Synthesis and photoluminescence properties of Ce3+ and Eu2+-activated Ca7Mg(SiO4)4 phosphors for solid state lighting

Physical Chemistry Chemical Physics (Impact Factor: 4.2). 02/2012; 14(10):3537-3542. DOI: 10.1039/C2CP23343F

ABSTRACT Ce3+ and Eu2+ singly doped and Ce3+/Eu2+-codoped Ca7Mg(SiO4)4 phosphors are synthesized by the conventional solid state reaction. The Ce3+ activated sample exhibits intense blue emission under 350 nm excitation, the composition-optimized Ca7Mg(SiO4)4 : 4%Ce3+ shows better color purity than the commercial blue phosphor, BaMgAl10O17 : Eu2+ (BAM : Eu2+) and exhibits superior external quantum efficiency (65%). The Ca7Mg(SiO4)4 : Eu2+ powder shows a broad emission band in the wavelength range of 400-600 nm with a maximum at about 500 nm. The strong excitation bands of the Ca7Mg(SiO4)4 : Eu2+ in the wavelength range of 250-450 nm are favorable properties for applications as light-emitting-diode conversion phosphors. Furthermore, the energy transfer from the Ce3+ to Eu2+ ions is observed in the codoped samples, the resonance-type energy transfer is determined to be due to the dipole-dipole interaction mechanism and the critical distance is obtained through the spectral overlap approach and concentration quenc

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    ABSTRACT: Ca14Mg2(SiO4)8:Eu2+ phosphors were synthesized by solid-state reaction method, and their luminescence properties were investigated. In the emission spectra, several overlapping emission bands originating from various Eu2+ sites were found. Eu2+ in Ca14Mg2(SiO4)8 exhibits green emission around 506 nm, and the sample doped with 0.1 mol% Eu2+ shows the strongest brightness under 365 nm excitation with the quantum efficiency of 63.6%. In the excitation spectra, strong and broad excitation bands from 250 to 450 nm were observed, which could well match with the emission wavelength of the light-emitting diode chip. The fabrication test on the InGaN chip indicates the Ca14Mg2(SiO4)8:Eu2+ phosphor could be promising candidate for white light-emitting diodes.
    Materials Research Bulletin 12/2014; 60:467-473. DOI:10.1016/j.materresbull.2014.08.054 · 1.97 Impact Factor
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    ABSTRACT: A series of blue-to-white emitting Mg2Al4Si5O18: Eu(2+), Mn(2+) phosphors were synthesized via high-temperature solid-state method, and their luminescence properties were investigated in detail. Under near-ultraviolet (UV) light excitation of 365 nm, Eu(2+)-doped Mg2Al4Si5O18 exhibits a broad blue emission band peaked at 469 nm, and Mn(2+)-doped Mg2Al4Si5O18 shows a broad orange-red emission band near 600 nm. The energy transfer from Eu(2+) to Mn(2+) in Mg2Al4Si5O18 host matrix can be found, and the resonant type is demonstrated by a dipole-quadrupole mechanism. The emission hue can be tuned from blue (0.17, 0.17) to bluish green (0.22, 0.29) and finally to white (0.31, 0.33) by properly varying the ratio of Eu(2+)/Mn(2+). The thermal quenching property of the sample was investigated, and the activation energy ΔE was estimated to be 0.30 eV. Additionally, the energy transfer critical distance between Eu(2+) and Mn(2+) was calculated. With appropriate tuning of activator content, the Mg2Al4Si5O18: Eu(2+), Mn(2+) phosphor may have potential application for UV light-emitting diodes.
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    ABSTRACT: ZnTiO3:Eu3+ phosphors were synthesized with different concentrations of Eu3+ doping through sol-gel method. The samples were calcined at different temperatures for 2 h in air. The synthesized powders were characterized by X-ray diffraction (XRD), scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS), transmission electron microscopy (TEM), Raman and photoluminescence spectroscopy. The XRD results showed that the ZnTiO3:Eu3+ phosphors doped with different concentrations of Eu3+ ions calcined at 600 °C were of single phase, which indicated that the Eu3+ ions had been successfully incorporated into the ZnTiO3 host lattice and did not destroy the lattice structure of ZnTiO3 host. The Raman spectrum, SEM and TEM also proved that the doping of Eu3+ did not change the lattice structure of hexagonal ZnTiO3 host. The photoluminescence (PL) of Eu3+ ions with the main emission peak at 614 nm was observed to increase with Eu3+ concentrations from 0.5 mol.% to 2.0 mol.% and decreased when the concentration was increased to 2.5 mol.%. The decrease in the PL intensity at higher Eu3+ concentrations could be associated with concentration quenching effect. The CIE1931 chromaticity diagram (x, y) of ZnTiO3:2.0 wt.%Eu3+ phosphors were located in the red region (x=0.652, y=0.347). The luminescence properties suggested that ZnTiO3:Eu3+ phosphors might be regarded as a potential red phosphor candidate for light emitting diodes (LEDs).
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