Papers by Keyword: Luminescence

Abstract: Calcium silicate phosphors, Ca2-xSiO4(CS):Eu3+x, CS:Eu2+x and Ca2-y-zMgSi2O7 (CMS):Eu2+y,Dy3+z were prepared by the solid state reaction. The phases in CS:Eu3+ system were β- and αL’ -types. The fluorescent color under a black-light irradiation was red and the emission spectrum consisted of 590nm(αL’), 615nm(β) and 625nm(αL’) peaks. The emission intensity took a maximum value at x=0.2. The addition of B3+ accelerated the solid solution of Eu3+. The phase in CS:Eu2+ system was β-type only. The fluorescent color was yellow-green(520nm). The emission intensity took a maximum value at x=0.01. The CMS product showed the akermanite phase. The lattice constants of CMS:Eu2+ increased with increasing Eu content, but those became constant at y>0.05. The fluorescent color of CMS:Eu2+ was yellow-green and the emission intensity took a maximum value at y=0.03. In the case of CMS:Eu2+0.03,Dy3+z, the fluorescent color and the afterglow color were same, yellow-green. The emission intensity took a maximum value at z=0.06. The longest afterglow time, 23min., was obtained at z=0.09. The trap depth were 0.64-0.69 eV.

Abstract: ZnGa₂O₄ phosphors have been synthesized by solid state reaction at different temperatures with different B₂O₃ concentration incorporated in the experiments. All samples present green (509 nm) and red (696 nm) emission bands under ultraviolet excitation (250 nm), whose intensity changes because of the increasing B₂O₃ contents. The green and the red long afterglow have been observed after removing the ultraviolet light and the performance largely improves with the introduction of B₂O₃. The effects of the doping contents of B₂O₃ as well as the sintering temperatures on the luminescent properties of the obtained products have been investigated. The introduction of B₂O₃ changes the ratio of the two emitting centers and increases the depth of the trap centers in the samples.

Abstract: A Eu³⁺ activated YInGe²O⁷phosphor was synthesized by solid-state reaction and lithium carbonate was added to change the morphology and photoluminescence properties. Scanning electron microscopy showed large particle size and necking shape were obtained as the concentrations of Li⁺ ions increase. In the PL studies, the excitation spectrum of YInGe²O⁷:Eu³⁺ phosphors exhibited a broad band in the UV region centered at about 272 nm attributed to charge transfer state (CTS) band, which has a little shift after Li⁺ ion was added. As the Li⁺ ion concentration increased, the photoluminescence intensity of the red emission at 620 nm of Eu³⁺ ions was enhanced, and the optimized concentration of of added Li⁺ ion is 0.05. The results showed that addition of Li⁺ ion allows YInGe²O⁷:Eu³⁺ phosphors emitting relatively pure red light.

Abstract: As a new-type material, luminescent coating has received increasingly extensive application in modern life. The varieties of luminescent coatings gradually increase with the progress of science and technology, of which each kind of them shows its own unique property. This thesis researched on the different properties of various luminescent coatings so as to make them into rational use on the interior interface, thus achieving the more appropriate and safer use in interior design for the sake of beautification space, economizing and environmental protection.

Abstract: Organic-inorganic hybrid materials doped with Eu3+, Tb3+ La3+ and lithium ions were produced by sol-gel method using Tetraethyl orthosilicate and poly(methyl methacrylate), ethyl methacrylate, butyl methacrylate, ethyl acetyloacetate as inorganic and organic precursors. Morphology and structure of the hybrids heated at 125°C were characterized by Scanning electron microscopy equipped with Energy dispersive X-ray spectroscopy (SEM/EDS, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), 29Si MAS Nuclear Magnetic Resonance. In all the hybrids, photoluminescence emissions from (5D3), 5D4 →7FJ and 5D0→7FJ transi^{Superscript text}tions of Eu3+ and Tb3+ ions were revealed.

Abstract: The mechanisms of intrinsic luminescence in the set of molybdate crystals of M^IM^III(MoO₄)₂ (M^I = Li, Na, K; M^III =Bi, Y, Fe) type are revealed in complex experimental and theoretical studies. The luminescence spectroscopy under vacuum ultraviolet (VUV) synchrotron excitations is applied together with the electronic structure calculations carried out by the FLAPW method. The energy gaps (E_g) values of the crystals are determined in simultaneous analysis of diffuse reflectance and luminescence excitation spectra. It is found that the molybdate groups MoO₄^2- play a dominant role in the processes of intrinsic luminescence in studied molybdate compounds

Abstract: Luminescence properties of the two series of the La_1-xEu_xVO₄ (x ranges from to 0.3) solid solutions synthesized by the solid state and co-precipitation methods were investigated.. Luminescence spectra of the investigated samples consist of narrow spectral lines caused by inner f - f electron transitions in the impurity Eu³⁺ ions. Excitation spectra consist of three main bands those correspond to different types of transitions in the investigated matrices. There are O - Eu³⁺ charge transfer transitions, band-to-band transitions in the matrix of the vanadate compounds and electron transitions in the VO₄^3- vanadate anion. Dependences of the structure and luminescence properties on rate compositions and method of synthesis were studied. Origins of the observed differences between luminescence characteristics of the samples obtained by two different methods are discussed.

Abstract: Ca3(VO4)2:Eu3+,Bi3+ nanophosphate was prepared in the presence of stearic acid. The samples obtained were intensively characterized using XRD, SEM, photoluminescence (PL) spectra and FTIR. The results show that the red emission located at about 614 nm was ascribed to 5D0–7F2 transition of Eu3+, and the excitation and emission spectra indicate that this nanophosphor can be effectively excited by ultraviolet (UV) (395 nm), and exhibits a satisfactory red performance (614 nm), nicely fitting in with the widely applied UV LED chips.

Abstract: Montmorillonite (MMT) mainly consist of hydrated aluminum silicate. Montmorillonite has particular properties and many practical applications, because of their special crystal structure. Here, mechano-chemical method was used to prepare MMT nanosheets by controlling the pH value. MMT nanosheets were obtained by ballmilling, and the impact of pH value on the nanosheets preparing was studied. TEM was employed to emamine the microstructure of MMT nanosheets. The size are analyzed to study the status of MMT nanosheets. Different rare earth ions as a fluorescence center were assembled on nanosheets，and composites were obtained. The luminescent properties of composite materials were studied.

Abstract: Tb³⁺ doped Yttrium hydroxide nanosheets were successfully synthesized from layer compound of Y₂(OH)₅NO₃ doped by Tb³⁺. Layer compound was obtained by hydrothermal reaction at 120°. After ion exchange reaction with sodium benzoate under the microwave condition, the layer space of the compound increases from 0.907 nm to 1.452 nm. stable nanosheets sol was obtained after exfoliation under ultrasonic condition. The structure of layer compound and the morphology of nanosheets were determined by XRD,SEM, Zeta Size, Zeta Potential, TEM and FL. The luminescence properties of terbium hydroxide nanosheets doped with Tb³⁺ were examined; the relationship between structure and spectra was discussed.