The purpose of this study was to determine the optimal firing condition and composition for Al2TiO5 crystal, which is suitable for stable coloration in glazes at high temperatures, using Cr2O3 as chromophore for the synthesis of Al2TiO5 system pigments. Al2TiO5 has a high refractive index and good solubility of chromophore in the Al2TiO5 lattice, making this structure a good candidate for the development of new ceramic pigments. Pigments were synthesized by using Al2O3 and TiO2 mainly. Various amounts of Cr2O3 such as 0.01, 0.02, 0.03, 0.04 and 0.05 mole were also added. Each compound was synthesized at 1300˚C, 1400˚C, and 1500˚C for 2 hours and cooled naturally. The crystal structure, solubility limit, and color of the synthesized pigments were analyzed by XRD, SEM, Raman spectroscopy, UV and UV-vis. The changes in color as the result of applying 6 wt% of the synthesized pigments to lime barium glaze were expressed as CIE-L*a*b* values. A Cr2O3 0.03 mole doped Al2TiO5 brown pigment was successfully synthesize at 1400˚C, and the values of CIE-L*a*b* parameters were L* = 44.62, a* = 3.10, and b* = 17.25. In the case of the pigment synthesized at 1500˚C, the brown color was obtained at 0.01 mole and 0.02 mole Cr2O3, and the CIE-L*a*b* values were 55.34, 1.73, 28.64, and 49.39, 0.51, 21.33, respectively. At 1500˚C, the maximum limit of solid solution was 0.03 mole Cr2O3. The glazed sample showed green color, and the values of the CIEL* a*b* parameters were L* = 45.69, a* = -0.98, and b* = 20.38.

Al2TiO5 has a high refractive index and good solubility of the chromophore in the Al2TiO5 lattice, which allowsthis structure to be a good candidate for the development of new ceramic pigments. However, pure Al2TiO5 is well knownto decompose on firing at 900~1100oC. However, this process can be inhibited by the incorporation of certain metal cationsinto its crystalline lattice. In this study, the synthesis of gray ceramic pigment was performed by doping cobalt on the Al2TiO5crystal structure. The Al2TiO5 was synthesized using Al2O3 and TiO2, and doped with Co3O4 as a chromophore material. Inorder to prevent the thermal decomposition during the cooling procedure, MgO was added to samples by 0.05mole, 0.1mole,and 0.15mole as a stabilizer. The samples were fired at 1500oC for 2 hours and cooled naturally. The crystal structure, solubilitylimit, and color of the synthesized pigment were analyzed using XRD, Raman spectroscopy, UV, and UV-vis. Al2O3 wasavailable for the formation of CoAl2O4, which should also be considered in order to explain the small amount of this phasedetected in the sample with the higher Co2+ content (≥0.03mole). It was found that the solubility limit of Co2+ in the Al2TiO5crystal was 0.02mole% through an analysis of Raman spectroscopy. Through the addition of a pigment with 0.02mole% ofCo2+ to lime-barium glaze, stabilized gray color pigments with 66.54, −2.35, and 4.68 as CIE-L*a*b* were synthesized.