Search

SrLaGa 3 O 7 :Eu3+ and SrLaGa 3 O 7 :Tb3+ fluorescent powders were synthesized using solid sintering procedure. The crystal structure and luminescence of the synthesized fluorescent powders were surveyed. XRD patterns of the synthesized fluorescent powders demonstrate that they have the single tetragonal phase. Under excitation at 392 nm, SrLaGa 3 O 7 :Eu3+ fluorescent powders exhibit photoluminescence bands rooting in 5D 0 → 7F 0, 1, 2, 3, 4 transitions of Eu3+. In SrLaGa 3 O 7 , La3+ ions are surrounded octahedrally by eight ions and there is only one mirror plane paralleling to c axis in these distorted octahedrons. This characteristic induces the existence of photoluminescence band resulting from 5D 0 → 7F 0 transition and the strongest photoluminescence band resulting from 5D 0 → 7F 2 transition. Under excitation at 265 nm, SrLaGa 3 O 7 :Tb3+ fluorescent powders show photoluminescence bands resulting from 5D 3 → 7F 3 and 5D 4 → 7F 6, 5, 4, 3 transitions of Tb3+. The band resulting from 5D 4 → 7F 5 transition is strongest because that this transition has the largest probability for both electric-dipole and magnetic-dipole transitions. The decay curves of SrLaGa 3 O 7 :Eu3+ and SrLaGa 3 O 7 :Tb3+ fluorescent powders show a single exponential characteristic. • Synthesis of Eu3+/Tb3+ doped SrLaGa 3 O 7. • Single tetragonal phase of synthesized Eu3+/Tb3+ doped SrLaGa 3 O 7. • Red/green light emitted by Eu3+/Tb3+ doped SrLaGa 3 O 7. [ABSTRACT FROM AUTHOR]

Luminescence characteristics of yttrium-aluminum garnet based phosphor samples differed by their elemental composition and prehistory of synthesis are studied. The morphology, structure, and elemental composition of phosphor samples, their excitation and emission spectra, efficiency of phosphor conversion of chip emission, and kinetics of luminescence decay are measured. The emission characteristics of phosphors are compared with their structural properties and elemental composition. [ABSTRACT FROM AUTHOR]

The cyan SrLaGa 3 O 7 :Bi3+ phosphors were prepared via the solid state sintering processes at 1400 °C. The optical performance was characterized and researched based on the theory calculation and experimental results. The phase and constitution of the prepared SrLaGa 3 O 7 :Bi3+ phosphors were ascertained by the X-ray diffraction and elemental composition analyses. The theory calculations were carried out based on the state density function. Upon the ultraviolet light excitation, SrLaGa 3 O 7 :Bi3+ phosphors yield broadband emission in 380–600 nm relating to the 3P 1 →1S 0 transitions of Bi3+. The full width of the half-maximum of emission band reaches ∼130 nm. Tunable light was achieved by adjusting the content of Bi3+ or changing the excitation wavelength. [Display omitted] • Synthesis of disordered SrLaGa 3 O 7 :Bi3+ phosphor with a wide cyan emission band. • Dependence of emission on excitation wavelength and doping concentration. • Influence of disordered structure on the luminescence of the phosphor. [ABSTRACT FROM AUTHOR]

In this paper, a series of Eu3+/Tb3+ doped La3Ga5SiO14 (LGS:Eu3+, Tb3+) phosphors with excellent performance have been synthesized by high-temperature solid-phase method. The effects of Eu3+ and Tb3+ doping in LGS on the host lattice were analyzed by X-ray diffraction (XRD). X-ray photoelectron spectroscopy (XPS) proved that the Eu3+ and Tb3+ ions were successfully doped into the LGS host. The doped Eu3+/Tb3+ ions only occupy the eight-coordinated La3+ sites. The concentration quenching points of LGS:Eu3+ and LGS:Tb3+ phosphors were determined to be 0.16 and 0.18, respectively. The luminescence performance and fluorescence lifetime of LGS:Eu3+, Tb3+ were studied. LGS:Eu3+, Tb3+ phosphors successfully realized Tb3+ → Eu3+ energy transfer to enhance Eu3+ luminescence. The energy transfer mechanism is speculated on using the experimental results. The energy transfer efficiency from Tb3+ to Eu3+ is about 66.83% in La2.46Tb0.18Eu0.36Ga5SiO14. The LGS:Eu3+, Tb3+ phosphors can achieve tunable luminescence by controlling the doping concentrations of Eu3+ and Tb3+. The ΔE is calculated to be 0.2567 eV for the La2.70Eu0.12Tb0.18Ga5SiO14 phosphor. [ABSTRACT FROM AUTHOR]

In this study, we synthesized series of La3Ga5SiO14:Pr3+ phosphors by high-temperature solid-state reactions. For the synthesized phosphors, X-ray diffraction (XRD), scanning electron microscope (SEM), energy-dispersive spectrum (EDS), Raman, infrared (IR), absorption, photoluminescence (PL) and photoluminescence excitation (PLE) characterizations and decay characteristics were performed. The XRD patterns indicate that the synthesized phosphors have the same D32 (P321) structure with La3Ga5SiO14 host. The SEM image and EDS pattern show the irregular morphology and the combined La, Ga, Si, O and Pr elements for the synthesized phosphors. The room temperature Raman and IR spectra show that the phonon modes of the La3Ga5SiO14:Pr3+ phosphors follow the overall mode distributions of La3Ga5SiO14 and no appreciable changes in the phonon properties are observed, indicating that the force fields in the La3Ga5SiO14:Pr3+ lattice are not strongly altered by Pr3+ doping. The UV-Vis absorption spectra show that the phosphors contain a strong absorption band and several moderate bands resulting from the 4f-5d and f-f transitions of Pr3+ ions, respectively. La3Ga5SiO14:Pr3+ phosphors produce white light when λex = 255 nm. On the basis of emission data, the concentration quenching mechanism of the Pr3+ emission was speculated as the dipole-dipole interaction. The decay time and thermal stability were investigated, and the CIE coordinates with the corresponding correlated color temperatures were also calculated. • Crystal analyses of LGS: Pr3+ phosphors. • Detail Raman characteristics of LGS: Pr3+ phosphors. • Generation of white light by LGS: Pr3+ phosphors upon the UV light excitation. • Unique temperature response characteristics of the LGS: Pr3+ phosphor. [ABSTRACT FROM AUTHOR]

The Bi3+ doped and the Bi3+/Eu3+ co-doped germanate phosphor powders were synthesized by high-temperature solid-state reaction and their luminescence properties were investigated. The XRD analysis results show that the crystalline phase of all samples is the tetragonal phase of BaGeO 3. The Bi3+ doped BaGeO 3 phosphors exhibited an intense near-white light emission and the wavelength of the luminescence center was located at 466 nm. The Bi3+ doped BaGeO 3 phosphors can be efficiently excited by the incident light of 260–430 nm. The tunability of the emission color can be achieved by changing the Bi3+ ion doping concentration and the high-temperature sintering time. The Bi3+/Eu3+ co-doped BaGeO 3 phosphors exhibited an intense red emission and the wavelength of the luminescence center was located from 466 to 705 nm. The Bi3+/ Eu3+ co-doped BaGeO 3 phosphors can be efficiently excited by the incident light of 312–532 nm. The emission color tunability can be obtained by changing the Eu3+ ions doping concentration and the wavelength of excitation. The visible region emission characteristics of BaGeO 3 :Bi3+, Bi3+/Eu3+ indicate that it can potentially be used as a new efficient near-white luminescent material. • The luminescence properties of Bi3+ doped and Bi3+/Eu3+ co-doped germanate phosphors were studied. • The color-tunable emission luminescence in the germanate phosphors by changing Bi3+ doping concentration or holding times. • Achieve white light emission in Ba 0.95GeO3:Bi0.05 by changing Eu3+ doping concentration. • The germanate phosphors could be potentially applicable in white light-emitting diodes (WLEDs). [ABSTRACT FROM AUTHOR]

A strategy by encapsulating organic dyes into the pores of a luminescent metal-organic framework (MOF) is developed to achieve white-light-emitting phosphor. Both the red-light emitting dye 4-( p-dimethylaminostyryl)-1-methylpyridinium ( DSM) and the green-light emitting dye acriflavine ( AF) are encapsulated into a blue-emitting anionic MOF ZJU-28 through an ion-exchange process to yield the MOF⊃dye composite ZJU-28⊃DSM/AF. The emission color of the obtained composite can be easily modulated by simply adjusting the amount and component of dyes. With careful adjustment of the relative concentration of the dyes DSM and AF, the resulting ZJU-28⊃DSM/AF (0.02 wt% DSM, 0.06 wt% AF) exhibits a broadband white emission with ideal CIE coordinates of (0.34, 0.32), high color-rendering index value of 91, and moderate correlated color temperature value of 5327 K. Such a strategy can be easily expanded to other luminescent MOFs and dyes, thus opening a new perspective for the development of white light emitting materials. [ABSTRACT FROM AUTHOR]

[Display omitted] • • Synthesis of Tb3+/Eu3+ doped SrLaGa 3 O 7 phosphors. • • Tunable luminescence induced by the Tb3+ → Eu3+ energy transfer. • • Excellent thermal stability of Tb3+/Eu3+ doped SrLaGa 3 O 7 phosphors. The Tb3+/Eu3+ doped SrLaGa 3 O 7 phosphors were synthesized via the calcining processes for the purpose of investigating their luminescence characteristics. The phase, luminescence spectra, lifetimes and tunability of emission were researched detailedly. The results show that the tunable luminescence in a wide range (greenish-yellow → yellow → orange) was obtained by designing energy transfer in the Tb3+/Eu3+ codoped SrLaGa 3 O 7 phosphors. The energy transfer efficiency is 64.273% in the SrLa 0.92 Tb 0.02 Eu 0.06 Ga 3 O 7 phosphor. The thermal stability was also revealed via the temperature-dependence emission spectra. The thermal quenching temperature is found to be ~ 400 K. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, effect of Eu3+ doping concentrations on microstructure and photoluminescence of Sr2SiO4 phosphors was investigated. The Sr2−x SiO4:xEu3+ phosphors with x=0.05, 0.1, 0.2, 0.3 were synthesized by microwave assisted sintering at 1200°C for 60min in air. X-ray powder diffraction analysis confirmed the formation of pure Sr2SiO4 phase without second phase or phases of starting materials irrespective of the adding amount of Eu3+. From scanning electron microscopy image, it is found that with more Eu3+ ions introduced to Sr2SiO4, the shape of the particles is not much different from each other, but the particle size decreases significantly from 1 to 2μm (when x=0.05) to less than 500nm (when x=0.3). The emission spectrum was located obviously at 617nm as the excitation spectrum at λ ex =395nm, and it had best emission intensity when x=0.1. [Copyright &y& Elsevier]