Cobalt green is an ambiguous term for either of two families of green inorganic

pigment A pigment is a powder used to add or alter color or change visual appearance. Pigments are completely or nearly solubility, insoluble and reactivity (chemistry), chemically unreactive in water or another medium; in contrast, dyes are colored sub ...

s. Both are obtained by doping cobalt(II) oxide into colorless host oxides.

Spinel-based cobalt green

Doping Co(II) into Mg(II) and Zn(II) sites of Mg₂TiO₄ and Zn₂TiO₄, respectively gives one family of cobalt greens. These materials adopt the

spinel Spinel () is the magnesium/aluminium member of the larger spinel group of minerals. It has the formula in the cubic crystal system. Its name comes from the Latin word , a diminutive form of ''spine,'' in reference to its pointed crystals. Prop ...

structure.Völz, Hans G. ''et al.'' "Pigments, Inorganic" in ''Ullmann's Encyclopedia of Industrial Chemistry'', 2006 Wiley-VCH, Weinheim. .

Rinman's green

Rinman's green, also referred to as Rinmann's green, is obtained by doping cobalt(II) oxide into zinc oxide. Sven Rinman, a Swedish chemist, discovered this compound in 1780.

Zinc oxide Zinc oxide is an inorganic compound with the Chemical formula, formula . It is a white powder which is insoluble in water. ZnO is used as an additive in numerous materials and products including cosmetics, Zinc metabolism, food supplements, rubbe ...

–derived pigments have been used in many industries and processes. It is rarely used because it is a weak chromophore and relatively expensive compared to

chromium(III) oxide Chromium(III) oxide (or chromia) is an inorganic compound with the formula . It is one of the principal oxides of chromium and is used as a pigment. In nature, it occurs as the rare mineral eskolaite. Structure and properties has the corundum s ...

. The structure and color of compositions Zn_1−xCo_xO depends on the value of x. For x ≤ 0.3, the material adopts the Wurtzite structure (of ZnO) and is intensely green. For x ≥ 0.7, the material has the

sodium chloride Sodium chloride , commonly known as Salt#Edible salt, edible salt, is an ionic compound with the chemical formula NaCl, representing a 1:1 ratio of sodium and chloride ions. It is transparent or translucent, brittle, hygroscopic, and occurs a ...

structure (of CoO) and is pink. Intermediate values of x give a mixture of the two phases. Cobalt green has been tested for use in " spintronic" devices. Cobalt green is attractive in this application because it is magnetic at room temperature.

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Pigments through the Ages
{{zinc compounds Inorganic pigments Cobalt compounds Zinc compounds Transition metal oxides

Spinel-based cobalt green

Rinman's green

See also

References

External links