Synthesis and characterization of environmentally benign calcium-doped Pr2Mo2O9 pigments: Applications in coloring of plastics

A new class of environmentally benign rare earth pigments of general formula Pr2−xCaxMo2O9−δ (x ranges from 0 to 1.0) displaying colors ranging from green to yellow were synthesized by traditional solid-state route, as alternatives to lead, cadmium and chromium colorants. The products were characterized by X-ray powder diffraction, UV–vis spectroscopy and CIE-L*a*b* 1976 color scales. The coloring mechanism is based on the strong absorptions of the pigments in the blue and red regions due to electronic transitions between 4f2→4f15d1 states of Pr3+. The designed pigments consist of non-toxic elements and further found to be thermally and chemically stable. The yellow–green pigments were found to be interesting alternatives to existing toxic pigments for coloration of plastics.