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Niobium powder, process for producing the same and solid electrolytic capacitor therefrom

a technology of niobium powder and process, which is applied in the direction of capacitors, electrolytic capacitors, electrical apparatus, etc., can solve the problems of large grain density of powder obtained by oxide reduction method, inability to incorporate impurities, and short distance between crystal particles, etc., to achieve excellent electrical properties and high purity niobium powder

Inactive Publication Date: 2006-01-26
CABOT SUPERMETALS
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

"The present invention relates to a method for producing high purity niobium powder. The inventors found that by removing the effect of water content in potassium niobate fluoride and improving the method for adding a reducing agent, they could obtain high purity niobium powder. The niobium powder obtained has properties where pores are not clogged even when formed using a relatively high voltage, resulting in the production of a niobium capacitor with excellent electrical properties. The niobium powder has a capacitance range of 80 to 240 kCV / g and a CV retention of 57% or higher. The percentage of pores having a diameter of 0.11 μm or greater is preferably 90% or greater. The method includes reducing potassium niobate fluoride in a diluent salt to produce niobium powder, where the water content is 1000 ppm or less. The method also includes introducing a reducing agent in a reaction vessel in advance and adding potassium niobate fluoride and the reducing agent in a predetermined amount, repeating this process to carry out a reaction. The resulting niobium powder has a relative leakage current value of 4 nA / CV or less and is suitable for use in capacitors."

Problems solved by technology

However, since supply of ore which is used as a raw material for potassium tantalate fluoride is unstable, solid capacitors using niobium powder which possesses properties close to tantalum powder and supply of raw materials thereof is stable, have been developed.
However, in the above method, there is a problem that a large number of impurities may be incorporated in crystals of metallic salt including niobium, such as potassium niobate fluoride, since the crystals are unstable unlike those of potassium tantalate fluoride, during a reducing reaction in which an apparatus may be seriously corroded.
However, the grain density of the powder obtained by the oxide reduction method is large and the distance between the crystal particles is short.
Accordingly, there is a problem that fine pores thereof are clogged due to the growth of oxidation film when formed using a high voltage, and the reduction of CV value due to high voltage formation becomes large.
Also, when the pulverization method is employed, coral like secondary particles of powder which may be produced by the above-mentioned reduction method cannot be obtained.
Accordingly, it is difficult to produce porous (thermal) agglomerate which controls the pore size distribution of a sintered body.

Method used

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  • Niobium powder, process for producing the same and solid electrolytic capacitor therefrom
  • Niobium powder, process for producing the same and solid electrolytic capacitor therefrom
  • Niobium powder, process for producing the same and solid electrolytic capacitor therefrom

Examples

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Effect test

example 1

[0056] A predetermined amount of potassium fluoride and potassium chloride as diluent salts were introduced into a reaction vessel whose inner surface was formed of nickel material, and it was heated to a reaction temperature. After this, a predetermined amount of potassium niobate fluoride and sodium were added in that order and this process was repeated to conduct a reduction reaction. In this manner, niobium powder was obtained.

[0057] The employed potassium niobate fluoride had a water content of 4000 ppm as determined based on the Karl Fischer method upon heating to 600° C.

[0058] Also, the water content of potassium fluoride and potassium chloride was 500 ppm and 50 ppm, respectively, as determined based on the Karl Fischer method upon heating to 700° C.

[0059] Moreover, the amount of water in the reaction system of the reduction reaction was 16100 ppm converted to the amount of niobium powder obtained.

[0060] The niobium powder thus obtained was subjected to post-processes, a...

example 2

[0061] A predetermined amount of potassium fluoride and potassium chloride as diluent salts were introduced into a reaction vessel whose inner surface was formed of nickel material, and it was heated to a reaction temperature. After this, a predetermined amount of potassium niobate fluoride and sodium were added in that order and this process was repeated to conduct a reduction reaction. In this manner, niobium powder was obtained.

[0062] The employed potassium niobate fluoride had a water content of 1000 ppm as determined based on the Karl Fischer method upon heating to 600° C.

[0063] Also, the water content of potassium fluoride and potassium chloride was 1000 ppm and 50 ppm, respectively, as determined based on the Karl Fischer method upon heating to 700° C.

[0064] Moreover, the amount of water in the reaction system of the reduction reaction was 14700 ppm converted to the amount of niobium powder obtained.

[0065] The niobium powder thus obtained was subjected to post-processes, ...

example 3

[0066] A predetermined amount of potassium fluoride and potassium chloride as diluent salts were introduced into a reaction vessel whose inner surface was formed of nickel material, and it was heated to a reaction temperature. After this, a predetermined amount of potassium niobate fluoride and sodium were added in that order and this process was repeated to conduct a reduction reaction. In this manner, niobium powder was obtained.

[0067] The employed potassium niobate fluoride had been heat-dried at about 100° C. under a reduced pressure of 2 kPa in a vessel to which a Teflon® lining was applied in advance, and it was introduced into the reaction vessel without being exposed in air. The water content of potassium niobate fluoride subjected to the heat-drying process under a reduced pressure was 1000 ppm as determined based on the Karl Fischer method upon heating to 600° C.

[0068] Also, the water content of potassium fluoride and potassium chloride used as diluent salts was 500 ppm ...

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Abstract

A niobium powder can be used to manufacture a niobium capacitor of excellent electrical properties The niobium powder when formed into a sintered body of 3.15 to 3.9 g / cm3 density exhibits a capacitance (CV value at a formation voltage of 20V) ranging from 80 to 240 kCV / g and a CV retention of 57% or higher. With respect to the production of the niobium powder, the employed potassium niobate fluoride has a water content of 1000 ppm or less as determined from the amount of water generated upon heating at 600° C. according to the Karl Fischer method.

Description

TECHNICAL FIELD [0001] The present invention relates to niobium powder, processes for producing the niobium powder, and solid electrolytic capacitors using the niobium powder [0002] The present invention is based on Japanese Patent Application No. 2002-306725, the content of which is incorporated herein by reference. BACKGROUND ART [0003] Tantalum capacitors are known as small solid capacitors having high capacity, and the use thereof has greatly increased, mainly for portable information terminals and mobile phones. Tantalum powder which is used as a raw material for anodes thereof may be obtained by reducing potassium tantalate fluoride. However, since supply of ore which is used as a raw material for potassium tantalate fluoride is unstable, solid capacitors using niobium powder which possesses properties close to tantalum powder and supply of raw materials thereof is stable, have been developed. [0004] As a method for producing the niobium powder, the same methods of producing t...

Claims

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Application Information

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Patent Type & Authority Applications(United States)
IPC IPC(8): C22C27/02B22F9/20B22F1/00B22F9/24C22B34/24C22C1/04H01G9/052
CPCB22F9/24H01G9/0525C22C1/045C22B34/24
Inventor KATAOKA, EIJITAKAYAMA, KOUICHIODA, YUKIO
Owner CABOT SUPERMETALS
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