Niobium dioxide
Chemical compound
From Wikipedia, the free encyclopedia
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.[1] It can be prepared by reducing Nb2O5 with H2 at 800–1350 °C.[1] An alternative method is reaction of Nb2O5 with Nb powder at 1100 °C.[3]
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| Names | |
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| IUPAC name
niobium(IV) oxide, niobium dioxide | |
| Other names
niobium(IV) oxide, columbium dioxide | |
| Identifiers | |
3D model (JSmol) |
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| ChemSpider | |
| ECHA InfoCard | 100.031.632 |
| EC Number |
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PubChem CID |
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CompTox Dashboard (EPA) |
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| Properties | |
| NbO2 | |
| Molar mass | 124.91 g/mol |
| Appearance | bluish black solid |
| Melting point | 1,915 °C (3,479 °F; 2,188 K)[1] |
| Structure | |
| Tetragonal, tI96 | |
| I41/a, No. 88 | |
| Hazards | |
| GHS labelling:[2] | |
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| Warning | |
| H315, H319, H335, H413 | |
| P261, P264, P264+P265, P271, P273, P280, P302+P352, P304+P340, P305+P351+P338, P319, P321, P332+P317, P337+P317, P362+P364, P403+P233, P405, P501 | |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Properties
The room temperature form of NbO2 has a tetragonal, rutile-like structure with short Nb-Nb distances, indicating Nb-Nb bonding.[4] The high temperature form also has a rutile-like structure with short Nb-Nb distances.[5] 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.[6]
NbO2 is insoluble in water and is a powerful reducing agent, reducing carbon dioxide to carbon and sulfur dioxide to sulfur.[1] In an industrial process for the production of niobium metal, NbO2 is produced as an intermediate, by the hydrogen reduction of Nb2O5.[7] The NbO2 is subsequently reacted with magnesium vapor to produce niobium metal.[8]