JP3444854B2 - Nickel powder, method for producing the same, and conductive paste - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a nickel powder, a method for producing the same, and a conductive paste for a monolithic ceramic capacitor. More specifically, it has a narrow particle size distribution, and is composed of an alkali metal, an alkaline earth metal, an element periodic table No. 4 Nickel powder with a small total amount of impurities consisting of transition metals (excluding nickel), sulfur and chlorine of the period, especially suitable for conductive paste used for forming thin and protrusion-free internal electrodes of multilayer ceramic capacitors, and method for producing the same And a conductive paste for a multilayer ceramic capacitor containing the nickel powder.

[0002]

2. Description of the Related Art A monolithic ceramic capacitor is one in which a plurality of alternately laminated ceramic dielectric layers and an internal electrode layer are integrated, and when forming such a monolithic ceramic capacitor, an internal electrode material is used. A metal fine powder is made into a paste to prepare a conductive paste, and the conductive paste is used to print on a ceramic dielectric green sheet,
A plurality of layers of ceramic dielectric green sheets and conductor paste layers are alternately laminated to form a ceramic dielectric layer and internal electrode layers which are fired at a high temperature in a reducing atmosphere to be integrated. It is common to integrate and.

Conventionally, platinum, palladium, silver-palladium, etc. have been used as the material of the internal electrodes. However, in order to reduce the cost, these platinum, palladium, and
Techniques using a base metal such as nickel instead of a noble metal such as silver-palladium have been developed and advanced.

In addition, electronic parts manufactured using conductive paste, such as multilayer ceramic capacitors, have become smaller and smaller in recent years, and along with this, the ceramic dielectric layers and internal electrode layers have become thinner and multilayered, Currently, for laminated parts, especially for laminated ceramic capacitors, the dielectric layer is 2 μm.
Hereinafter, a component having an internal electrode film thickness of 1.5 μm or less and a laminated number of 100 or more is manufactured.

In order to obtain a thin internal electrode layer, it is considered to use fine metal powder having a small average particle diameter corresponding to it, but coarse particles are mixed even if the average particle diameter is within a predetermined range. When an internal electrode layer is formed using a conductive paste containing such fine metal powder, such coarse particles form protrusions on the internal electrode layer, and the protrusions penetrate through the thin ceramic dielectric layer to form internal electrodes. May cause a short circuit between them. In order to prevent such a short circuit between the internal electrodes, it is necessary to use metal fine powder having an average particle size considerably smaller than the metal fine powder having an average particle size suitable for obtaining a thin internal electrode layer.

For example, in JP-A-11-189801, the abundance ratio of coarse particles having an average particle diameter of 0.2 to 0.6 μm and having a particle diameter of 2.5 times or more the average particle diameter is found. Nickel ultrafine powder, which is 0.1% or less on the number basis, is described, and the fourth column, lines 21 to 24 states, "For example, if the grain size of coarse particles is limited to about 1.5 μm or more, It is necessary to limit the average particle size of nickel ultrafine powder to 0.6 μm. ”, And it is necessary to use metal fine powder having a considerably small average particle size in order to obtain a thin internal electrode layer. . However, there is a problem that the finer the powder, the higher the viscosity of the paste containing such fine powder,
There is also a problem that heat shrinkage and oxidation are promoted during firing.

[0007]

DISCLOSURE OF THE INVENTION The present invention has a narrow particle size distribution and comprises an alkali metal, an alkaline earth metal, a transition metal of the 4th period of the periodic table of elements (excluding nickel), sulfur and chlorine. Nickel powder, which has a small total amount of impurities and is suitable for a conductive paste used for forming a thin and projection-free internal electrode layer of a multilayer ceramic capacitor without unnecessarily reducing the particle size of the nickel powder, An object of the present invention is to provide a manufacturing method and a conductive paste for a laminated ceramic capacitor containing such nickel powder.

[0008]

Means for Solving the Problems The inventors of the present invention have conducted extensive studies to achieve the above-mentioned object, and as a result, in the nickel powder, the content ratio of coarse particles was made relatively small, and most of the nickel powder particles were By keeping the diameter within the specified range,
Without unnecessarily making nickel powder fine, an internal electrode layer without protrusions can be formed on the surface to prevent short-circuiting between internal electrodes, and since there are few fine particles, oxidation is suppressed and heat shrinkage occurs. That the nickel powder can be suppressed, and that such nickel powder can be obtained by satisfying a predetermined condition at the time of generation and reduction of nickel hydroxide, and a conductive paste containing such nickel powder is particularly suitable for a laminated ceramic capacitor. They found it suitable and completed the invention.

That is, in the nickel powder of the present invention, the number of particles having a particle size 1.2 times or more of the average particle size by SEM (scanning electron microscope) observation is 5% or less of the total number of particles, The number of particles having a particle diameter of 0.8 times or less of the particle diameter is 5% or less of the total number of particles. The conductive paste for a monolithic ceramic capacitor of the present invention is characterized by containing the above-mentioned nickel powder of the present invention.

Further, the method for producing nickel powder of the present invention is
The nickel hydroxide-containing slurry obtained by adding the nickel salt aqueous solution to the alkali metal hydroxide aqueous solution is contacted with a hydrazine-based reducing agent under a temperature condition of 55 ° C. or higher to reduce the nickel hydroxide. It is characterized by doing.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION In the nickel powder of the present invention,
For convenience, the number of particles having a particle size 1.2 times or more the average particle size by SEM observation of about 10,000 times is 5 times the total number of particles.
% Or less, preferably 4% or less, and the number of particles having a particle size of 0.8 times or less of the average particle size is 5% of the total number of particles.
% Or less, preferably 4% or less, that is, the content ratio of coarse particles is relatively small, and the particle diameter of each nickel particle in the nickel powder is considerably uniform. For example, in a multilayer ceramic capacitor obtained by using a paste, it is possible to form an internal electrode layer that is considerably thinner than the average particle size of nickel powder, and no protrusion is formed on the surface of the internal electrode layer. Therefore, a short circuit between the internal electrodes does not occur. Further, since the content ratio of the fine particles is relatively small, such a paste containing nickel powder does not cause a problem of increasing viscosity, and neither heat shrinkage nor oxidation is promoted during firing.

In the nickel powder of the present invention, the nickel powder
Scatter and measure the volume distribution by laser diffraction scattering method
Particle size corresponding to 50% of cumulative distribution under the sieve of the obtained particle size distribution
(D ₅₀) And maximum particle size (D_max) Is calculated and (D
_max/ D₅₀) Is 4 or less, that is, D₅₀Against
Do D_maxRatio is preferably 4 times or less, and 3 times
It is more preferable that it is less than or equal to 2.5 times, and less than or equal to 2.5 times.
And are most preferred. Here is the measurement of the above particle size distribution
Use an appropriate laser diffraction / scattering particle size distribution analyzer
Fill the prescribed dispersant solution with nickel powder.
Disperse in 1 minute, stir with an ultrasonic disperser, and then measure.
And is desired.

In the nickel powder of the present invention, the number of particles having a particle size of 1.2 times or more of the average particle size by SEM observation is 5% or less of the total number of particles, and the average particle size of 0.
When the number of particles having a particle size of 8 times or less is 5% or less of the total number of particles and the ratio of D _{max to} D ₅₀ is 4 times or less, a conductive paste containing such nickel powder is used. In a multilayer ceramic capacitor obtained as a result, for example, the formation of protrusions on the surface of the internal electrode layer is more sufficiently prevented, and it becomes possible to form a very uniform, dense and thin film, and therefore a short circuit between internal electrodes occurs. Are more fully prevented.

In the nickel powder of the present invention, when a multilayer ceramic capacitor is manufactured using a paste containing such nickel powder, it is preferable that the average particle diameter by SEM observation is 0.1 to 1 μm, 0.2 ~
More preferably, it is 0.6 μm.

Further, in the nickel powder of the present invention, a high-purity reagent is used for the production thereof, and the following predetermined conditions are satisfied at the time of producing and reducing nickel hydroxide, whereby the alkali metal and alkali metal in the nickel powder can be obtained. The total amount of impurities including earth metals, transition metals of the 4th period of the periodic table (titanium, vanadium, chromium, manganese, iron, cobalt, copper and zinc, but not nickel), sulfur and chlorine is 60.
It can be 0 ppm or less. These impurities tend to suppress or accelerate sintering during the production of a monolithic ceramic capacitor, and also tend to reduce the dielectric breakdown voltage of the resulting monolithic ceramic capacitor, and thus the monolithic ceramic obtained. Since the electric characteristics of the capacitor tend to be adversely affected, it is significant that the total amount of these impurities can be 600 ppm or less.

The conductive paste for a monolithic ceramic capacitor of the present invention contains the nickel powder of the present invention satisfying the conditions described above, and the conductive paste for a monolithic ceramic capacitor of the present invention is excellent as described above. It is suitable for forming a particularly thin and uniform internal electrode because it contains nickel powder with excellent characteristics, and the concentration of certain impurities that adversely affect the dielectric is low. It is possible to reduce the deterioration of electrical characteristics and the variation in performance of the monolithic ceramic capacitor.

Next, a preferred method for producing the conductive paste for laminated ceramic capacitors of the present invention will be described. The conductive paste for a monolithic ceramic capacitor of the present invention is composed of the above-mentioned nickel powder of the present invention, a resin, a solvent, and the like,
Further, if necessary, a dispersant, a sintering inhibitor, etc. may be contained. Specifically, as the resin, a cellulose derivative such as ethyl cellulose, an acrylic resin, a polyvinyl butyral resin, a vinyl-based non-curable resin such as polyvinyl alcohol, an epoxy resin, a thermosetting resin such as an acrylic resin, which preferably contains a peroxide, is used. Can be used. As the solvent, terpineol, tetralin, butyl carbitol, carbitol acetate, etc. can be used alone or in combination. Further, a glass frit may be added to this paste, if necessary. The conductive paste for a monolithic ceramic capacitor of the present invention is obtained by mixing and stirring the above raw materials using a mixing machine such as a ball mill or a triple roll.

In the method for producing nickel powder of the present invention, a slurry containing nickel hydroxide obtained by adding an aqueous solution of a nickel salt to an aqueous solution of an alkali metal hydroxide is added to a hydrazine-based slurry under a temperature condition of 55 ° C. or higher. It is characterized by contacting with a reducing agent to reduce nickel hydroxide, and examples of the nickel salt used at this time include nickel halides such as nickel sulfate, nickel nitrate, and nickel chloride. Examples of hydroxides include sodium hydroxide and potassium hydroxide, and examples of hydrazine-based reducing agents include hydrazine, hydrazine hydrate, hydrazine sulfate, hydrazine carbonate, and hydrazine hydrochloride.

In the production method of the present invention, it is important to use a slurry containing nickel hydroxide obtained by adding the nickel salt aqueous solution to the alkali metal hydroxide aqueous solution. The reason for this is that when an aqueous solution of a nickel salt is added to an aqueous solution of an alkali metal hydroxide, nickel powder having a uniform particle size can be obtained due to the low slurry viscosity at the time of nickel hydroxide precipitation. However, on the contrary, when the alkali metal hydroxide aqueous solution is added to the nickel salt aqueous solution, the slurry viscosity at the time of precipitation of nickel hydroxide increases, and it becomes extremely difficult to obtain nickel powder having a uniform particle size. Is.

In the production method of the present invention, the nickel salt aqueous solution is preferably gradually added to the alkali metal hydroxide aqueous solution to form a nickel hydroxide-containing slurry,
It is preferable to immediately contact the slurry with a hydrazine-based reducing agent. However, the nickel salt aqueous solution is preferably gradually added to the alkali metal hydroxide aqueous solution to form a nickel hydroxide-containing slurry, and then at least a part of the nickel hydroxide is precipitated by leaving it as it is or storing it. Even afterwards, the mixture may be sufficiently stirred to return to a slurry state and brought into contact with a hydrazine-based reducing agent,
Alternatively, the nickel salt aqueous solution is preferably gradually added to the alkali metal hydroxide aqueous solution to form a nickel hydroxide-containing slurry, and the alkali metal hydroxide is recovered from the slurry in a wet state or a dry state and stored. Water and alkali metal hydroxide may be added to the mixture, and the mixture may be sufficiently stirred to return to a strongly alkaline slurry state and brought into contact with a hydrazine-based reducing agent.

The concentration of the nickel salt aqueous solution used in the production of the above nickel hydroxide-containing slurry is preferably 10 to 150 g / L as the nickel ion concentration,
It is more preferably 50 to 150 g / L. By using the nickel salt aqueous solution having such a concentration, a narrow particle size distribution, which is a feature of the nickel powder of the present invention, can be achieved, and at the same time, favorable results can be obtained in terms of production efficiency.

The concentration of the alkali metal hydroxide aqueous solution used in the production of the above nickel hydroxide-containing slurry is 20 to
It is preferably 300 g / L, and 60 to 250 g / L.
More preferably, it is L. Moreover, the relative amount of the nickel salt aqueous solution and the alkali metal hydroxide aqueous solution is such that the alkali metal hydroxide in the alkali metal hydroxide aqueous solution is 1.1 to 2 equivalents relative to the nickel salt in the nickel salt aqueous solution. Is preferable, and 1.3 to 1.8 equivalents is more preferable. By using such relative amounts, the production state of nickel hydroxide is stabilized, and at the same time cost is balanced, which is preferable.

In the production method of the present invention, it is important to bring the nickel hydroxide-containing slurry into contact with a hydrazine-based reducing agent under a temperature condition of 55 ° C. or higher to reduce the nickel hydroxide. When the temperature at the time of this reduction is less than 55 ° C., it is difficult to obtain nickel powder with a uniform particle size, and a larger amount of coarser nickel powder is mixed and generated. In addition, the mixing ratio of the alkali metal which is an impurity is increased. Therefore, in the production method of the present invention, the reaction temperature for reducing nickel hydroxide is 55 ° C. or higher, preferably 60 ° C.
That is all.

In particular, the nickel powder obtained by contacting with an aqueous hydrazine solution at 55 ° C. or higher, preferably 60 ° C. or higher, to reduce the above nickel hydroxide is SEM.
The particle size measured by observation is uniform, and the total amount of impurities consisting of alkali metals, alkaline earth metals, transition metals of the 4th period of the Periodic Table of Elements (excluding nickel), sulfur and chlorine derived from the reaction raw materials Is reduced to 600 ppm or less.

In the production method of the present invention, a slurry containing nickel hydroxide obtained by adding an aqueous solution of nickel salt to an aqueous solution of alkali metal hydroxide is used, but the particle size distribution of nickel powder is narrower. In order to do so, it is preferable that the nickel salt aqueous solution contains a nickel complex. The nickel complex may be separately formed and then added to the nickel salt aqueous solution, but it is preferable to generate the nickel complex in the nickel salt aqueous solution. When forming a nickel complex in an aqueous solution of nickel salt, it is preferable to use a water-soluble compound having a carboxyl group and / or an amino group. Such a compound easily forms a complex with nickel and can make the nickel particle diameter more uniform.

As a method of forming a nickel complex in a nickel salt aqueous solution, even if a nickel salt and a water-soluble compound having a carboxyl group and / or an amino group are dissolved in water in any order, the nickel salt aqueous solution is treated with a carboxyl group. Even if a water-soluble compound having a group and / or an amino group is dissolved,
Alternatively, the nickel salt may be dissolved in an aqueous solution of a water-soluble compound having a carboxyl group and / or an amino group. In short, it suffices to generate an aqueous solution containing a nickel salt and a water-soluble compound having a carboxyl group and / or an amino group.

Specific examples of the above water-soluble compounds having a carboxyl group and / or an amino group include ethylenediaminetetraacetic acid, acetic acid, oxalic acid, malonic acid, salicylic acid, thioglycolic acid, glycine, ethylenediamine, alanine and citric acid. Examples thereof include glutamic acid, lactic acid, malic acid, tartaric acid and triethanolamine.

When a nickel complex is formed in an aqueous nickel salt solution, the amount of the water-soluble compound having a carboxyl group and / or an amino group added is 0.005 to a molar ratio with respect to the nickel salt in the aqueous nickel salt solution. It is preferably 0.5, and more preferably 0.01 to 0.1. Such an addition amount is preferable because the particle size distribution of the nickel powder can be further narrowed and at the same time the cost can be balanced.

In the production method of the present invention, after the reduction reaction is carried out, the obtained nickel powder may be pulverized to obtain a monodisperse powder, and such pulverization treatment may be carried out. More preferable. As the disintegration treatment, a high-speed rotary collision pulverization treatment in which nickel powder is collided with a rotating portion rotating at high speed to pulverize, a media agitation pulverization treatment in which nickel powder is agitated together with beads or the like, nickel particles Examples of the method include high-pressure hydraulic disintegration treatment in which the slurry of (1) is collided with high water pressure from two directions to be pulverized, and jet abutment treatment.

As a classification of the apparatus for carrying out such a treatment, there are a high-speed moving body collision type air flow type pulverizer, an impact type pulverizer, a cage mill, a medium stirring type mill, an axial flow mill, a jet abutment device and the like. Specifically, super hybrid mill (made by Ishikawajima Harima Heavy Industries), jet mill (made by Ebara Corporation), supermass colloider (made by Masuyuki Sangyo), beads mill (made by Irie Shokai), ultimizer (made by Sugino Machine), NC mill (made by Ishii Grinding Machinery Co., Ltd., Disintegrator (Otsuka Iron Works), ACM Pulverizer (Hosokawa Micron), Turbo Mill (Matsubo), Super Micron (Hosokawa Micron), Micros (Nara Machinery), New Cosmomizer (Nara Machinery) ), Fine Victor Mill (made by Hosokawa Micron), Ecoplex (made by Hosokawa Micron), CF Mill (made by Ube Industries), Hybridizer (made by Nara Machinery), Pin Mill (made by Alpine), Pressure Homogenizer (made by Nippon Seiki Seisakusho),
There are Harrel homogenizer (made in Japan), mechanofusion system (made by Hosokawa Micron), sand mill (made by Yodocasting), etc.

[0031]

EXAMPLES The present invention will be specifically described below based on Examples and Comparative Examples. Example 1 Nickel sulfate hexahydrate 44.8 kg (quality 22.2% by mass) and citric acid monohydrate 1.8 kg were purified water 80 L.
Aqueous solution obtained by dissolving in
While maintaining the liquid temperature at 60 ° C, 100 g of a g / L aqueous solution was slowly added dropwise to deposit nickel hydroxide.
While maintaining the liquid temperature at 60 ° C., 30 kg of hydrazine monohydrate was added to this slurry over 30 minutes to reduce nickel hydroxide to nickel, and the resulting nickel powder was purified with pure water to adjust the pH of the cleaning liquid. Washed until 9 or less,
After filtering and drying, it was put into a Parverizer AP-1SH type (manufactured by Hosokawa Micron) equipped with a knife-type hammer, and pulverized at a rotation speed of 2500 rpm to obtain nickel powder.

The nickel powder was observed with a SEM of 10,000 times, and the particle diameters of 1500 particles in a total of 5 fields randomly selected were measured. As a result, the average particle diameter was 0.58 μm, which was 0.69 μm (0.58 × 1.
The number of particles having a particle size exceeding 2 = 0.696) is 5
3 and 0.47 μm (0.58 × 0.8 = 0.4
The number of particles having a particle size smaller than 64) was 44.

Further, 0.1 g of this nickel powder is added to 0.1%.
After mixing with an SN Dispersant 5468 aqueous solution (manufactured by San Nopco) and dispersing with an ultrasonic homogenizer (manufactured by Nippon Seiki Seisakusho, US-300T) for 5 minutes, a laser diffraction scattering particle size distribution analyzer Micro Trac HRA 9320-X1
As a result of determining the particle size (D ₅₀ ) and the maximum particle size (D _max ) corresponding to 50% of the under-sieve cumulative distribution of the particle size distribution obtained by measuring the volume distribution using a 00 type (manufactured by Leeds + Northrup), D
₅₀ was 0.66 μm and D _max was 1.46 μm, so D _max / D ₅₀ was 2.2.

Further, the total concentration of sodium and potassium is 262 ppm, the total concentration of magnesium and calcium is 51 ppm, the sulfur concentration is 80 ppm, the chlorine concentration is 8 ppm, and the periodic table of elements other than nickel is shown. The total concentration of transition metals (titanium, vanadium, chromium, manganese, iron, cobalt, copper, zinc) in the fourth period was 89 ppm, and the total amount of these impurities was 490
It was ppm.

To 50 parts by mass of this nickel powder, 5 parts by mass of ethyl cellulose, 60 parts by mass of mineral spirit and 35 parts by mass of butyl carbitol were added and kneaded with a three-roll to form a paste, and this conductive paste was used to form a dielectric layer. A capacitor having a thickness of 2 μm, an internal electrode layer thickness of 1.5 μm, and a stacking number of 350 layers and a size of 2.0 × 1.25 × 1.25 mm was fired. The 200 ceramic capacitors obtained were examined for defects. As a result, the number of defective products having electrical characteristics such as poor insulation and poor dielectric properties was 2, and the defective rate was 1%.

Example 2 Nickel sulfate hexahydrate 44.8 kg (quality 22.2% by mass) and sodium ethylenediaminetetraacetate 2.8 k
An aqueous solution obtained by dissolving 80 g of pure water in 80 L of pure water is added to 100 L of an aqueous solution having a sodium hydroxide concentration of 200 g / L at a liquid temperature of 60 ° C.
While maintaining the above temperature, the solution was slowly added dropwise to precipitate nickel hydroxide. While maintaining the liquid temperature at 60 ° C., 42 kg of hydrazine monohydrate was added to this slurry over 20 minutes to reduce nickel hydroxide to nickel, and the obtained nickel powder was purified with pure water to adjust the pH of the cleaning liquid. To 9 or less, filtered, dried, and then hybridized N
Rotation speed 4000r using HS-3 type (manufactured by Nara Machinery)
Pelletization was performed for 5 minutes at pm to obtain nickel powder.

The nickel powder was observed with a SEM of 10,000 times, and the particle diameters of 1500 particles in a total of 5 fields selected at random were measured. As a result, the average particle diameter was 0.52 μm, which was 0.62 μm (0.52 × 1.
The number of particles having a particle size exceeding 2 = 0.624) is 5
5 and 0.42 μm (0.52 × 0.8 = 0.4
The number of particles having a particle size smaller than 16) was only 28.

0.1 g of this nickel powder was added to 0.1%.
After mixing with an SN Dispersant 5468 aqueous solution (manufactured by San Nopco) and dispersing with an ultrasonic homogenizer (manufactured by Nippon Seiki Seisakusho, US-300T) for 5 minutes, a laser diffraction scattering particle size distribution analyzer Micro Trac HRA 9320-X1
As a result of determining the particle size (D ₅₀ ) and the maximum particle size (D _max ) corresponding to 50% of the under-sieve cumulative distribution of the particle size distribution obtained by measuring the volume distribution using a 00 type (manufactured by Leeds + Northrup), D
₅₀ was 0.57 μm and D _max was 1.31 μm, so D _max / D ₅₀ was 2.3.

Further, the total concentration of sodium and potassium is 248 ppm, the total concentration of magnesium and calcium is 55 ppm, the sulfur concentration is 94 ppm, the chlorine concentration is 10 ppm, and the periodic table of elements other than nickel is shown. The total transition metal concentration in the 4th period is 58 ppm
And the total amount of these impurities was 565 ppm.

To 50 parts by mass of this nickel powder, 5 parts by mass of ethyl cellulose, 60 parts by mass of mineral spirit and 35 parts by mass of butyl carbitol were added and kneaded with a three-roll to form a paste, and this conductive paste was used to form a dielectric layer. A capacitor having a thickness of 2 μm, an internal electrode layer thickness of 1.5 μm, and a stacking number of 350 layers and a size of 2.0 × 1.25 × 1.25 mm was fired. The 200 ceramic capacitors obtained were examined for defects. As a result, the number of defective products having electrical characteristics such as poor insulation and poor dielectric properties was 2, and the defective rate was 1%.

Example 3 An aqueous solution obtained by dissolving 44.8 kg of nickel sulfate hexahydrate (quality 22.2% by mass) and 0.65 kg of glycine in 80 L of pure water was prepared, and the concentration of sodium hydroxide was 200 g / L. While maintaining the liquid temperature at 70 ° C., the solution was slowly added dropwise to 100 L of the aqueous solution to precipitate nickel hydroxide. While maintaining the liquid temperature at 70 ° C., 42 kg of hydrazine monohydrate was added to this slurry over 30 minutes to reduce nickel hydroxide to nickel, and the obtained nickel powder was purified with pure water to adjust the pH of the cleaning liquid. Washed to 9 or less, filtered,
After drying, using an Ebara Triad Jet PM100 type (manufactured by EBARA CORPORATION), which is a jet mill, pulverization treatment was performed at an air pressure of 6 kg / cm ² and 2 kg / hour to obtain nickel powder.

The nickel powder was observed with a SEM of 10,000 times, and the particle diameters of 1500 particles in total of 5 fields randomly selected were measured. As a result, the average particle diameter was 0.54 μm, which was 0.64 μm (0.54 × 1.
The number of particles having a particle size exceeding 2 = 0.648) is 3
6 pieces, 0.44 μm (0.54 × 0.8 = 0.4
The number of particles having a particle size smaller than 32) was only 51.

0.1 g of this nickel powder was added to 0.1%.
After mixing with an SN Dispersant 5468 aqueous solution (manufactured by San Nopco) and dispersing with an ultrasonic homogenizer (manufactured by Nippon Seiki Seisakusho, US-300T) for 5 minutes, a laser diffraction scattering particle size distribution analyzer Micro Trac HRA 9320-X1
As a result of determining the particle size (D ₅₀ ) and the maximum particle size (D _max ) corresponding to 50% of the under-sieve cumulative distribution of the particle size distribution obtained by measuring the volume distribution using a 00 type (manufactured by Leeds + Northrup), D
₅₀ was 0.66 μm and D _max was 1.36 μm, so D _max / D ₅₀ was 2.1.

Furthermore, the total concentration of sodium and potassium is 40 ppm, the total concentration of magnesium and calcium is 46 ppm, the sulfur concentration is 45 ppm, the chlorine concentration is 7 ppm, and the periodic table of elements other than nickel is shown. The total transition metal concentration in the fourth cycle was 47 ppm, and the total amount of these impurities was 185 ppm.

To 50 parts by mass of this nickel powder, 5 parts by mass of ethyl cellulose, 60 parts by mass of mineral spirits and 35 parts by mass of butyl carbitol were added and kneaded with a three-roll to form a paste, and this conductive paste was used to form a dielectric layer. A capacitor having a thickness of 2 μm, an internal electrode layer thickness of 1.5 μm, and a stacking number of 350 layers and a size of 2.0 × 1.25 × 1.25 mm was fired. The 200 ceramic capacitors obtained were examined for defects. As a result, the number of defective products having electrical characteristics such as poor insulation and poor dielectric properties was 2, and the defective rate was 1%.

Comparative Example 1 100 L of an aqueous solution having a sodium hydroxide concentration of 200 g / L
44.8 kg of nickel sulfate hexahydrate (grade 22.
(2% by mass) was dissolved in 80 L of pure water, and the solution was slowly added dropwise while maintaining the liquid temperature at 50 ° C. to precipitate nickel hydroxide. While maintaining the liquid temperature at 50 ° C., 42 kg of hydrazine monohydrate was added to this slurry over 20 minutes to reduce nickel hydroxide to nickel, and the resulting nickel powder was purified with pure water to adjust the pH of the cleaning liquid. Was washed to 9 or less, filtered, and dried to obtain nickel powder.

This nickel powder was observed with a SEM of 10,000 times, and the particle diameters of 1500 particles in a total of 5 fields randomly selected were measured. As a result, the average particle diameter was 0.61 μm and 0.73 μm (0.61 × 1.
The number of particles having a particle size exceeding 2 = 0.732) is 1
33, 0.49 μm (0.61 × 0.8 = 0.
The number of particles having a particle size of less than 488) was 85.

Further, 0.1 g of this nickel powder was added to 0.1%.
After mixing with an SN Dispersant 5468 aqueous solution (manufactured by San Nopco) and dispersing with an ultrasonic homogenizer (manufactured by Nippon Seiki Seisakusho, US-300T) for 5 minutes, a laser diffraction scattering particle size distribution analyzer Micro Trac HRA 9320-X1
As a result of determining the particle size (D ₅₀ ) and the maximum particle size (D _max ) corresponding to 50% of the under-sieve cumulative distribution of the particle size distribution obtained by measuring the volume distribution using a 00 type (manufactured by Leeds + Northrup), D
₅₀ was 1.10 μm and D _max was 6.27 μm, so D _max / D ₅₀ was 5.7.

Further, the total concentration of sodium and potassium is 380 ppm, the total concentration of magnesium and calcium is 168 ppm, and the sulfur concentration is 79 ppm.
The chlorine concentration is 8 ppm, and the total transition metal concentration in the 4th period of the periodic table of elements excluding nickel is 101 pp.
m, and the total amount of these impurities was 736 ppm.

To 50 parts by mass of this nickel powder, 5 parts by mass of ethyl cellulose, 60 parts by mass of mineral spirit and 35 parts by mass of butyl carbitol were added and kneaded with a three-roll to form a paste. Using this conductive paste, a dielectric layer was formed. A capacitor having a thickness of 2 μm, an internal electrode layer thickness of 1.5 μm, and a stacking number of 350 layers and a size of 2.0 × 1.25 × 1.25 mm was fired. The 200 ceramic capacitors obtained were examined for defects. As a result, the number of defective products having electrical characteristics such as poor insulation and poor dielectric properties is 12, and the defective rate is 6%.
Met.

Comparative Example 2 An aqueous solution obtained by dissolving 44.8 kg of nickel sulfate hexahydrate (quality 22.2% by mass) in 80 L of pure water was added to 100 L of an aqueous solution having a sodium hydroxide concentration of 200 g / L to obtain a liquid temperature. 5
While maintaining the temperature at 0 ° C, the solution was slowly added dropwise to precipitate nickel hydroxide. While maintaining the liquid temperature at 50 ° C., 42 kg of hydrazine monohydrate was added to this slurry over 20 minutes to reduce nickel hydroxide to nickel, and the resulting nickel powder was purified with pure water to adjust the pH of the cleaning liquid. Was washed to 9 or less, filtered, and dried, and then put into a Parverizer AP-1SH type (manufactured by Hosokawa Micron) equipped with a knife-type hammer, and pulverized at a rotation speed of 2500 rpm to obtain nickel powder. .

This nickel powder was observed with a SEM of 10,000 times, and the particle diameters of 1500 particles in a total of 5 fields randomly selected were measured. As a result, the average particle diameter was 0.59 μm and 0.70 μm (0.59 × 1.
The number of particles having a particle size exceeding 2 = 0.708) is 9
9 pieces, 0.48 μm (0.59 × 0.8 = 0.4
The number of particles having a particle size smaller than 72) was 78.

0.1 g of this nickel powder was added to 0.1%.
After mixing with an SN Dispersant 5468 aqueous solution (manufactured by San Nopco) and dispersing with an ultrasonic homogenizer (manufactured by Nippon Seiki Seisakusho, US-300T) for 5 minutes, a laser diffraction scattering particle size distribution analyzer Micro Trac HRA 9320-X1
As a result of determining the particle size (D ₅₀ ) and the maximum particle size (D _max ) corresponding to 50% of the under-sieve cumulative distribution of the particle size distribution obtained by measuring the volume distribution using a 00 type (manufactured by Leeds + Northrup), D
₅₀ was 0.88 μm and D _max was 2.75 μm, so D _max / D ₅₀ was 3.1.

Further, the total concentration of sodium and potassium is 350 ppm, the total concentration of magnesium and calcium is 150 ppm, and the sulfur concentration is 72 ppm.
The chlorine concentration is 11 ppm, and the total transition metal concentration in the 4th period of the periodic table of elements excluding nickel is 66 pp.
m, and the total amount of these impurities was 649 ppm.

To 50 parts by mass of this nickel powder, 5 parts by mass of ethyl cellulose, 60 parts by mass of mineral spirit and 35 parts by mass of butyl carbitol were added and kneaded with a three-roll to form a paste, and this conductive paste was used to form a dielectric layer. A capacitor having a thickness of 2 μm, an internal electrode layer thickness of 1.5 μm, and a stacking number of 350 layers and a size of 2.0 × 1.25 × 1.25 mm was fired. The 200 ceramic capacitors obtained were examined for defects. As a result, the number of defective products having electrical characteristics such as poor insulation and poor dielectric properties is 7, and the defective rate is 3.5.
%Met.

[0056]

INDUSTRIAL APPLICABILITY The nickel powder of the present invention has a narrow particle size distribution and contains impurities such as alkali metals, alkaline earth metals, transition metals of the 4th period of the periodic table of elements (excluding nickel), sulfur and chlorine. Since it is a small amount of nickel powder, it can be used for various purposes, especially when it is used to form the internal electrodes of a monolithic ceramic capacitor, it can be made thin and have high capacity without unnecessarily reducing the particle size of the nickel powder. It is possible to reduce the generation of defective products.

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yoshiharu Toyoshima 1-1-1 Hikoshima Nishiyamamachi, Shimonoseki City, Yamaguchi Prefecture Mitsui Mining & Smelting Co., Ltd. (56) Reference JP-A-11-152507 (JP, A) ) JP-A-11-302709 (JP, A) JP-A-63-274706 (JP, A) JP-A-60-238406 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) B22F 9 / 24,1 / 00 H01B 5 / 00,1 / 00

Claims (3)

(57) [Claims] 1. A hydrazine-based reducing agent is prepared by adding an aqueous solution of a nickel salt containing a nickel complex to an aqueous solution of an alkali metal hydroxide, and producing a slurry containing the nickel hydroxide produced at a temperature of 55 ° C. or higher. And a method for producing nickel powder, which comprises reducing the nickel hydroxide by contacting with nickel. 2. A nickel salt aqueous solution containing a nickel complex is obtained by producing an aqueous solution containing a nickel salt and a water-soluble compound having a carboxyl group and / or an amino group. The manufacturing method according to claim 1. 3. The production method according to claim 1, wherein the nickel powder obtained after the reduction reaction is pulverized to obtain a monodisperse powder.