Colour performance of ceramic nano-pigments

Ceramic nano-pigments have been recently developed for ink-jet decoration of ceramic tiles using quadrichromic technology (cyan, magenta, yellow, and black colours). The colouring mechanisms and performance of CoAl2O4, Au, (Ti,Cr,Sb)O2 and CoFe2O4 nano-pigments were investigated by DRS, XRD and colorimetry. The nano-pigments were dispersed in several ceramic glazes and glassy coatings and their colour performance was compared with that of conventional micro-pigments. Each nano-pigment was characterized in terms of its colour mechanism and chemico-physical stability. Although the micro-pigments provided more saturated hues, intense colours were achievable in nano-pigments despite their very small particle size (<50 nm). Limitations to the use of nano-pigments arose for very high firing temperatures (>1200 °C) due to particle growth (e.g. Au) or dissolution in the glassy phase (e.g. titania).