| Summary: | Novel Eu<sup>3+</sup>-doped Na<sub>5</sub>Zn<sub>2</sub>Gd(MoO<sub>4</sub>)<sub>6</sub> 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 Na<sub>5</sub>Zn<sub>2</sub>Gd<sub>1−x</sub>(MoO<sub>4</sub>)<sub>6</sub>: xEu<sup>3+</sup> phosphor consisted of a pure phase with monoclinic structure. Under excitation at 465 nm, the Na<sub>5</sub>Zn<sub>2</sub>Gd<sub>1−x</sub>(MoO<sub>4</sub>)<sub>6</sub>: xEu<sup>3+</sup> phosphor exhibits an intensive red emission band around 610 nm corresponding to the transition of <sup>5</sup>D<sub>0</sub>→<sup>7</sup>F<sub>2</sub> which is much higher than that <sup>5</sup>D<sub>0</sub>→<sup>7</sup>F<sub>1</sub> 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 Eu<sup>3+</sup> was 25 mol.% and the molar ratio of citric acid to metal ions was 2:1. Na<sub>5</sub>Zn<sub>2</sub>Gd<sub>0.75</sub>(MoO<sub>4</sub>)<sub>6</sub>: 0.25 Eu<sup>3+</sup> with the color coordinates (x = 0.658, y = 0.341) is a more stable red phosphor for blue-based white LEDs than the commercial Y<sub>2</sub>O<sub>2</sub>S: Eu<sup>3+</sup> red phosphor (0.48, 0.50) due to its being closer to the NTSC standard values (0.670, 0.330).
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