Color and structural analysis of CoxZn7−xSb2O12 pigments

Abstract

The polymeric precursor method was successfully used to synthesize Co x Zn 7Àx Sb 2 O 12 (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 Co 2+ 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 Co 7 Sb 2 O 12 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. #

Synthesis, characterization and influence of calcination temperature on magnetic properties of nanocrystalline spinel Co-ferrite prepared by polymeric precursor method

“…This method has been used as alternative to the conventional sol-gel method to obtain nanocrystalline materials for different applications because of low cost, versatility, control of the stoichiometry, simplicity, low processing temperature, high degree of homogeneity due to the reagents are mixed at the molecular level [22].…”

“…This method has received a lot of attention due to its simplicity, low cost, homogeneous mixing at the molecular level, good stoichiometric control, low processing temperature and the use of an aqueous-based processing system. Gouveia et al [22] and Lessing [23] provided a description and discussion of such synthesis method.…”

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

“…Later, the metal chelates react with ethylene glycol, a polyhydric alcohol, in order to occur the polyester formation. A better description and discussion of this method is provided by Gouveia et al [8], Kakihana [9], Lessing [10]. The Co x Zn 1Àx Al 2 O 4 (x ¼ 0; 0.1; 0.3; 0.5; 0.7; 0.9 and 1) system was synthesized using the aforementioned polymeric precursor method.…”

“…Therefore, the present paper aims at synthesizing ceramic blue pigments from the Co x Zn 1Àx Al 2 O 4 (x ¼ 0; 0.1; 0.3; 0.5; 0.7; 0.9 and 1) system, synthesized by means of the polymeric precursor method. Gouveia et al [8], Kakihana [9] and Lessing [10] provide a description and discussion of such synthesis method. The Co x Zn 1Àx Al 2 O 4 system allows for a reduction of the production costs and also for minimizing the environmental damage, as the amount of Co is reduced.…”

Intense Blue Colors in Wolframite‐Type Co2+:MgWO4 Oxides Through Distortion in Co2+ Octahedra.

“…As a consequence of these electrons become more delocalized in the complex than they are in the free ion. The expansion of the electron cloud is known as the nephelauxetic effect . An important feature of the nephelauxetic effect is that it is directly related to covalence.…”