Search

In this study, fully concentrated Eu3+-based Na3Eu(VO4)2 vanadate phosphor was synthesized by solid-state reaction process. The as-obtained product presented a single monoclinic phase with the space group of Cc (9) and rod shape with micron size, as revealed by X-ray diffraction pattern and scanning electron microscope. Their luminescence performances were investigated by the excitation and emission spectra, temperature-dependent photoluminescence spectra. At the excitation of 395 nm, they displayed a strong red emission at 620 nm and the Gd3+ and La3+ ions incorporation did not lead to luminescent quenching in this Na3Eu(VO4)2 phosphor. When the temperature was as high as 420 K, the emission intensity kept 84% of the initial value at 303 K, which implied the Na3Eu(VO4)2 phosphors had excellent thermal stability. Further, the activation energy (Ea) was calculated to be 0.326 eV. Meanwhile, the quantum yield of this phosphor was as high as 70.6%. Finally, by coating the mixtures of red phosphors Na3Eu(VO4)2, commercial green phosphors (Sr, Ba)2SiO4:Eu2+ and blue phosphors BaMgAl10O17:Eu2+ on the surface of NUV chip (395 nm), a LED lamp was obtained and exhibited white light with good color rendering index of 93. These results exhibited the commercialized prospect of Na3Eu(VO4)2 compound as a red phosphor in the field of solid-state lighting. [ABSTRACT FROM AUTHOR]

Currently, the poor stability of inorganic perovskite CsPbX3 (X = Cl , Br, I) nanocrystals restricts their practical application in optoelectronic devices. Therefore, improving the stability of this material remains an urgent task for most researchers. In this study, incorporation of CsPbBr3 nanocrystals into porous AlO(OH) matrices through simple in situ synthesis was demonstrated to be an efficient approach for improving the nanocrystal stability. X-ray diffraction (XRD) revealed that the as-obtained product was composed of cubic CsPbBr3 nanocrystals and orthorhombic AlO(OH) compounds. In addition, transmission electron microscopy (TEM) revealed that the CsPbBr3 nanocrystals were successfully encapsulated by AlO(OH) matrices. The Brunauer–Emmett–Teller (BET) specific surface area was 234.96 m2 g − 1 for AlO(OH) and 60.08 m2 g − 1 for the CsPbBr3@AlO(OH) composites. The decrease in surface area could be attributed to the filling of the AlO(OH) pores by the CsPbBr3 nanocrystals. Further, the as-prepared composites showed red-shifted emission at 522 nm and a larger full width at half-maximum (FWHM) as 26 nm, compared with those of the CsPbBr3 nanocrystals with the emission at 517 nm and FWHM as 17 nm. More importantly, the emission intensity preserved 67% of the original value after a storage time of 120 h, but bare CsPbBr3 nanocrystals rapidly degraded within only 1 h in the polar ethanol solution. Finally, a light-emitting diode (LED) device was fabricated by coating the CsPbBr3@AlO(OH) composites and red commercial K2SiF6:Mn 4 + phosphors on the surface of a blue InGaN chip, covering 96% of National Television Standards Committee. The results indicate that the obtained composites could be promising luminescent materials for backlit displays. The incorporation of CsPbBr3 nanocrystals into porous AlO(OH) matrixes has been demonstrated to be an efficient approach for improving the nanocrystal stability. The as-prepared composites exhibited the emission at 522 nm, the full width at half-maximum as 26 nm and photoluminescence quantum yield as 52%, which would guarantee their potential application in backlit display. [ABSTRACT FROM AUTHOR]

In this study, Eu3+-doped LiCa 2 Mg 2 V 3 O 12 (LCMVO) phosphors with multicolor luminescent property were prepared by the solid phase reaction. Their structure, morphology and luminescent property were studied systematically by X-ray diffraction, scanning electron microscope and photoluminescence spectra. The LCMVO phosphors showed pure cubic crystal structure with space group (I a 3 ¯ d) and irregular spherical morphology. The excitation spectra showed a strong absorption to ultraviolet light. Under the excitation wavelength at 360 nm, they exhibited a cyan emission with a luminescence center at 520 nm. When Eu3+ ions were doped into LCMVO system, the Eu3+ characteristic emissions were also observed and the emission colors were tuned from cyan to orange via adjusting Eu3+ ion concentration. Further, electric dipole-quadrupole interaction and luminescence decay curves were adopted to explain the energy transfer from (VO 4)3- to Eu3+. The emission spectra of as-obtained phosphors at different temperature were measured to evaluate their thermal stability. The quantum efficiency values were measured to be 42.5% for LCMVO host and 38.6% for LCMVO: 0.01Eu3+ sample. The final prepared LED lamp showed easeful warm white light with suitable Ra of 89 and CCT of 3847 K, respectively. These results suggest LCMVO phosphors may be applied in near ultraviolet chip-excited white light-emitting diodes. [ABSTRACT FROM AUTHOR]

The narrow band phosphors with excellent thermal stability have received growing attention from academic and industrial researchers. In this work, a novel Ba5SiO4Cl6: Eu2+ phosphor was prepared via solid phase reaction. Their crystal structure, phase composition, morphology and optical performance containing photoluminescence (PL) emission, PL excitation and temperature-dependence PL spectra were systematically analyzed. Compared with commercial BaMgAl10O17: Eu2+ blue phosphor, the as-obtained Ba5SiO4Cl6: Eu2+ phosphor displays a narrower band blue emission (λem = 440 nm) with a full width at half maximum of 32 nm under the near ultraviolet light excitation and an excellent thermal stability for 83.3% of the initial intensity at 150 °C. The quantum yield of the Ba4.98Eu0.02SiO4Cl6 phosphors was estimated to be as high as 57.2%. Finally, a LED device coupling UV-chip (400 nm) with Ba5SiO4Cl6: Eu2+, (Sr, Ba)2SiO4: Eu2+, (Sr, Ca)AlSiN3: Eu2+ phosphors display attractive optical performance with LE = 45 lm/W, CCT = 3407 K and Ra = 94. Therefore, there are good reasons for believing that the Ba5SiO4Cl6: Eu2+ phosphor will be a market prospect phosphor for the application of lighting and display. [ABSTRACT FROM AUTHOR]

In this study, novel Eu3+-, Dy3+-, and Sm3+-activated Na 3 La(VO 4) 2 phosphors were synthesized using a solid state reaction method. X-ray diffraction analysis results indicated that the Na 3 La(VO 4) 2 phosphors had an orthorhombic crystal structure with the Pbc21 space group. There were two different La(1)O 8 and La(2)O 8 polyhedra with high asymmetry in the crystal structure. Scanning electron microscopy revealed that the product had a sheet morphology with an irregular particle size. Further, the luminescence properties, including the excitation and emission spectra, and luminescence decay curve, were investigated using a fluorescence spectrometer. The results showed that the Na 3 La(VO 4) 2 compound was an excellent host for activating the luminescence of Eu3+ (614 nm), Dy3+ (575 nm), and Sm3+ (647 nm) ions. Further, Dy3+/Eu3+ co-doped Na 3 La(VO 4) 2 phosphors were exploited, and the energy transfer from Dy3+ to Eu3+ was demonstrated in detail by the photoluminescence excitation, photoluminescence spectra, and luminescent decay curves. The results showed that the energy transfer efficiency from Dy3+ to Eu3+ was highly efficient, and the energy transfer mechanism was dipole–dipole interactions. Finally, tunable emissions from the yellow region of CIE (0.3925, 0.4243) to the red region of CIE (0.6345, 0.3354) could be realized by rationally controlling the Dy3+/Eu3+ concentration ratio. These phosphors may be promising materials for the development of solid-state lighting and display systems. [ABSTRACT FROM AUTHOR]