8 wt%, 1 wt%, 1.5 wt%, or 1.75 wt%, or a range consisting of any two of the above values ​​and any value within that range.

[0107] In some embodiments of the present invention, when the nickel ion solution is mixed with the dispersant, the stirring speed is 2000–2500 rpm and the stirring time is 30–60 min. Exemplarily, the stirring speed can be any value between 2200 rpm and 2350 rpm.

[0108] In some embodiments of the present invention, in step S4, the nickel ion solution is mixed with barium titanate particles by stirring or ultrasonic mixing. Preferably, the mixing speed is 3500-4000 rpm and the mixing time is 1-2 hours.

[0109] In some embodiments, the precipitant is used in an amount sufficient to precipitate almost all nickel ions in the nickel ion solution. In some embodiments, the precipitant is used at a molar ratio of (0.5–2):1 relative to nickel ions in the nickel ion solution. Preferably, the precipitant is used in an equimolar amount or equimolar equivalent to the nickel ions.

[0110] In some embodiments of the present invention, the precipitant is oxalic acid.

[0111] In some embodiments of the present invention, in step S5, the post-processing includes separating, washing, drying and dehydrating, and sintering the reaction products.

[0112] In some embodiments of the present invention, the sintering temperature is 600–900°C, and the sintering apparatus is a vacuum atmosphere furnace. Exemplarily, the sintering temperature can be 700°C or 800°C; the vacuum degree of the vacuum atmosphere furnace is 0.01–0.1 Pa; and the sintering time can be 100–200 min.

[0113] It is worth noting that the nickel layer in the nickel-coated barium titanate composite powder prepared by the method described above using the present invention exhibits high crystallinity and low oxygen content. This is because as the temperature increases, the crystallinity of the nickel powder gradually improves, and the crystallization becomes more complete. The metallic nickel particles generated from the decomposition of nickel oxalate can form highly crystalline ultrafine nickel powder through nucleation and growth processes; nickel oxalate decomposes to generate metallic nickel and oxides. In a vacuum environment, the oxygen concentration is extremely low, which limits the occurrence of oxidation reactions. Therefore, the oxygen content in the generated nickel powder is low. Furthermore, the nickel-coated barium titanate composite powder of the present invention has the characteristics of small particle size, uniform distribution, and controllable morphology, which helps to improve its application performance in fields such as electronic ceramics, capacitors, and sensors. The uniform and dense nickel coating layer is firmly bonded to the barium titanate core, which helps to improve the stability and durability of the product.

[0114] Third aspect

[0115] The present invention provides a slurry for preparing the internal electrode of a multilayer ceramic capacitor, the raw materials of the slurry comprising: the composite powder described above, or the composite powder prepared by the method described above; and a binder and a first solvent.

[0116] In some embodiments of the present invention, the first solvent is at least one of terpineol, butyl carbitol, dodecyl alcohol ester, hydrogenated terpineol, dihydroacetic acid terpineol, a mixture of alkanes, and diethylene glycol ethyl ether acetate.

[0117] In some embodiments of the present invention, the mass ratio of the nickel-coated barium titanate composite powder, the binder, and the first solvent in the raw materials of the slurry is (49.5-50.5):(39-41):(9-11.5).

[0118] In some embodiments of the present invention, the adhesive is a mixture of resin and a second solvent, preferably, the mass ratio of the resin and the second solvent is (5-10):(90-95).

[0119] In some embodiments of the present invention, the resin is at least one of ethyl cellulose resin, acrylic resin, and PVB resin.

[0120] In some embodiments of the present invention, the second solvent is at least one of terpineol, butyl carbitol, dodecyl alcohol ester, and hydrogenated terpineol.

[0121] Fourth aspect

[0122] This invention provides a method for preparing the above-mentioned slurry. The method involves mixing the above-mentioned raw materials and then processing them using various conventional slurry dispersion methods such as stirring, ultrasonic dispersion, and homogenization to obtain the slurry. It is understood that specific dispersion process parameters, such as rotation speed and duration, can be adjusted and selected according to the actual application scenario.

[0123] Fifth aspect See Figure 3 The present invention provides a multilayer ceramic capacitor, the multilayer ceramic capacitor including an inner electrode, a dielectric layer and an outer electrode, the inner electrode being disposed on the dielectric layer, and the two ends of the inner electrode being connected to the outer electrode by a spacer; wherein, the inner electrode of the multilayer ceramic capacitor is obtained by the above-mentioned composite powder preparation, or by the composite powder preparation obtained by the above-mentioned method, or by the above-mentioned slurry preparation.

[0125] Example 1

[0126] In this embodiment, the above-mentioned nickel-coated barium titanate composite powder is prepared through the following steps:

[0127] S1 is selected from materials prepared by the solid-state method, with a D50 of 80 nm and a specific surface area of ​​20.6 m². 2 / g of barium titanate particles;

[0128] S2, use analytical grade alcohol to ultrasonically clean the barium titanate particles in step S1. The ultrasonic frequency is 40kHz and the cleaning time is 30min. Then, centrifuge at 4000rpm for 5min and discard the supernatant.

[0129] S3, prepare a 0.5L nickel ion solution with a nickel ion concentration of 0.5mol / L, then add polyethylene glycol with a molecular weight of 6000, wherein the mass fraction of polyethylene glycol relative to the nickel ion solution is 1wt.%, and stir at 2500rpm for 30min using a high-speed stirrer;

[0130] S4. The barium titanate particles obtained in step S2 are dispersed in a nickel ion solution and stirred at 4000 rpm for 2 hours using a high-speed disperser. Then, oxalic acid with an equal molar amount to the nickel ion solution is added to obtain a precipitate.

[0131] S5. Separate the precipitate, wash the precipitate obtained in step S4 with deionized water, place it in an oven, dry it at 100°C until the water content is less than 0.3 wt.%, and then put it into a vacuum atmosphere furnace and sinter it at 850°C for 120 min under a vacuum of 0.05 Pa to obtain the nickel-coated barium titanate composite powder.

[0132] The thickness of the nickel layer in the nickel-coated barium titanate composite powder obtained in this embodiment was 120.5 nm, as measured by transmission electron microscopy. The crystallinity of the nickel layer in the nickel-coated barium titanate composite powder obtained in this embodiment was 96%, as measured by XRD. The oxygen content of the nickel layer in the nickel-coated barium titanate composite powder obtained in this embodiment was 0.11%, as measured by a Horiba EMGA-830 oxygen and nitrogen content analyzer. The composite powder was screen-printed into an electrode line 0.3 mm wide and 6 cm long. The resistance of the line segment was tested with a multimeter, and the electrode thickness was tested with a film thickness gauge. The resistivity of the nickel-coated barium titanate particles in the nickel-coated barium titanate composite powder obtained in this embodiment was measured to be 2*10⁻⁶. -4 Ω·cm.

[0133] Furthermore, the nickel-coated barium titanate composite powder obtained in this embodiment is made into a slurry; specifically, the mass ratio of the nickel-coated barium titanate composite powder, the first solvent, and the binder in the slurry is 49.7:39.6:10.7.

[0134] Example 2

[0135] In this embodiment, the above-mentioned nickel-coated barium titanate composite powder is prepared through the following steps:

[0136] S1 is selected from materials prepared by the solid-state method, with a D50 of 102 nm and a specific surface area of ​​19.2 m². 2 / g of barium titanate particles;

[0137] S2, use analytical grade alcohol to ultrasonically clean the barium titanate particles in step S1. The ultrasonic frequency is 40kHz and the cleaning time is 30min. Then, centrifuge at 4000rpm for 5min and discard the supernatant.

[0138] S3, prepare a 0.5L nickel ion solution with a nickel ion concentration of 0.5mol / L, then add polyethylene glycol with a molecular weight of 6000, wherein the mass fraction of polyethylene glycol relative to the nickel ion solution is 1wt.%, and stir at 2500rpm for 30min using a high-speed stirrer;

[0139] S4. The barium titanate particles obtained in step S2 are dispersed in a nickel ion solution and stirred at 4000 rpm for 2 hours using a high-speed disperser. Then, oxalic acid with an equal molar amount to the nickel ion solution is added to obtain a precipitate.

[0140] S5. Separate the precipitate, wash the precipitate obtained in step S4 with deionized water, place it in an oven, dry it at 100°C until the water content is less than 0.3 wt.%, and then put it into a vacuum atmosphere furnace and sinter it at 850°C for 120 min under a vacuum of 0.05 Pa to obtain the nickel-coated barium titanate composite powder.

[0141] The thickness of the nickel layer in the nickel-coated barium titanate composite powder obtained in this embodiment was 170.8 nm, as measured by transmission electron microscopy. The crystallinity of the nickel layer in the nickel-coated barium titanate composite powder obtained in this embodiment was 96%, as measured by XRD. The oxygen content of the nickel layer in the nickel-coated barium titanate composite powder obtained in this embodiment was 0.15%, as measured by a Horiba EMGA-830 oxygen and nitrogen content analyzer. The composite powder was screen-printed into an electrode line 0.3 mm wide and 6 cm long. The resistance of the line segment was measured using a multimeter, and the electrode thickness was measured using a film thickness gauge. The resistivity of the nickel-coated barium titanate particles in the nickel-coated barium titanate composite powder obtained in this embodiment was measured to be 3*10⁻⁶. -4 Ω·cm.

[0142] Furthermore, the nickel-coated barium titanate composite powder obtained in this embodiment is made into a slurry; specifically, the mass ratio of the nickel-coated barium titanate composite powder, the first solvent, and the binder in the slurry is 49.8:40.8:9.4.

[0143] Example 3

[0144] In this embodiment, the above-mentioned nickel-coated barium titanate composite powder is prepared through the following steps:

[0145] S1 is selected from materials prepared by the solid-state method, with a D50 of 110.2 nm and a specific surface area of ​​18.3 m². 2 / g of barium titanate particles;

[0146] S2, use analytical grade alcohol to ultrasonically clean the barium titanate particles in step S1. The ultrasonic frequency is 40kHz and the cleaning time is 30min. Then, centrifuge at 4000rpm for 5min and discard the supernatant.

[0147] S3, prepare a 0.5L nickel ion solution with a nickel ion concentration of 0.5mol / L, then add polyethylene glycol with a molecular weight of 6000, wherein the mass fraction of polyethylene glycol relative to the nickel ion solution is 1wt.%, and stir at 2500rpm for 30min using a high-speed stirrer;

[0148] S4. The barium titanate particles obtained in step S2 are dispersed in a nickel ion solution and stirred at 4000 rpm for 2 hours using a high-speed disperser. Then, oxalic acid with an equal molar amount to the nickel ion solution is added to obtain a precipitate.

[0149] S5. Separate the precipitate, wash the precipitate obtained in step S4 with deionized water, place it in an oven, dry it at 100°C until the water content is less than 0.3 wt.%, and then put it into a vacuum atmosphere furnace and sinter it at 850°C for 120 min under a vacuum of 0.05 Pa to obtain the nickel-coated barium titanate composite powder.

[0150] The thickness of the nickel layer in the nickel-coated barium titanate composite powder obtained in this embodiment was 190.9 nm, as measured by transmission electron microscopy. The crystallinity of the nickel layer in the nickel-coated barium titanate composite powder obtained in this embodiment was 97%, as measured by XRD. The oxygen content of the nickel layer in the nickel-coated barium titanate composite powder obtained in this embodiment was 0.19%, as measured by a Horiba EMGA-830 oxygen and nitrogen content analyzer. The composite powder was screen-printed into an electrode line 0.3 mm wide and 6 cm long. The resistance of the line segment was tested with a multimeter, and the electrode thickness was tested with a film thickness gauge. The resistivity of the nickel-coated barium titanate particles in the nickel-coated barium titanate composite powder obtained in this embodiment was measured to be 3*10⁻⁶. -4 Ω·cm.

[0151] Furthermore, the nickel-coated barium titanate composite powder obtained in the above embodiment is made into a slurry; specifically, the mass ratio of the nickel-coated barium titanate composite powder, the first solvent, and the binder in the slurry is 50.1:39.5:10.4.

[0152] Example 4

[0153] In this embodiment, the above-mentioned nickel-coated barium titanate composite powder is prepared through the following steps:

[0154] S1 is selected from materials prepared by the solid-state method, with a D50 of 120.1 nm and a specific surface area of ​​18.3 m². 2 / g of barium titanate particles;

[0155] S2, use analytical grade alcohol to ultrasonically clean the barium titanate particles in step S1. The ultrasonic frequency is 40kHz and the cleaning time is 30min. Then, centrifuge at 4000rpm for 5min and discard the supernatant.

[0156] S3, prepare a 0.5L nickel ion solution with a nickel ion concentration of 0.5mol / L, then add polyethylene glycol with a molecular weight of 6000, wherein the mass fraction of polyethylene glycol relative to the nickel ion solution is 1wt.%, and stir at 2500rpm for 30min using a high-speed stirrer;

[0157] S4. The barium titanate particles obtained in step S2 are dispersed in a nickel ion solution and stirred at 4000 rpm for 2 hours using a high-speed disperser. Then, oxalic acid with an equal molar amount to the nickel ion solution is added to obtain a precipitate.

[0158] S5. Separate the precipitate, wash the precipitate obtained in step S4 with deionized water, place it in an oven, dry it at 100°C until the water content is less than 0.3 wt.%, and then put it into a vacuum atmosphere furnace and sinter it at 850°C for 120 min under a vacuum of 0.05 Pa to obtain the nickel-coated barium titanate composite powder.

[0159] The thickness of the nickel layer in the nickel-coated barium titanate composite powder obtained in this embodiment was 220.1 nm, as measured by transmission electron microscopy. The crystallinity of the nickel layer in the nickel-coated barium titanate composite powder obtained in this embodiment was 97%, as measured by XRD. The oxygen content of the nickel layer in the nickel-coated barium titanate composite powder obtained in this embodiment was 0.12%, as measured by a Horiba EMGA-830 oxygen and nitrogen content analyzer. The composite powder was screen-printed into an electrode line 0.3 mm wide and 6 cm long. The resistance of the line segment was tested with a multimeter, and the electrode thickness was tested with a film thickness gauge. The resistivity of the nickel-coated barium titanate particles in the nickel-coated barium titanate composite powder obtained in this embodiment was measured to be 8*10⁻⁶. -5 Ω·cm.

[0160] Furthermore, the nickel-coated barium titanate composite powder obtained in the above embodiment is made into a slurry; specifically, the mass ratio of the nickel-coated barium titanate composite powder, the first solvent, and the binder in the slurry is 49.7:39.2:11.1.

[0161] Example 5

[0162] In this embodiment, the above-mentioned nickel-coated barium titanate composite powder is prepared through the following steps:

[0163] S1 is selected from materials prepared by the solid-state method, with a D50 of 103.6 nm and a specific surface area of ​​19.2 m². 2 / g of barium titanate particles;

[0164] S2, use analytical grade alcohol to ultrasonically clean the barium titanate particles in step S1. The ultrasonic frequency is 40kHz and the cleaning time is 30min. Then, centrifuge at 4000rpm for 5min and discard the supernatant.

[0165] S3, prepare a 0.5L nickel ion solution with a nickel ion concentration of 0.5mol / L, then add polyethylene glycol with a molecular weight of 6000, wherein the mass fraction of polyethylene glycol relative to the nickel ion solution is 1wt.%, and stir at 2500rpm for 30min using a high-speed stirrer;

[0166] S4. The barium titanate particles obtained in step S2 are dispersed in a nickel ion solution and stirred at 4000 rpm for 2 hours using a high-speed disperser. Then, oxalic acid with an equal molar amount to the nickel ion solution is added to obtain a precipitate.

[0167] S5. Separate the precipitate, wash the precipitate obtained in step S4 with deionized water, place it in an oven, dry it at 100°C until the water content is less than 0.3 wt.%, and then put it into a vacuum atmosphere furnace and sinter it at 850°C for 120 min under a vacuum of 0.05 Pa to obtain the nickel-coated barium titanate composite powder.

[0168] The thickness of the nickel layer in the nickel-coated barium titanate composite powder obtained in this embodiment was 230.3 nm, as measured by transmission electron microscopy. The crystallinity of the nickel layer in the nickel-coated barium titanate composite powder obtained in this embodiment was 98%, as measured by XRD. The oxygen content of the nickel layer in the nickel-coated barium titanate composite powder obtained in this embodiment was 0.23%, as measured by a Horiba EMGA-830 oxygen and nitrogen content analyzer. The composite powder was screen-printed into an electrode line 0.3 mm wide and 6 cm long. The resistance of the line segment was tested with a multimeter, and the electrode thickness was tested with a film thickness gauge. The resistivity of the nickel-coated barium titanate particles in the nickel-coated barium titanate composite powder obtained in this embodiment was measured to be 6*10⁻⁶. -5 Ω·cm.

[0169] Furthermore, the nickel-coated barium titanate composite powder obtained in this embodiment is made into a slurry; specifically, the mass ratio of the nickel-coated barium titanate composite powder, the first solvent, and the binder in the slurry is 49.8:40.5:9.7.

[0170] Example 6

[0171] In this embodiment, the above-mentioned nickel-coated barium titanate composite powder is prepared through the following steps:

[0172] S1 is selected from materials prepared by the solid-state method, with a D50 of 130.1 nm and a specific surface area of ​​17.6 m².2 / g of barium titanate particles;

[0173] S2, use analytical grade alcohol to ultrasonically clean the barium titanate particles in step S1. The ultrasonic frequency is 40kHz and the cleaning time is 30min. Then, centrifuge at 4000rpm for 5min and discard the supernatant.

[0174] S3, prepare a 0.5L nickel ion solution with a nickel ion concentration of 0.5mol / L, then add polyethylene glycol with a molecular weight of 6000, wherein the mass fraction of polyethylene glycol relative to the nickel ion solution is 1wt.%, and stir at 2500rpm for 30min using a high-speed stirrer;

[0175] S4. The barium titanate particles obtained in step S2 are dispersed in a nickel ion solution and stirred at 4000 rpm for 2 hours using a high-speed disperser. Then, oxalic acid with an equal molar amount to the nickel ion solution is added to obtain a precipitate.

[0176] S5. Separate the precipitate, wash the precipitate obtained in step S4 with deionized water, place it in an oven, dry it at 100°C until the water content is less than 0.3 wt.%, and then put it into a vacuum atmosphere furnace and sinter it at 850°C for 120 min under a vacuum of 0.05 Pa to obtain the nickel-coated barium titanate composite powder.

[0177] The thickness of the nickel layer in the nickel-coated barium titanate composite powder obtained in this embodiment was 243.1 nm, as measured by transmission electron microscopy. The crystallinity of the nickel layer in the nickel-coated barium titanate composite powder obtained in this embodiment was 96%, as measured by XRD. The oxygen content of the nickel layer in the nickel-coated barium titanate composite powder obtained in this embodiment was 0.16%, as measured by a Horiba EMGA-830 oxygen and nitrogen content analyzer. The composite powder was screen-printed into an electrode line 0.3 mm wide and 6 cm long. The resistance of the line segment was measured using a multimeter, and the electrode thickness was measured using a film thickness gauge. The resistivity of the nickel-coated barium titanate particles in the nickel-coated barium titanate composite powder obtained in this embodiment was measured to be 8*10⁻⁶. -5 Ω·cm.

[0178] Furthermore, the nickel-coated barium titanate composite powder obtained in the above embodiment is made into a slurry; specifically, the mass ratio of the nickel-coated barium titanate composite powder, the first solvent, and the binder in the slurry is 50.1:39.7:10.2.

[0179] Example 7

[0180] In this embodiment, the above-mentioned nickel-coated barium titanate composite powder is prepared through the following steps:

[0181] S1 is selected from materials prepared by the solid-state method, with a D50 of 140.1 nm and a specific surface area of ​​16.9 m². 2 / g of barium titanate particles;

[0182] S2, use analytical grade alcohol to ultrasonically clean the barium titanate particles in step S1. The ultrasonic frequency is 40kHz and the cleaning time is 30min. Then, centrifuge at 4000rpm for 5min and discard the supernatant.

[0183] S3, prepare a 0.5L nickel ion solution with a nickel ion concentration of 0.5mol / L, then add polyethylene glycol with a molecular weight of 6000, wherein the mass fraction of polyethylene glycol relative to the nickel ion solution is 1wt.%, and stir at 2500rpm for 30min using a high-speed stirrer;

[0184] S4. The barium titanate particles obtained in step S2 are dispersed in a nickel ion solution and stirred at 4000 rpm for 2 hours using a high-speed disperser. Then, oxalic acid with an equal molar amount to the nickel ion solution is added to obtain a precipitate.

[0185] S5. Separate the precipitate, wash the precipitate obtained in step S4 with deionized water, place it in an oven, dry it at 100°C until the water content is less than 0.3 wt.%, and then put it into a vacuum atmosphere furnace and sinter it at 850°C for 120 min under a vacuum of 0.05 Pa to obtain the nickel-coated barium titanate composite powder.

[0186] The thickness of the nickel layer in the nickel-coated barium titanate composite powder obtained in this embodiment was measured to be 251.9 nm using transmission electron microscopy. The crystallinity of the nickel layer in the nickel-coated barium titanate composite powder obtained in this embodiment was measured to be 95% using XRD. The oxygen content of the nickel layer in the nickel-coated barium titanate composite powder obtained in this embodiment was measured to be 0.21% using a Horiba EMGA-830 oxygen and nitrogen content analyzer. The composite powder was screen-printed into an electrode line with a width of 0.3 mm and a length of 6 cm. The resistance of the line segment was measured using a multimeter, and the electrode thickness was measured using a film thickness gauge. The resistivity of the nickel-coated barium titanate particles in the nickel-coated barium titanate composite powder obtained in this embodiment was measured to be 9*10⁻⁶. -5 Ω·cm.

[0187] Furthermore, the nickel-coated barium titanate composite powder obtained in this embodiment is made into a slurry; specifically, the mass ratio of the nickel-coated barium titanate composite powder, the first solvent, and the binder in the slurry is 49.7:39.6:10.7.

[0188] Example 8

[0189] In this embodiment, the above-mentioned nickel-coated barium titanate composite powder is prepared through the following steps:

[0190] S1, prepared by the solid-state method, has a D50 of 93.6 nm and a specific surface area of ​​19.8 m². 2 / g of barium titanate particles;

[0191] S2, use analytical grade alcohol to ultrasonically clean the barium titanate particles in step S1. The ultrasonic frequency is 40kHz and the cleaning time is 30min. Then, centrifuge at 4000rpm for 5min and discard the supernatant.

[0192] S3, prepare a 0.5L nickel ion solution with a nickel ion concentration of 0.5mol / L, then add polyethylene glycol with a molecular weight of 6000, wherein the mass fraction of polyethylene glycol relative to the nickel ion solution is 1wt.%, and stir at 2500rpm for 30min using a high-speed stirrer;

[0193] S4. The barium titanate particles obtained in step S2 are dispersed in a nickel ion solution and stirred at 4000 rpm for 2 hours using a high-speed disperser. Then, oxalic acid with an equal molar amount to the nickel ion solution is added to obtain a precipitate.

[0194] S5. Separate the precipitate, wash the precipitate obtained in step S4 with deionized water, place it in an oven, dry it at 100°C until the water content is less than 0.3 wt.%, and then put it into a vacuum atmosphere furnace and sinter it at 850°C for 120 min under a vacuum of 0.05 Pa to obtain the nickel-coated barium titanate composite powder.

[0195] The thickness of the nickel layer in the nickel-coated barium titanate composite powder obtained in this embodiment was 269.2 nm, as measured by transmission electron microscopy. The crystallinity of the nickel layer in the nickel-coated barium titanate composite powder obtained in this embodiment was 95%, as measured by XRD. The oxygen content of the nickel layer in the nickel-coated barium titanate composite powder obtained in this embodiment was 0.13%, as measured by a Horiba EMGA-830 oxygen and nitrogen content analyzer. The composite powder was screen-printed into an electrode line 0.3 mm wide and 6 cm long. The resistance of the line segment was measured using a multimeter, and the electrode thickness was measured using a film thickness gauge. The resistivity of the nickel-coated barium titanate particles in the nickel-coated barium titanate composite powder obtained in this embodiment was measured to be 1*10⁻⁶. -5 Ω·cm.

[0196] Furthermore, the nickel-coated barium titanate composite powder obtained in this embodiment is made into a slurry; specifically, the mass ratio of the nickel-coated barium titanate composite powder, the first solvent, and the binder in the slurry is 49.8:40.1:10.1.

[0197] Example 9

[0198] In this embodiment, the above-mentioned nickel-coated barium titanate composite powder is prepared through the following steps:

[0199] S1 is selected from materials prepared by the solid-state method, with a D50 of 170.1 nm and a specific surface area of ​​14.2 m². 2 / g of barium titanate particles;

[0200] S2, use analytical grade alcohol to ultrasonically clean the barium titanate particles in step S1. The ultrasonic frequency is 40kHz and the cleaning time is 30min. Then, centrifuge at 4000rpm for 5min and discard the supernatant.

[0201] S3, prepare a 0.5L nickel ion solution with a nickel ion concentration of 0.5mol / L, then add polyethylene glycol with a molecular weight of 6000, wherein the mass fraction of polyethylene glycol relative to the nickel ion solution is 1wt.%, and stir at 2500rpm for 30min using a high-speed stirrer;

[0202] S4. The barium titanate particles obtained in step S2 are dispersed in a nickel ion solution and stirred at 4000 rpm for 2 hours using a high-speed disperser. Then, oxalic acid with an equal molar amount to the nickel ion solution is added to obtain a precipitate.

[0203] S5. Separate the precipitate, wash the precipitate obtained in step S4 with deionized water, place it in an oven, dry it at 100°C until the water content is less than 0.3 wt.%, and then put it into a vacuum atmosphere furnace and sinter it at 850°C for 120 min under a vacuum of 0.05 Pa to obtain the nickel-coated barium titanate composite powder.

[0204] The thickness of the nickel layer in the nickel-coated barium titanate composite powder obtained in this embodiment was 277.2 nm, as measured by transmission electron microscopy. The crystallinity of the nickel layer in the nickel-coated barium titanate composite powder obtained in this embodiment was 97%, as measured by XRD. The oxygen content of the nickel layer in the nickel-coated barium titanate composite powder obtained in this embodiment was 0.11%, as measured by a Horiba EMGA-830 oxygen and nitrogen content analyzer. The composite powder was screen-printed into an electrode line 0.3 mm wide and 6 cm long. The resistance of the line segment was measured using a multimeter, and the electrode thickness was measured using a film thickness gauge. The resistivity of the nickel-coated barium titanate particles in the nickel-coated barium titanate composite powder obtained in this embodiment was measured to be 2*10⁻⁶. -5 Ω·cm.

[0205] Furthermore, the nickel-coated barium titanate composite powder obtained in this embodiment is made into a slurry; specifically, the mass ratio of the nickel-coated barium titanate composite powder, the first solvent, and the binder in the slurry is 50.1:39.2:10.7.

[0206] Example 10

[0207] In this embodiment, the above-mentioned nickel-coated barium titanate composite powder is prepared through the following steps:

[0208] S1 is selected from materials prepared by the solid-state method, with a D50 of 127.8 nm and a specific surface area of ​​17.6 m². 2 / g of barium titanate particles;

[0209] S2, use analytical grade alcohol to ultrasonically clean the barium titanate particles in step S1. The ultrasonic frequency is 40kHz and the cleaning time is 30min. Then, centrifuge at 4000rpm for 5min and discard the supernatant.

[0210] S3, prepare a 0.5L nickel ion solution with a nickel ion concentration of 0.5mol / L, then add polyethylene glycol with a molecular weight of 6000, wherein the mass fraction of polyethylene glycol relative to the nickel ion solution is 1wt.%, and stir at 2500rpm for 30min using a high-speed stirrer;

[0211] S4. The barium titanate particles obtained in step S2 are dispersed in a nickel ion solution and stirred at 4000 rpm for 2 hours using a high-speed disperser. Then, oxalic acid with an equal molar amount to the nickel ion solution is added to obtain a precipitate.

[0212] S5. Separate the precipitate, wash the precipitate obtained in step S4 with deionized water, place it in an oven, dry it at 100°C until the water content is less than 0.3 wt.%, and then put it into a vacuum atmosphere furnace and sinter it at 850°C for 120 min under a vacuum of 0.05 Pa to obtain the nickel-coated barium titanate composite powder.

[0213] The thickness of the nickel layer in the nickel-coated barium titanate composite powder obtained in this embodiment was 297.2 nm, as measured by transmission electron microscopy. The crystallinity of the nickel layer in the nickel-coated barium titanate composite powder obtained in this embodiment was 97%, as measured by XRD. The oxygen content of the nickel layer in the nickel-coated barium titanate composite powder obtained in this embodiment was 0.20%, as measured by a Horiba EMGA-830 oxygen and nitrogen content analyzer. The composite powder was screen-printed into an electrode line 0.3 mm wide and 6 cm long. The resistance of the line segment was tested with a multimeter, and the electrode thickness was tested with a film thickness gauge. The resistivity of the nickel-coated barium titanate particles in the nickel-coated barium titanate composite powder obtained in this embodiment was measured to be 6*10⁻⁶. -4 Ω·cm.

[0214] Furthermore, the nickel-coated barium titanate composite powder obtained in this embodiment is made into a slurry; specifically, the mass ratio of the nickel-coated barium titanate composite powder, the first solvent, and the binder in the slurry is 49.8:40.3:9.9.

[0215] Comparative Example 1

[0216] The comparative example used commercially available nickel paste (Guoci Hongyuan mass-produced paste N2074) with a nickel powder content of 50 wt.% and a barium titanate content of 3 wt.%.

[0217] Comparative Example 2

[0218] The comparative example used commercially available nickel paste (Guoci Hongyuan mass-produced paste PEN1160) with a nickel powder content of 51 wt.% and a barium titanate content of 2 wt.%.

[0219] Comparative Example 3

[0220] The comparative example is based on Example 1 of patent CN109265880B, in which the powder is prepared by mixing nickel-coated barium titanate composite powder, a first solvent, and a binder in a mass ratio of 49.7:40.1:10.2 to obtain slurry 1.

[0221] Slurry 1 was obtained.

[0222] Comparative Example 4

[0223] The comparative example is based on Example 2 of patent CN109265880B, in which the powder is prepared by mixing nickel-coated barium titanate composite powder, a first solvent, and a binder in a mass ratio of 49.9:39.6:10.5 to obtain slurry 2.

[0224] The parameters of the powders in the above embodiments and comparative examples are summarized and recorded as follows, resulting in Table 1.

[0225] Table 1. Parameters of various embodiments and comparative examples of the present invention.

[0226]

[0227]

[0228] The time it takes for barium titanate (barium titanate is white, nickel powder is black) to float in the slurry, as shown in Table 1, can indicate its storage stability, and the variance of the capacitance can show its performance consistency.

[0229] As can be seen from Table 1 above, the resistivity of the electrode film layer made from the slurry provided in the embodiments of the present invention reaches or is lower than that of the mass-produced nickel internal electrode reference slurry. The good conductivity helps to improve the reduction of equivalent series resistance (ESR) of MLCC, improve frequency response, and reduce self-heating.

[0230] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims. Furthermore, specific examples have been used in the specification to illustrate the principles and implementation methods of the present invention. The above description of the embodiments is only for the purpose of helping to understand the method and core ideas of the present invention, and the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A composite powder, characterized in that, The composite powder includes core-shell particles, wherein the core-shell particles include a barium titanate core and a nickel shell layer covering the barium titanate core; The mass ratio of the barium titanate core to the nickel shell in the core-shell particles is 1:(17-20).

2. The composite powder according to claim 1, characterized in that, The barium titanate comprises tetragonal barium titanate and / or cubic barium titanate. Preferably, the barium titanate contains at least 30 wt.% tetragonal barium titanate.

3. The composite powder according to claim 1, characterized in that, The composite powder has a D50 of 270–800 nm, preferably 300–750 nm; And / or, the tap density of the composite powder is 4-6 g / cm³. 3 The preferred concentration is 4.5–6 g / cm³. 3 .

4. The composite powder according to claim 1 or 3, characterized in that, The D50 of the barium titanate core is 70–200 nm, preferably 80–180 nm.

5. The composite powder according to claim 1, characterized in that, The thickness of the nickel layer is 100–300 nm; And / or, the oxygen content of the nickel layer is less than 0.3 wt.%, preferably less than 0.25 wt.%.

6. The composite powder according to claim 1, characterized in that, The crystallinity of the nickel shell layer is greater than 95%.

7. A method for preparing the composite powder as described in any one of claims 1 to 6, characterized in that, The method includes the following steps: S1 provides barium titanate particles; S2, optionally, the barium titanate particles are subjected to surface treatment; S3, to prepare a nickel ion solution; S4, mix and react the nickel ion solution obtained in step S3, the barium titanate particles obtained in step S2, and the precipitant. S5. The reaction product obtained in step S4 is post-processed to obtain the nickel-coated barium titanate composite powder.

8. The method according to claim 7, characterized in that, Includes at least one of the following features: In step S1, the barium titanate particles include tetragonal barium titanate. Preferably, the mass percentage of tetragonal barium titanate in the barium titanate particles is at least 30 wt.%. And / or, in step S1, the D50 of the barium titanate particles is 70-200 nm, preferably 80-180 nm; And / or, in step S1, the specific surface area of ​​the barium titanate particles is 13–21 m². 2 / g.

9. The method according to claim 7, characterized in that, In step S2, the surface treatment is ultrasonic cleaning; Preferably, alcohol is used as the medium for ultrasonic cleaning; Preferably, the ultrasonic cleaning power is 35-40 kHz and the cleaning time is 30-60 min; Preferably, in step S2, after ultrasonic cleaning, the sample is centrifuged at 3000-4000 rpm for 5-10 minutes.

10. The method according to claim 7, characterized in that, It includes at least one of the following features: in step S3, the molar concentration of nickel ions in the nickel ion solution is 0.1 to 3 mol / L; The nickel ion solution is selected from at least one of nickel chloride, nickel nitrate, nickel acetate, nickel sulfate, and nickel ammonium sulfate (NiSO4·(NH4)2SO4) solutions; The nickel ion solution contains a dispersant; Preferably, the dispersant is at least one of polyethylene glycol, polyoxyethylene, and fatty acid polyethylene glycol ester; preferably, the molecular weight of the dispersant, polyethylene glycol, is 5000 to 7000. The dispersant is used in an amount of 0.1-2 wt% relative to the nickel ion solution; and When mixing the nickel ion solution with the dispersant, the stirring speed is 2000-2500 rpm and the stirring time is 30-60 min.

11. The method according to claim 7, characterized in that, In step S4, the method includes at least one of the following features: The nickel ion solution is mixed with barium titanate particles by stirring or ultrasonic mixing. Preferably, the mixing speed is 3500-4000 rpm and the mixing time is 1-2 hours. The precipitant is used at a molar ratio of (0.5-2):1 relative to nickel ions in the nickel ion solution; The precipitant is oxalic acid.

12. The method according to claim 7, characterized in that, In step S5, the post-processing includes separating, washing, drying and dehydrating, and sintering the reaction products. Preferably, the sintering temperature is 600–900°C, and the sintering apparatus is a vacuum atmosphere furnace.

13. A paste for preparing internal electrodes of a multilayer ceramic capacitor, characterized in that, The raw materials for the slurry include: The composite powder according to any one of claims 1 to 6, or the composite powder prepared by the method according to any one of claims 7 to 12; and Adhesives, primary solvents.

14. The slurry according to claim 13, characterized in that, The first solvent is at least one of terpineol, butyl carbitol, dodecyl alcohol ester, hydrogenated terpineol, dihydroacetic acid terpineol, a mixture of alkanes, and diethylene glycol ethyl ether acetate; And / or, in the raw materials of the slurry, the mass ratio of the composite powder, the binder, and the first solvent is (49.5-50.5):(39-41):(9-11.5).

15. The slurry according to claim 13, characterized in that, The adhesive is a mixture of resin and a second solvent, preferably, the mass ratio of the resin and the second solvent is (5-10):(90-95); The resin is at least one of ethyl cellulose resin, acrylic resin, and PVB resin, or the second solvent is at least one of terpineol, butyl carbitol, dodecyl alcohol ester, hydrogenated terpineol, dihydroacetic acid terpineol, alkane mixture, and diethylene glycol ethyl ether acetate.

16. A multilayer ceramic capacitor, characterized in that, The multilayer ceramic capacitor includes an inner electrode, a dielectric layer, and an outer electrode. The inner electrode is disposed on the dielectric layer, and the two ends of the inner electrode are connected to the outer electrode by a spacer. The internal electrode of the multilayer ceramic capacitor is formed from a composite powder as described in any one of claims 1 to 6, or from a composite powder obtained by any one of claims 7 to 12, or from a slurry as described in any one of claims 13 to 15.

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