Method for the production of valve metal powders

Abstract

The present invention relates to a process for the deoxidation of valve metal primary powders by means of reducing metals and/or metal hydrides, and a process for the production of tantalum powders that are suitable as anode material for electrolytic capacitors.

1 - 17 . (canceled) 
     
     
         18 . A tantalum powder with a specific surface of 4 to 8 m 2 /g., which after pressing at a pressing density of 5 g/cm 3  and sintering at 1210° C. over 10 minutes has, after forming up to a forming voltage of 10V, a capacity of 220,000 to 350,000 μFV/g. 
     
     
         19 . A tantalum powder with a specific surface of 3.5 to 6 m 2 /g, which after pressing at a pressing density of 5 g/cm 3  and sintering at 1210° C. over 10 minutes has, after forming up to a forming voltage of 10V, a capacity of 180,000 to 250,000 μFV/g. 
     
     
         20 . The tantalum powder according to  claim 18 , wherein the powder has after forming has up to a forming voltage of 16V has a capacity of 200,000 to 300,000 μFV/g. 
     
     
         21 . The tantalum powder according to  claim 18 , wherein said powder has a bulk density of 25 to 35 g/inch 3 . 
     
     
         22 . The tantalum powder according to  claim 19 , wherein said powder has a bulk density of 25 to 35 g/inch 3 . 
     
     
         23 . The tantalum powder according to  claim 18 , wherein said powder has a content of sodium and potassium that is overall less than 5 ppm and a content of iron, chromium and nickel that is overall less than 25 ppm. 
     
     
         24 . The tantalum powder according to  claim 19 , wherein said powder has a content of sodium and potassium that is overall less than 5 ppm and a content of iron, chromium and nickel that is overall, less than 25 ppm. 
     
     
         25 . The tantalum powder according to  claim 23 , wherein said powder has a content of sodium and potassium that is overall less than 2 ppm. 
     
     
         26 . The tantalum powder according to  claim 25 , wherein said powder has a content of iron, chromium and nickel that is overall less than 15 ppm. 
     
     
         27 . The tantalum powder according to  claim 24 , wherein said powder has a content of sodium and potassium that is overall less than 2 ppm. 
     
     
         28 . The tantalum powder according to  claim 27  with a content of iron, chromium and nickel that is overall less than 15 ppm. 
     
     
         29 . A process for the production of tantalum powder for electrolytic capacitors which comprises subjecting a tantalum primary powder with a specific surface of 4 to 20 m 2 /g to a deoxidation with magnesium vapor at a magnesium vapor pressure of 5 to 110 hPa without contact with liquid magnesium. 
     
     
         30 . The process as claimed in  claim 29 , wherein the tantalum powder is formed by reducing tantalum oxide to form the tantalum primary powder.