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LiCaSiO:Eu phosphors with single phase were successfully synthesized by the solid state reaction method and their photoluminescence properties were studied. The experimental results on LiCaSiO:Eu, summarized in effective absorption and excitation in the ultra-violet region, strong emission in the blue spectrum and the CIE Chromaticity coordinate (0.10, 0.20), indicate this phosphor has great potential in ultra-violet chip pumped white LEDs. A comparative investigation of the emission intensity suggests that LiCaSiO:Eu has the best performance with Eu concentration of 1% and excitation of 375 nm. Compound phosphors of LiCaSiO:Eu and LiSrSiO:Eu show two emission bands in the blue and yellow region. With the molar ratio of LiCaSiO:Eu to LiSrSiO:Eu being 1:1 and excitation of 390 nm, the CIE Chromaticity coordinate was tuned to be (0.32, 0.36), which is close to that of natural white light, indicating this may become blue phosphor candidate for ultra-violet chip pumped and multi-phosphors converted white LEDs. [ABSTRACT FROM AUTHOR]

Herein, Ce3+ and Ce3+/Dy3+ co-doped Ca 3 Al 2 O 6 phosphors have been designed and synthesized via a facile citrate-based sol-gel technique, and their structural, photoluminescence properties and energy transfer phenomenon were investigated comprehensively. The XRD analysis indicated that pure Ca 3 Al 2 O 6 phase can be synthesized at low temperature (1000 °C) for merely 2 h. The photoluminescence spectra showed the dominant emission of Ce3+ singly doped phosphors is located in the blue region even at low Ce3+ doping level, which indeed favors the energy transfer from Ce3+ to other luminescent centers. When Dy3+ is co-doped into Ca 3 Al 2 O 6 :Ce3+ phosphors, the remarkable sensitizing effect of Ce3+ on Dy3+ is validated by comparatively analyzing the excitation, emission spectra and average lifetimes of the series of samples. Through the concentration quenching theory, the critical distance between Ce3+ and Dy3+ is calculated to be 13.50 Å. Furthermore, the energy transfer mechanism between them is most likely ascribed to electric dipole-dipole interaction. In virtue of the variation of the emission intensities of Ce3+ and Dy3+, the emitting colors of Ca 3 Al 2 O 6 :Ce3+, Dy3+ phosphors can realize tunable luminescence from deep blue to bluish-white region through controlling the Dy3+ content. Based on these analysis, Ca 3 Al 2 O 6 :Ce3+, Dy3+ phosphors could potentially be applied as a single-phase color-tunable phosphors pumped by near-ultraviolet (n-UV) radiation. • Developed a facile sol-gel method to prepare successfully Ca 3 Al 2 O 6 compound. • The blue emission of as-prepared Ca 3 Al 2 O 6 :Ce3+ phosphors dominates, which favors the energy transfer process. • The possible mechanism for the dominance of blue emission was discussed. • The energy transfer phenomenon in Ca 3 Al 2 O 6 :Ce3+, Dy3+ phosphors was investigated in detailed. • Ca 3 Al 2 O 6 :Ce3+, Dy3+ can serve as a single-phase color-tunable phosphors excited by near-ultraviolet radiation. [ABSTRACT FROM AUTHOR]

Abstract: The crystal structure and photoluminescence properties of Eu2+ doped Li2Ca0.7Sr0.3SiO4 phosphors were investigated. The Li2Ca0.7Sr0.3SiO4 is not an alloy between the tetragonal Li2CaSiO4 and hexagonal Li2SrSiO4 but crystallizes in orthorhombic structure similar to Li2(CaSr)SiO4. Photoluminescence properties of the Li2Ca0.7Sr0.3SiO4:Eu2+ phosphors, summarized in effective excitation in the UV region, strong emission in the blue light range (with a peak at 427nm) and the CIE chromaticity coordinate (0.154, 0.038), indicate this phosphor has great potential in UV-chip pumped white LEDs. White light output by mixing the Li2Ca0.7Sr0.3SiO4:Eu2+ blue and Li2SrSiO4:Eu2+ yellow phosphor was attempted. With proper molar ratio of these two compound phosphors, warm white light with CIE chromaticity coordinate close to that of the nature white light (0.33, 0.33) and color temperature about 5000K was obtained. The results indicated that the Li2Ca0.7Sr0.3SiO4:Eu2+ may become an important phosphor candidate for ultra-violet chip pumped and multi-phosphors converted white LEDs. [Copyright &y& Elsevier]