Papers by Keyword: Strontium Aluminate

Abstract: In this work strontium aluminate doped with trivalent europium ion was prepared by the method of evaporation of poly vinyl alcohol and their luminescence, structural and thermal properties were investigated. The samples were characterized by thermal differential and thermogravimetry analysis, structural analysis was performed by X-ray diffraction and Fourier transform infrared spectroscopy and luminescence by fluorescence emission spectroscopy. The thermal analysis of aluminate samples showed two mass losses accompanied by endothermic and exothermic processes during the calcination process, not depending on the time employed in calcination. The infrared spectra exhibited characteristic bands of the metals involved in the synthesis of the material demonstrating the formation of strontium aluminate. The diffratogram patterns showed the formation of cubic phase Sr₃Al₂O₆. The fluorescence characterization showed two emission bands attributed to matrix and europium excited states and it was observed that as the calcination time and temperature were increased, the emission of europium in the material was less efficient.

Abstract: SrO-Al₂O₃ ceramics has prospective applications due to its photo-luminescence and persistent afterglow properties. Sr₃Al₂O₆-SrAl₂O₄ eutectic glass was prepared by using the aerodynamic levitator equipped with a CO₂ laser device. The prepared Sr₃Al₂O₆-SrAl₂O₄ eutectic glass beads were further heat-treated at temperature from 880°C to 980°C. The phase evolution, crystallization behavior, optical transmittance and mechanical properties of the annealed eutectic glass ceramics were investigated. The as-prepared glass is colorless and transparent over a wide range from ultraviolet to near-infrared region, and the average in-line transmittance is over 80% in the range of 260-3200nm. There were two crystal phases Sr₃Al₂O₆ and SrAl₂O₄ crystallized from the glass beads. With increasing heat-treatment temperature, the transparency of the samples decreased, and the hardness increased. The prepared Sr₃Al₂O₆-SrAl₂O₄ eutectic glass and glass ceramics may be a promising candidate for the development of photo-luminescence and persistent afterglow materials.

Abstract: Cooper doped SrAl₂O₄:xCu powders were synthesized by combustion method. The doping concentrations were x= 0.1%, 0.3%, 0.5%, and 1.0 at.%. X-ray diffraction patterns indicate that all Cu doped/undoped powders has monoclinic phase. Also, TEM images show that the size of the nanoparticles decreases as the content of Cu increases. The photocatalytic degradation of Congo red (CR) was studied by monitoring intensity of its characteristic absorbance band centered at 494 nm. The best result was obtained with the 0.1% Cu doped sample, since it degraded 100% of CR after 120 minutes under sunlight excitation. Hence, our results suggest that SrAl₂O₄:xCu powders could be suitable candidates for photocatalytic degradation of dye pollutants under sunlight.

Abstract: Polystyrene encapsulated phosphors SrAl2O4:Eu2+,Dy3+ were prepared by dispersing the phosphors into the matrix of polystyrene. The phase, morphology and optical properties of the polystyrene encapsulated phosphors were characterized with X-ray diffractometry, scanning electron microscopy and photoluminescence (PL) spectroscopy, respectively. It has been observed that both the PL spectrum and the luminescent color of the polystyrene encapsulated phosphors can be dramatically modified although the phosphorescence of the polystyrene encapsulated phosphors is not affected. Tunable photoluminescent colors from green to deep-blue are expected for the polystyrene encapsulated phosphors by the control of the weight percentage of the phosphors in the composites.

Abstract: The long afterglow luminescent materials Sr₃Al₂O₆: Eu, Sm and Sr₃Al₂O₆: Eu, Dy (denoted as S1 and S2, respectively) were synthesized via solid-state reaction. X-ray diffraction, fluorescence spectrophotometer and thermal luminescent spectroscope were employed to characterize the phosphors. The excitation spectra are all well simulated by eight Gaussian curves, indicating that they originate from the 4f⁷(⁸S_7/2)–4f⁶5d(⁸H_J) transitions of Eu²⁺. The excitation spectra intensity of S1 is much stronger than that of S2, which indicates that there is a more efficient energy transfers from Sm³⁺ to Eu²⁺. The thermally stimulated luminescence (TSL) curve can be fitted to four TSL peaks and the low-temperature TSL peak is responsible for the long lasting phosphorescence. The proposed explanation for the afterglow property is discussed.

Abstract: Eu²⁺, Dy³⁺ co-doped alkaline earth aluminates MAl₂O₄: Eu²⁺, Dy³⁺ (M = Ba, Sr) have been prepared by in situ self-propagating high temperature synthesis (SHS) method. The influence of co-doping rare earth ions (Eu²⁺, Dy³⁺) on the luminescence of MAl₂O₄:Eu²⁺, Dy³⁺ were described in this study. The particles morphology, photoluminescence and afterglow properties of the phosphors were studied. Broad band UV excited luminescence was observed for BaAl₂O₄:Eu²⁺, Dy³⁺ and SrAl₂O₄:Eu²⁺, Dy³⁺ in the green region peak at _max = 503 nm and 523 nm, respectively. The dopant (Eu²⁺) and co-dopant (Dy³⁺) concentrations affect the crystallinity and luminescence properties of the materials.

Abstract: The long afterglow luminescent materials Sr3Al2O6: Eu2+, Re3+ ( Re= La, Ce, Pr, Nd, Sm, Gd, Dy, Er) were synthesized via solid-state reaction. X-ray diffraction and fluorescence spectrophotometer were employed to characterize the phosphors. The excitation spectra were all well simulated by eight Gaussian curves, indicating that they originated from the 4f7 (8S7/2) – 4f65d (8HJ) transitions of Eu2+ ions. The excitation spectra intensity of Sr3Al2O6: Eu2+, Sm3+ is much stronger than the others, which indicates that there is a more efficient energy transfers from Sm3+ to Eu2+. The simulated results of the emission spectra showed that they generated from the Eu2+ ions in the Sr2+ sites of SrO6 and SrO7 polyhedral, which indicated that the Eu2+ ions were apt to occupy low-coordination crystallographic site. The proposed explanation for excitation spectra and emission spectra property were also discussed

Abstract: The detailed preparation process of Eu2+ and Dy3+ ion co-doped phosphor powders in Sr4Al14O25:Eu2+/Dy3+ phosphor system with bluish-green long afterglow produced by solid state reaction method under reducing atmosphere is here reported. X-ray diffraction (XRD), scanning electron microscopy (SEM), and particle size analysis were made to assign the effects of Eu and Dy ions on the luminescent properties of the synthesized phosphors, which were determined by measuring the photoluminescence spectra. The maximum emission intensity of these phosphors under excitation was investigated. As a result, the relevant values were obtained from the phosphorescent pigment with 0.21% and 0.05% molar percent of Eu2+ and Dy3+.

Abstract: Well known long-persistent phosphorous strontium aluminates were synthesized by conventional combustion method in a furnace at about 600oC. By incorporating the obtained phosphorous strontium aluminates into organic host polystyrene, we prepared the organic-inorganic composite material (i.e., phosphor-polystyrene) which could be cast into flexible and green-light- emitting films. The morphology of the obtained phosphorous strontium aluminates and the phosphorescence of the organic-inorganic composite films were characterized with the scanning electron microscopy and the fluorescence spectroscopy, respectively. Our results show that the organic-inorganic composite films can be used as green-light- emitting roll-able screens in the industry of information displays.

Abstract: Strontium aluminate-based phosphors SrAl2O4:Eu2+,Dy3+ (SAO-ED) are coated directly by the interfacial coordination chemistry method with maleic anhydride to prevent their hydrolysis in moist air. SEM, XPS, TG and DSC methods are used to characterize the coating. The results showed SAO-ED phosphors coordinated with maleic anhydride by the coordination bond and . The introduction of maleic anhydride doesn’t change the excitation and emission spectra of SAO-ED phosphors, which is proved by the photoluminescence measurement. The SAO-ED phosphor coated with 30 wt. % maleic anhydride has higher water-resistance at the cost of a minor loss of persistent phosphorescence than that of SAO-ED phosphor.