JP5835077B2 - Nickel powder and method for producing the same - Google Patents

Description

  The present invention relates to a nickel powder having a small particle size suitable as an internal electrode material of a multilayer ceramic capacitor and a method for producing the same.

  Conventionally, nickel powder has been used as a material for a conductive paste for producing a thick film conductor. Thick film conductors are used not only for the formation of electric circuits, but also for electrodes of multilayer ceramic components such as multilayer ceramic capacitors and multilayer ceramic substrates. Especially in multilayer ceramic capacitors, the use of conductive paste has increased significantly due to the demand for smaller size and higher capacity, and the amount of conductive paste used has increased significantly. Therefore, avoid the use of expensive precious metals as the metal powder used in conductive paste. Inexpensive base metals such as nickel are the mainstream.

  The multilayer ceramic capacitor has a structure in which external electrodes are provided at both ends of a ceramic multilayer body in which internal electrode layers and dielectric layers are alternately stacked, and is manufactured, for example, by the following method. That is, nickel powder, a resin such as ethyl cellulose, and an organic solvent such as terpineol are kneaded, the obtained conductive paste is screen-printed on the dielectric green sheet, and the dielectric green sheet is overlaid thereon. This operation is repeated, and a plurality of dielectric green sheets and conductive pastes are alternately stacked, and after pressure bonding, cut into a predetermined size.

  Next, the obtained laminate is subjected to a binder removal treatment, and then fired at a high temperature up to 1300 ° C. to form a ceramic laminate in which internal electrode layers and dielectric layers are alternately stacked. A ceramic capacitor is obtained. Here, since the base powder such as nickel is more prevalent than the precious metal as the metal powder in the conductive paste to be the internal electrode, the binder removal treatment of the laminate does not oxidize the nickel powder or the like. Thus, it is performed in an atmosphere containing a very small amount of oxygen.

  In recent years, multilayer ceramic capacitors have been reduced in size and capacity. To increase the capacity, it is necessary to increase the number of stacked dielectric layers and internal electrode layers. However, increasing the number of stacked layers increases the size of the capacitor and makes it difficult to reduce the size. For this reason, miniaturization and high capacity are being promoted by thinning the layer thickness per layer. For example, the thickness of the internal electrode has decreased from the conventional several μm to about 1 to 3 μm, and a thickness of 1 μm or less has appeared.

  However, when reducing the size and increasing the capacity of the multilayer ceramic capacitor by reducing the thickness, if the nickel powder used as the internal electrode material contains coarse particles, the coarse particles break through the dielectric layer and other internal electrode layers There is a possibility that a sufficient capacity cannot be obtained. For this reason, spherical nickel powder having a small average particle diameter and high monodispersibility is required as an internal electrode material of the multilayer ceramic capacitor, and many proposals have been made to meet this demand.

  For example, in Patent Document 1, in a method of producing nickel powder by reducing an aqueous nickel salt solution with hydrazine, an aqueous solution containing 5-5000 ppm of palladium with respect to nickel and an aqueous nickel salt solution are added to an alkaline hydrazine aqueous solution. A method of maintaining the reaction temperature at 50 to 90 ° C. has been proposed. In this method, palladium is used as a catalyst for promoting reduction, and since palladium acts as a nucleus for nickel particle precipitation, nickel powder having a small average particle diameter can be obtained. However, when palladium, which is the nucleus, aggregates, nickel grows around the aggregated nucleus and single particles are interconnected or single coarse particles are generated. It has not yet been suppressed.

  In Patent Document 2, a colloidal solution in which colloidal particles of palladium and silver are dispersed, a reducing agent, and an alkaline substance are mixed to prepare an alkaline colloidal solution, and an aqueous nickel salt solution is added to the alkaline colloidal solution. And the manufacturing method of the nickel powder which produces | generates nickel particle is proposed. According to this method, aggregation of colloidal particles serving as nuclei is suppressed, so that the coarsening of precipitated nickel particles is suppressed. However, although the generation of coarse particles due to aggregation of composite colloidal particles acting as a catalyst can be suppressed, the generation of coarse particles in nickel powder is not sufficiently suppressed.

JP 2004-332055 A JP 2007-138291 A

  The present invention has been made in view of the above-described problems of the prior art, and has a small particle size suitable as an internal electrode material for thick film conductors, particularly multilayer ceramic capacitors corresponding to miniaturization and high capacity. An object of the present invention is to provide nickel powder with sufficiently small coarse particles and a method for producing the same.

  In order to achieve the above object, the present inventors have conducted extensive research on the suppression of the formation of coarse particles in nickel powder, and as a result, coarse solid particles contained in the raw material solution used for the production of nickel powder by wet reduction, The knowledge that it is a big cause which produces the coarse particle of nickel powder was acquired. Further, the present invention has been completed by obtaining further knowledge that coarse solid particles are insoluble and can be easily removed by filtering the solution solution.

That is, the method for producing nickel powder according to the present invention uses a nickel salt aqueous solution, a reducing agent solution, and an alkaline solution as raw material solutions, and reduces the nickel salt in a reaction solution in which these are mixed, so that the average particle size is 0.05 to 0.05. Nickel particles having a particle diameter of more than 1 μm, which is 0.3 μm, and is photographed with 100 fields of view of a 19.2 μm vertical × 25.6 μm visual field at a magnification of 5000 using a scanning electron microscope In the nickel powder manufacturing method for obtaining nickel powder having a total number of 10 or less, the nickel concentration in the reaction solution is 2 to 10 g / l, and the particle diameter is 1 μm as a nickel salt aqueous solution, a reducing agent solution and an alkaline solution. It is characterized by using a material from which excess solid particles have been removed.

  In the method for producing nickel powder according to the present invention, the reducing agent solution and the alkali solution are added to a colloidal solution in which colloidal particles of palladium and silver are dispersed to form an alkaline colloidal solution, and then the alkaline colloidal solution is added to the nickel colloidal solution. Can be mixed with an aqueous salt solution. In this case, it is preferable to use the alkaline colloid solution from which solid particles having a particle diameter of more than 1 μm have been removed.

  In the method for producing nickel powder according to the present invention, gelatin is preferably added to the colloid solution as a protective colloid agent. When gelatin is added, it is preferable to use gelatin as a solution when preparing the colloidal solution, and remove solid particles having a particle size of more than 1 μm from the gelatin solution.

  In the method for producing nickel powder according to the present invention, the solid particles are preferably removed by filtration using a filter. The pore diameter of the filter used at that time is preferably 0.05 to 0.8 μm, and more preferably 0.05 to 0.5 μm. The nickel concentration in the reaction solution is more preferably 2 to 6 g / l.

  The nickel powder provided by the present invention has an average particle diameter of 0.05 to 0.3 μm, and a field of view of 19.2 μm × 25.6 μm was photographed at 100 magnifications at a magnification of 5000 using a scanning electron microscope. In this case, the total number of nickel particles having a particle diameter exceeding 1 μm detected in a photograph of 100 fields of view is 10 or less. The total number of nickel particles having a particle size exceeding 1 μm is preferably 5 or less.

  In the present invention, the “particle diameter” is determined by measuring the maximum length of the particles by observation with a scanning electron microscope or an optical microscope. The “average particle size” is the number average of the measured particle sizes.

  According to the present invention, nickel having a small average particle diameter of 0.05 to 0.3 μm and very few coarse particles (including connected particles) having a particle diameter exceeding 1 μm are suitable as a material for thick film conductors. Powders can be manufactured and provided easily and on a mass production scale. In particular, if the nickel powder of the present invention is used as the internal electrode material of a multilayer ceramic capacitor that is becoming thinner, it can prevent short-circuiting between internal electrode layers. can do.

  In the course of research related to the suppression of the formation of coarse particles of nickel powder, the present inventors have observed solid particles by direct spectroscopic method for the raw material solution used for the production of nickel powder by the wet reduction method. The solid particles were observed by filtering the raw material solution using a filter having a pore size of 0.2 μm, staining the solid particles captured on the filter, and observing them under an optical microscope. In the wet reduction method of nickel powder, a nickel salt aqueous solution, a reducing agent solution, an alkaline solution, and a diluting solvent (pure water) are generally used as a raw material solution.

  Therefore, 1 ml each of nickel chloride aqueous solution, hydrazine hydrate aqueous solution, sodium hydroxide aqueous solution, and pure water was filtered through a 0.2 μm pore size filter, and the solid particles remaining on the filter were counted. About 10000 solid particles were confirmed, about 1000 hydrazine hydrate aqueous solution, about 600 solid hydroxide aqueous solution, and about 2000 solid water pure water. The size of the observed solid particles was mostly about 5 to 100 μm in any raw material solution.

  Next, in order to remove the solid particles contained in the raw material solution, each raw material solution is filtered through a cartridge filter having a pore size of 0.1 μm, and then the solid particles remaining in the filtrate are observed and the number of particles is measured. Was performed in the same manner as described above. As a result, about 20 solid particles remaining in the filtrate were confirmed for the nickel chloride aqueous solution, about 300 for the sodium hydroxide aqueous solution, about 20 for the hydrazine hydrate aqueous solution, and about 200 for pure water. It was. Moreover, it was confirmed that all the sizes of the observed solid particles were about 1 μm or less, and it was confirmed that both the number and size of the particles were significantly reduced as compared with those before filtration.

  That is, from the observation result of the solid particles in each raw material solution described above, the coarse nickel particles contained in the nickel powder obtained by the conventional method are converted into the nickel salt aqueous solution, the reducing agent solution, and the alkaline solution that are the raw material solution. It has come to the knowledge that it is produced by growing the coarse solid particles contained therein as a nucleus.

  The method for producing nickel powder according to the present invention has been made based on the above knowledge. A nickel salt aqueous solution, a reducing agent solution, and an alkaline solution are used as raw material solutions, and the nickel salt is reduced in a reaction solution obtained by mixing them. When obtaining nickel powder, one of the major features is to use a raw material solution from which solid particles having a particle diameter of more than 1 μm are removed. As a result, it is possible to prevent nickel particles from being generated using solid particles having a particle diameter of more than 1 μm as nuclei, and to significantly reduce the generation of coarse nickel particles having a particle diameter of more than 1 μm.

  Incidentally, as the reducing agent and the alkaline substance, solids may be used in the conventional method, but in the present invention, a reducing agent solution and an alkaline solution are used, and solid particles having a particle diameter of more than 1 μm are removed. Use it. That is, insoluble solid particles having a particle diameter of more than 1 μm may be removed from each raw material solution before the nickel particles are reduced and precipitated from the nickel salt in the reaction solution in which the raw material solutions are mixed.

  In the nickel powder production method of the present invention, in order to further suppress the coarsening of nickel particles and to reliably obtain nickel powder having a small average particle size, colloidal particles of palladium (Pd) and silver (Ag) are used. A method of adding a reducing agent solution and an alkaline solution to the dispersed colloidal solution to form an alkaline colloidal solution and mixing the alkaline colloidal solution with a nickel salt aqueous solution is preferable. In addition, about the manufacturing method itself of nickel powder using the said alkaline colloid solution, a well-known method can be used, for example, the method and conditions disclosed by the said patent document 2 are employable.

  In the present invention, even in the method of producing nickel powder using the alkaline colloid solution, solid particles having a particle size of more than 1 μm are removed from the alkaline colloid solution before mixing the alkaline colloid solution with the nickel salt aqueous solution. By preserving it, coarse particles can be further reduced. In addition, it is natural to use a reducing agent solution, an alkali solution, and a nickel salt aqueous solution, which are raw material solutions used for producing an alkaline colloidal solution, from which solid particles having a particle size exceeding 1 μm have been removed. By this method, nickel particles having a particle size in the nickel powder exceeding 1 μm can be further reduced.

  When the alkaline colloidal solution is used, it is preferable to disperse the colloidal particles of palladium and silver by adding gelatin as a protective colloid agent when preparing the colloidal solution. By adding gelatin, the aggregation of colloidal particles can be suppressed, so that the generation of nickel particles having a particle size exceeding 1 μm with the aggregated colloidal particles as a nucleus can be further reduced.

  In the case of adding gelatin, it is preferable to make gelatin into a gelatin solution before the addition, and to remove solid particles having a particle size exceeding 1 μm from the gelatin solution. Solid particles may be removed after preparing the alkaline colloid solution as described above. However, when gelatin is added, colloidal particles having fine and good dispersibility can be obtained, so the solid particles in the alkaline colloid solution are obtained. Many are derived from gelatin. Therefore, it is preferable to remove the solid particles from the gelatin solution after making the gelatin into a gelatin solution. In addition to gelatin, it is preferable to use a palladium solution and a silver solution, a solvent, a reducing agent, and the like used for preparing a colloidal solution from which solid particles are removed.

  In the present invention, the particle size in the nickel powder obtained by removing solid particles having a particle size of more than 1 μm from each raw material solution as described above or from the alkaline colloid solution prepared using each raw material solution. Coarse nickel particles exceeding 1 μm can be greatly reduced. More preferably, by removing solid particles having a particle size exceeding 0.5 μm, coarse nickel particles having a particle size exceeding 1 μm can be more reliably reduced. Coarse nickel particles having a particle size exceeding 1 μm are reduced in this way because solid particles having a particle size exceeding 1 μm or 0.5 μm are removed, so that nickel during reduction adheres to the solid particles. This is because the growth due to is suppressed.

  The removal of the solid particles from each raw material solution described above can also be achieved by using a raw material solution that does not contain a component that becomes a solid particle, but the solid particles are filtered by filtering the raw material solution in a solution state with a filter. The removal method is preferable because it is simple and easy. The filtration method using a filter may be a generally used method. For example, the raw material solution may be filtered by passing through a cartridge type filter. Although an ultrafiltration membrane can be used, it is excessive because it collects even particles having a very small particle diameter, resulting in an increase in cost. The material of the filter is not particularly limited, but it is preferable to use a fluororesin material such as PTFE in order to suppress the elution of impurities from the filter.

  As the filter, it is preferable to use a filter having a pore diameter of 0.05 to 0.8 μm. As described above, in order to remove solid particles having a particle diameter exceeding 1 μm, the upper limit of the filter pore diameter needs to be 1 μm or less. In order to ensure removal, the upper limit of the pore size of the filter is preferably 0.8 μm. In addition, when removing solid particles having a particle size exceeding 0.5 μm, the upper limit of the filter pore size is preferably set to 0.5 μm. From the viewpoint of removing solid particles, the smaller the pore diameter, the better. However, if the pore diameter is too small, filtration becomes difficult and the cost increases. Therefore, the lower limit of the filter pore size is preferably 0.05 μm from the standpoint of collecting solid particles and ease of filtration.

  In the present invention, in order to suppress the formation of nickel particles having a particle size exceeding 1 μm, the raw material solution from which the solid particles having a particle size exceeding 1 μm are removed is used, and the nickel concentration in the reaction solution is set to 2 to 2. The range is 10 g / l. This is because when the nickel concentration exceeds 10 g / l, aggregation occurs between the nickel particles, so that it is difficult to suppress the generation of nickel particles having a particle size exceeding 1 μm. On the other hand, if the nickel concentration is less than 2 g / l, the number of nickel particles in the reaction solution becomes too small, which not only decreases productivity but also increases costs for wastewater treatment and the like. The nickel concentration in the reaction solution is particularly preferably in the range of 2 to 6 g / l.

  Next, conditions etc. are demonstrated in detail about the manufacturing method of the nickel powder of this invention. First, the nickel powder production method of the present invention is a method of mixing a nickel salt aqueous solution, a reducing agent solution and an alkaline solution, and reducing the nickel salt in the reaction solution to obtain nickel powder. A known technique can be basically used except that the raw material solution from which solid particles exceeding 1 μm are removed is used. In addition, as a nickel powder production apparatus, a nickel powder production apparatus by a normal wet reduction method, for example, a reaction apparatus with a stirring means and a temperature control means can be used.

  As the nickel salt aqueous solution, for example, an aqueous solution containing at least one kind of nickel salt selected from nickel chloride, nickel nitrate, nickel sulfate and the like can be used. Among these aqueous solutions, an aqueous nickel chloride solution that can be easily treated with water is particularly preferable. The alkaline substance used in the alkaline solution is not particularly limited, and may be any water-soluble alkaline substance such as sodium hydroxide, potassium hydroxide, ammonia, etc. Among them, wastewater treatment is easy. Sodium hydroxide is preferred.

Regarding the reducing agent solution, the reducing agent to be used is not particularly limited. For example, it is preferable to use at least one selected from hydrazine (N ₂ H ₄ ), a hydrazine compound, sodium borohydride and the like. Among these reducing agent solutions, it is more preferable to use a hydrazine aqueous solution using a water-soluble hydrazine compound. Of the water-soluble hydrazine compounds, hydrazine and hydrazine hydrate are particularly preferable in terms of few impurities.

  The pH of the reaction solution obtained by mixing the nickel salt aqueous solution, the reducing agent solution, and the alkali solution is preferably adjusted to 10 or more. When the pH of the reaction solution is less than 10, the reaction rate becomes slow, so that nickel reduction precipitation is difficult to occur. Moreover, as reaction temperature at the time of a reduction | restoration, 50-90 degreeC is preferable and 60-80 degreeC is still more preferable. When the reaction temperature is less than 50 ° C., the reduction and precipitation of nickel is difficult to proceed, the shape of the obtained nickel powder becomes indefinite, and the particle size distribution width may be widened. On the other hand, if the reaction temperature exceeds 90 ° C., the decomposition of hydrazine proceeds too much, so that the amount added needs to be increased, which is not economical.

  According to the above-described method for producing nickel powder of the present invention, the average particle diameter is 0.05 to 0.3 μm, and at the same time, a field of view of 19.2 μm in length × 25.6 μm in width is magnified 5000 times using a scanning electron microscope. When 100 fields of view are photographed, a nickel powder in which the total number of nickel particles having a particle diameter exceeding 1 μm detected in the 100 fields of view is reduced to 10 or less, more preferably 5 or less, can be obtained.

[Example 1]
As a raw material solution, a nickel chloride aqueous solution having a nickel concentration of 100 g / l, a 60% by mass hydrazine aqueous solution, and a sodium hydroxide aqueous solution having a sodium concentration of 210 g / l were prepared. Each of these raw material solutions was filtered using a PTFE cartridge filter (ADVANTEC) having a filter pore size of 0.1 μm.

  Further, 0.05 g of gelatin is dissolved in pure water to prepare a gelatin solution, and 0.1 g of a 60 mass% hydrazine aqueous solution is mixed with the gelatin solution, and then a colloidal solution containing 0.0025 g of palladium and 0.0000 g of silver. Was dropped into a composite colloidal solution. The obtained composite colloidal solution was filtered using a filter having a filter pore size of 0.2 μm.

  After each raw material solution and the composite colloid solution were filtered as described above, the solid particles captured on the filter were each stained, and the solid particles were observed with an optical microscope. As a result, it was confirmed that none of the solid particles captured on the filter had a particle size exceeding 1 μm.

  Next, the composite colloidal solution was diluted to 6 liters with water, placed in a beaker, and heated to 75 ° C. with stirring in a thermostatic bath. Thereafter, 135 ml of the sodium hydroxide aqueous solution was added to the diluted composite colloid solution, and then 185 ml of the hydrazine aqueous solution was added to obtain an alkaline colloid solution for reducing nickel. The content of palladium, silver and gelatin in the alkaline colloidal solution is 50 mass ppm of palladium, 0.5 mass ppm of silver and 1000 mass ppm of gelatin with respect to the mass of nickel in the aqueous nickel salt solution to be mixed. . In addition, the said water used what was filtered similarly to each raw material solution, and it was confirmed that there is no thing exceeding a particle size of 1 micrometer after filtration.

  Next, 500 ml of the nickel chloride aqueous solution was dropped into the alkaline colloidal solution to reduce and precipitate nickel particles. The nickel concentration in the reaction solution at this time is 7.3 g / l. After the reduction reaction, solid-liquid separation was performed to recover nickel powder, which was then washed with water and dried.

  About the obtained nickel powder, a scanning electron microscope (trade name JSM-5510, manufactured by JEOL Ltd.) was used to photograph 100 fields of view of 19.2 μm in length and 25.6 μm in width at a magnification of 5000 times. The entire range of each photograph taken with 100 fields of view was observed, and the number of coarse nickel particles having a particle size exceeding 1 μm was measured. Regarding the diameter of the connected particles, the maximum diameter of each particle was regarded as the diameter. The obtained measurement results are shown in Table 1 below together with the presence or absence of the filter filtration for the gelatin solution, the composite colloid solution, and the raw material solution.

[Example 2]
The nickel powder was produced in the same manner as in Example 1 except that the gelatin solution was filtered without filtering the composite colloidal solution, and the number of coarse nickel particles having a particle size exceeding 1 μm in the obtained nickel powder was determined. The measurement results are shown in Table 1 below.

[Example 3]
Except that the composite colloidal solution was not filtered, nickel powder was produced in the same manner as in Example 1, and the number of coarse nickel particles having a particle diameter exceeding 1 μm in the obtained nickel powder was measured. The measurement results are shown in Table 1 below.

[Example 4]
A nickel powder was produced in the same manner as in Example 1 except that the composite colloidal solution was not filtered and 350 ml of a nickel chloride aqueous solution was added dropwise so that the nickel concentration in the reaction solution was 5.3 g / l. The number of coarse nickel particles having a particle diameter exceeding 1 μm in the obtained nickel powder was measured, and the measurement results are shown in Table 1 below.

[Example 5]
Nickel powder was produced in the same manner as in Example 1 except that the composite colloidal solution was not filtered and 250 ml of a nickel chloride aqueous solution was added dropwise so that the nickel concentration in the reaction solution was 3.6 g / l. The number of coarse nickel particles having a particle diameter exceeding 1 μm in the obtained nickel powder was measured, and the measurement results are shown in Table 1 below.

[Comparative Example 1]
Except that no filtration by a filter was performed, nickel powder was produced in the same manner as in Example 1, and the number of coarse nickel particles having a particle diameter exceeding 1 μm in the obtained nickel powder was measured. The measurement results are shown in Table 1 below.

[Comparative Example 2]
A nickel powder was produced in the same manner as in Example 1 except that no filtration through a filter was performed and 250 ml of a nickel chloride aqueous solution was added dropwise so that the nickel concentration in the reaction solution was 3.6 g / l. The number of coarse nickel particles having a particle diameter exceeding 1 μm in the obtained nickel powder was measured, and the measurement results are shown in Table 1 below.

  As can be seen from the results in Table 1 above, in Comparative Examples 1 and 2 in which the raw material solution was not filtered at all by the filter, regardless of the nickel concentration in the reaction solution, The number of coarse nickel particles having a detected particle size exceeding 1 μm both exceeds 10.

  On the other hand, in Examples 1 to 5 in which the raw material solution was filtered according to the present invention, the number of coarse nickel particles having a particle size exceeding 1 μm detected in 100-view photographs with a scanning electron microscope was 10 or less, and the above comparison Compared to Examples 1 and 2, it was confirmed that the nickel powder had very few coarse particles.

  In particular, Example 1 in which the composite colloid solution was filtered with the raw material solution, Example 2 in which the gelatin solution was filtered with the raw material solution, and the gelatin solution and the composite colloid solution were not filtered, but the nickel concentration in the reaction solution was 6 g / l or less. In Examples 4 and 5, the number of coarse nickel particles having a particle size exceeding 1 μm was 5 or less, and it was confirmed that the nickel particles had very few coarse particles.

Claims (10)

  A nickel salt aqueous solution, a reducing agent solution, and an alkaline solution are used as raw material solutions, and the nickel salt is reduced in a reaction solution in which these are mixed. The average particle size is 0.05 to 0.3 μm, and a scanning electron microscope is used. When a field of view of 19.2 μm in length and 25.6 μm in width is taken with 100 magnifications at a magnification of 5000, nickel powder having a total number of nickel particles exceeding 1 μm in particle size detected in 100 fields of view is obtained. In the method for producing nickel powder, the nickel concentration in the reaction solution is set to 2 to 10 g / l, and the nickel salt aqueous solution, the reducing agent solution, and the alkaline solution from which solid particles having a particle diameter exceeding 1 μm are removed are used. A method for producing nickel powder characterized by the above.   The colloidal solution in which palladium and silver colloidal particles are dispersed is added with the reducing agent solution and the alkaline solution to obtain an alkaline colloidal solution, and then the alkaline colloidal solution is mixed with the aqueous nickel salt solution. Item 2. A method for producing nickel powder according to Item 1.   3. The method for producing nickel powder according to claim 2, wherein the alkaline colloid solution is one from which solid particles having a particle diameter of more than 1 [mu] m have been removed.   The method for producing nickel powder according to claim 2, wherein gelatin is added to the colloid solution as a protective colloid agent.   The method for producing nickel powder according to claim 4, wherein gelatin is used as a solution when the colloidal solution is prepared, and solid particles having a particle size exceeding 1 µm are removed from the gelatin solution.   The nickel powder solution according to any one of claims 1 to 5, wherein the nickel salt aqueous solution, the reducing agent solution, and the alkaline solution are prepared by removing solid particles having a particle size of more than 0.5 µm. Production method.   The method for producing nickel powder according to any one of claims 1 to 6, wherein the solid particles are removed by filtration using a filter.   The method for producing nickel powder according to claim 7, wherein the pore diameter of the filter is 0.05 to 0.8 μm.   The method for producing nickel powder according to claim 7 or 8, wherein the filter has a pore diameter of 0.05 to 0.5 µm. The nickel concentration in the said reaction liquid shall be 2-6 g / l, The manufacturing method of the nickel powder in any one of Claims 1-9 characterized by the above-mentioned.