Papers by Keyword: Blue Emission

Abstract: Long afterglow blue emission silicate (SMS) phosphor doped with Eu²⁺ and Ce³⁺ was synthesized via traditional solid-state reaction in the weak reducing atmosphere. X-ray diffractometer (XRD), field-emission scanning electron microscope (FE-SEM) and energy dispersive X-ray (EDX) spectroscope were employed to characterize its crystal phases, surface morphology and elements composition. The photoluminescence (PL) properties were characterized by PL Spectrophotometer. It was found that the excitation wavelength played a significant role in photoluminescence emission intensity.

Abstract: LiTaO₃: Tm³⁺, Yb³⁺ powders were synthesized by a high-energy ball-milling (HEB) method compared with the conventional solid-state reaction (SSR) method. Under the excitation of 980 nm laser, the strong blue emission (477 nm) band is observed and attributed to ¹G₄- ³H₆ of Tm³⁺. Because of it causing high local temperature and narrow particles size, increasing the contact area between the particles and improved crystallinity of the host, synthesis by high-energy ball milling show higher photoluminescence (PL) intensity compared to the solid state reaction method. In the process of mechanical milling, Tm³⁺, Yb³⁺ co-doped LiTaO₃ phosphors with high photoluminescence property could be achieved at a relatively low reaction temperature.

Abstract: Nanocrystalline ZnO films were deposited on Quartz substrates by RFMS. A strong blue emission (430 ~ 460nm) and UV emission were observed. PL of the integrated intensity and peak intensity, XRD peak intensity and half width (FWHM) and their relationship with growth temperature are given. It was found that 300 °C ~ 350 °C temperature is favorable to the growth of thin film growth, and can get a strong blue emission spectrum. It was initially confirmed that the blue emission (430 ~ 460nm) of ZnO thin films is from the shallow donor electrons to the valence band on the top of the transition which is formed by the Vo or Zni, or Vo to the formation of shallow donor level of Vzn the formation of shallow acceptor level of the composite.

Abstract: Flower-like ZnO nanostructures have been synthesized using zinc nitrate hexahydrate and hexamethylenetetramine (HMT) by a low-temperature hydrothermal technique. The prepared ZnO nanostructures exhibit hexagonal wurtzite structure, well-defined flower-like morphology, and a strong blue emission photoluminescence. Flower-like ZnO nanostructures consisting of multilayered petals are formed with the length of about 1 μm. All the flower petals exhibit the tapering feature with the root size of 300-500 nm and tip size of 50-100 nm. The prepared ZnO sample has been studied using x-ray diffraction technique, energy dispersive x-ray analysis, scanning electron microscope and FTIR spectroscopy. The photoluminescence spectrum demonstrated two emission bands, a near band edge (NBE) emission in the UV region centering at 386 nm and a high intensity deep band emission (DBE) in the visible region centering at 483 nm.

Abstract: Upon the 325 nm excitation from a helium-cadmium laser, the photoluminescence (PL) from aged porous silicon was investigated with fluorescence spectroscopy. Each PL spectrum of the aged porous silicon films contained two luminescent bands, one of the luminescent bands peaked at about 466.7 nm whereas the other luminescent band peaked at about 596.1 nm. The origin of the blue PL from aged porous silicon was discussed, and our results indicated that the blue photoluminescence of porous silicon films originated from the silicon oxide itself.

Abstract: A novel blue phosphor based on phosphate host matrix, MgAl(PO₄)O doped with Eu²⁺ was prepared by solid state reaction. The phosphor invariably emits blue luminescence with a peak wavelength at around 450 nm under ultraviolet excitation. The excitation spectrum showed that the phosphor can be efficiently excited by UV-visible light from 250 nm to 420 nm, which is coupled well with the emission of UV LED (350-410 nm). The results indicated that this novel phosphor may become the candidate of blue radiation-converting phosphor for white light emitting diodes in the further.

Abstract: A series of phosphor of MBPO7:Tm3+, and MBPO7:Tm3+, Gd3+ (M= Mg, Sr, Ca) were prepared and studied. The XRD data showed Tm3+, Gd3+ didn’t affects the lattice parameters. Excitation spectra exhibited high absorption in vacuum ultraviolet (VUV) region. There existed strong emission peaking at 453nm and 363nm correspond to the 1D2 →3HJ (J=4, 6) emission transition of Tm 3+ when excited under VUV. With the changes of cation in the samples, the excitation spectra changed greatly, and lead a great change in its emission spectra. The crystal lattice parameters affect the ratio of intensity of the peak at 454nm and 312nm.

Abstract: To improve luminescent properties of the phosphor, spherical BaMgAl10O17:Eu2+ particles have been synthesized using a liquid phase reaction composed of two-stage precipitations. This phosphor particles exhibited uniform size (0.4 ㎛) with narrow distribution and were well-dispersed without agglomeration. The single phase of phosphor was formed by firing at the temperature of about 1350°C. The preparation conditions in this synthetic process for spherical BaMgAl10O17:Eu2+ particles were optimized on the basis of emission intensity by the excitation at 147 nm. The emission spectra showed the typical broad band due to the transition of Eu2+ activator from 4f65d1 to 4f7 in BaMgAl10O17:Eu2+. The maximum emission intensity for this spherical blue phosphor was obtained by reduction treatment at 1450°C.