Search

Abstract A series of Eu2+ and/or Tb3+ doped Sr 3 NaSc(PO 4) 3 F phosphors were prepared under a high temperature solid-state reaction. The crystal structure and morphology of the phosphors were characterized by the X-ray diffraction and field emission scanning electron microscopy. Blue phosphor Sr 3 NaSc(PO 4) 3 F:Eu2+ has the high quantum efficiency and can be excited by the intense broad excitation from 220 to 420 nm, matching well with the commercial near-UV chips. The photoluminescence properties and quantum efficiency are substantially improved by the doping of Eu2+ ions into the Sr 3 NaSc(PO 4) 3 F:Tb3+ phosphors, which is attributed to the efficient energy transfer from Eu2+ to Tb3+. Furthermore, the energy transfer process from Eu2+ to Tb3+ in Sr 3 NaSc(PO 4) 3 F is demonstrated by fluorescence spectra and decay time, where a resonant type via a dipole-dipole mechanism was demonstrated. In addition, the color tunable emission from blue to green can be realized by adjusting the Eu2+/Tb3+ ratio. The temperature-dependent photoluminescence results of as-prepared samples revealed that the Sr 3 NaSc(PO 4) 3 F:Eu2+ and Sr 3 NaSc(PO 4) 3 F:Eu2+,Tb3+ phosphors have excellent thermal stability, being available to near-UV LEDs. Graphical abstract fx1 [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]

A non-rare-earth doped double perovskite La 2 ZnTiO 6 :Mn4+ phosphor with the single-phase was prepared by solid-state reaction. The composition and the distribution of La 2 ZnTiO 6 :0.5%Mn4+ phosphor was confirmed by the scanning electron microscope and energy-dispersive spectroscopy. The optical band gap of La 2 ZnTiO 6 was analyzed by density functional theory using the CASTEP code, which matched well with the result of diffuse the reflectance spectra (DRS). The excitation spectra of La 2 ZnTiO 6 :Mn4+ show two broad bands with peaks at about 342 nm and 504 nm. Emissions characteristic of Mn4+ ions from 650 nm to 750 nm were observed, with the 4E g →4A 2g transition near 708 nm. The result of the temperature-dependent photoluminescence shows good thermal stability and the luminous mechanism is explained by schematic energy level diagram of Mn4+ ion. Above all, a significant overlap was found between the far-red emission band of La 2 ZnTiO 6 :0.5%Mn4+ and the absorption spectrum of the phytochrome P FR , indicating that La 2 ZnTiO 6 :Mn4+ phosphor has great potentiality to be used as indoor plant artificial light. • The deep red phosphor La 2 ZnTiO 6 :Mn4+ for NUV-based white LEDs was synthesized successfully. • The double perovskite crystal structure, XRD, SEM and EDS of samples were studied in detail. • The electronic structure, optical band gap and photoluminescence properties of La 2 ZnTiO 6 :Mn4+ was studied systematically. • La 2 ZnTiO 6 :Mn4+ phosphor has potential applications in indoor plant artificial light. [ABSTRACT FROM AUTHOR]