Ecofriendly High NIR Reflectance Ceramic Pigments Based on Rare Earths Compared with Classical Chromophores Prepared by DPC Method

A high NIR reflectance ceramic pigments palette based on rare earths except black (La,Li-SrCuSi4O10 blue wesselsite, Pr-CeO2 red-brown cerianite, Mo-Y2Ce2O7 yellow cerate, Sr4Mn2CuO9 black hexagonal perovskite) was compared with the coolest traditional pigments palette prepared by dry powder coating (DPC) to obtain “core-shell” pigments (Co-willemite blue, Cr-franklinite brown, Ni,Sb-rutile yellow, Co,Cr-spinel black). Adding CaCO3 as a binder, normalized NIR reflectance at L* = 85, 55 and 30 was compared for yellow, brown and blue-black powders, respectively. Rare earths lack intense absorption bands in the NIR range and therefore its pigments show higher NIR reflectance, but normalized measurements show smaller differences and even have an inverse result for blue pigments. The pigmenting capacity and stability study in different media show that the stability of cool rare earth pigments is lower than that of DPC classical pigments, except in the case of the red-brown Pr-cerianite pigment