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Abstract: Single-phase broad-band red-emitting Ca3Si2O7:Eu2+ phosphors, with photoluminescence features that qualify them as candidates for white light-emitting diodes applications, were successfully synthesized via a modified solid-state reaction method that employed H3BO3 as a flux. The phosphors produced have an intense broad red emission band, with a peak at 603nm, a full width at half maximum of 110nm, and color coordinates of (0.550, 0.438). Concentration quenching occurred at 0.01mol Eu2+. The discussion of the results shows that Eu2+ ions should be accommodated at the Ca-sites of the lattice, dipole–dipole interactions should predominantly govern the energy transfer mechanism among them, and the critical distance between them is ∼31Å. [Copyright &y& Elsevier]

Abstract: CaSi2O2N2 phosphors co-doped with Ce3+ and Eu2+ was synthesized via solid-state reaction method. The experiments aimed at optimizing the composition of those phosphors for achieving the highest luminescence intensity as well as at shedding light in the mechanism that governs their luminescence behavior. The overlap of the blue emission spectrum due to Ce3+ with the yellow excitation spectrum due to Eu2+ suggests resonance-type energy transfer mechanism from Ce3+ to Eu2+ taking place in the CaSi2O2N2 host lattice, where electric dipole–dipole interactions dominate. The properties of the produced phosphors qualify them for further consideration in the technology of white light-emitting diodes. [ABSTRACT FROM AUTHOR]

A series of Ce3+ and Eu2+ co-doped SrSi2O2N2 phosphors, whose features qualify them for consideration in white-light UV or blue light-emitting diodes (LEDs), was synthesized via a high temperature solid-state reaction under a reductive atmosphere. The dependence of luminescence properties of the produced powders on the Concentration of an activator (Eu2+) and a coactivator (Ce3+) was investigated. The experimentally recorded luminescence spectra and the calculations of the efficiency of energy transfer from Ce3+ to Eu2+ and the critical distance between Ce3+ and Eu2+ suggest a resonance-type energy-transfer mechanism from Ce3+ to Eu2+ due to dipole-dipole interactions. [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]