Synthesis Of Ceramic Pigments And Their Spectral Properties

At present in our country, the studies on ceramic pigments are still based on traditional empirical methods, theoretical analysis is lack. On the other hand, the underglaze pigments are really short, only cobalt-blue and underglaze red are widely used so far. Therefore, optimizing synthetic conditions, developing novel underglaze pigments and investigating color-produced mechanisms are imperative.Several ceramic pigments containing Co²⁺ and Cr³⁺ as well as YAG:Ce were prepared by using high temperature solid state reaction method according to the traditional formulations of these pigments. Co²⁺ and Cr³⁺ in these pigments were replaced by other non-color cations, such as Mg²⁺, Zn²⁺ and Cr³⁺ for modifying their colors. The main results are as follows:1. Several ceramic pigments were prepared by using high temperature solid reaction methods, the phase present was examined by XRD, and the optimized synthesis conditions were determined. The results indicate:cobalt-blue, malachite-green, cobaltous-silicate-purple and YAG:Ce yellow may be used or potentially used as underglaze pigments.2. In the pigments of the cobalt-blue, malachite-green and cobaltous-silicate-purple, by replacing Co²⁺ and Cr³⁺ by Mg²⁺, Zn²⁺ or Al³⁺, the solid solutions were formed by and the solid solution ranges were determined by calculating the unit cell volume based on XRD data. The colors of the pigments could be continuously adjusted in the solid solution ranges by changing the contents of Mg²⁺, Zn²⁺ or Al³⁺ in the pigments.3. The color-produced mechanisms of Co²⁺ in tetrahedral field and octahedral field were discussed. Co²⁺ performed different colors in different crystalline fields. In the tetrahedral field, the three absorption peaks of Co²⁺ were located in red and green regions from 500 to 700 nm, which could be assigned to the transitions ⁴A₂? ²A₁ in 627 nm,⁴A₂?⁴T₁ in 592 nm, and ⁴A₂? ²A₁ in 627 nm and these absorptions resulted in blue color. In the octahedral field, the absorption peaks were located in blue and green regions, mainly at 500 nm, due to the transition ⁴T_1g?F?? ⁴T_1g?P?, while the absorption in the purple regions is relatively weak, resulting in purple color. In addition, the color-produced mechanism of Cr²⁺ in the octahedral field was also analyzed. The two absorption peaks of Cr²⁺appeared at 392 nm and 552 nm, due to the transitions from ⁴A₂ to ⁴T₁ and 4T2, respectively.4. The diffusive reflection spectra of the pigments studied in this thesis were measured. The results showed:each pigment had its characteristic spectrum; the absorption peaks could be assigned, and the color coordinates of the pigments could be calculated based on the spectra. Actually the observed colors of the pigments not only depended on the color coordinates, but also depends on the brightness ?reflectivity?.