Chemical compound

Cobalt(II) oxide is an inorganic compound that has been described as an olive-green[3] or gray[4] solid. It is used extensively in the ceramics industry as an additive to create blue colored glazes and enamels as well as in the chemical industry for producing cobalt(II) salts. A related material is cobalt(II,III) oxide, a black solid with the formula Co3O4.

Structure and properties

CoO crystals adopt the periclase (rock salt) structure with a lattice constant of 4.2615 Å.[5]

It is antiferromagnetic below 16 °C.[6]


Cobalt(II) oxide is prepared by oxidation of cobalt powder with air or by thermal decomposition of cobalt(II) nitrate or the carbonate.[3][4]

Cobalt(II,III) oxide decomposes to cobalt(II) oxide at 950 °C:[7]

2 Co3O4 → 6 CoO + O2

It may also be prepared by precipitating the hydroxide, followed by thermal dehydration:[citation needed]

CoX2 + 2 KOH → Co(OH)2 + 2 KX
Co(OH)2 → CoO + H2O


As can be expected, cobalt(II) oxide reacts with mineral acids to form the corresponding cobalt salts:[citation needed]

CoO + 2 HX → CoX2 + H2O


Cobalt(II) oxide has for centuries used as a coloring agent on kiln fired pottery. The additive provides a deep shade of blue named cobalt blue. The band gap (CoO) is around 2.4 eV.[citation needed] It also is used in cobalt blue glass.

See also


  1. ^ Lide, David R., ed. (2006). CRC Handbook of Chemistry and Physics (87th ed.). Boca Raton, FL: CRC Press. ISBN 0-8493-0487-3.
  2. ^ Advanced Search – Alfa Aesar – A Johnson Matthey Company Archived 2011-07-19 at the Wayback Machine. Retrieved on 2011-11-19.
  3. ^ a b Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 978-0-08-037941-8.
  4. ^ a b Donaldson, John Dallas; Beyersmann, Detmar (2005). "Cobalt and Cobalt Compounds". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a07_281.pub2.
  5. ^ Kannan, R.; Seehra, Mohindar S. (1987). "Percolation effects and magnetic properties of the randomly diluted fcc system CopMg1-pO". Physical Review B. 35 (13): 6847–6853. doi:10.1103/PhysRevB.35.6847.
  6. ^ Silinsky, P. S.; Seehra, Mohindar S. (1981). "Principal magnetic susceptibilities and uniaxial stress experiments in CoO". Physical Review B. 24: 419–423. doi:10.1103/PhysRevB.24.419.
  7. ^ US 4389339, James, Leonard E.; Crescentini, Lamberto & Fisher, William B., "Process for making a cobalt oxide catalyst", published 1983-06-21