Color and structural analysis of CoxZn7−xSb2O12 pigments

The polymeric precursor method was successfully used to synthesize CoxZn7−xSb2O12 (x = 0–7) powders. Pigments were evaluated using colorimetry, X-ray diffraction, UV–vis and infrared spectroscopy. The optical band gap values vary with the Co2+ substitution. These results suggest that the concomitant presence of Co and Zn in the spinel lattice leads to the rupture of the Végard law, as well as other properties of the studied system, such as unit cell volume. The Co-richer samples display a higher absorbance than the Co-lean samples. The high absorption of the Co7Sb2O12 sample at most of the visible region makes this compound a candidate for a black pigment. It was shown that color depends on the site where the chromophore ion is located, in agreement with the ligand field theory.