Tune color of single-phase LiGd(MoO4)2-X(WO4)X: Sm3+, Tb3+ via adjusting the proportion of matrix and energy transfer to create white-light phosphor

A series of LiGd(MO₄)₂: Sm³⁺, Tb³⁺ (M = Mo, W) phosphors was prepared by a conventional solid state reaction method. Powder X-Ray diffraction (XRD) analysis reveals that the compounds are of the same structure type. Their luminescent properties have been studied. The optimal doping concentrations are 8% for Sm³⁺ and 18% for Tb³⁺ in the LiGd(MoO₄)₂ host. Sm³⁺ and Tb³⁺ have different sensitivity to the Mo/W ratio. For LiGd(MoO₄)_2-X(WO₄)_X: Sm³⁺ (X = 0, 0.4, 0.8, 1.2, 1.6, 2.0), the strongest emission intensity is 1.766 times than that of the weakest, while 171 times for LiGd(MoO₄)_2-X(WO₄)_X: Tb³⁺. The experimental results show that Mo/W ratio strong influences on the properties of LiGd(MoO₄)_2-X(WO₄)_X: Tb³⁺. With the increasing of WO₄²⁻ groups concentration, the shape of characteristic excitation peaks of Tb³⁺ is almost the same and the excitation intensity gradually increase. Moreover, the energy transfer from Tb³⁺ to Sm³⁺ has been realized in the co-doped phosphors. The experimental analysis and theoretical calculations reveal that the quadrupole–quadrupole interaction is the dominant mechanism for the Tb³⁺→Sm³⁺ energy transfer. Therefore, luminous intensity can be adjusted by different sensitivities to matrix composition and energy transfer from Tb³⁺→Sm³⁺. By this tuning color method, white-light-emitting phosphor has been prepared. The excitation wavelength is 378 nm, and this indicates that the white-light-emitting phosphor could be pumped by near-UV light.