Cobalt(II) oxide is an inorganic compound that has been described as an olive-green
[ or gray][ solid. It is used extensively in the ]ceramic
A ceramic is any of the various hard, brittle, heat-resistant and corrosion-resistant materials made by shaping and then firing an inorganic, nonmetallic material, such as clay, at a high temperature. Common examples are earthenware, porcelain ...
s 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
Cobalt(II,III) oxide is an inorganic compound with the formula Co3O4. It is one of two well characterized cobalt oxides. It is a black antiferromagnetic solid. As a mixed valence compound, its formula is sometimes written as CoIICoIII2O4 and some ...
, a black solid with the formula
In science, a formula is a concise way of expressing information symbolically, as in a mathematical formula or a ''chemical formula''. The informal use of the term ''formula'' in science refers to the general construct of a relationship betwee ...
Co3O4.
Structure and properties
CoO crystals adopt the periclase
Periclase is a magnesium mineral that occurs naturally in Contact metamorphism, contact metamorphic rocks and is a major component of most basic refractory bricks. It is a Cubic crystal system, cubic form of magnesium oxide (magnesium, Mgoxygen, ...
(rock salt
Halite (), commonly known as rock salt, is a type of salt, the mineral (natural) form of sodium chloride ( Na Cl). Halite forms isometric crystals. The mineral is typically colorless or white, but may also be light blue, dark blue, purple, pi ...
) structure with a lattice constant of 4.2615 Å.
It is antiferromagnetic
In materials that exhibit antiferromagnetism, the magnetic moments of atoms or molecules, usually related to the spins of electrons, align in a regular pattern with neighboring spins (on different sublattices) pointing in opposite directions. ...
below 16 °C.
Preparation
Cobalt(II) oxide is prepared by oxidation of cobalt powder with air or by thermal decomposition of cobalt(II) nitrate
Cobalt is a chemical element with the symbol Co and atomic number 27. As with nickel, cobalt is found in the Earth's crust only in a chemically combined form, save for small deposits found in alloys of natural meteoric iron. The free element, p ...
or the carbonate.Cobalt(II,III) oxide
Cobalt(II,III) oxide is an inorganic compound with the formula Co3O4. It is one of two well characterized cobalt oxides. It is a black antiferromagnetic solid. As a mixed valence compound, its formula is sometimes written as CoIICoIII2O4 and some ...
decomposes to cobalt(II) oxide at 950 °C:
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
A kiln is a thermally insulated chamber, a type of oven, that produces temperatures sufficient to complete some process, such as hardening, drying, or chemical changes. Kilns have been used for millennia to turn objects made from clay int ...
fired pottery. The additive provides a deep shade of blue named cobalt blue
Cobalt blue is a blue pigment made by sintering cobalt(II) oxide with aluminum(III) oxide (alumina) at 1200 °C. Chemically, cobalt blue pigment is cobalt(II) oxide-aluminium oxide, or cobalt(II) aluminate, CoAl2O4. Cobalt blue is lighter ...
. The band gap (CoO) is around 2.4 eV.
It also is used in cobalt blue glass
Cobalt glass—known as "smalt" when ground as a pigment—is a deep blue coloured glass prepared by including a cobalt compound, typically cobalt oxide or cobalt carbonate, in a glass melt. Cobalt is a very intense colouring agent and very litt ...
.
See also
*Cobalt oxide nanoparticles
In materials and electric battery research, cobalt oxide nanoparticles usually refers to particles of cobalt(II,III) oxide of nanometer size, with various shapes and crystal structures.
Cobalt oxide nanoparticles have potential applications in ...
*Cobalt
Cobalt is a chemical element with the symbol Co and atomic number 27. As with nickel, cobalt is found in the Earth's crust only in a chemically combined form, save for small deposits found in alloys of natural meteoric iron. The free element, pr ...
*Cobalt(II,III) oxide
Cobalt(II,III) oxide is an inorganic compound with the formula Co3O4. It is one of two well characterized cobalt oxides. It is a black antiferromagnetic solid. As a mixed valence compound, its formula is sometimes written as CoIICoIII2O4 and some ...
References
{{Oxides
Cobalt(II) compounds
Transition metal oxides
Rock salt crystal structure