Formula NbO2 Melting point 1,915 °C Pubchem 82839 | Molar mass 124.91 g/mol Appearance bluish black | |
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Niobium dioxide, is the chemical compound with the formula NbO2. It is a bluish black non-stoichiometric solid with a composition range of NbO1.94-NbO2.09 It can be prepared by reacting Nb2O5 with H2 at 800–1350 °C. An alternative method is reaction of Nb2O5 with Nb powder at 1100 °C.
The room temperature form NbO2 has a tetragonal, rutile-like structure with short Nb-Nb distances indicating Nb-Nb bonding. High temp form also has a rutile-like structure with short Nb-Nb distances. Two high pressure phases have been reported one with a rutile-like structure, again with short Nb-Nb distances, and a higher pressure with baddeleyite-related structure.
NbO2 is insoluble in water and is a powerful reducing agent, reducing carbon dioxide to carbon and sulfur dioxide to sulfur. In an industrial process for the production of niobium metal [1], NbO2 is produced as an intermediate, by the hydrogen reduction of Nb2O5. The NbO2 is subsequently reacted with magnesium vapour to produce niobium metal.