Glycothermal synthesis of scheelite-type LiEuW₂O₈ nanophosphors and their structural characterization

The formation of LiEuW₂O₈ from a tungsten source and acetates of lithium and europium(III) by autoclave treatment in 1 ,4butylene glycol, i.e., by a glycothermal reaction, was studied to explore a novel low-temperature wet chemical synthesis of scheelite-type tungstate compounds with WO₄ units. When dodecatungstophosphoric acid hexahydrate (DPA) was chosen as a tungsten source, a glycothermal reaction at 300 °C produced crystalline scheelite-type LiEuW₂O₈ (LEW) nanophosphors in a single phase. In contrast, phase-pure crystalline LEW was not obtained using the other tungsten sources. According to the results obtained by inductively coupled plasma atomic emission spectroscopy, infrared absorption spectroscopy, and Raman spectroscopy, the DPA-derived sample contained PO₄ groups, which had probably substitutionally replaced WO₄. PO₄ groups could play a significant role in the nucleation of scheelite-type LEW, which is composed of WO₄ groups. We also discuss the nonstoichiometric structural properties of the crystalline scheelite-type LEW. LEW nanophosphors, which are an alternative for organic dyes, may be one of promising materials because of their optical function of color conversion from near UV and blue to red.