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Tb 3+ ions activated Ba 4 La 6 O(SiO 4 ) 6 (BLSO:Tb 3+ ) phosphors were synthesized by a citrate sol-gel method. The X-ray diffraction pattern confirmed their oxyapatite structure. The field-emission scanning electron microscope image established that the BLSO:Tb 3+ phosphor particles were closely-packed and acquired irregular shapes. The photoluminescence (PL) excitation spectra of BLSO:Tb 3+ phosphors showed intense f–d transitions along with low intense peaks corresponding to the f–f transitions of Tb 3+ ions in the lower energy region. The PL emission spectra displayed the characteristic emission bands of Tb 3+ ions, and the optimized concentrations were found to be at 1 and 6 mol% for blue and green emission peaks, respectively. The cathodoluminescece (CL) spectra exhibited a similar behavior that was observed in the PL spectra except the intensity variations in the blue and green regions. The CL spectra of the BLSO:6 mol% Tb 3+ phosphor unveiled accelerating voltage induced luminescent properties. [ABSTRACT FROM AUTHOR]

A series of Dy3+ ion single-doped and Dy3+/Eu3+ ion co-doped white-light emitting SrY2O4 nanocrystalline phosphors were synthesized by a citrate sol–gel method. After the samples were annealed at 1300 °C, the X-ray diffraction patterns confirmed their orthorhombic structure. The particles were closely-packed and their optical properties were monitored by photoluminescence spectroscopy. The Dy3+ ions acted as luminescent centers and substituted Y3+ ions in the SrY2O4 host lattice, where they are located in Cs sites, and the characteristic emission of Dy3+ ions (4F9/2→6H15/2 and 4F9/2→6H13/2 transitions) with intense yellow emission band at 578 nm occurred. When the Eu3+ ions were co-doped into the SrY2O4:Dy3+ (1 mol%) nanocrystalline phosphor, white-light emission was observed under excitation at 381 nm. The energy transfer between Eu3+ and Dy3+ ions was calculated and the chromaticity coordinates were also presented. The cathodoluminescence (CL) spectra confirmed that the penetration depth is inversely proportional to the total atomic weight and atomic number of the compound. From CL analysis, the emission intensities of Dy3+ ion single-doped and Dy3+/Eu3+ co-doped SrY2O4 nanocrystalline phosphors increased continuously upon increasing both the accelerating voltage from 1 to 5 kV and the filament current from 30 to 47 μA. [ABSTRACT FROM AUTHOR]

Abstract: We reported the novel red-emitting phosphors of trivalent europium (Eu3+) ions activated CaGd4O7 (CG) prepared by a sol–gel method. After the samples were annealed at 1500°C, the X-ray diffraction patterns confirmed their monoclinic structure and the transmission electron microscopy image showed the nanocrystallinity of the CG: Eu3+ phosphor. The photoluminescence excitation spectra exhibited the efficient energy transfer from the Gd3+ to Eu3+ by overlapping the f–f transition of Gd3+ excitation band with charge transfer band of Eu3+ ions. The photoluminescence (PL) spectra showed the emission band in the entire visible region at lower Eu3+ concentration and the red emission at higher Eu3+ concentration. All the decay curves were well fitted by single exponential functions. The temperature dependent luminescence measurements were performed for identifying the thermal stability of CG: Eu3+ phosphors at elevated temperatures. The cathodoluminescent (CL) spectra also presented a similar behavior to that observed in PL spectra. Form the PL, CL, and decay analysis the optimum concentration of Eu3+ ions in the CG host lattice was found to be 5mol%. The CIE chromaticity coordinates varied from yellow to red in visible spectral region by increasing the Eu3+ concentration. [Copyright &y& Elsevier]

Oxyapatite Ca2Gd8(SiO4)6O2(CGS) nanostructures with nanorod bundle-likemorphologyare prepared by mixed solvothermal and hydrothermal reaction methods.Detailed structural and morphological studies are performed usingX-ray diffraction, Fourier transform infrared spectroscopy, scanningelectron microscopy, and transmission electron microscopy measurements.CGS nanorod bundles are formed by crystal splitting, and the growthmechanism as a function of reaction time is discussed. The size andcrystal splitting of the nanorod bundles are controlled by varyingthe concentration of 2-propanol. The annealing temperature does nothave any effect on the morphology of CGS nanorod bundles, and thebundles can sustain high temperatures, which confirms the crystalsplitting of nanorod bundles. Photoluminescence and cathodoluminescentstudies are carried out by activating the Eu3誉 inthe CGS host lattice as a function of annealing temperature. The correspondingCIE chromaticity coordinates are in close proximity to the commercialred emitting phosphor chromaticity coordinates. [ABSTRACT FROM AUTHOR]

Abstract: Blue and green light emissive nanocrystalline Ca2Gd8Si6O26 (CGS):Tm3+ and CGS:Er3+ phosphors with high color purity were prepared by solvothermal reaction method. The structural and morphological properties of these phosphors were evaluated by the powder X-ray diffraction (XRD) and scanning electron microscopy, respectively. From the XRD results, Tm3+:CGS and Er3+:CGS phosphors had the characteristic peaks of oxyapatite in the hexagonal lattice structure. The visible luminescence properties of phosphors were obtained by ultraviolet (UV) or near-UV light and low voltage electron beam (0.5–5kV) excitation. The photoluminescence and cathodoluminescence properties were investigated by changing the variation of Tm3+ or Er3+ concentrations and the acceleration voltage, respectively. The CGS:Tm3+ phosphors exhibited the blue emission due to 1D2→3F4 transition, while the CGS:Er3+ phosphors showed the green emission due to 4S3/2→4I15/2 transition. The color purity and chromaticity coordinates of the fabricated phosphors are comparable to or better than those of standard phosphors for lighting or imaging devices. [Copyright &y& Elsevier]