Method for production of niobium and tantalum powder

Process for the production of tantalum powder, from which capacitors having a specific capacity of 60,000 to 160,000 μFV/g can be produced by compacting and sintering at 1200 to 1250° C., characterised in that a tantalum pentoxide powder is reduced under a vapour pressure of 5 to 110 hPa the overall pressure in the reaction space during the entire reduction is less than 1000 hPa, and at a temperature of below 880° C. by means of magnesium vapour, such that a metal powder having a specific surface area of 6 to 15 m2/g is produced, then after mixing with a slightly hyperstoichiometric amount of magnesium at a temperature of 680 to 850° C. the surface of the metal powder is reduced by a factor of at least 3 to 0.9 to 4 m2/g.

A process for the production of valve metal powders by reduction of corresponding valve metal oxide powders by means of vaporous reducing metals and/or hydrides thereof, characterised in that the reduction is performed under a vapour pressure of the reducing metal/metal hydride of 5 to 110 hPa and the overall pressure in the reaction chamber during all or part of the reduction period is less than 1000 hPa wherein the metal powder that is produced is mixed with hyperstoichiometric amounts of magnesium in a further step and heated to 680 to 850° C., so that the specific surface area of the valve metal powder is reduced to less than ⅓ of the specific surface area of the valve metal powder before the subsequent treatment.