Synthesis and photoluminescence property of red phosphors LiEu1−xYx(WO4)0.5(MoO4)1.5 for white LED

A series of novel red phosphors LiEu1−x Y x (WO4)0.5(MoO4)1.5 (x=0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.8) were synthesized by conventional solid state reaction method with the starting materials: WO3, MoO3, Eu2O3, Li2CO3 and Y2O3. The spectrum and the crystal structure of the phosphors were characterized by F-4500 and XRD respectively. Meanwhile the effects of flux and Y3+ concentration on the crystal structure and luminescent properties of the phosphors were investigated. The results showed that the optimal content of flux (\( W_{AIF_3 } /W_{H_3 BO_3 } = 1/1 \)) was 1 wt% and the optimal doping concentration of Y3+ was 0.5 mol. The emission spectrum showed the most intense peak was located at 615 nm, which corresponds to the 5 D 0→7 F 2 transition of Eu3+ and that Eu3+ occupied the lattice site of noncentrosymmetric environment in the scheelite phases. The excitation spectrum displayed that these phosphors could be effectively excited by ultraviolet (UV) (396 nm) and blue (466 nm) light, nicely in correspondence with the widely applied output wavelengths of ultraviolet or blue LED chips. The influence of flux on the luminescent properties of LiEu0.5Y0.5(WO4)0.5(MoO4)1.5 phosphor was analyzed. The XRD spectra indicated that the flux could help to crystallize the phosphor, and no other phases were formed except the tetragonal. When adding flux, the relative intensity of LiEu0.5Y0.5(WO4)0.5(MoO4)1.5 became much stronger and the average particle size of the phosphor decreased.