[Influence of Bi3+ doping on properties of CaMoO4 : Eu3+ phosphors]

Europium doped CaMoO4 and bismuth co-doped CaMoO4 : Eu3+ phosphors were prepared via microemulsion-hydrothermal method. The structure, morphology and luminescence properties of samples were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and fluorescence spectroscopy, respectively. The XRD patterns of as-prepared samples were in agreement with the PDF # 29-0351 of CaMoO4, which indicated that the phosphor possessed tetragonal crystal structure. SEM images showed that the samples were basically flake in shape and their average size was 1.5-2.5 microm. The critical molar concentration of activator (Eu3+) in CaMoO4 : Eu3+ was 5%, and the predominant peak of CaMoO4 : Eu3+ located at 616 nm, corresponding to the 5D0 -->7 F2 electronic dipole transition of Eu3+. The photoluminescence color can be tuned from orange-yellow (0.514, 0.537) to white (0.339, 0.333) by adjusting the doping concentrations of Eu3+ ions. To enhance the red emission intensity of Eu3+, Bi3+ was used to co-dope CaMoO4 : Eu3+ as sensitizers. When the concentration of Bi3+ is 3%, luminescence intensity was maximum. The chromaticity coordinates (CIE) varied from orange (0.497, 0.347) to red (0.585, 0.349) with increasing the content of Bi3+.