Method for producing low-oxygen valve-metal sintered bodies having a large surface area

A valve metal powder comprising:

• oxygen in an amount of more than 4100 ppm·g/m2,
• nitrogen in an amount below 300 ppm,
• boron in an amount below 10 ppm,
• sulfur in an amount below 20 ppm,
• silicon in an amount below 20 ppm,
• arsenic in an amount below 10 ppm, and
• phosphorus in an amount below 20 ppm,
• wherein, the ppm values are each based on parts by mass.

A sintered body obtainable by a process comprising:

• pressing a powder comprising or consisting of at least one valve metal so as to provide a pellet around a wire, the wire being made from at least one valve metal;
• providing the pellet together with a reducing agent so that the pellet is not in a direct contact with and does not come into a direct contact with the reducing agent;
• heating so that the powder in the pellet is sintered to form a sintered body, an oxygen content of the at least one valve metal within the sintered body is simultaneously reduced, and the reducing agent is oxidized to an oxidized reducing agent;
• and
• removing the oxidized reducing agent with at least one mineral acid,
• wherein,
• the powder comprising or consisting of the at least one valve metal comprises an oxygen content of >4,100 ppm·g/m2, and
• the sintered body comprises a wire pull strength of 2.7 to 11, the wire pull strength being determined by inserting the wire through an orifice of a holder plate having a diameter of 0.25 mm, clamping a free end of the wire into a holding clamp of a force gauge, and subjecting the free end to a load until the wire is pulled out of the sintered body.