Cobalt(II) oxide
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Through Solid, Chemical formula and Kiln
Structure and properties
CoO crystals adopt the periclase (rock salt) structure with a lattice constant of 4.2615 Å.
It is antiferromagnetic below 289 K.
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Preparation
Cobalt(II) oxide is prepared by oxidation of cobalt powder with air or by thermal decomposition of cobalt(II) nitrate or the carbonate.
Cobalt(II,III) oxide decomposes to cobalt(II) oxide at 950 °C:
- 2 Co3O4 → 6 CoO + O2
It may also be prepared by precipitating the hydroxide, followed by thermal dehydration:
- CoX2 + 2 KOH → Co(OH)2 + 2 KX
- Co(OH)2 → CoO + H2O
Reactions
As can be expected, cobalt(II) oxide reacts with mineral acids to form the corresponding cobalt salts:
- CoO + 2 HX → CoX2 + H2O
Applications
Cobalt(II) oxide has for centuries been 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. It also is used in cobalt blue glass.