Environmentally Benign Rare Earth Pigments: Effect of Calcium Dopant and Tuning of Bandgaps for Different Color Hues
Abstract Environmentally benign rare earth pigments having the general formula Ca0.1 Ln0.9 PO4 ( Ln = Y , Pr , mixed rare rearth oxides, RE and Di ) have been prepared by a traditional solid state route. The samples were characterized by X–ray diffraction diffraction, UV–vis Spectroscopy, scanning electron microscope (SEM), particle size distribution, color coordinates determination, acid/alkali test, thermo gravimetric (TG) analysis and CIE–1976 L*a*b* color scales. Among the various lanthanide ions and calcium ion as dopant, the pigment composition shows various hues ranges from green to yellow. The coloring mechanism is based on the tuning of band gap by the dopant like calcium in various rare earth host lattice. The designed pigments consist of non–toxic elements and were further found to possess high thermal and chemical stability. The pigments were also found to be appropriate candidates for the coloration of polymer substrates.Thus, the present environmental friendly pigment powders may find potential alternative to the classical toxic inorganic pigments for various applications.