Colour performance of ceramic nano-pigments

Ceramic nano-pigments have been recently developed for ink-jet printing decoration of ceramic tiles by the quadrichromy technology (cyan, magenta, yellow, and black colours). The colouring mechanisms and performance of these nano-pigments (CoAl2O4, Au, (Ti,Cr,Sb)O2, CoFe2O4) were investigated by DRS, XRD and colourimetry. Nano-pigments were dispersed in several ceramic glazes and glassy coatings and their colour performance compared with that of conventional micro-pigments. Each nano-pigment is characterized by its own colour mechanism and chemico-physical stability in ceramic applications. Intense colours are achievable, besides the very small particle size of pigments ( 50 nm) even though the colour of high quality micro-pigments appears to be more saturated. Limitations to the use of nano-pigments arose for very high firing temperatures (1200ºC) due to particle growth (e.g. Au) or dissolution in the glassy phase (e.g. titania).