Niobium dioxide

Niobium dioxide
IUPAC name

niobium(IV) oxide, niobium dioxide
Other names

niobium(IV) oxide, columbium dioxide
Identifiers
CAS number 12034-59-2 Y
Properties
Molecular formula NbO2
Molar mass 124.91 g/mol
Appearance bluish black
Melting point

1915 °C [1]
Structure
Crystal structure Tetragonal, tI96
Space group I41/a, No. 88
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Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

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 reacting Nb2O5 with H2 at 800–1350 °C.[1] An alternative method is reaction of Nb2O5 with Nb powder at 1100 °C.[2]

The room temperature form NbO2 has a tetragonal, rutile-like structure with short Nb-Nb distances indicating Nb-Nb bonding.[3] High temp 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[1], NbO2 is produced as an intermediate, by the hydrogen reduction of Nb2O5.[6] The NbO2 is subsequently reacted with magnesium vapour to produce niobium metal.[7]

References

  1. ^ a b c d C. K. Gupta, A. K. Suri, S Gupta, K Gupta (1994), Extractive Metallurgy of Niobium, CRC Press, ISBN 0849360714
  2. ^ Pradyot Patnaik (2002), Handbook of Inorganic Chemicals,McGraw-Hill Professional, ISBN 0070494398
  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: 9. 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. doi:10.1103/PhysRevB.59.13650. 
  6. ^ Patent EP1524252, Sintered bodies based on niobium suboxide, Schnitter C, Wötting G
  7. ^ Method for producing tantallum/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.)