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In order to acquire a red light-emitting component for an efficient w-LEDs device, we synthesized a series of Eu3+-doped Sr2GaTaO6 (SGT) phosphors using a traditional high-temperature solid-phase technique. The results of UV diffuse reflectance proved that the SGT host possesses a broad optical energy bandgap (Egap) of 4.47 eV (calculated value). The relevant characteristic spectra were also tested. By monitoring the emission at 612 nm, the excitation peak at 466 nm matches the blue light region (460–470 nm) of the popular blue LED chips on the market. The photoluminescence (PL) spectra of SGT: Eu3+ phosphors at room temperature consisting of four obvious PL bands (5D0 → 7F1, 5D0 → 7F2, 5D0 → 7F3, and 5D0 → 7F4) in the visible range. And the PL properties are necessarily analyzed by fluorescence decay curves. And it exhibits a decent photoluminescence quantum yield (39.88%). Moreover, the color purity and the ∆E of the SGT: 0.2Eu3+ sample are 96.5% and 0.29 eV, respectively, demonstrating that the ∆E of SGT: Eu3+ phosphor is superior to other reported Eu3+-doped materials for w-LEDs applications. The results manifest that the Eu3+ doped SGT phosphors can be outstanding candidates for w-LEDs applications with high color purity and activation energy. [ABSTRACT FROM AUTHOR]

A series of single-phase Sr3YNa(PO4)3F:Dy3+ phosphors were successfully synthesized via a conventional solid state reaction process. The powder X-ray diffraction patterns were utilized to confirm the phase composite and crystal structure. The phosphor could be excited by the ultraviolet visible light in the region from 300 to 420 nm, and it shown two dominant emission bands peaking at 484 nm (blue light) and 580 nm (yellow light) which originated from the transitions of 4F9/2→6H15/2 and 4F9/2→6H13/2 of Dy3+, respectively. The optimum dopant concentration of Dy3+ ions was confirmed to be 7 mol% in Sr3YNa(PO4)3F:Dy3+ system and the concentration quenching mechanism is dipole-dipole interaction. The lifetime values of Dy3+ ions at different concentrations (x = 0.03, 0.05, 0.07, 0.09 and 0.11) were determined to be about 0.855, 0.759, 0.686, 0.606 and 0.546 ms, respectively. The thermal stability of luminescence of Sr3YNa(PO4)3F:0.07Dy3+ phosphor was also investigated and the activated energy was deduced to be 0.228 eV, which shows good thermal stability. The chromaticity coordinates fall in the white-light region calculated by the emission spectrum. These results show that Sr3YNa(PO4)3F:Dy3+ phosphor can be a promising white emitting phosphor for white LEDs. [ABSTRACT FROM AUTHOR]

Phase pure Ce3+ and Tb3+ singly doped and Ce3+/Tb3+ co-doped Ba3GdNa(PO4)3F samples have been synthesized via the high temperature solid-state reaction. The crystal structures, photoluminescence properties, fluorescence lifetimes, thermal properties and energy transfer of Ba3GdNa(PO4)3F:Ce3+,Tb3+ were systematically investigated. Rietveld structure refinement indicates that Ba3GdNa(PO4)3F crystallizes in a hexagonal crystal system with the space group P-6. For the co-doped Ba3GdNa(PO4)3F:Ce3+,Tb3+ samples, the emission color can be tuned from blue to green by varying the doping concentration of the Tb3+ ions. The intense green emission was realized in the Ba3GdNa(PO4)3F:Ce3+,Tb3+ phosphors on the basis of the highly efficient energy transfer from Ce3+ to Tb3+. Also the energy transfer mechanism has been confirmed to be quadrupole-quadrupole interaction, which can be validated via the agreement of critical distances obtained from the concentration quenching (13.84 Å). These results show that the developed phosphors may possess potential applications in near-ultraviolet pumped white light-emitting diodes. [ABSTRACT FROM AUTHOR]