Preparation and luminescence properties of Gd (MoO ) :Eu red phosphors with high colour purity.

Gd (MoO ) :Eu red phosphors assigned to different crystal systems were prepared using a sol-gel method with ammonium molybdate, Gd O , and Eu O as starting materials. X-ray diffraction (XRD) patterns showed that when annealing temperature was 700°C or 800°C, Eu doping concentration was the main factor affecting sample structure. When the Eu doping concentration was 0-2.00 mol%, samples had a monoclinic structure, but when the Eu 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 Eu doping concentration, and all samples could be assigned to the orthorhombic system. Change in structure also affected the luminescence properties of the samples. Gd (MoO ) :Eu 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 Eu D → F transition. Finally, when Eu 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.