The Preparation of LiCeMo₂O₈ for Novel Inorganic Yellow Pigments using Solid-State Reaction Method

Abstract

Some molybdates containing rare earth elements were prepared by a solid-state reaction method and their hues were evaluated for the purpose of the preparation of new inorganic pigments without harmful elements. LiPrMo₂O₈ and LiNdMo₂O₈ had narrow and sharp absorption bands of 4f-4f transition. Thus absorption bands of 4f-4f transition of trivalent rare earth ions were narrow and sharp, leading to poor reducing power. In contrast, LiCeMo₂O₈ had a broad absorption band of 4f-5d transition. It is obvious that 4f-5d transition is more suitable than 4f-4f transition as an inorganic pigment.
The LiCeMo₂O₈ possessing yellow hue was investigated further. The amount of Na in Na, CeMo₂O₈ had strong influence on its hue compared with that of Li in Li_xCeMo₂O₈. It seemed to be caused by the difference of arrangement between Na and Li in the structure. Yellow hue was also obtained in LiCe_yY_1-y, Mo₂O₈ even when y was as low as 0.2. In LiCe (Mo_1-zW_z) ₂O₈, hue shifted from yellow to light yellowish gray with increasing z. The split of energy level by MoO₄^2- also had influence on hue of LiCe (Mo_1-zW_z) ₂O₈.