Synthesis and Properties of a Red Na 5 Zn 2 Gd 1−x (MoO 4) 6 : xEu 3+ Phosphor.

Novel Eu³⁺-doped Na₅Zn₂Gd(MoO₄)₆ triple molybdate phosphors were fabricated by the sol-gel method. The structure, morphology, and luminescent properties have been characterized by X-ray diffraction (XRD), thermogravimetric differential thermal analysis (TG-DTA), scanning electron microscopy (SEM), FTIR spectroscopy, and luminescence spectroscopy. The results indicated that the synthesized Na₅Zn₂Gd_1−x(MoO₄)₆: xEu³⁺ phosphor consisted of a pure phase with monoclinic structure. Under excitation at 465 nm, the Na₅Zn₂Gd_1−x(MoO₄)₆: xEu³⁺ phosphor exhibits an intensive red emission band around 610 nm corresponding to the transition of ⁵D₀→⁷F₂ which is much higher than that ⁵D₀→⁷F₁ at 594 nm, which was appropriate for a blue LED. According to the influence of the synthesis conditions, the phosphors showed the highest emission intensity when the doping concentration of Eu³⁺ was 25 mol.% and the molar ratio of citric acid to metal ions was 2:1. Na₅Zn₂Gd_0.75(MoO₄)₆: 0.25 Eu³⁺ with the color coordinates (x = 0.658, y = 0.341) is a more stable red phosphor for blue-based white LEDs than the commercial Y₂O₂S: Eu³⁺ red phosphor (0.48, 0.50) due to its being closer to the NTSC standard values (0.670, 0.330). [ABSTRACT FROM AUTHOR]