Niobium dioxide, is the

chemical compound A chemical compound is a chemical substance composed of many identical molecules (or molecular entities) containing atoms from more than one chemical element held together by chemical bonds. A molecule consisting of atoms of only one element ...

with the formula NbO₂. It is a bluish-black

non-stoichiometric In chemistry, non-stoichiometric compounds are chemical compounds, almost always solid inorganic compounds, having elemental composition whose proportions cannot be represented by a ratio of small natural numbers (i.e. an empirical formula); m ...

solid with a composition range of NbO_1.94-NbO_2.09. It can be prepared by reducing Nb₂O₅ with H₂ at 800–1350 °C. An alternative method is reaction of Nb₂O₅ with Nb powder at 1100 °C.Pradyot Patnaik (2002), ''Handbook of Inorganic Chemicals'',McGraw-Hill Professional,

Properties

The room temperature form of NbO₂ has a

tetragonal In crystallography, the tetragonal crystal system is one of the 7 crystal systems. Tetragonal crystal lattices result from stretching a cubic lattice along one of its lattice vectors, so that the cube becomes a rectangular prism with a squar ...

rutile Rutile is an oxide mineral composed of titanium dioxide (TiO2), the most common natural form of TiO2. Rarer polymorphs of TiO2 are known, including anatase, akaogiite, and brookite. Rutile has one of the highest refractive indices at visib ...

-like structure with short Nb-Nb distances, indicating Nb-Nb bonding. The high temperature form also has a

-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 Carbon dioxide ( chemical formula ) is a chemical compound made up of molecules that each have one carbon atom covalently double bonded to two oxygen atoms. It is found in the gas state at room temperature. In the air, carbon dioxide is trans ...

to carbon and sulfur dioxide to sulfur. In an industrial process for the production of niobium metal, NbO₂ is produced as an intermediate, by the hydrogen reduction of Nb₂O₅.Patent EP1524252, Sintered bodies based on niobium suboxide, Schnitter C, Wötting G The NbO₂ is subsequently reacted with magnesium vapor to produce niobium metal.Method for producing tantalum/niobium metal powders by the reduction of their oxides by gaseous magnesium, US patent 6171363 (2001), Shekhter L.N., Tripp T.B., Lanin L.L. (H. C. Starck, Inc.)

References

{{oxygen compounds Niobium(IV) compounds Non-stoichiometric compounds Transition metal oxides