Blue pigments based on Co sub(xZn) sub(1)-xAl sub(2O) sub(4) spinels synthesized by the polymeric precursor method

The Co sub(xZn) sub(1)-xAl sub(2O) sub(4) 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 DTA curves showed an exothermic peak corresponding to the enthalpy of the transition taking place at about 700 degree C. The infrared spectra displayed vibrations at about 650, 550, 540, 520, 500, 490 cm super(-1, which were ascribed to the spinel structure. The UV-vis spectra presented three bands at 550, 580 and 620 nm attributed to the Co) super(2)+ spin transitions in tetrahedral sites. The colorimetric data point out the formation of blue pigments, corresponding to highly negative values of b super(*. The lightness, coordinate L) super(,) increases with the heat treatment temperature. These facts reveal that Co sub(xZn) sub(1)-xAl sub(2O) sub(4) is a promising system that can be employed to obtain ceramic blue pigments.