The synthesis, characterization and optical properties of silicon and praseodymium doped Y 6MoO 12 compounds: Environmentally benign inorganic pigments with high NIR reflectance

Abstract

Novel, yellow, brown and brick-red colored, near-infrared reflective pigments based on yttrium molybdate doped with metal ions such as Si 4+ or Pr 4+ are described. Replacing Si 4+ for Y 3+ in Y 6MoO 12 changed the color from light-yellow to dark-yellow and the band gap decreased from 2.60 to 2.45 eV due to O 2p-Mo 4d charge transfer transitions. In contrast, replacing Pr 4+ for Y 3+ changed the color from light-yellow to dark brown and the band gap shifted from 2.60 to 1.90 eV. The coloring mechanism is based on the introduction of an additional 4f 1 electron energy level of Pr 4+ between the valence and conduction bands. The NIR reflectance of the pigments on asbestos cement sheet was measured.