The invention relates to a niobium powder capable of providing a capacitor
having small amounts of leakage current, wherein the average nitrogen
concentration in the layer of 50 to 200 nm from the surface to 0.29 to 4%
by mass and preferably controlling that in the depth within 50 nm from the
surface to 0.19 to 1% by mass, the sintered body, the formed body and the
capacitor using the same.
