A process for producing Nb or Ta as powder (>99 pct pure) from its pentoxide consisted of nitriding in nh3 at 1,100 deg.-1,500 Deg. C for 40-50 h to remove o, and then, to remove n, heating either 5-10 min at approximately 3,000 deg. C or 4-5 h at 1,850 deg. C in vacuum. Niobium is nitrided in two stages, first forming an oxynitride in 2-3 h at 650 deg.-850 Deg. C and then reacting further with nh3 for 2-3 h at 1,100 deg.-1,500 Deg. C to remove o more completely. A suitable apparatus for the nitriding is described in which nh3 can be passed through a batch of 325-mesh oxide on a porous support inside a closed tube of heat resisting metal or ceramic, which in turn is inside an electric furnace. Metal of 99.5- 99.95 pct purity was produced from oxide by this method of intermediate nitriding.
U.S. Pat. 3,775,096; Nov. 27, 1973; Chem. Abstr. 80:P73,027a