Blue pigments based on CoxZn1-xAl2O4 spinels synthesized by the polymeric precursor method

The CoxZn1-xAl2O4 system (x=0; 0.1; 0.3; 0.5: 0.7; 0.9 and 1) was synthesized by the polymeric precursor method and characterized by the techniques XRD, TG-DTA, IR, UV-vis and colorimetry. The XRD patterns displayed the characteristic peaks of the spinel structure and a good crystallinity. The ETA curves showed an exothermic peak corresponding to the enthalpy of the transition taking place at about 700 degrees C. The infrared spectra displayed vibrations at about 650, 550, 540, 520, 500, 490 cm 1, which were ascribed to the spinel structure. The UV-vis spectra presented three bands at 550, 580 and 620 nm attributed to the Co2+ spin transitions in tetrahedral sites. The colorimetric data point out the formation of blue pigments, corresponding to highly negative values of b*. The lightness, coordinate L*, increases with the heat treatment temperature. These facts reveal that CoxZn1-xAl2O4 is a promising system that can be employed to obtain ceramic blue pigments. (C) 2008 Elsevier Ltd. All rights reserved.