New sustainable yellow pigments in scheelite-type solid solutions: (LiLaCa)1/3MoO4-BiVO4 with high NIR reflectance as cool colorants

Abstract

New toxic-metal-free sustainable yellow pigments have been developed in scheelite-type solid solutions: [(Li0.33Ca0.33La0.33)xBi1-x][MoxV1-x]O4. The developed pigments show a structural transition from monoclinic to tetragonal scheelite-type structures upon the substitution of LiCaLaMoO4 into the BiVO4 system. The absorption edge is gently blue-shifted from the parent BiVO4 by widening the bandgap upon the incorporation of various metal ions such as Li, La, Ca, and Mo into the lattice, allowing different intense yellow hues to be produced. The typical pigment [(LiLaCa)0.198Bi0.8][Mo0.2V0.8]O4 showed the most vivid yellow hue with a b*value of 78.32, which is comparable to the commercial Sicopal yellow (b*= 76.9). Further, the developed toxic-metal-free pigments have high near-infrared reflectance, making them sustainable as eco-friendly cool colorants for paint and plastic formulations.