Nitrogen-containing metal powder, production process thereof, and porous sintered body and solid electrolytic capacitor using the metal powder
An object of the present invention is to provide nitrogen-containing metallic powder at high productivity, which powder contains a metal such as niobium or tantalum containing nitrogen uniformly, and enables production of an anode electrode that has high specific capacitance and low leakage current and that exhibits excellent reliability for a prolonged period of time. There is provided nitrogen-containing metallic powder which is a solid solution containing 50–20,000 ppm nitrogen, in which the metal that constitutes the metallic powder is niobium or tantalum. The nitrogen-containing metallic powder is produced through the process in which while a metallic compound is reduced with a reducing agent, a nitrogen-containing gas is introduced into a reaction system to thereby form metal, and nitrogen is simultaneously incorporated into metal. A porous sintered body comprising the nitrogen-containing metallic powder and a solid electrolytic capacitor comprising the powder have low leakage current and exhibit excellent reliability for a prolonged period of time.
1. A nitrogen-containing metallic powder consisting essentially of tantalum containing 50–20,000 ppm nitrogen in a form of solid solution, and optionally containing phosphorus, boron, oxygen, or combinations thereof, and wherein substantially all of any nitrogen present in said nitrogen-containing metallic powder is in the form of solid solution, and
said nitrogen-containing metallic powder has a mean particle size of 80 to 360 nm.
2. A porous sintered body which is produced by sintering a nitrogen-containing metallic powder as recited in claim 1 .
3. A solid electrolytic capacitor comprising an anode electrode which is formed of the porous sintered body as recited in claim 2 .
4. The porous sintered body of claim 2 , wherein said sintering is at a temperature of from about 1,000 to about 1,400° C.
5. The nitrogen-containing metallic powder of claim 1 , wherein said nitrogen is uniformly present in said metallic powder.
6. The nitrogen-containing metallic powder of claim 1 , wherein said metallic powder contains from 4,200 to 5,900 ppm nitrogen.
7. The nitrogen-containing metallic powder of claim 1 , wherein said metallic powder has a BET surface area of from about 0.8 to about 1.8 m 2 /g.
8. The nitrogen-containing metallic powder of claim 1 , wherein said metallic powder is agglomerated.
9. The nitrogen-containing metallic powder of claim 1 , wherein said metallic powder comprises column shaped particles.
10. The nitrogen-containing metallic powder of claim 1 , wherein oxygen is present in said metallic powder in an amount of from 2,800 to 4,800 ppm.
11. The nitrogen-containing metallic powder of claim 1 , wherein said metallic powder has a mean particle size of from 249 nm to 360 nm.
12. The nitrogen-containing metallic powder of claim 1 , wherein said metallic powder has an interplane distance of Ta (110) planes of from 2.3399 to 2.3400 Å.
13. The nitrogen-containing metallic powder of claim 1 , wherein said metallic powder has an interplane distance of Ta (110) planes that is about 0.1% greater than an interplane distance of Ta (110) planes of a nitrogen-containing metallic powder in which the nitrogen is not in a form of solid solution.
14. The nitrogen-containing metallic powder of claim 1 , wherein phosphorous or boron, or both are present.
15. The nitrogen-containing metallic powder of claim 14 , wherein said phosphorous or boron is present in an amount of 10 to 300 ppm.