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
Appearance	grey solid
Odor	odorless
Density	7.30 g/cm3
Melting point	1,937 °C (3,519 °F; 2,210 K)
Solubility	slightly soluble in HCl ; insoluble in nitric acid
Structure
Crystal structure	Cubic, cP6
Space group	Pm3m, No. 221
Lattice constant	a = 0.4211 nm
Formula units (Z)	3
Thermochemistry
Heat capacity (C)	41.3 J/(mol·K)
Std molar; entropy (S⦵298)	48.1 J/(mol·K)
Std enthalpy of; formation (ΔfH⦵298)	−405.85 kJ/mol
Gibbs free energy (ΔfG⦵)	−378.6 kJ/mol
Hazards
	GHS labelling:
Pictograms
Signal word	Warning
Hazard statements	H315, H319, H335
Precautionary statements	P261, P264, P264+P265, P271, 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). verify (what is ?) Infobox references

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

Structure and electronic properties

NbO adopts an unusual cubic structure, similar to the rock salt structure but with some missing atoms compared to it, so that both niobium and oxygen atoms have square planar coordination geometries. 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.^[5]

It is a superconductor with a transition temperature of 1.38 K.^[6] It is used in capacitors where a layer of Nb₂O₅ is formed around NbO grains as the dielectric.^[7]^[8]^[9]

Preparation

NbO can be prepared by reduction of Nb₂O₅ by hydrogen. More typically, it is prepared by comproportionation:^[10]

Nb₂O₅ + 3 Nb → 5 NbO

References

^ ^a ^b ^c ^d ^e Haynes, p. 4.76
^ ^a ^b 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
^ PubChem. "Niobium oxide (NbO)". pubchem.ncbi.nlm.nih.gov. Retrieved 2026-02-14.
^ Schulz, Werner W.; Wentzcovitch, Renata M. (1993). "Electronic band structure and bonding in Nb₃O₃". Physical Review B. 48 (23): 16986–16991. 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. S2CID 122554738.
^ 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.
^ Nico, Cláudio; Rino, Luís; Matos, Mariana; Monteiro, Rui; Costa, Florinda M.; Monteiro, Teresa; Graça, Manuel P.F. (2013). "NbO/Nb₂O₅ core–shells by thermal oxidation". Journal of the European Ceramic Society. 33 (15–16): 3077–3083. doi:10.1016/j.jeurceramsoc.2013.06.020.
^ 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, Florida: CRC Press. ISBN 9781498754293.

[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] PubChem. "Niobium oxide (NbO)". pubchem.ncbi.nlm.nih.gov. Retrieved 2026-02-14.

[5] Schulz, Werner W.; Wentzcovitch, Renata M. (1993). "Electronic band structure and bonding in Nb₃O₃". Physical Review B. 48 (23): 16986–16991. Bibcode:1993PhRvB..4816986S. doi:10.1103/PhysRevB.48.16986. PMID 10008298.

[6] 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. S2CID 122554738.

[Nico-7] 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.

[Nico2-8] Nico, Cláudio; Rino, Luís; Matos, Mariana; Monteiro, Rui; Costa, Florinda M.; Monteiro, Teresa; Graça, Manuel P.F. (2013). "NbO/Nb₂O₅ core–shells by thermal oxidation". Journal of the European Ceramic Society. 33 (15–16): 3077–3083. doi:10.1016/j.jeurceramsoc.2013.06.020.

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

[10] 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.

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