New insight into the coloration mechanism and synthesis of ultrafine Pr-ZrSiO4 yellow pigments

It is of particular significance to unveil the authentic coloration mechanism of the multivalent praseodymium colored ZrSiO 4 yellow pigments for advanced decoration applications. We herein adopted a facile strategy to modulate the fluorine-assisted zircon crystallization and thereby obtained ultrafine Pr-ZrSiO 4 yellow pigments, which have a remarkably narrow size distribution and average diameters within 250–400 nm. By virtue of some cogent combinative spectra of reflection, absorption, excitation, and emission from three types of elaborately-designed H 2 -, air-, and O 2 -based pigments, the coloration mechanism for the Pr-colored zircon was systematically unveiled: both Pr 4+ and Pr 3+ coexist invariably in the pigments, while the former contributes primarily to the ligand-to-metal charge transfer from O 2p to Pr(IV) 4f for the blue–violet absorption to generate the yellow hue, and the latter is inclined to discolor the pigments. Therefore, an oxidizing atmosphere is preferable to produce brilliant Pr-ZrSiO 4 pigments with enhanced chromatic properties. The stark spectroscopic distinctions between the wide-band absorption from the nonluminescent tetravalency and the narrow-band absorption from the luminescent trivalency can expand our understanding to the rare-earth-based inorganic pigments.