JP2012036440A - Method of manufacturing niobium powder, and method of manufacturing niobium monoxide powder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing a niobium powder to obtain the niobium monoxide powder having a powder resistance (electric conductivity) suitable for a capacitor.SOLUTION: The method of manufacturing the niobium powder by reducing a niobium oxide with a high oxidation number includes: a primary reduction process of mixing the niobium oxide with the high oxidation number and a grain growth inhibitor inhibiting a bonding between grains produced by a reduction reaction, performing a reduction using a base metal as a reducing agent, and removing the grain growth inhibitor to produce a primary reduced niobium powder; and a secondary reduction process of mixing the primary reduction niobium powder and the grain growth inhibitor, performing a reduction using a base metal as a reducing agent, and removing the grain growth inhibitor to produce a secondary reduction niobium powder.

Description

  The present invention relates to a method for producing niobium powder and niobium monoxide powder by reduction treatment, and particularly relates to a method for producing niobium powder for obtaining niobium monoxide powder having powder resistance (conductivity) suitable for a capacitor. .

  In recent years, the amount of niobium oxide used as a raw material for electronic parts such as frequency filters and capacitors, a target material for sputtering, and the like is rapidly increasing. In addition, niobium capacitors have become widespread as new types of capacitors, and niobium powder and niobium monoxide powder (NbO) are used as the raw material. A niobium capacitor has a feature that it can realize a small size and a large capacity, and has excellent electrical stability and high reliability.

  Various manufacturing methods have been proposed for such niobium powder and niobium monoxide powder for use in capacitors (see Patent Documents 1 to 5).

In Patent Document 1, at least a sintering step and a crushing step are sequentially performed using a mixture of niobium powder obtained by various production methods and an activator (pore forming agent) as a raw material, and then a sintering step or a crushing step. There has been proposed a method for producing niobium powder for a capacitor by removing the activator in any of the steps. According to this prior art, it is possible to average particle diameter D _{50 (50%} diameter in cumulative fraction of the volume reference in the laser diffraction scattering method particle size distribution) to produce a niobium powder 10 to 1000 [mu] m.

In Patent Documents 2 and 3, niobium powder obtained by reducing niobium pentoxide powder (Nb ₂ O ₅ ) with an alkaline earth metal or rare earth metal is further reduced to produce niobium powder. A so-called two-stage reduction process manufacturing method has been proposed. The niobium powder having an average particle diameter D50 of ₁₀₀ to 300 μm can also be produced by this two-stage reduction treatment.

In Patent Document 4, niobium dioxide powder (NbO ₂ ) obtained by reducing niobium pentoxide powder (Nb ₂ O ₅ ) with hydrogen (H ₂ ) is reduced with magnesium (Mg) and niobium. A production method for obtaining powder has been proposed. According to the production method of Patent Document 4, niobium powder having an average particle diameter D50 of ₂₀ to 250 μm can be produced.

According to these prior arts, although niobium powder as a raw material suitable for capacitor use can be produced, when producing niobium monoxide powder using these niobium powders, for example, in Patent Document 5, Niobium monoxide powder is reacted with niobium dioxide powder obtained by reducing niobium pentoxide powder in a hydrogen-containing atmosphere because the method of reacting niobium pentoxide powder with niobium powder is not suitable. A method for producing flour has been proposed. This method, excellent fluidity, the average particle diameter D ₅₀ can be produced niobium monoxide powder of about 200 [mu] m. As in Patent Document 5, when niobium pentoxide powder or niobium dioxide powder is brought into contact with a niobium powder to cause a chemical reaction, it is based on a so-called solid-phase reaction. It is important that the particle diameters of these are close. When niobium powder having the average particle size of secondary particles as shown in Patent Documents 1 to 4 is used, the mixed state of niobium oxide powder and niobium powder is uniform due to the difference in particle size distribution of the secondary particle size. Therefore, it tends to be difficult to produce niobium monoxide powder having a uniform particle size.

  Moreover, although the niobium powder as a primary particle produced | generated at the time of manufacture in patent document 1 is fine, since the secondary particle (aggregated particle) is formed, a grinding | pulverization process is required for refinement | miniaturization. . However, when the pulverization process is performed, the niobium powder may be deformed in particle shape or mixed with impurities, and a niobium powder manufacturing technique that does not require the pulverization process is also required. And about the niobium powder obtained by the conventional prior art, the powder resistance which affects a capacitor characteristic is not examined especially.

Japanese Patent No. 410868 Japanese Patent No. 4384011 Patent No. 4202609 JP 2008-274443 A Japanese Patent No. 4317091

The present invention has been made in the background as described above, and by improving the conventional method for producing niobium powder by reduction treatment, a finer niobium powder can be realized without the need for a pulverization step. manufacturing method, specifically, aims to provide a manufacturing technique having an average particle production method of niobium powder which diameter D ₅₀ can be realized niobium powder such that less than 10 [mu] m, and smaller niobium monoxide powder powder resistance And

  In order to solve the above-mentioned problems, the present inventor has conducted intensive studies on a conventionally proposed method for producing niobium powder by a two-stage reduction process. The inventors have found that fine niobium powder can be produced by suppressing the binding, and that niobium monoxide powder having a low powder resistance can also be produced, and the present invention has been conceived.

  The present invention relates to a method for producing niobium powder in which niobium powder is produced by reducing high-oxidation number niobium oxide, and a particle growth inhibitor that suppresses bonding between high-oxidation number niobium oxide and particles produced by a reduction reaction. The first reduction treatment for reducing the particle growth inhibitor to produce primary reduced niobium powder, the primary reduced niobium powder, and the particle growth inhibitor. And a second reduction treatment that performs reduction using a base metal as a reducing agent and removes the particle growth inhibitor to produce secondary reduced niobium powder.

The high oxidation number niobium oxide in the present invention is niobium pentoxide (Nb ₂ O ₅ ) or niobium dioxide (NbO ₂ ), and includes an intermediate oxidation number niobium oxide. Specifically, high oxidation number niobium oxides such as Nb ₁₂ O ₂₉ , NbO _1.64 and Nb ₄ O ₅ are also included. The high oxidation number niobium oxide in the present invention is preferably niobium pentoxide (Nb ₂ O ₅ ).

The niobium powder manufacturing method according to the present invention uses a base metal as a reducing agent and performs a two-step reduction treatment, and mixes a particle growth inhibitor that suppresses bonding between particles generated by a reduction reaction during the reduction treatment. To do. In the first reduction treatment, primary reduced niobium powder (niobium powder containing a large amount of oxygen) having an average particle diameter D50 of _0.5 to 2.0 μm is generated. By the primary reductive niobium powder to the second reduction process, it is possible to average particle diameter D ₅₀ to produce secondary reduction niobium powder of less than 10μm (oxygen less niobium powder).

  The removal of the particle growth inhibitor of the present invention can be carried out in accordance with the chemical properties of the particle growth inhibitor, and the removal method is not limited. For example, a method of gasifying and removing the particle growth inhibitor by thermal decomposition or volatilization, or a method of removing the particle growth inhibitor by dissolving it in a solution such as alkali or acid can be adopted. The removal process can be performed by selecting one or a plurality of methods that are easy to remove in consideration of specific characteristics.

  The particle growth inhibitor in the present invention is preferably an alkaline earth metal salt or an alkaline earth metal oxide. This is because an alkaline earth metal salt or an alkaline earth metal oxide has an excellent effect of suppressing the bonding between particles generated by a reduction reaction. Specifically, alkaline earth metal salts (cation species: any of magnesium (Mg), calcium (Ca), strontium (Sr), and barium (Ba)), carbonates, nitrates, sulfates, acetates Oxalate, phosphate, chloride, fluoride and the like. Examples of the oxide include magnesium oxide (MgO), calcium oxide (CaO), strontium oxide (SrO), barium oxide (BaO), and the like.

  The base metal as the reducing agent in the present invention is one or a combination of two or more of lithium (Li), magnesium (Mg), aluminum (Al), calcium (Ca), strontium (Sr), and barium (Ba). Preferably it consists of. In particular, it is more preferable to use magnesium as a reducing agent.

High oxidation number niobium oxide in the present invention preferably has a mean particle diameter _{D 50} is 0.5 to 10 [mu] m, it is desirable that the average particle diameter _{D 50} of the particle growth inhibitor is 1 to 100 [mu] m.

  Mixing the high oxidation number niobium oxide with the particle growth inhibitor can dry-mix both powders without solvent, or wet-dry both powders using a suitable solvent. You can also. As the wet-mixing solvent, both aqueous and non-aqueous (alcohol and hydrocarbon) solvents can be used. Moreover, as a mixer used for mixing, the commercially available apparatus used for normal mixing processes, such as a V-type mixer, a ball mill, a disperser, can be applied. The mixing process and the drying process are performed in an inert atmosphere such as argon or nitrogen. Alternatively, vacuum drying is applied to the drying process.

  The first reduction treatment in the present invention is preferably performed in a temperature range of 800 ° C. to 1100 ° C., and after holding the reduction treatment for 3 hours or more, it is preferable to cool the furnace to room temperature and take out the powder.

  The taken-out powder is preferably put into, for example, an alkali or acid solution to dissolve and remove the base metal oxide contained as a particle growth inhibitor or a reducing agent. Thereafter, it is preferable to perform a drying process or a vacuum drying process in an inert atmosphere such as argon or nitrogen. In this way, primary reduced niobium powder is obtained.

  The second reduction treatment is preferably carried out in the temperature range of 700 ° C. to 1000 ° C. using the obtained primary reduced niobium powder. After holding the reduction treatment time for 3 hours or more, the furnace is cooled to room temperature and powdered Is preferably taken out.

  As in the first reduction treatment, the taken-out powder is preferably introduced into, for example, an alkali or acid solution to dissolve and remove the base metal oxide contained as a particle growth inhibitor or a reducing agent. . Thereafter, it is preferable to perform a drying process or a vacuum drying process in an inert atmosphere such as argon or nitrogen. In this way, secondary reduced niobium powder is obtained.

According to the method for producing niobium powder according to the present invention, the average particle diameter D50 which is a 50% diameter in the volume-based integrated fraction in the laser diffraction / scattering particle diameter distribution is less than 10 μm, preferably 1 μm to ₅ μm. in the particle size D ₉₀ is 90% diameter in cumulative fraction of volume based 50μm or less, preferably it is possible to produce a niobium powder is 30μm or less.

  Using the secondary reduced niobium powder obtained by the niobium powder manufacturing method according to the present invention described above, the secondary reduced niobium powder and the high oxidation number niobium oxide are mixed and subjected to reduction treatment in an atmosphere containing hydrogen. When niobium monoxide powder is produced, it becomes niobium monoxide powder in the form of secondary particles having fine primary particles and voids, which are suitable for capacitor applications. In the prior art, when niobium pentoxide powder and niobium powder are reacted in the presence of hydrogen to produce niobium suboxide powder (niobium monoxide powder), the volume of niobium pentoxide is changed to niobium suboxide. It is known that contraction occurs to cause the niobium oxide powder to become coarse, resulting in niobium oxide powder that is disadvantageous for capacitor characteristics (see, for example, Patent Document 5). However, when secondary reduction niobium powder produced using a particle growth inhibitor such as the present invention and high oxidation number niobium oxide are mixed and subjected to reduction treatment in an atmosphere containing hydrogen, it is suitable for capacitor applications. The niobium monoxide powder in the form of secondary particles having fine primary particles and voids can be produced.

  The niobium monoxide powder obtained by the method for producing niobium monoxide powder according to the present invention is characterized in that the half-value width of the peak of niobium monoxide obtained from powder X-ray diffraction is 0.09 to 0.20 degrees. And Such X-ray characteristics indicate that the crystallinity is very high and the crystal structure is more stabilized, so that the niobium monoxide powder having a low powder resistance is obtained.

Further, the niobium monoxide powder obtained by the niobium monoxide powder manufacturing method according to the present invention has a conductivity of 500 S / cm or more when compressed to a compact density of 3.0 g / cm ³ and pelletized. . Since the niobium monoxide powder in the present invention has a low powder resistance, it is extremely suitable as a capacitor raw material.

NbO powder obtained by the production method of niobium monoxide powder of the present invention, an average particle diameter _{D 50} of 30~200μm, and the specific surface area (BET method) is 0.8 m ² / g or more. Niobium monoxide powder for use in capacitors is required to have powder fluidity and improve capacitor characteristics, but niobium monoxide powder according to the present invention is a niobium oxide that is extremely suitable as a raw material for capacitors. Become.

In the method for producing niobium monoxide powder according to the present invention, the high oxidation number niobium oxide is preferably niobium pentoxide (Nb ₂ O ₅ ).

  As described above, according to the present invention, it is possible to efficiently produce fine niobium powder, which is a suitable raw material for capacitor applications, without performing pulverization that tends to cause deformation of particles or contamination of impurities. It becomes. The niobium monoxide powder obtained by the present invention is fine and has a low powder resistance, so that it is possible to realize good capacitor characteristics even with a small capacitor.

  Embodiments of the present invention will be described below with reference to examples.

First, the results of primary reduction treatment of niobium pentoxide powder will be described. As Example 1-1, 64 g of metal magnesium (Mg) powder was prepared with respect to 100 g of niobium pentoxide powder (Nb ₂ O ₅ ). Then, a powder of magnesium oxide (MgO) as a particle growth inhibitor is added in an amount corresponding to 0.1 wt% with respect to the amount of niobium pentoxide powder, and after dry mixing for 3 hours in a ball mill, reduction is performed. Processed. The reduction treatment conditions were as follows: heat treatment was performed at 1100 ° C. for 4 hours in an argon atmosphere, and after cooling to room temperature, the extracted powder was washed with a 30 wt% nitric acid solution (2 L) and washed with water. Then, it dried and obtained primary reduced niobium powder.

The primary reduced niobium powder of Example 1 was measured for average particle diameter D ₅₀ , BET specific surface area, and oxygen content. Table 1 shows the measurement results. Moreover, each measurement condition is as follows.

Average particle diameter D ₅₀ : Volume-based median diameter (D ₅₀ : small particle) by measuring the particle size distribution using a laser diffraction / scattering particle size distribution measuring device (LA-920 manufactured by Horiba, Ltd.) The particle diameter at a cumulative volume of 50% from the diameter side) was determined.

BET specific surface area: BET specific surface area is a nitrogen-helium mixed gas containing niobium monoxide powder as an evaluation sample, about 30% by volume of nitrogen as an adsorbate gas and about 70% by volume of helium as a carrier gas. Using a BET specific surface area measuring apparatus (manufactured by Shimadzu Corporation, Micromeritics Flow Soap II2300), JIS R 1626 “Method for measuring specific surface area of fine ceramic powder by gas adsorption BET method” 6 Measurements were made according to the (3.5) single point method of the .2 flow method.

Oxygen amount: Oxygen amount is the weight when niobium powder or niobium monoxide powder is oxidized to niobium pentoxide powder by heating to 600 ° C in an air atmosphere using a thermal analyzer (TG, manufactured by Mac Science). Calculated from change.

In addition, as Examples 1-2 to 1-5, primary reduced niobium powder in which the amount of magnesium oxide added as the particle growth inhibitor of Example 1-1 was changed was produced. In Example 1-2, the amount of magnesium oxide added was 1 wt%, Example 1-3 was 5 wt%, Example 1-4 was 10 wt%, and Example 1-5 was 20 wt%. Other conditions were the same as in Example 1-1. Then, for each primary reduction niobium powder of Example 1-2～1-5, average particle diameter _D 50, BET method specific surface area, measured oxygen content was carried out. Table 1 shows the measurement results.

Further, as Example 1-6, a primary reduced powder was produced when calcium oxide was used as the particle growth inhibitor. In Example 1-6, 8 g of metal magnesium (Mg) powder was prepared for 40 g of niobium pentoxide powder (Nb ₂ O ₅ ). Then, calcium oxide (CaO) powder as a particle growth inhibitor is added in an amount corresponding to 1 wt% with respect to the amount of niobium pentoxide powder, and dry mixed in a ball mill for 3 hours, followed by reduction treatment. It was. The reduction treatment conditions were as follows: heat treatment at 1100 ° C. for 4 hours in an argon atmosphere, cooling to room temperature, washing the extracted powder with nitric acid solution (2 L) having a concentration of 30 wt%, and washing with water. Then, it dried and obtained primary reduced niobium powder. For the primary reduced niobium powder of this Example 1-6, the average particle diameter D ₅₀ , the BET specific surface area, and the oxygen content were measured. Table 1 shows the measurement results.

As Comparative Example 1-1, primary reduced niobium powder was produced based on the prior art disclosed in Patent Document 2. In Comparative Example 1-1, 64 g of metal magnesium (Mg) powder was prepared for 100 g of niobium pentoxide powder (Nb ₂ O ₅ ), and reduction treatment was performed without adding a particle growth inhibitor. . The reduction treatment conditions were as follows: heat treatment was performed at 900 ° C. for 4 hours in an argon atmosphere, and after cooling to room temperature, the extracted powder was washed with a 30 wt% sulfuric acid solution (2 L) and washed with water. Then, it dried and obtained primary reduced niobium powder. Then, the primary reduction niobium powder of Comparative Example 1-1, the average particle diameter D _50, BET method specific surface area, measured oxygen content was carried out. Table 1 shows the measurement results.

As Comparative Example 1-2, primary reduced niobium powder was produced based on the prior art disclosed in Patent Document 4. In Comparative Example 1-2, 100 g of niobium pentoxide powder (Nb ₂ O ₅ ) was subjected to reduction treatment at 1100 ° C. for 4 hours in a hydrogen atmosphere, and cooled to room temperature to obtain primary reduced niobium powder. Then, the primary reduction niobium powder of Comparative Example 1-2, the average particle diameter D _50, BET method specific surface area, measured oxygen content was carried out. Table 1 shows the measurement results.

As shown in Table 1, the primary reduction niobium powder of Example 1-1 to 1-6, the average particle diameter _{D 50} is less than 1 [mu] m. On the other hand, Comparative Example is a conventional art 1-1, Comparative Example 1-2, the average particle diameter D ₅₀ becomes a very large value is confirmed. As for the amount of oxygen, Comparative Example 1-2 had the largest value because the primary reduced niobium powder of Comparative Example 1-2 was niobium dioxide powder (NbO ₂ ). On the other hand, it turned out that the primary reduced niobium powder of Examples 1-1 to 1-6 is a niobium powder having a larger amount of oxygen than the secondary reduced niobium powder described below.

  Subsequently, the result of reducing the above-described primary reduced niobium powder again to produce secondary reduced niobium powder will be described.

  First, as Example 2-1, 8 g of metal magnesium (Mg) powder was prepared with respect to 40 g of the primary reduced niobium powder obtained as Example 1-1. Then, magnesium oxide (MgO) powder as a particle growth inhibitor was added in an amount corresponding to 0.1 wt% with respect to the amount of primary reduced niobium powder and dry-mixed, followed by reduction treatment. The reduction treatment conditions were as follows: heat treatment at 900 ° C. for 4 hours in an argon atmosphere, and after cooling to room temperature, the extracted powder was washed with a 30 wt% nitric acid solution (2 L) and washed with water. Then, it dried and obtained secondary reduction niobium powder.

  Moreover, as Example 2-2 to 2-5, the secondary reduction niobium which changed each addition amount of the magnesium oxide of a particle growth inhibitor using each primary reduction niobium powder of the said Examples 1-2 to 1-5. Powder was produced. Example 2-2 uses the primary reduced niobium powder of Example 1-2, the amount of magnesium oxide added is 1 wt%, Example 2-3 uses the primary reduced niobium powder of Example 1-3, and magnesium oxide The amount of addition was 5 wt%, Example 2-4 used the primary reduced niobium powder of Example 1-4, the amount of magnesium oxide added was 10 wt%, and Example 2-5 was the primary reduced niobium of Example 1-5. Powder was used and the magnesium oxide addition amount was 20 wt%. Other conditions were the same as in Example 2-1.

  Further, as Example 2-6, primary reduced niobium powder of Example 1-6 was used, and secondary reduced niobium powder was produced using calcium oxide as a particle growth inhibitor. In Example 2-6, 40 g of the primary reduced niobium powder of Example 1-6 and 8 g of metal magnesium powder were prepared. Then, a powder of calcium oxide as a particle growth inhibitor was added in an amount corresponding to 1 wt% with respect to the amount of primary reduced niobium powder, and after dry mixing for 3 hours in a ball mill, reduction treatment was performed. The reduction treatment conditions were as follows: heat treatment at 900 ° C. for 4 hours in an argon atmosphere, and after cooling to room temperature, the extracted powder was washed with a 30 wt% nitric acid solution (2 L) and washed with water. Then, it dried and obtained secondary reduction niobium powder.

  As Comparative Example 2-1, 40 g of primary reduced niobium powder of Comparative Example 1-1 and 8 g of metal magnesium powder were prepared, and the reduction treatment was performed without adding the particle growth inhibitor. The reduction treatment conditions were as follows: heat treatment was performed at 800 ° C. for 2 hours in an argon atmosphere, and after cooling to room temperature, the extracted powder was washed with a 30 wt% sulfuric acid solution (2 L) and washed with water. Then, it dried and obtained secondary reduction niobium powder.

  As Comparative Example 2-2, 80 g of primary reduced niobium powder (niobium dioxide powder) of Comparative Example 1-2 and 43 g of metal magnesium powder were prepared, and reduction treatment was performed without adding the particle growth inhibitor. The reduction treatment conditions were as follows: heat treatment was performed at 1000 ° C. for 4 hours in an argon atmosphere, and after cooling to room temperature, the extracted powder was washed with a nitric acid solution (2 L) having a concentration of 30 wt% and washed with water. Then, it dried and obtained secondary reduction niobium powder.

For the secondary reduced niobium powders of Examples 2-1 to 2-6 and Comparative Examples 2-1 and 2-2, the average particle size D ₅₀ , the particle size D ₉₀ , the BET specific surface area, and the amount of oxygen were measured. . Table 2 shows the measurement results. Incidentally, the particle diameter D _90, the particle size distribution measured by a laser diffraction scattering method particle size distribution measuring apparatus (manufactured by HORIBA, Ltd. LA-920), the particle size in cumulative volume of 90% from the smaller particle size side It is the result of having calculated | required.

As shown in Table 2, the secondary reduction niobium powder of Example 2-1 to 2-6, the average particle diameter _{D 50} is less than 5 [mu] m. On the other hand, the secondary reduction niobium powder of the comparative example has a BET specific surface area of embodiments the same level, the average particle diameter D ₅₀ was to exceed 100 [mu] m. Also. From the results of the oxygen amount measurement, each secondary reduced niobium powder was found to be niobium powder.

  Finally, the results of producing niobium monoxide powder using the secondary reduced niobium powder described above will be described.

As Examples 3-1 to 3-5, niobium monoxide powder was produced using each secondary reduced niobium powder obtained in Examples 2-1 to 2-5. 30 g of secondary reduced niobium powder of each example and 24 g of niobium pentoxide powder (Nb ₂ O ₅ ) were put into a ball mill, and subjected to a wet mixing process for 3 hours using pure water in an inert atmosphere. Then, after drying, a baking treatment was performed. Firing conditions were as follows: heat treatment at 1500 ° C. for 5 hours in a hydrogen atmosphere, cooling to room temperature, and selecting with a sieve to obtain the powder under the sieve as niobium monoxide powder in each example.

  As Example 3-6, niobium monoxide powder was produced using the secondary reduced niobium powder obtained in Example 2-6. After putting 30 g of the secondary reduced niobium powder of Example 2-6 and 24 g of niobium pentoxide powder into a ball mill, and performing a wet mixing process for 3 hours using pure water in an inert atmosphere, after drying The baking process was performed. Firing conditions were as follows: heat treatment at 1450 ° C. for 5 hours in a hydrogen atmosphere, cooling to room temperature, and selecting with a sieve to obtain the powder under the sieve as niobium monoxide powder.

  As Comparative Example 3-1, 30 g of the secondary reduced niobium powder of Comparative Example 2-1 and 19 g of niobium pentoxide powder were charged into a ball mill, and wet for 3 hours using pure water in an inert atmosphere. The mixture was processed, dried, and then fired. Firing conditions were as follows: heat treatment at 1400 ° C. for 5 hours in a hydrogen atmosphere, cooling to room temperature, and selecting with a sieve to obtain the powder under the sieve as niobium monoxide powder.

  As Comparative Example 3-2, 30 g of the secondary reduced niobium powder of Comparative Example 2-2 and 21 g of niobium pentoxide powder were charged into a ball mill, and wet for 3 hours using pure water in an inert atmosphere. The mixture was processed, dried, and then fired. Firing conditions were as follows: heat treatment at 1400 ° C. for 5 hours in a hydrogen atmosphere, cooling to room temperature, and selecting with a sieve to obtain the powder under the sieve as niobium monoxide powder.

For each niobium monoxide powder of Examples 3-1 to 3-6 and Comparative Examples 3-1 and 3-2, measurement of average particle diameter D ₅₀ , BET specific surface area, oxygen amount, and conductivity and X-ray diffraction The full width at half maximum of the niobium monoxide peak was measured. And about the Example and the comparative example 3-1, the sieve screening test for coarse grain confirmation was done. Table 3 shows the measurement results. In addition, the conductivity was measured as follows.

Conductivity: Using a powder resistance measurement system (MCP-PD51 type, manufactured by Mitsubishi Chemical Analytech Co., Ltd.), 1 g of niobium monoxide powder to be measured is measured, and the density of the powder is 3.0 g / The powder resistivity was measured by compressing to cm ³ and pelletizing, and the conductivity was calculated from the reciprocal thereof.

X-ray diffraction measurement: Niobium monoxide powder was measured using an X-ray diffractometer (MXP18, manufactured by Mac Science Co., Ltd.). In this measurement, a copper (Cu) target was used, and the diffracted X-ray intensity was measured with Cu-Kα ₁ line. Other measurement conditions were a tube voltage of 40 kV, a tube current of 150 mA, a measurement range 2θ = 10 ° to 80 °, a sampling width of 0.02 °, and a scanning speed of 4.0 ° / min. The half width was in accordance with the half width (θ _1/2 ) in FIG. 6 of JIS K 0131-1996 “General Rules for X-ray Diffraction Analysis”. The unit of the half-value width is “rad” in “12. Measurement of crystallite size and non-uniform strain” of the same JIS, but here it is indicated by “°”. The X-ray diffraction in the present invention was analyzed in the order of the peak intensity of the diffraction X-ray peaks obtained by irradiating the material with CuKα rays, and the peak due to Cu-Kα ₁ line and the peak due to Cu-Kα ₂ line were analyzed. also separate and was analyzed by using only K [alpha ₁ line.

Sieve selection test: Each niobium monoxide powder was subjected to sieve selection with a sieve having an opening of 300 μm, and the ratio of coarse particles remaining on the sieve was examined.

As shown in Table 3, when comparing the measurement results of the respective Examples and Comparative Examples, the average particle size D ₅₀ and the BET specific surface area was the same level, conductivity values of each of Examples, Comparative It turned out to be about twice as large as the example. The reason why the powder conductivity has increased is that the average particle size of the niobium powder when producing the niobium monoxide powder has been reduced, so that the mixing property is improved and the crystallinity of the produced niobium monoxide powder. This is probably due to the increase in Moreover, although the coarse particle of 300 micrometers or more was hardly contained in the Example, it was contained in the ratio of 10% or more in the comparative example 3-1. In Comparative Example 3-1, since the particle growth inhibitor is not used, the size of the secondary particles of niobium powder cannot be controlled, and the finally obtained monoxide powder has coarse particles having a diameter exceeding 300 μm. It is thought that it was generated.

  According to the present invention, it is possible to easily provide a niobium capacitor that can realize a large capacity with a small-sized chip and has excellent electrical stability and high reliability.

Claims (9)

In the method for producing niobium powder, in which niobium powder is produced by reducing high oxidation number niobium oxide,
Mixing high-oxidation niobium oxide with a particle growth inhibitor that suppresses the bonding between particles produced by the reduction reaction, reducing the base metal as a reducing agent, removing the particle growth inhibitor, and performing primary reduction A first reduction treatment for producing niobium powder;
The primary reduction niobium powder and a particle growth inhibitor are mixed, and reduction is performed using a base metal as a reducing agent, and the second reduction treatment is performed to remove the particle growth inhibitor and generate a secondary reduced niobium powder. The manufacturing method of niobium powder characterized by the above-mentioned. The method for producing niobium powder according to claim 1, wherein the particle growth inhibitor is an alkaline earth metal salt or an alkaline earth metal oxide. The method for producing niobium powder according to claim 1 or _2, wherein the high-oxidation number niobium oxide is niobium pentoxide (Nb ₂ O ₅ ). The method for producing niobium powder according to any one of claims 1 to 3, wherein the base metal is one or a combination of two or more of lithium, magnesium, aluminum, calcium, strontium, and barium. A niobium powder obtained by the niobium powder manufacturing method according to any one of claims 1 to 4,
Less than 10μm average particle diameter D ₅₀ is 50% diameter in cumulative fraction of the volume reference in the laser diffraction scattering method particle size distribution, and wherein the particle size D ₉₀ 90% diameter is 50μm or less Niobium powder. The secondary reduced niobium powder obtained by the niobium powder production method according to any one of claims 1 to 4 is mixed with a high oxidation number niobium oxide, subjected to a reduction treatment in an atmosphere containing hydrogen, and then oxidized. A method for producing niobium monoxide powder that produces niobium powder. The method for producing niobium monoxide powder according to claim 6, wherein the high oxidation number niobium oxide is niobium pentoxide (Nb ₂ O ₅ ). Niobium monoxide powder characterized in that the half-value width of the peak of niobium monoxide obtained from powder X-ray diffraction is 0.09 to 0.20 degrees. The niobium monoxide powder having an electric conductivity of 500 S / cm or more when compressed to a pellet density of 3.0 g / cm ³ and pelletized.