Niobium monoxide

Niobium monoxide
Names
	Other names niobium(II) oxide
Identifiers
CAS Number	12034-57-0 ;
3D model (JSmol)	Interactive image;
ChemSpider	74751 ;
ECHA InfoCard	100.031.631
PubChem CID	82838;
CompTox Dashboard (EPA)	DTXSID101014241 ;
	InChI InChI=1S/Nb.O Key: BFRGSJVXBIWTCF-UHFFFAOYSA-N ;
	SMILES O=[Nb];
Properties
Chemical formula	NbO
Molar mass	108.905 g/mol[1]
Appearance	grey solid[1]
Odor	odorless
Density	7.30 gcm3[1]
Melting point	1,937 °C (3,519 °F; 2,210 K)[1]
Solubility	slightly soluble in HCl ; insoluble in nitric acid
Structure[2]
Crystal structure	Cubic, cP6
Space group	Pm3m, No. 221
Lattice constant	a = 0.4211 nm
Formula units (Z)	3
Thermochemistry[3]
Heat capacity (C)	41.3 J/(mol·K)
Std molar; entropy (So298)	48.1 J/(mol·K)
Std enthalpy of; formation (ΔfH⦵298)	= -405.85 kJ/mol
Gibbs free energy (ΔfG˚)	-378.6 kJ/mol
	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

Niobium monoxide is the inorganic compound with the formula Nb O. It is a grey solid with metallic conductivity.[1]

Structure and electronic properties

NbO adopts an unusual structure, being cubic as is rock salt structure, but where both niobium and oxygen atoms are four coordinate square planar. The niobium centers are arranged in octahedra, and there is a structural similarity to the octahedral niobium clusters in lower halides of niobium. In NbO the Nb-Nb bond length is 298 pm which compares to 285 pm in the metal.[2] One study of the bonding concludes that strong and nearly covalent bonds exist between the metal centers.[4]

It is a superconductor with a transition temperature of 1.38 K.[5] It is used in capacitors where a layer of Nb₂O₅ is formed around NbO grains as the dielectric.[6][7][8]

Preparation

NbO can be prepared by reduction of Nb₂O₅ by H₂ More typically, it is prepared by comproportionation:[9]

Nb₂O₅ + 3 Nb → 5 NbO

References

Haynes, p. 4.76
Pialoux, A.; Joyeux, M.L; Cizeron, G. (1982). "Étude du comportement du niobium sous vide par diffraction des rayons X à haute température". Journal of the Less Common Metals. 87: 1–19. doi:10.1016/0022-5088(82)90036-4.
Haynes, p. 5.29
Schulz, Werner W.; Wentzcovitch, Renata M. (1993). "Electronic band structure and bonding in Nb₃O₃". Physical Review B. 48 (23): 16986. Bibcode:1993PhRvB..4816986S. doi:10.1103/PhysRevB.48.16986. PMID 10008298.
Hulm, J. K.; Jones, C. K.; Hein, R. A.; Gibson, J. W. (1972). "Superconductivity in the TiO and NbO systems". Journal of Low Temperature Physics. 7 (3–4): 291–307. Bibcode:1972JLTP....7..291H. doi:10.1007/BF00660068.
Nico, C.; Soares, M. R. N.; Rodrigues, J.; Matos, M.; Monteiro, R.; Graça, M. P. F.; Valente, M. A.; Costa, F. M.; Monteiro, T. (2011). "Sintered NbO Powders for Electronic Device Applications". The Journal of Physical Chemistry C. 115 (11): 4879–4886. doi:10.1021/jp110672u.
"NbO/Nb₂O₅ core–shells by thermal oxidation". doi:10.1016/j.jeurceramsoc.2013.06.020. Cite journal requires |journal= (help)
Naito, Kazumi and Kabe, Isao (2005) "Production method of solid electrolytic capacitor" U.S. Patent 6,882,522
Reed, T. B.; Pollard, E. R.; Lonney, L. E.; Loehman, R. E.; Honig, J. M. (2007). "Niobium Monoxide". Inorganic Syntheses. pp. 108–110. doi:10.1002/9780470132616.ch22. ISBN 9780470132616.

Cited sources

Haynes, William M., ed. (2016). CRC Handbook of Chemistry and Physics (97th ed.). Boca Raton, FL: CRC Press. ISBN 9781498754293.

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[crc-1] Haynes, p. 4.76

[str-2] Pialoux, A.; Joyeux, M.L; Cizeron, G. (1982). "Étude du comportement du niobium sous vide par diffraction des rayons X à haute température". Journal of the Less Common Metals. 87: 1–19. doi:10.1016/0022-5088(82)90036-4.

[3] Haynes, p. 5.29

[4] Schulz, Werner W.; Wentzcovitch, Renata M. (1993). "Electronic band structure and bonding in Nb₃O₃". Physical Review B. 48 (23): 16986. Bibcode:1993PhRvB..4816986S. doi:10.1103/PhysRevB.48.16986. PMID 10008298.

[5] Hulm, J. K.; Jones, C. K.; Hein, R. A.; Gibson, J. W. (1972). "Superconductivity in the TiO and NbO systems". Journal of Low Temperature Physics. 7 (3–4): 291–307. Bibcode:1972JLTP....7..291H. doi:10.1007/BF00660068.

[Nico-6] Nico, C.; Soares, M. R. N.; Rodrigues, J.; Matos, M.; Monteiro, R.; Graça, M. P. F.; Valente, M. A.; Costa, F. M.; Monteiro, T. (2011). "Sintered NbO Powders for Electronic Device Applications". The Journal of Physical Chemistry C. 115 (11): 4879–4886. doi:10.1021/jp110672u.

[Nico2-7] "NbO/Nb₂O₅ core–shells by thermal oxidation". doi:10.1016/j.jeurceramsoc.2013.06.020. Cite journal requires |journal= (help)

[8] Naito, Kazumi and Kabe, Isao (2005) "Production method of solid electrolytic capacitor" U.S. Patent 6,882,522

[9] Reed, T. B.; Pollard, E. R.; Lonney, L. E.; Loehman, R. E.; Honig, J. M. (2007). "Niobium Monoxide". Inorganic Syntheses. pp. 108–110. doi:10.1002/9780470132616.ch22. ISBN 9780470132616.