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Abstract: A series of phosphors with nominal compositions of Sr1.7M0.3SiO4−x F x :0.01Eu2+, 0.08Mn2+ (x=0, 0.01, 0.05, 0.1, 0.2) were synthesized through solid-state reaction technique. Their luminescent properties were studied. Three emission bands with peaks at 455, 550 and 670nm are observed in the phosphors under 380nm light excitation. When doped with fluorine, the crystal phases of the phosphors were changed slightly, while the luminescent intensities were remarkably enhanced and colorimetric parameters (chromaticity coordinates, color rendering index and color temperature) were improved. The colorimetric parameters and thermal quenching properties of Sr1.7Mg0.3SiO4−x F x :0.01Eu2+, 0.08Mn2+ phosphors with the comparison with those of commercial 467nm stimulated YAG:Ce3+ phosphors were systematically investigated. These results indicate that the phosphor with optimized composition could be a promising phosphor as a white light-emitting phosphor for near-ultraviolet light-emitting diodes. [Copyright &y& Elsevier]

Abstract: Transparent oxyfluoride glasses doped with Tb3+ were prepared by melt quenching method. The transmittance spectra show the glasses have good transmittance in the visible spectrum region. The emission spectra under 376nm light and X-ray excitations were recorded. Tb3+ doped oxyfluoride glasses show intense green emissions under both excitations. The optimum concentrations of Tb3+ ion are around 8mol% and around 10mol% under 376nm light excitation and X-ray excitation, respectively. The lifetimes of 541nm emission of oxyfluoride glasses doped with Tb3+ are in the range from 2.65ms to 3.02ms. The results indicate that Tb3+-doped oxyfluoride glasses could be an X-ray scintillating material suitable to X-ray detection for slow event. [Copyright &y& Elsevier]

Abstract: Rare earth ions (Ln3+) doped optical materials manifest sharp and tunable emission, high photostability, long luminescent lifetime and low cytotoxicity, and find diverse applications in optics, optoelectronic devices and bio-labelling. Herein, we employed a conventional hydrothermal approach to control the size and tune the phase as well as the morphology of GdF3:Tb3+,Yb3+ nanocrystals, wherein the effects of the synthetic conditions, such as pH, time, the ratio of the Gd to F and the surfactant, have been detailed investigated, producing sphere, platelet, rice, flower-shaped GdF3 nanoparticles. Diffuse reflectance spectra, photoluminescence emission and excitation spectra, and photoluminescence lifetime measurements were employed to characterize the optical spectroscopic properties of GdF3:Tb3+,Yb3+ nanocrystals. No efficient energy transfer from Tb3+ to Yb3+ is observed in GdF3:Tb3+,Yb3+ nanocrystals and the Yb3+ shows a concentration quenching effect at high doping levels. [Copyright &y& Elsevier]

Abstract: Orange emitting Sr2.96−x Ba x SiO5: Eu2+ phosphors have been synthesized by a method using Sr2SiO4 instead of simple oxides and carbonate as precursor. The photoluminescence properties, radiative lifetime and formation process were investigated by PL spectra, lifetime decay and XRD analysis, respectively. X-ray diffraction analysis indicates that the phosphor has a single phase of Sr3SiO5 without residual Sr2SiO4 and BaSi4O9 phases. Under 460nm excitation, the emission band of Sr2.96−x Ba x SiO5: Eu2+ has a red-shift from 580–598nm due to varied Ba2+ concentration. Particularly, the emission intensity of Sr2.56Ba0.4SiO5: 0.02Eu2+ sample increased significantly in comparison with the commercial SSE phosphor. The radiative lifetime τ 0 are estimated to be 1.999, 2.316, 2.716 and 2.932μs for samples of x=0, 0.2, 0.4 and 0.6, respectively. It indicates that Eu2+ ions are in different surroundings and the Sr2+ sites were substituted by Ba2+ completely. Compare with the conventional solid-state reaction method, the Sr2.96−x Ba x SiO5: Eu2+ phosphors synthesized by this method show higher crystallinity and more efficient orange emission. [Copyright &y& Elsevier]

Abstract: A blue-emitting phosphor, Eu2+-activated Mg3Ca3(PO4)4 phosphor was synthesized by conventional solid-state reaction. X-ray powder diffraction (XRD) analysis confirmed the phase formation. Photoluminescence (PL) results showed that Mg3Ca3(PO4)4: Eu2+ could be efficiently excited by UV–visible light from 250 to 430nm, which matched well with the emission wavelengths of near-UV and UV LED chips. The effects of the doped-Eu2+ concentration in Mg3Ca3(PO4)4: Eu2+ on the PL were also investigated. The result reveals that Mg3Ca3(PO4)4: Eu2+ is a potential blue-emitting phosphor for white LEDs. [Copyright &y& Elsevier]

Abstract: A novel Ce3+/Eu2+ co-activated LiSr4(BO3)3 phosphor has been synthesized by traditional solid-state reaction. The samples could display varied color emission from blue towards white and ultimately to yellow under the excitation of ultraviolet (UV) light with the appropriate adjustment of the relative proportion of Ce3+/Eu2+. The resonance-type energy transfer mechanism from Ce3+ to Eu2+ in LiSr4(BO3)3:Ce3+, Eu2+ phosphors is dominant by electric dipole–dipole interaction, and the critical distance is calculated to be about 29.14Å by the spectra overlap method. White light was observed from LiSr4(BO3)3:mCe3+, nEu2+ phosphors with chromaticity coordinates (0.34, 0.30) upon 350nm excitation. The LiSr4(BO3)3:Ce3+, Eu2+ phosphor has potential applications as an UV radiation-converting phosphor for white light-emitting diodes. [Copyright &y& Elsevier]

Abstract: Eu2+ doped silicate glasses were prepared of the system 52SiO2–48MO: xEu2+(in molar ratio, M=Ca, Sr, Ba; x=1, 3, 5, 7, 9) by a high temperature melt-quenching method in a reducing atmosphere. Glass ceramics containing MSiO3:Eu2+(M=Ca, Sr, Ba) nano-phosphors were obtained after the heat treatment of the glass samples. The excitation, emission spectra and lifetime decay curves of 4f65d1→4f7 of Eu2+ were measured and interpreted with respect to their crystal structures and multi-site occupations of divalent europium in the hosts. Their excitation bands mainly extend from 450 to 250nm, which is adaptable to the main emission region of the UV LED chip. With UV light excitation, the Eu2+ emission in CaSiO3, SrSiO3 and BaSiO3 shows blue, green and yellow colors centered at 440, 505 and 555nm, respectively. The critical Eu2+concentration was studied and determined to be x=5 for both CaSiO3 and SrSiO3 and x=7 for BaSiO3 phosphors. The results show that the Eu2+ doped glass ceramic phosphors containing MSiO3 (M=Ca, Sr, Ba) nano-crystals can be used as potential matrix materials for a high power white LED pumped by the UV LED chip. [Copyright &y& Elsevier]

Abstract: Transparent Eu2+/Mn2+ co-doped new glass ceramics (GC) containing β-Zn2SiO4 nanocrystals were prepared under a reduced atmosphere. The optical properties of these samples have been investigated. The emission spectra of Eu2+/Mn2+ co-doped glass ceramics show two broadband peakings at 458 and 560nm under ultraviolet radiation, which can be attributed to 4f 65d 1→4f 7 transition of Eu2+ and 4 T 1(4 G)→ 6 A 1(6 S) transition of Mn2+, respectively. Energy transfer (ET) from Eu2+ to Mn2+ is discovered by directly observing significant overlap of the excitation spectrum of Mn2+ and the emission spectrum of Eu2+. ET from Eu2+ to Mn2+ in glass ceramics is further confirmed by fluorescence studies performed on the samples with various activator (Mn2+) concentrations. The optimal composition generates white light with chromaticity coordinates (0.291, 0.344). The results indicate that Eu2+/Mn2+ co-doped glass ceramics is potential material for white light-emitting diodes (LEDs). [ABSTRACT FROM AUTHOR]