Red Pigments Based on CeO2-MO2-Pr6O11 (M=Zr and Sn): Solid Solutions for the Coloration of Plastics

New inorganic pigments based on fluorite solid solutions, Ce0.95MxPr0.05-xO2 (M=Zr and Sn; x ranges from 0 to 0.05) have been prepared by the conventional solid-state route with a goal of preparing environmentally benign colorants. The pigments obtained displayed better color characteristics than that of Ce0.95Pr0.05O2 system showing colors from brick red to dark brown. The coloring mechanism is based on the introduction of an additional electronic energy level of unpaired 4f electron of the praseodymium ion into the cerianite band. Further, the cosubstitution of Zr or Sn in Ce0.95Pr0.05O2 system raises the slope of the absorption edge with a blue shift resulting in enhanced lightness. Their applicability for wide spread use, chemical and thermal stability, and capacity to produce pigmentation in plastics, has been investigated. These findings suggest that the developed red pigments may form a viable and potential alternative to traditional toxic red pigments such as cadmium sulfoselenide.