Preparation and luminescence properties of Gd₂ (MoO₄ )₃ :Eu³⁺ red phosphors with high colour purity

Gd₂ (MoO₄ )₃ :Eu³⁺ red phosphors assigned to different crystal systems were prepared using a sol-gel method with ammonium molybdate, Gd₂ O₃ , and Eu₂ O₃ as starting materials. X-ray diffraction (XRD) patterns showed that when annealing temperature was 700°C or 800°C, Eu³⁺ doping concentration was the main factor affecting sample structure. When the Eu³⁺ doping concentration was 0-2.00 mol%, samples had a monoclinic structure, but when the Eu³⁺ doping concentration was increased to 4.00-10.00 mol%, the samples changed to a mixed crystal structure (with existence of both monoclinic and orthorhombic structures). When the annealing temperature was increased to 900°C, annealing temperature became the main factor affecting sample structure, that is sample structure did not change with change in Eu³⁺ doping concentration, and all samples could be assigned to the orthorhombic system. Change in structure also affected the luminescence properties of the samples. Gd₂ (MoO₄ )₃ :Eu³⁺ phosphors with different crystal systems could be effectively excited by blue light (466 nm wavelength); red light at 614 nm wavelength gave better colour purity and color stability, corresponding to the Eu³⁺⁵ D₀ →⁷ F₂ transition. Finally, when Eu³⁺ concentration was 0.02 mol, the luminescence intensity of the orthorhombic system was higher than that of the monoclinic system; when the concentration was 0.04 mol, the luminescence intensity of the mixed system was almost the same as that of the orthorhombic system.