WO2002004152A1

WO2002004152A1 - Metallic powder containing nitrogen, process for producing the same, and porous sinter and solid electrolytic capacitor both obtained from the same

Info

Publication number: WO2002004152A1
Application number: PCT/JP2001/005998
Authority: WO
Inventors: Isayuki Horio; Tomoo Izumi
Original assignee: Cabot Supermetals K.K.
Priority date: 2000-07-12
Filing date: 2001-07-11
Publication date: 2002-01-17
Also published as: JP2002030301A

Abstract

A nitrogen-containing tantalum or niobium powder which has a nitrogen content of 500 to 30,000 ppm and in which the difference in nitrogen content between any two particles is 100% or less. This powder can be produced by a process comprising a nitrogen treatment step in which a tantalum or niobium powder is heated with stirring in a nitrogenous atmosphere to incorporate nitrogen into the powder. This powder is inhibited from sintering at an excessively high rate, so that a sintering step is easy to adequately control. Hence, a porous sinter even in pore size and distribution can be produced and a high-CV capacitor can be provided.

Description

Specification

Nitrogen-containing metal powder and method for producing the same

And porous sintered body and solid electrolytic capacitor using the same

The present invention relates to a nitrogen-containing tungsten powder or a nitrogen-containing niobium powder suitable for forming an anode electrode of a solid electrolytic capacitor and a method for producing the same.

This application is based on a patent application to Japan (Japanese Patent Application No. 2000-211825), and the contents of the Japanese application are incorporated herein as a part. Back owl technology

In recent years, the capacity of tantalum capacitors has been increasing, and finer and larger surface area tantalum powder has been used as a raw material. Development of niobium capacitors using niobium powder is also underway.

At present, the tantalum powder that is mainly used is obtained by subjecting evening powder obtained by sodium reduction of tantalum fluoride potassium salt to a vacuum heat treatment and then deoxidizing it. Tantalum powder capable of achieving a high CV value of about 100000 FVZ g has been obtained.

To manufacture a capacitor, tantalum powder is press-molded, vacuum-sintered, and then anodized to form a dielectric layer. After that, a solid electrolyte is formed in the pores of the tantalum sintered body.

In recent years, however, the pores have become finer as the tantalum powder has become finer. It has become more difficult to form a solid electrolyte.

In addition, the uniformity of pore size and distribution is most affected by the sintering process in the capacitor manufacturing process. ·-If the sintering proceeds too much, for example, because the sintering temperature is too high, it is not possible to secure enough pores to form a solid electrolyte, and the capacity of the capacitor will decrease. On the other hand, if the progress of sintering is insufficient due to factors such as the sintering temperature being too low, the stability of the dielectric film becomes insufficient, such as an increase in leakage current.

Furthermore, as the tantalum powder becomes finer, the size and distribution of pores become more uniform. The properties are more likely to depend on such sintering conditions, and slight changes in conditions such as the sintering temperature greatly change the state of vacancies, making it impossible to stably obtain tantalum powder having desired physical properties. There was a case.

In order to control the sintering process and stably produce a tantalum sintered body having the desired physical properties, heating such as making the temperature distribution in the sintering zone of the vacuum sintering furnace used during sintering uniform is required. There is a way to devise a method. In addition, using tantalum powder whose sintering rate is moderately suppressed as a raw material, the progress of sintering does not vary even if the sintering conditions fluctuate slightly, and the pore size and distribution are uniform. There is a method for manufacturing a sintered body.

To suppress the sintering speed of tantalum powder, it is necessary to add phosphorus, silicon, zeolite, boron, and nitrogen to the tantalum powder in U.S. Pat. No. 3,825,502 and U.S. Pat. No. 03.

Also, U.S. Pat. No. 5,448,447 and U.S. Pat. No. 2,316,444 disclose that by adding nitrogen to tan powder, it is possible to reduce the amount to less than 300 FV / g. It discloses effects of dielectric film stability such as reduction of leakage current when CV powder is subjected to high-pressure formation at 100 V or more.

U.S. Pat. No. 1,875,988 discloses reducing thermal leakage by reducing the amount of oxygen by performing thermal nitriding at 450 below after deoxygenation.

However, the methods disclosed in U.S. Pat. No. 3,852,502 and U.S. Pat. No. 4,544,043 are intended for tantalum powder having a relatively small particle size and a low CV value. No method is disclosed for uniformly adding these elements to fine, high surface area, high CV tantalum powder.

The methods described in U.S. Pat.No. 5,444,447, U.S. Pat.No. 2,316,444 and U.S. Pat. For the purpose, it does not describe a method for controlling the sintering process by uniformly adding nitrogen to finer, high surface area tantalum powder having a high CV value. Disclosure of the invention

It is an object of the present invention to provide fine and high surface area tantalum or niobium powder with nitrogen. To provide a tungsten powder or a niobium powder that suppresses the sintering rate and facilitates appropriate control of the sintering process, and produces a porous sintered body with uniform pore size and distribution. And provide a high CV capacitor.

The nitrogen-containing tantalum powder or the nitrogen-containing niobium powder of the present invention contains 500 to 300 ppm of nitrogen, and the variation of the nitrogen content among the particles is 100% or less. Features.

In the method for producing a nitrogen-containing powder or a nitrogen-containing niobium powder according to the present invention, the titanium powder or the niobium powder is heated while moving in a nitrogen-containing atmosphere to contain nitrogen in the tantalum powder or the niobium powder. And a nitrogen treatment step of causing

The porous sintered body of the present invention is characterized by sintering the above-mentioned nitrogen-containing tantalum powder or nitrogen-containing niobium powder.

A solid electrolytic capacitor according to the present invention includes an anode electrode made of the porous sintered body described above. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a graph showing the relationship between the nitrogen content of the nitrogen-containing tantalum powder produced in the example and the density ratio D s ZD g before and after sintering.

FIG. 2 is a graph showing the relationship between the nitrogen content and the breakdown voltage (B DV) of the nitrogen-containing tantalum powder produced in the example. BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, the present invention will be described in detail.

The nitrogen-containing tantalum powder or the nitrogen-containing niobium powder of the present invention contains 500 to 300 ppm of nitrogen. When nitrogen is contained in such a proportion, excessive progress of sintering is suppressed when sintering nitrogen-containing oxygen powder or nitrogen-containing niobium powder. As a result, a porous sintered body having pores of a size suitable for forming a solid electrolyte uniformly can be obtained. This is because the surface diffusion of tantalum atoms, which occurs at the sintering neck of the primary particles, is inhibited by nitrogen atoms present in the surface layer of the primary particles. Conceivable.

If the nitrogen content is less than 500 ppm, the effect of suppressing the sintering of tantalum powder or niobium powder by nitrogen is insufficient. On the other hand, when it exceeds 30,000 ppm, the distribution of nitrogen in the tantalum powder or the niobium powder becomes uneven, and nitride crystals are generated, thereby reducing the capacity of the finally obtained capacitor. The preferred nitrogen content of the nitrogen-containing tantalum powder or the nitrogen-containing niobium powder is 3000-15000 ppm.

Further, in the nitrogen-containing tantalum powder or the nitrogen-containing niobium powder of the present invention, the variation in the nitrogen content among the particles is 100% or less.

Here, “variation in the nitrogen content among the particles” is a value determined as follows. First, a fixed amount of nitrogen-containing tantalum powder or nitrogen-containing niobium powder is used as a measurement sample, which is burned and the NOx gas generated is quantified to measure the mass of nitrogen contained in the sample. ) Determine the average nitrogen content (p pm) of the powder. The measurement sample is usually about 1 g.

Then, the electron beam probe micro area measurement (EPMA) is used to determine the nitrogen content of each of the 10 randomly extracted particles in the area with a spot diameter of 30 m to determine the nitrogen content (p pm) of each particle. . Then, the difference ΔΝ between the maximum nitrogen content (ppm) and the minimum nitrogen content (ppm) is calculated. Then, the value of the ratio of Δ to the percentage expressed as a percentage is defined as the variation (%) of the nitrogen content among the particles. ■

If the variation of the nitrogen content among the particles exceeds 100%, the effect of suppressing the sintering of nitrogen is exhibited as the whole powder, but the sintering progresses unevenly. As a result, the size and distribution of the pores in the porous sintered body become non-uniform, making the capacitor unsuitable for use as an anode electrode of a capacitor. More preferably, the variation in the nitrogen content among the particles is 50% or less.

The particle size and surface area of the nitrogen-containing tantalum powder or nitrogen-containing niobium powder of the present invention are not particularly limited, but preferably have an average particle diameter of 0.7 to 3 m, and a surface area of 3000 to 30000 cm ² by a BET method. / g. With such nitrogen-containing evening powder or nitrogen-containing niobium powder, more than 40,000 zFVZg High-capacity capacitors can be manufactured.

Such a nitrogen-containing tantalum powder or a nitrogen-containing niobium powder usually includes a reduction step of reducing a tantalum compound or a niobium compound as a raw material to obtain a tantalum powder or a niobium powder, and a heat treatment for thermally coagulating the tantalum powder or the niobium powder. It can be obtained by a production method having an agglomeration step, a deoxidation step of heating and deoxidizing a tantalum powder or a niobium powder in the presence of a reducing agent, and a nitrogen treatment step of including nitrogen in the evening powder or the niobium powder.

In the reduction step, a eutectic salt such as KC 1-KF or KC 1-NaC 1 is usually heated to 800 to 900 ° C. and melted in a dilute salt to form a tantalum compound or a niobium compound. And the reducing agent are aliquoted little by little or continuously charged and reacted. After the reaction between the tantalum compound or the niobium compound and the reducing agent is completed, the diluted salt is cooled, and the obtained agglomerate is repeatedly washed with water, a weakly acidic aqueous solution, etc. to remove the diluted salt, and the tantalum powder or the niobium powder is removed. obtain. In this case, if necessary, separation operations such as centrifugation and filtration may be performed in combination, or the particles may be washed and purified with a solution in which hydrofluoric acid and hydrogen peroxide are dissolved.

The tantalum compound or niobium compound used as a raw material is not particularly limited, and compounds of these metals can be used, but potassium fluoride salts and halides are preferable. The potassium fluoride _{_{salt, K 2 T a F 7,}} K 2 N b F 7, K 2 N b F 6 , and examples of the halides, niobium pentachloride, lower niobium chloride, Goshio tantalum, Chloride such as lower tantalum chloride, iodide, bromide and the like can be mentioned. Particularly, niobium compounds include niobium fluoride such as potassium fluoroniobate and oxides such as niobium pentoxide.

Examples of the reducing agent include alkali metals and alkaline earth metals such as sodium, magnesium and calcium, and hydrides thereof, ie, magnesium hydride, calcium hydride and the like.

The amount of the diluting salt is preferably set to be about 2 to 10 times the mass of the total mass of the tantalum compound or the niobium compound and the reducing agent. If the amount of the diluting salt is less than twice, the reaction rate is high because the concentration of the tantalum compound or the niobium compound as the raw material is high, and the particle size of the generated tantalum particles may be too large. on the other hand, If the amount of the dilute salt exceeds 10 times, the reaction rate will decrease and the productivity will decrease. In the heat coagulation step, the tantalum powder or niobium powder obtained in the reduction step is heated in a vacuum at 800 to 140, for 0.5 to 2 hours to heat coagulate, and the powder is stored in the powder. The existing ultra-fine particles are considered to be relatively large secondary particles. Prior to the thermal aggregation step, a preliminary aggregation step of adding an amount of water to uniformly wet the entire powder may be performed while applying vibration to the tantalum powder or the niobium powder. By performing this preliminary aggregation step, a stronger aggregate can be obtained. Also, by adding about 10 to 300 ppm of phosphorus, boron, etc. to the metal in advance to the water added in the pre-aggregation step, fusion growth of primary particles is suppressed and a high surface area is maintained. It can be thermally agglomerated while heating. Examples of the form of phosphorus added here include phosphoric acid, phosphorus hexafluoride and the like.

Next, the cake-like powder obtained in the heat coagulation process is crushed in the air or in an inert gas, and then heated in the presence of a reducing agent such as magnesium, sodium, calcium, etc., to reduce oxygen in the particles and oxygen. A deoxygenation step of reacting the reducing agent is performed.

The deoxygenation step is performed in an atmosphere of an inert gas such as argon at a temperature not lower than the melting point of the reducing agent and not higher than the boiling point for 1 to 3 hours.

Thereafter, the tantalum powder or the niobium powder is moved in a nitrogen-containing atmosphere and heated while being brought into contact with nitrogen to perform a nitrogen treatment step of causing the tantalum powder or the niobium powder to contain nitrogen.

The method of moving the tantalum powder or the niobium powder in a nitrogen-containing atmosphere is not particularly limited, and a rotary kiln or a fluidized bed heating furnace can be used, but a rotary kiln is preferably used. After charging the tantalum powder or niobium powder into the rotary kiln, the inside of the rotary kiln is set to a nitrogen-containing atmosphere, and then the rotary kiln is rotated and the temperature is raised. By this rotation, the contents in the rotary kiln are sufficiently brought into contact with nitrogen, and a nitrogen-containing powder is obtained. Also, by monitoring the partial pressure of nitrogen during the nitrogen treatment process, it is possible to observe how the tantalum powder or niobium powder absorbs nitrogen.

When the tantalum powder or niobium powder is moved in a nitrogen-containing atmosphere and heated while being sufficiently in contact with the nitrogen as described above, compared to heating without moving the powder. Thus, since each particle is uniformly contacted with nitrogen, the variation in the nitrogen content between each particle is reduced.

For example, if tantalum powder or niobium powder is placed in a sample dish and heated in a furnace kept in a nitrogen-containing atmosphere, the powder in the upper layer of the sample dish comes into contact with nitrogen, and the However, since the powder in the lower layer of the sample dish does not come into direct contact with nitrogen, the nitrogen content is reduced. As a result, the nitrogen content varies greatly depending on the particles, and when such a powder is sintered, the progress of sintering becomes uneven, and a porous sintered body having a uniform pore distribution suitable for forming a solid electrolyte is obtained. Can not be.

However, by moving the tantalum powder or niobium powder in a nitrogen-containing atmosphere using a rotary kiln or the like and heating while sufficiently contacting the nitrogen, the variation in the nitrogen content among the particles can be suppressed.

The volume in the rotary kiln used is preferably about 5 to 50 times the volume of the tantalum powder or niobium powder to be charged. The number of revolutions of the rotary kiln is not particularly limited, but is usually about 0.5 to 5 rpm.

The nitrogen-containing atmosphere is preferably a nitrogen atmosphere or an inert atmosphere in which nitrogen is diluted with an inert gas other than nitrogen, such as argon or helium. The nitrogen content of the tantalum powder or niobium powder can be arbitrarily adjusted by changing the nitrogen partial pressure in the nitrogen-containing atmosphere or adjusting the nitrogen treatment time and temperature.

The heating conditions in the nitrogen treatment step are not particularly limited, but usually, the tantalum powder or the niobium powder is heated to about 800 to 100,000 at a heating rate of 3 to 30 / min. Then, keep at this temperature for about 1 to 6 hours, and then cool to about room temperature. When the temperature of the contents reaches about room temperature, air is introduced into the rotary kiln and a gradual oxidation process is performed to form a stable film on the surface of the tantalum or niobium particles. After that, the contents are taken out, washed with an acid and pure water to remove the remaining reducing agent and substances derived from the reducing agent used in the deoxidizing step, and then dried.

In this way, it is possible to produce a nitrogen-containing tantalum powder or a nitrogen-containing niobium powder in which the variation of the nitrogen content among the particles is suppressed to 100% or less.

The nitrogen treatment step may be performed at any time, not only after the deoxidation step, but also in the reduction step. It may be performed after or after the thermal aggregation step.

Further, in the production method of the present invention, the nitrogen treatment step can be performed during the deoxidation step without separately performing the deoxidation step and the nitrogen treatment step.

When the nitrogen treatment step is performed during the deoxidation step, the number of steps can be reduced as compared with the case where the deoxidation step and the nitrogen treatment step are separately performed, and the nitrogen-containing tantalum powder and the nitrogen-containing niob powder can be efficiently produced. Industrially more preferred.

As a specific method of performing the nitrogen treatment step during the deoxidation step, for example, the following method can be mentioned.

First, a mixture of a tantalum powder or a niobium powder and a reducing agent added is charged into a rotary kiln, and a nitrogen-containing gas is sealed in the rotary kiln. Then, while rotating the rotary kiln, heat at a heating rate of about 3 to 30 "CZmin. Immediately after the start of heating, the surface of the tantalum powder or niobium powder grains is covered with an oxide film. When the temperature reaches about 600 ° C, the oxide film rapidly diffuses due to the action of the reducing agent to expose tantalum or niobium, and the exposed tantalum or niobium comes into contact with nitrogen, absorbs nitrogen, and removes nitrogen. After heating to about 800 to 100, and if necessary, maintaining at that temperature for 1 to 6 hours, stop heating and allow to cool.

As another method, first, a mixture obtained by adding a reducing agent to tantalum powder or niobium powder is charged into a rotary kiln, and an inert gas other than nitrogen such as argon is filled in the rotary kiln, and the rotary kiln is filled. Heat the kiln while rotating it to deoxygenate the tantalum powder or niobium powder. Then, after reaching the predetermined temperature, the temperature is gradually lowered, and when the temperature becomes about 200 to 500, the inside of the rotary kiln is replaced with a nitrogen-containing gas and kept at this temperature for a certain time. In this way, nitrogen is absorbed by tantalum or niobium to obtain a tantalum powder or a niobium powder containing nitrogen. Then, stop heating and allow to cool.

In addition, in such a method, the nitrogen-containing gas may be passed through without being enclosed in the rotary kiln.

In this way, using a rotary kiln and moving the tantalum powder or niobium powder while performing the nitrogen treatment process during the deoxidation process is more stable than when not moving. In addition to controlling the process, the variation in the nitrogen content among the particles can be suppressed.

For example, a mixture obtained by adding a reducing agent to tantalum powder or niobium powder is placed in a sample dish or the like, and left standing in a furnace maintained in a nitrogen-containing atmosphere and heated, so that the nitrogen treatment step is performed during the deoxidation step. Do. Then, immediately after the start of the temperature rise, the particle surface of the tantalum powder or niobium powder is covered with an oxide film, and when the temperature reaches about 600, the oxide film rapidly diffuses to expose tantalum or niobium. Therefore, when the temperature exceeds 600, the exothermic reaction between nitrogen and tantalum or niobium in the uppermost layer in contact with nitrogen rapidly progresses, while nitrogen is not supplied to the lower layer powder at a sufficient speed. State. As a result, the powder in the upper layer of the sample dish has a very high nitrogen content, and the powder in the lower layer of the sample dish has a very low nitrogen content, resulting in a very large variation in the nitrogen content between particles. .

Also, for example, a mixture of a tantalum powder or a niobium powder and a reducing agent added thereto is placed in a sample dish or the like, and left in a furnace kept in an argon atmosphere or the like, heated to perform a deoxidation step, and when the temperature is lowered thereafter, A nitrogen treatment step is performed by setting the inside of the system to a nitrogen-containing atmosphere. Then, after the oxide film is removed from the particle surface of the tantalum powder or niobium powder, the tantalum powder or niobium powder comes into contact with nitrogen, so that if the temperature in the system is reduced to about 450, it is relatively low. A tantalum powder or a niobium powder containing nitrogen uniformly is obtained. However, because the temperature in the system is low and the diffusion rate of nitrogen is low, it takes about 10 to several hours for nitrogen treatment to contain 500 to 300 ppm of nitrogen. Not suitable for

If the temperature in the system is 500 or more, the nitrogen diffusion rate increases, but only the powder in the upper layer of the sample dish comes into contact with nitrogen and a runaway reaction occurs locally. As a result, the nitrogen content in the upper layer powder and the lower layer powder in the sample dish fluctuated extremely, and nitride crystals such as Ta ₂ N and Ta N were found in the powder in the upper layer of the sample dish. Will be generated.

However, by performing a nitrogen treatment process during the deoxidation process while moving the tantalum powder or niobium powder using a rotary kiln or the like, 500 to 300 ppm without runaway reaction occurs Of nitrogen can be uniformly contained in each particle. Nitrogen-containing tantalum powder or nitrogen-containing nitrogen obtained by such a method In Bed powder, Painda one as 3-5 wt% of camphor (C, .H _{1 6} 〇) and the like by press molding by adding, then 1 0-3 0 min 1 2 0 0-1 5 0 0 It is heated to a certain degree and sintered to produce a porous sintered body.

When this porous sintered body is used as an anode electrode, a lead wire is embedded in a nitrogen-containing tantalum powder or a nitrogen-containing niobium powder, then press-molded and sintered to integrate the lead wire. Then, the pressure is raised to 20 to 60 V at a current density of 40 to 80 mAZg in an electrolytic solution such as phosphoric acid or nitric acid having a temperature of 30 to 90 and a concentration of about 0.1% by mass. Then, the mixture is treated for 1 to 3 hours, and then subjected to chemical oxidation to form an anode electrode for a solid electrolytic capacitor.

Then, a solid electrolyte layer such as manganese dioxide, lead oxide or a conductive polymer, a graphite layer, and a silver paste layer are sequentially formed on the porous sintered body by a known method, and then a cathode terminal is soldered thereon. After connection, a resin jacket is formed to form a solid electrolytic capacitor.

Such a manufacturing method includes a nitrogen treatment step in which the tantalum powder or the niobium powder is heated in a nitrogen-containing atmosphere while being brought into contact with the nitrogen and heated to contain the nitrogen. Therefore, the tantalum powder or niobium powder is in uniform contact with nitrogen, contains 500 to 300 ppm of nitrogen, and the variation of the nitrogen content among the particles is suppressed to 100% or less. Nitrogen-containing tantalum powder or nitrogen-containing niobium powder can be stably produced.

Further, by performing such a nitrogen treatment step during the deoxidation step, the number of steps can be reduced as compared with the case where the deoxidation step and the nitrogen treatment step are performed separately, and the nitrogen-containing tantalum powder and the nitrogen-containing Can produce niobium powder and is more industrially preferred.

When the nitrogen-containing tantalum powder or the nitrogen-containing niobium powder thus obtained is used, excessive sintering can be suppressed when this is sintered. As a result, a porous sintered body having pores of a size suitable for forming a solid electrolyte can be obtained. By using such a porous sintered body as the anode electrode, a high CV solid electrolytic capacitor can be stably provided. Example

Hereinafter, the present invention will be described specifically with reference to examples.

[Example;! ~ Four]

The tantalum powder obtained by reducing potassium tantalum fluoride (K ₂ TaF ₇ ) with sodium is heated to 1400 ° C in a vacuum to cause thermal coagulation, and the obtained cake-like powder is crushed. To obtain a tantalum powder having a nominal CV value of 50000 FV / g. Then, 975 g of this tantalum powder was mixed with 25 g of magnesium powder, and 1 kg of the obtained mixture was charged into a rotary kiln having an internal volume of 6 L. Then, after filling the kiln with nitrogen gas and argon gas, the kiln is rotated at 1 rpm to move the mixture particles, and the heating rate is increased to 85 Ot.

After heating at in. and holding at 850 for 4 hours, heating was stopped and allowed to cool.

Thus, the nitrogen treatment step was performed during the deoxidation step. In this step, the partial pressure of nitrogen gas was adjusted as shown in Table 1.

After the obtained nitrogen-containing tantalum powder has reached room temperature, air is introduced into the rotary kiln to perform a slow oxidation treatment, followed by acid washing, pure water washing, and vacuum drying. A nitrogen-containing tantalum powder having an average nitrogen content shown in Table 1 was produced. Table 1 also shows the variation in nitrogen content.

These nitrogen-containing tantalum powders were compacted to a density of D g = 5.5 g / cm ³ and then vacuum-sintered at 1350 ^ and 1450 for 20 minutes to produce sintered bodies. The obtained sintered body was formed in a 0.51% aqueous phosphoric acid solution of 901 at a formation voltage of 30 V, and then subjected to CV measurement in 25 30.5Vo 1% aqueous solution of sulfuric acid. The breakdown voltage (BDV) of this sintered body was also measured. The breakdown voltage (BDV, according to EIAJ-RC-3881B, paragraph 6.2) was measured at a current density of 3 OmAZg in a 10 wt% phosphoric acid aqueous solution at 90 ° C. .

Further, the change in density due to sintering, that is, the ratio DsZDg of the density Dg of the compact and the density Ds of the sintered body was determined. These characteristics are shown in Table 1 and FIGS.

The average nitrogen content and the variation in the nitrogen content were determined as follows. (1) Average nitrogen content

Combustion of 1 g of nitrogen-containing tantalum powder to determine the amount of N〇x gas generated , The mass of nitrogen contained in the sample was measured (combustion gas component determination method), and the average nitrogen content (ppm) of the powder was determined.

An oxygen and nitrogen analyzer (HOR IBA · EMGA520) was used for the combustion gas component determination method.

(2) Variation in nitrogen content

By electron beam probe micro area measurement (EPMA), the nitrogen mass in the area of spot diameter 30; ttm was quantified for each of the 10 tantalum particles randomly extracted, and the nitrogen content (p pm) of each particle was calculated. Was. Then, of these, the difference ΔΝ between the maximum nitrogen content (p pm) and the minimum nitrogen content (p pm) was calculated, and the value of the ratio of Δ 【to N The variation (%) of the nitrogen content between particles was used.

[Comparative Examples 1 to 5]

Rather than in a rotary kiln, 1 kg of a mixture obtained by mixing 975 g of tantalum powder and 25 g of magnesium powder was placed in a heating furnace (stationary furnace) that was placed on a sample dish. The nitrogen treatment step was performed during the deoxidation step in the same manner as in Examples 1 to 4 except that the contents were as shown in Table 1. In Comparative Example 1, only argon gas was sealed.

The obtained nitrogen-containing tantalum powder was post-treated in the same manner as in Example 1 to produce a nitrogen-containing tantalum powder having an average nitrogen content shown in Table 1. Table 1 also shows the variation in nitrogen content.

A sintered body was produced from these nitrogen-containing tantalum powders in the same manner as in Example 1, and the CV measurement and the breakdown voltage (BDV) measurement were performed in the same manner as in Example 1. Further, the density ratio D s / D g was calculated in the same manner as in Example 1. These characteristics are shown in Table 1 and FIGS.

[Example 5]

The tantalum powder obtained by reducing potassium tantalum fluoride (K ₂ TaF ₇ ) with sodium is heated to 1400 in a vacuum to thermally coagulate, and the cake-like powder obtained is obtained. The powder was crushed and pulverized to obtain a tantalum powder having a nominal CV value of 50000 F VZg. Then, 975 g of this tantalum powder was mixed with 25 g of magnesium powder, and 1 kg of the obtained mixture was charged into a rotary kiln having an internal volume of 6 L. Then, after filling the kiln with argon gas, the kiln was rotated at 1 rpm to move the mixture particles and heated to 850 ° C at a heating rate of 6 ° CZmin.

After that, the heating was stopped to lower the temperature.When the inside of the kiln reached 300 ° C, the inside of the kiln was replaced with a mixed gas of nitrogen gas and argon gas while the temperature was maintained at 300 ° C, and the kiln was deoxygenated. A nitrogen treatment step was performed during.

Then, by monitoring the pressure of nitrogen gas, until the pressure no longer decreases, i.e., after the tantalum powder was held ^{(60 X 1 0 3 P a} ) until no absorption of nitrogen, is et in a nitrogen partial pressure 1Z3 ( The temperature was reduced to 20 X 10 ³ Pa) and the treatment was performed at 300 ° C for 60 minutes. The obtained nitrogen-containing tantalum powder was post-treated in the same manner as in Example 1 to produce a nitrogen-containing tantalum powder having an average nitrogen content shown in Table 1. Table 1 also shows the variation in nitrogen content.

From this nitrogen-containing tantalum powder, a sintered body was manufactured in the same manner as in Example 1, and the CV measurement and the breakdown voltage (BDV) measurement were performed in the same manner as in Example 1. Further, the density ratio Ds / Dg was calculated in the same manner as in Example 1. Table 1 and Figure 2 show these characteristics.

[Example 6]

A nitrogen treatment step was performed during the deoxidation step in the same manner as in Example 5 except that the temperature of the nitrogen treatment step was changed to 450.

Then, the obtained nitrogen-containing tantalum powder was post-treated in the same manner as in Example 1 to produce a nitrogen-containing tantalum powder having an average nitrogen content shown in Table 1. Table 1 also shows the variation in nitrogen content.

From this nitrogen-containing tantalum powder, a sintered body was manufactured in the same manner as in Example 1, and the CV measurement and the breakdown voltage (BDV) measurement were performed in the same manner as in Example 1. Further, the density ratio Ds / Dg was calculated in the same manner as in Example 1. These characteristics are shown in Table 1 and Figure 2. [Example 7]

The tantalum powder obtained by reducing potassium tantalum fluoride (K ₂ Ta F ₇ ) with sodium is heated to 1400 in a vacuum to thermally coagulate, and the resulting cake-like powder is crushed. It was pulverized to obtain a tantalum powder having a nominal CV value of 50000 FV / g. Then, 975 g of this tantalum powder was mixed with 25 g of magnesium powder, and 1 kg of the obtained mixture was charged into a rotary kiln having an internal volume of 6 L. Then, after filling the kiln with argon gas, the kiln was rotated at 1 rpm to move the mixture particles, and the mixture was heated to 85 Ot: at a heating rate e Zmin.

After that, the heating was stopped to lower the temperature, and when the inside of the kiln reached 500 ° C, while maintaining the temperature at 500 ° C, nitrogen gas with a flow rate of about 120 ml Zmin was passed through the kiln for 30 minutes. Thereafter, the nitrogen gas was stopped and the temperature was maintained for another 30 minutes, and a nitrogen treatment step was performed during the deoxidation step.

The obtained nitrogen-containing tantalum powder was post-treated in the same manner as in Example 1 to produce a nitrogen-containing tantalum powder having an average nitrogen content shown in Table 1. Also, the variation in nitrogen content

5 to 1 ~.

A sintered body was manufactured from this nitrogen-containing tantalum powder in the same manner as in Example 1, and the CV measurement and the breakdown voltage (BDV) measurement were performed in the same manner as in Example 1. Further, the density ratio D 3/08 was calculated in the same manner as in Example 1. Table 1 and Figure 2 show these characteristics.

[Example 8]

The nitrogen treatment step was performed during the deoxidation step in the same manner as in Example 7, except that the flow rate of the nitrogen gas circulated in the nitrogen treatment step was 250 m 1 Zmin.

From this nitrogen-containing tantalum powder, a sintered body was manufactured in the same manner as in Example 1, and the CV measurement and the breakdown voltage (BDV) measurement were performed in the same manner as in Example 1. Further, the density ratio Ds / Dg was calculated in the same manner as in Example 1. These characteristics are shown in Table 1 and Figure 2. You. [Comparative Example 6]

Rather than in a rotary kiln, 1 kg of a mixture obtained by mixing 975 g of tantalum powder and 25 g of magnesium powder was placed in a sample dish and placed in a heating furnace, followed by nitrogen gas and argon. A nitrogen-containing tantalum powder was produced in the same manner as in Example 6, except that the inside of the heating furnace was replaced and sealed with a gas mixture of gas, and the temperature at which the nitrogen treatment step was performed was set at 500. When nitrogen gas was introduced, a rise in furnace temperature of about 8 Ot: was observed.

From this nitrogen-containing tantalum powder, a sintered body was manufactured in the same manner as in Example 1, and the CV measurement and the breakdown voltage (BDV) measurement were performed in the same manner as in Example 1. Further, the density ratio D s / D g was calculated in the same manner as in Example 1. Table 1 and Figure 2 show these characteristics.

[Comparative Example 7]

Rather than in a rotary kiln, 1 kg of a mixture obtained by mixing 975 g of tantalum powder and 25 g of magnesium powder was placed in a sample dish and placed in a heating furnace, followed by nitrogen gas and argon. A nitrogen-containing tantalum powder was produced in the same manner as in Example 6 except that the inside of the heating furnace was replaced and sealed with a gas mixture of gas, and the temperature at which the nitrogen treatment step was performed was set at 850. When nitrogen gas was introduced, an increase in furnace temperature of about 80 was observed.

From this nitrogen-containing tantalum powder, a sintered body was manufactured in the same manner as in Example 1, and the CV measurement and the breakdown voltage (BDV) measurement were performed in the same manner as in Example 1. Further, the density ratio D s / D g was calculated in the same manner as in Example 1. Table 1 and Figure 2 show these characteristics. Dimension

table 1

Average used ^^ Weight 135 o Conclusion 1450 ° C 'Crane partial pressure

CV BDV Ds / Dg BDV [Pa] [p pmj [%]

[^ FV / g] [V] [%] [V]

6.7X10 ³ [Π Ρ 1720 40 52 550 105 1.215 41950 130 Difficult 2 13 X 10 ^{3 3} 640 30 54 420 98 1.156 44 920 140 Difficult 3 27 X 10 ³ 1 * ν 6670 30 54 670 118 1.111 46 210 133 Difficult case 4 40 X 10 ³ 12 550 20 54 980 88 1.093 48 184 120 t 瞧 10 Stationary furnace 140 20 50 520 90 1.247 38 900 104

1: 瞧 2 2.7 X 10 ³ Stationary furnace 470 130 50 490 82 1.251 38700 112: Inversion 3 13X 10 ³ Stationary furnace 3600 400 52 530 84 1.185 42730 89

27 X 10 ³ Stationary furnace 7500 320 53 120 79 1.159 44 230 105

1: Yu 5 40X 10 ³ Stationary furnace 9430 380 53 420 85 1.145 45 140 98 Difficult 5 6 OX 10 ³ ΙΞΜΡ 590 90 52020 95 1.233 40 370 148 — 2 OX 10 ³

Difficult example 6 6 OX 10 ³ ΙΕΜΡ 2900 30 56 220 118 1.158 44730 145 → 2 OX 10 ³

Hunger 7 8030 40 56 110 100 1.091 46920 135 Difficult 8 13790 20 56650 105 1.073 48610 115

1; translation 6 6 OX 10 ³ Stationary furnace 35 230 70 41 440 73 1.007 40 950 68 → 2 OX 10 ³

]; 瞧 7 6 OX 10 ³ 90000 90 36790 74 1.015 36780 73 → 2 OX 10 ³

In the table, tu¾ ^ indicates Θ¾ kiln.

(1) For Examples 7 and 8, the description of the crane partial pressure in the table is omitted.

< The following became clear from Table 1 and FIGS.

(1) When compared at the same nitrogen content, the tantalum powder obtained in the example has a small density ratio before and after sintering, and suppresses excessive shrinkage due to sintering, making it suitable for forming a solid electrolyte. Had voids.

On the other hand, the tantalum powder obtained in the comparative example had a large shrinkage due to sintering, and was not suitable for forming a solid electrolyte. -

(2) When compared at the same nitrogen content, the tantalum powder obtained in the example has a large breakdown voltage (BDV) and uniform pores, so that it is possible to perform positive oxidation to a high voltage. You can see that.

On the other hand, the tantalum powder obtained in the comparative example had a low breakdown voltage (B DV) and did not have uniform pores suitable for forming a solid electrolyte. Industrial applicability

As described above, the nitrogen-containing evening powder or the nitrogen-containing niobium powder of the present invention is fine, has a large surface area, and contains nitrogen uniformly. Therefore, when this is sintered, the sintering speed at the time of sintering is moderately suppressed, the progress of sintering is easily controlled appropriately, and a porous sintered body with a uniform size and distribution of pores is obtained. Can be. Such a porous sintered body is most suitable for use as the anode electrode of a high CV capacitor.

In addition, the production method of the present invention includes a nitrogen treatment step of heating the tantalum powder or the niobium powder while moving in a nitrogen-containing atmosphere, so that the nitrogen-containing powder is fine, has a large surface area, and has a uniform nitrogen content. Even powder or nitrogen-containing niobium powder can be produced stably. Furthermore, by performing the nitrogen treatment step during the deoxygenation treatment step, it is possible to efficiently produce nitrogen-containing tantalum powder or nitrogen-containing niobium powder in a small number of steps. ...

The present invention may be embodied in various other forms without departing from its spirit or essential characteristics. Therefore, the above-described embodiment is merely an example in every aspect, and should not be construed as limiting. The scope of the present invention is defined by the appended claims, and is not restricted by the specification. Further, all modifications and changes belonging to the equivalent scope of the claims are within the scope of the present invention.

Claims

The scope of the claims

Nitrogen-containing tantalum powder or nitrogen-containing powder, which contains 1.5 to 300 ppm of nitrogen and has a nitrogen content variation between particles of 100% or less. Niobium powder.

2. A nitrogen-containing powder having a nitrogen treatment step of heating the powder or niobium powder while moving it in a nitrogen-containing atmosphere to cause the tantalum powder or the niobium powder to contain nitrogen. Method for producing powder or nitrogen-containing niobium powder.

3. The nitrogen-containing tantalum powder or nitrogen according to claim 2, wherein the nitrogen treatment step is performed during a deoxidation step in which the tantalum powder or the niobium powder is deoxygenated by heating in the presence of a reducing agent. Method for producing niobium-containing powder.

4. The method for producing a nitrogen-containing tantalum powder or a nitrogen-containing niobium powder according to claim 2, wherein the nitrogen treatment step is performed using a rotary kiln.

5. A nitrogen-containing tantalum powder or a nitrogen-containing niob powder, which is produced by the method for producing a nitrogen-containing tantalum powder or a nitrogen-containing niobium powder according to claim 2.

6. A porous sintered body obtained by sintering the nitrogen-containing tantalum powder or the nitrogen-containing niobium powder according to claim 1.

7. A porous sintered body obtained by sintering the nitrogen-containing tantalum powder or the nitrogen-containing niobium powder according to claim 5.

8. An anode electrode made of the porous sintered body according to claim 6 is provided. Solid electrolytic capacitor characterized by <

9. A solid electrolytic capacitor comprising an anode electrode made of the porous sintered body according to claim 7.