Niobium dioxide

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.[2]

Niobium dioxide
Names
IUPAC name
niobium(IV) oxide, niobium dioxide
Other names
niobium(IV) oxide, columbium dioxide
Identifiers
3D model (JSmol)
ECHA InfoCard 100.031.632
EC Number
  • 234-809-7
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
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Properties

The room temperature form of NbO2 has a tetragonal, rutile-like structure with short Nb-Nb distances, indicating Nb-Nb bonding.[3] The high temperature form also has a rutile-like structure with short Nb-Nb distances.[4] 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.[5]

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.[6] The NbO2 is subsequently reacted with magnesium vapor to produce niobium metal.[7]

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References
  1. C. K. Gupta, A. K. Suri, S Gupta, K Gupta (1994), Extractive Metallurgy of Niobium, CRC Press, ISBN 0-8493-6071-4
  2. Pradyot Patnaik (2002), Handbook of Inorganic Chemicals,McGraw-Hill Professional, ISBN 0-07-049439-8
  3. Wells A.F. (1984) Structural Inorganic Chemistry 5th edition Oxford Science Publications ISBN 0-19-855370-6
  4. Bolzan, A; Fong, Celesta; Kennedy, Brendan J.; Howard, Christopher J. (1994). "A Powder Neutron Diffraction Study of Semiconducting and Metallic Niobium Dioxide". Journal of Solid State Chemistry. 113 (1): 9–14. Bibcode:1994JSSCh.113....9B. doi:10.1006/jssc.1994.1334.
  5. Haines, J.; Léger, J. M.; Pereira, A. S. (1999). "High-pressure structural phase transitions in semiconducting niobium dioxide". Physical Review B. 59 (21): 13650. Bibcode:1999PhRvB..5913650H. doi:10.1103/PhysRevB.59.13650. hdl:10183/198788.
  6. Patent EP1524252, Sintered bodies based on niobium suboxide, Schnitter C, Wötting G
  7. 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.)
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