An x-ray investigation on the formation of oxides of niobium

Abstract

The oxidation behaviour of pure niobium powder has been studied in air at temperatures upto 1400°C. Various oxides which formed at different temperatures were identified by x-ray diffraction method. The metal is found to oxidise in air at and above 400°C to its stable oxide. Nb2O5. Below 400°C, oxygen enters into solid solution with niobium while above this temperature, the pentoxide, is Nb2O5 formed. Two allotropic forms of Nb2O5 were detected. The low temperature a-form which is found to exist upto 900°C transforms irreversibly to the high temperature b-form. (Dr. J.P. Guha, Scientist and Mr. P. Chakravarty, Junior Research Fellow, National Metallurgical Laboratory, Jamshedpur)