Effect of anionic group [SiO4]4-/[PO4]3- on the luminescence properties of Dy3+-doped tungstate structural compounds

Novel scheelite structures of Li2Ca(WO4)(2), Li2Ca2(WO4)(SiO4), and LiCa2(WO4)(PO4) fluorescent materials were successfully prepared using a high-temperature solid-phase process. The compounds were characterized by X-ray diffraction and energy dispersive spectroscopy. The tests revealed that the substitution of [WO4](2-) by [SiO4](4-) or [PO4](3-) tetrahedron in tungstate had no significant influence on the crystal structure of the Li2Ca(WO4)(2). When Dy3+ ions were introduced as an activator at an optimum doping concentration of 0.08 mol%, all of the as-prepared phosphors generated yellow light emissions, and the emission peak was located close to 576 nm. Replacing [WO4](2-) with [SiO4](4-) or [PO4](3-) tetrahedron significantly increased the luminescence of the Li2Ca(WO4)(2) phosphors. Among them, the LiCa2(WO4)(PO4):0.08Dy(3+) phosphor had the best luminescence properties, decay life (tau = 0.049 ms), and thermal stability (87.8%). In addition, the as-prepared yellow Li2Ca(WO4)(2):0.08Dy(3+), Li2Ca2(WO4)(SiO4):0.08Dy(3+), and LiCa2(WO4)(PO4):0.08Dy(3+) phosphor can be used to fabricate white light emitting diode (LED) devices.