Homogeneous precipitation synthesis and photolumi-nescence properties of La2O2 SO4 : Eu3+ quasi-spherical phosphors
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Synthesis and photoluminescence properties of La2O2SO4 : Eu3+ quasi-spherical phosphors were investigated by homogeneous precipitation from La(NO3)3,Eu(NO3)3, (NH4)2SO4 and urea ((CO(NH2)2) as the starting materials. It was found that the yield of the precursor is strongly dependent on m value, namely, the molar ratio of urea to La(NO3)3, and the optimal m value is 10. Thermal analysis, FT-IR and XRD show the optimal precursor is composed of La2(OH)2CO3SO4 • 2H2O and can be converted into pure La2O2SO4 phase at a temperature higher than 600 o C for 1 h in air. SEM observation shows that the obtained La2O2SO4 phosphor particles are quasi-spherical in shape and narrow distribution with a mean particle size of about 2 μm. Photoluminescence spectra reveal that the emission intensities of the La2O2SO4 : Eu3+ phosphors depend on the calcination temperature and the strongest emission peak is located at 620 nm under 280 nm UV light excitation for the La2O2SO4 : Eu3+ phosphors calcined at 1000 o C, which corresponds to the 5 D0 → 7 F2 transition of Eu3+ ions. The quenching concentration of Eu3+ ions is 5 mol% and the concentration quenching mechanism is the electric dipole-quadrupole interaction for the 5 D0 → 7 F2 transition of Eu3+ ions.
Abstract
Synthesis and photoluminescence properties of La2O2SO4 : Eu3+ quasi-spherical phosphors were investigated by homogeneous precipitation from La(NO3)3,Eu(NO3)3, (NH4)2SO4 and urea ((CO(NH2)2) as the starting materials. It was found that the yield of the precursor is strongly dependent on m value, namely, the molar ratio of urea to La(NO3)3, and the optimal m value is 10. Thermal analysis, FT-IR and XRD show the optimal precursor is composed of La2(OH)2CO3SO4 • 2H2O and can be converted into pure La2O2SO4 phase at a temperature higher than 600 o C for 1 h in air. SEM observation shows that the obtained La2O2SO4 phosphor particles are quasi-spherical in shape and narrow distribution with a mean particle size of about 2 μm. Photoluminescence spectra reveal that the emission intensities of the La2O2SO4 : Eu3+ phosphors depend on the calcination temperature and the strongest emission peak is located at 620 nm under 280 nm UV light excitation for the La2O2SO4 : Eu3+ phosphors calcined at 1000 o C, which corresponds to the 5 D0 → 7 F2 transition of Eu3+ ions. The quenching concentration of Eu3+ ions is 5 mol% and the concentration quenching mechanism is the electric dipole-quadrupole interaction for the 5 D0 → 7 F2 transition of Eu3+ ions.
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