Novel Environmentally Benign Yellow Inorganic Pigments Based on Solid Solutions of Samarium-Transition Metal Mixed Oxides

摘要

A new class of environmentally benign yellow inorganic pigments having the general formula Sm_(6-x)W_(1-y)Zr_xMo_yO_(12+δ) (x ranges from 0 to 0.6 and y ranges from 0 to 1) have been synthesized by a simple solid-state route and characterized by various spectroscopic techniques. The systematic substitution of Mo~(6+) for W~ (6+) in Sm_6WO_(12) gently shifted the absorption edge from 374 to 460 nm and consequently the designed compounds exhibited colors ranging from white to yellow. The band gap of the resultant pigments varied from 3.29 to 2.69 eV. The coloring mechanism is based on the O_(2p)-Mo_(4d) charge transfer transitions. Furthermore, the doping of Zr~(4+) for Sm~(3+) in Sm_6MoO_(12) lattice produced intrinsic strain, which further red shifted the absorption edge to 479 nm. This intensified the yellow hue of the resultant compounds with band gap decreasing to 2.58 eV. The designed pigments possess good chromatic properties, especially the hue angle, which is found to be similar to those observed for industrial pigments such as PbCrO_4, BiVO_4, CdS, NiTiO_3, and praseodymium yellow and also showed thermal and chemical stabilities. The coloring performance of the developed yellow pigments was evaluated by incorporating it into a polymer substrate material.