Papers by Keyword: YAG:Ce

Abstract: Due to the rapid growth in the use of blue-light-based electrical panels and much brighter lighting environments, the socioeconomic impact by retinal light injury is critical. Understanding the material property and mechanisms underlying this hazard is important for both effective and user-friendly product development. The InGaN based blue LED has been applied to excite the yellow phosphor (Y₃Al₅O₁₂:Ce³⁺) for white light generation. In this study, custom-made phosphor-converted white light emitting diode (pc-WLED) with correlated color temperature (CCT) ranging from 2700K to 6500K were used for exposure treatments to assess the potential retinal injury. We examined LED induced retinal neuronal cell damage in a rat model through functional and histopathological measurements. Electroretinography (ERG), hematoxylin and eosin (H&E) staining, and transmission electron microscopy (TEM) were used for pathological examinations. The experimental results indicate that blue-rich-LED light could induce more photochemical injury to the retina after the exposure. The results of this study suggest that retinal injury is mainly induced by photosensitizer-and photopigment-mediated oxidative stress with color temperature dependent effect, and users should be more aware of this effect before switching to LED lamps for domestic lighting.

Abstract: YAG:Ce phosphors were synthesized by co-precipitation method. The photoluminescence intensity of samples sintered by the two-step route increases by about 10%, and with 0.5 wt.% NH4Cl added as flux, surface morphologies and size distribution are improved. The white LEDs were fabricated using as-obtained phosphors. It shows natural white light with chromaticity coordinates of (0.3083, 0.3163), color temperature (Tc) of 6886 K, the average CRI of 75, and the luminous efficacy of 85 ml/W. Therefore, The as-obtained YAG:Ce phosphors could be regard to have potential application in white LED devices.

Abstract: A series of Re3+ (Re=Lu, Gd, La) co-doped YAG phosphors were successfully synthesized by a sol-gel combustion method and characterized with XRD and photoluminescent spectrum. The phase composition and luminescent properties of YAG:Ce under different Re co-doped concentrations were investigated. Doping only 50 mol% of La3+ to replace Y3+ sites, the main phase of sample has transformed into LaAlO3. While the concentration of Gd3+ reached 90~99 mol%, it was still cubic YAG. Lu3+ could replace Y3+ ions completely with the garnet structure. The location of the emission peak of Gd-codoped YAG:Ce3+ shifted to red region 21 nm corresponding to the maximum emission intensity before the appearance of GdAlO3. In addition, it had a 24 nm blue shift when Y3+ replaced by Lu3+ completely.

Abstract: Due to its high quantum efficiency (QE) for luminescence, conventional coarse-grained YAG:Ce (Y3Al5O12:Ce) finds widespread use in light conversion and scintillator applications. Nanocrystalline YAG:Ce may possess modified optical properties which are advantageous for technological applications, but this will depend on highly efficient energy conversion. In this work, the effect of the particle size and Ce concentration on the quantum efficiency and the optical lifetime of the YAG:Ce emission will be characterized and discussed. Nanocrystalline YAG:Ce with an average particle size of 20 to 50 nm was synthesized by the chemical vapour reaction (CVR) method and subsequently analyzed using various techniques. When comparing the nanocrystalline samples to a coarse-grained reference sample, the particle size and doping concentration was found to have a significant influence on quantum efficiency. It was established that the nanocrystalline samples investigated exhibit a lower QE at ambient temperature than the coarse-grained reference. The results of the optical lifetime measurements are discussed in relation to this reduction in QE.

Abstract: Nano-crystalline YAG:Ce (Y3Al5O12:Ce) with an average particle size of 10-50 nm was synthesized by the vapour phase reaction (CVR) in a hot-wall reactor. This nano-crystalline luminescent material has the advantage of a high light-conversion efficiency associated with superior light-scattering properties. Phases and compositions were analyzed by XRD and EDX, respectively. Photoluminescence was used to investigate the optical properties of the YAG host lattice doped with Cerium. As a first step the conditions for the in-situ production of the YAG phase were established. On the basis of previous DSC investigations of YAG phase formation, the DSC results were analyzed according to the Kissinger theory for thermally activated transformations. From the results it is predicted that, with sufficient heat transfer during the residence time of the particles in the hot zone of the reactor, YAG can be obtained in-situ during the CVR process. By modifying the parameters and the CVR setup it was possible to achieve conditions, which allow the production of in-situ YAG. Samples with Ce doping concentrations ranging from 0 to 2.65 at.% Ce were prepared to investigate the influence of the doping concentration on the luminescence of YAG:Ce.