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Highly efficient CaSi2O2N2:Eu2+ green phosphors were synthesized via solid-state reaction method. The produced phosphors are effectively excited with UV-vis light of wavelength between 300 and 460 nm and emit a single, intense, and broad emission band centered at 538 nm. The experimental results and their analysis suggest that the energy transfer mechanism should occur due to dipole-dipole interactions among Eu2+ ions, resulting in a shift in emission spectrum toward longer wavelengths with increasing Eu2+ concentration. The quenching concentration of Eu2+ (i.e., where the emission intensity maximizes) is approximately 2 at. %. Accordingly, the produced CaSi2O2N2:Eu2+ green phosphors are qualified for further consideration and experimentation for potential use in white light emitting diodes. [ABSTRACT FROM AUTHOR]

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]

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: Ba2+-doped Sr2SiO4:Eu2+ phosphors were synthesized with the high-temperature solid-state reaction technique. The experimental results, summarized in the successful production of a single-phase powder with fine microstructure of spherical particles with smooth surface, suggest that Ba2+-doping favors the stabilization of α′-Sr2SiO4. Rietveld refinement of X-ray diffractograms suggests that Ba2+ and Eu2+ ions occupy the sites of Sr2+ in the lattice of α′-Sr2SiO4. The produced phosphors show two intense emission bands at green and yellow regions of spectrum, originated from Eu2+ ions accommodated at two different sites in the host crystal, whose peaks depend on the concentrations of Ba2+ and Eu2+. Intense and broad excitation spectra extend from ultraviolet to the blue region. [Copyright &y& Elsevier]