Ink-jet printing techniques with ceramic ink, which contains ceramic pigments as colorant, are in increasingly use in the ceramic industry. Generally, ceramic pigments that are produced by conventional method show diameters of several micrometers; these micrometer sized particles in the ink-jet printing process can cause undesirable behavior such as print head nozzle clogging. To prevent this problem, a particle size reduction process is required. In this study, CMYK (cyan, magenta, yellow, black) pigments were synthesized via solid state method. Each pigment particle was milled to submicron size by an attrition mill. The effects of micronizing on the morphology, mechanical property, crystal structure and color property of the CMYK ceramic pigments were investigated by field emission scanning electron microscopy (FE-SEM), particle size analysis (PSA), X-ray diffraction (XRD) and CIE L*a*b*.

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.