Synthesis of nanosized (Zn1−xCox)Al2O4 spinels: New pink ceramic pigments

The Zn1−xCoxAl2O4 system has been reported to show a blue color with particles sizes that range from 36 nm to 30 μm. However, we have observed a pink color in this system with nanoparticles of an average size of 10 nm.Such differences in the optical properties of this nanosystem are related to the distribution of the cobalt cations in octahedral sites rather than in tetrahedral sites as in standard cobaltite spinels.The solid solution Zn1−xCoxAl2O4 (x = 0.2, 0.4, 0.6, 0.8 and 1) was synthesized by a co-precipitation reaction from the metallic salts and subsequent calcinations.The color properties and the high thermal stability (1400 °C) of these nanostructures suggest that they have the potential to be applied as satisfactory ceramic pigments.

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► Nanopowders of Co2+/ZnAl2O4 were synthesized.
► These nanopowders have an average size of 10 nm.
► These nanopowders show different optical properties from their bulk counterpart.
► The color of the bulk system is blue and the color of the nanosystem is pink.