Method for producing tantalum powder for capacitors by reducing tantalum oxide with alkaline earth metal

A method for producing tantalum powder by reducing tantalum oxide with an alkaline earth metal, the method comprising the steps of:

• (1) mixing tantalum oxide with an excessive alkaline earth metal reducing agent, simultaneously mixing at least one alkali metal or alkaline earth metal halide accounting for 10-200% of the weight of the tantalum oxide, heating the obtained mixture to a temperature of 700-1200° C. in a heating furnace filled with an inert gas, and soaking so that the tantalum oxide and the reducing agent are subjected to a reduction reaction;
• (2) at the end of soaking, lowering the temperature of the heating furnace to 600-800° C., vacuumizing the interior of the heating furnace to 10 Pa or less, and soaking under the negative pressure so that the excessive magnesium and the tantalum powder mixture are separated;
• (3) thereafter, raising the temperature of the heating furnace to 750-1200° C., in the presence of an inert gas, and soaking so that the tantalum powder is further sintered in the molten salt, wherein the inert gas in step (3) is the same as or different from the inert gas in step (1);
• (4) then cooling to room temperature and passivating to obtain a mixed material containing halide and tantalum powder;
• and
• (5) separating the tantalum powder from the resulting mixture.