A series of CaMoO_4:Tb^(3+),Eu^(3+) phosphors were prepared by the method of precipitation. The structure and morphology of the phosphors were characterized by the X-ray diffraction(XRD) and field emission scanning electron microscopy(FE-SEM). The photoluminescence properties of the prepared products were researched, and the energy transfer from Tb^(3+) to Eu^(3+) in CaMoO_4 phosphors was studied. By adjusting the doping concentration of Eu^(3+) ions in CaMoO_4:Tb^(3+),Eu^(3+) phosphors, the emitting color of the phosphors could be easily tuned from green to red. With Tb^(3+) doped in the phosphors, the red luminescence of Eu^(3+) by near UV excitation was significantly enhanced. The energy transfer efficiency, rate and average distance between Tb^(3+) and Eu^(3+) in CaMoO_4:5%Tb^(3+),x%Eu^(3+)(mole percent) phosphors(x=0.3–10) were calculated. It was found that the interaction type between Tb^(3+) and Eu^(3+) was electric dipole-dipole interaction in the phosphors.
We synthesized NaY(MoO4)2:Eu3+phosphors of different doping concentrations by a molten salt method.This facile way possesses advantages such as simple process,lower calcination temperature(350℃)and small particle size(70 nm).The crystal system is tetragonal phase and crystal lattice is body centered.The photo luminescence measurements including emission spectra,excitation spectra and fluorescence decay curves were carried out,elucidating that NaY(MoO4)2:Eu3+can be effectively excited by near UV and blue light.Moreover,it can be concluded that Eu3+energy transfer type is exchange interaction.Huang-Rhys factor and the critical energy transfer distance(Rc)were calculated to be 0.043 and 0.995 nm,respectively.Auzel’s model was used to obtain the intrinsic radiative transition lifetime of5 D0 level(τ0=0.923 ms).Furthermore,a calculation method was used to calculate refractive index n of nontransparent NaY(MoO4)2:1 mol%Eu3+phosphor,and n was obtained to be 1.86.
Eu3+ doped Gd2WO6 and Gd2(WO4)3 nanophosphors with different concentrations were prepared via a co-precipitation method. The structure and morphology of the nanocrystal samples were characterized by using X-ray diffraction (XRD) and field emission scanning electron microscopy (FE-SEM), respectively. The emission spectra and excitation spectra of samples were measured. J-O parameters and quantum efficiencies of Eu3+ 5D0 energy level were calculated, and the concentration quenching of Eu3+ luminescence in different matrixes were studied. The results indicated that effective Eu3+:5D0-7F2 red luminescence could be achieved while excited by 395 nm near-UV light and 465 nm blue light in Gd2WO6 host, which was similar to the familiar Gd2(WO4)3:Eu. Therefore, the Gd2WO6:Eu red phosphors might have a potential application for white LED.
Tetragonal phase Na Y(WO4)2:Eu3+ phosphors were synthesized through a molten salt method. The X-ray powder diffraction(XRD) and field emission scanning electron microscopy(FE-SEM) were utilized to characterize the crystal structure and morphology. The emission and excited spectra were used to study the photoluminescence properties. The results of XRD and FE-SEM indicated that the samples prepared by this method were pure phase and the particle size was about 50 nm. The PL results showed that Eu3+5D0→7F2 red luminescence at 616.5 nm could be excited by 394.5 nm near-UV light and 465 nm blue light in Na Y(WO4)2 host effectively, and the quenching concentration was 30 mol.%. The critical energy transfer distance and J-O parameters were calculated. The energy transfer type between Eu3+ was proved. What's more, the quantum efficiencies of the 5D0 level of Eu3+ were calculated as well.
