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):0.08Dy³⁺ phosphor had the best luminescence properties, decay life (τ = 0.049 ms), and thermal stability (87.8%). In addition, the as-prepared yellow Li₂Ca(WO₄)₂:0.08Dy³⁺, Li₂Ca₂(WO₄)(SiO₄):0.08Dy³⁺, and LiCa₂(WO₄)(PO₄):0.08Dy³⁺ phosphor can be used to fabricate white light emitting diode (LED) devices.