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Up-Conversion Photoluminescence of Sol–Gel Derived CaY <sub/>2</sub> O <sub/>4</sub> Powders Under 980 nm Excitation
摘要： Up-conversion is an anti-stokes process that can convert near-infrared light into visible light. Besides the requirement of high optical conversion ef?ciency, the thermochemical stability of the host materials is critical for in practical applications, and a stable oxide host material is optimal. CaY2O4 follows the same ordered structure of CaFe2O4, which is composed of an (R2O4)2? (R = rare earth metal) framework of double octahedral moieties with rare earth ions residing within the framework. CaY2O4 is a promising host material due to its favorable characteristics such as high chemical and thermal stability, low-phonon energy, and environment friendliness. Rare earth ion (Er3+ and Yb3+)-doped nano-crystalline phosphors were prepared by a sol–gel process. The synthesized sample was characterized by X-ray diffraction analysis and the crystallite size was con?rmed by Scherrer’s formula and transmission electron microscopy. The surface morphology of the powders was determined by scanning electron microscopy. X-ray diffraction patterns con?rmed their pure orthorhombic structure after annealing at 1,200 °C and the morphology of particles was found to be a nearly spherical shape with a diameter of the order of ～100 nm. Photoluminescence properties of the powders were measured by exciting the samples with a 980 nm diode laser at room temperature. Under the 980-nm laser excitation, the green and red up-conversion emissions were observed at around 520–540 nm, 540–570 nm and 640–680 nm, which, are attributed to the transitions of 2H11/2 →4I15/2, 4S3/2 →4I15/2 and 4F9/2 →4I15/2 of Er3+ ions, respectively. The up-conversion intensity as a function of laser power shows that the up-conversion mechanism corresponding to green and red emissions occurs via a two-photon process.
关键词： Up-Conversion Phosphor,CaY2O4,Luminescence
更新于2025-09-09 09:28:46
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Design and control luminescence of Li2ZnGe3O8:Cr3+ in NIR ? region by cationic regulation
摘要： Li2ZnGe3O8:Cr3+ deep-red phosphor is synthesized, and the excitation spectrum ranges from 250 nm to 640 nm, and the emission peak locates at 713nm. In order to obtain NIR light, Mg2+/Ca2+/Sr2+/Ba2+ ions were introduced into Li2ZnGeO8:Cr3+. The emission spectra ?rstly show a blue shift and then present an obvious red shift by tuning the Zn/Mg ratio. A common e?ect between the crystal ?eld splitting and the nephelauxetic e?ect makes it possible to blue shift, and the red shift is ascribed to the reduced site symmetry around some Cr3+ ions caused by the disorder. In addition, the emission spectra have a red shift when Zn2+ is substituted by Ca2+, Sr2+ or Ba2+, which is also a common e?ect between the crystal ?eld splitting and the nephelauxetic e?ect. As a results, the luminescence materials realize the regulation from deep red to near-infrared light by increasing the doping ionic (Ca2+, Sr2+, and Ba2+) radii.
关键词： Phosphor,Li2ZnGe3O8:Cr3+,NIR ? region,Cationic regulation,Luminescence
更新于2025-09-09 09:28:46
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[IEEE 2018 IEEE International Conference on Electrical Engineering and Photonics (EExPolytech) - Saint Petersburg, Russia (2018.10.22-2018.10.23)] 2018 IEEE International Conference on Electrical Engineering and Photonics (EExPolytech) - Dispersity and Surface Characterization of Yttrium Vanadate and Phosphate Based Luminescent Phosphors
摘要： The surface properties of Eu(III)-activated yttrium vanadate, yttrium phosphate and mixed yttrium vanadate-phosphate phosphors with different europium content synthesized via self-propagating high temperature synthesis are studied by low temperature nitrogen adsorption, scanning electron microscopy, aqueous slurry pH measurements and adsorption of acid-base indicators. Among the materials synthesized under similar conditions, phosphate based phosphors possess with a significantly more acidic surface (due to the presence of Lewis acidic centers probably corresponding to phosphorous atoms) and coarse dispersity compared with vanadate analogs, while mixed vanadate-phosphate compounds feature with the most fine dispersity.
关键词： Lewis centers,vanadate,yttrium,luminescent phosphor,phosphate,adsorption,surface,Br?nsted centers
更新于2025-09-09 09:28:46
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Applicability of Dy-doped yttrium aluminum garnet (YAG:Dy) in phosphor thermometry at different oxygen concentrations
摘要： Phosphor thermometry is a method used to measure temperature based on the temperature-dependent phosphorescence of phosphors and elucidate heat transfer phenomena, such as high-temperature gas flow. Although various rare earth-doped thermographic phosphors are in use, the effect of oxygen concentration on their phosphorescence has not been sufficiently explored. We explore herein the applicability of Dy-doped yttrium aluminum garnet (YAG:Dy), a well-known rare earth-doped phosphor with temperature sensitivity above 1000 K, in phosphor thermometry at different oxygen concentrations. A third-harmonic Nd:YAG laser excited the sample. Phosphorescence was measured using a photomultiplier tube for lifetime detection. A spectrometer was used to detect the intensity ratio between two emission lines. The chamber was filled with a nitrogen–oxygen mixture with a controlled concentration. The phosphorescence intensity ratio depended on temperature over a wide temperature range and varied with the oxygen concentration, especially above 1000 K. The YAG:Dy lifetimes could be detected over the entire temperature range and remained constant up to 1000 K. In addition, the lifetimes decreased with the increasing oxygen concentration, especially above 1000 K, confirming the oxygen quenching effect. Consequently, YAG:Dy is confirmed to be sensitive to oxygen concentration for determining the intensity ratio and lifetime, especially above 1000 K.
关键词： Lifetime method,Intensity ratio method,Oxygen quenching,Phosphor thermometry
更新于2025-09-04 15:30:14
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Luminescence properties of Tb <sup>3+</sup> doped Gd <sub/>2</sub> (WO <sub/>4</sub> ) <sub/>3</sub> phosphor prepared by hydrothermal method
摘要： The Gd2(WO4)3:Tb3+ phosphors have been successfully prepared using the hydrothermal method calcined at 900℃ in this work. The crystal structure, PLE/PL and fluorescence decay behavior of samples were investigated in detail. Under the 270 nm excitation (4f8→4f75d1 transition of Tb3+), the (Gd2-xTbx)(WO4)3 (x=0.01-0.15) phosphors emit the strong green emission at 547 nm (5D4→7F5 transition of Tb3+). The quenching concentration was found to be ~10% owing to the exchange reaction between Tb3+. The Tb3+ addition did not influence the CIE chromaticity coordinates (~0.33±0.02, ~0.60±0.02) and color temperatures (~5542 K) of the (Gd2-xTbx)(WO4)3 phosphors. However, due to the energy transfer between Tb3+, the fluorescence lifetime for 547 nm emission decreased with the Tb3+ content increasing. The Gd2(WO4)3:Tb3+ phosphors with strong green emission are expected to be widely used in white light LED and display areas.
关键词： Tb3+ doped,Gd2(WO4)3 phosphor,hydrothermal method,Luminescence,green emission
更新于2025-09-04 15:30:14
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The influence of dopants on thermoluminescence of Sr2MgSi2O7
摘要： We report the influence of dopants on the thermoluminescence of Sr2MgSi2O7. Samples studied comprise undoped Sr2MgSi2O7 and doped versions, namely, Sr2MgSi2O7:Dy3+, Sr2MgSi2O7:Eu3+, Sr2MgSi2O7:Tb3+ and Sr2MgSi2O7:Tb3+,Eu3+ phosphors. All samples show a broad glow peak near 60oC when measured at 1 °C/s after irradiation to 10 Gy. The peak changes with partial heating, irradiation and fades between irradiation and measurement in a manner expected of a composite one. The behaviour is used to exemplify the analysis of a composite peak on the basis that particular features reflect those of the dominant component.
关键词： dose response,thermoluminescence,glow curve,phosphor
更新于2025-09-04 15:30:14
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Preparation and Optical Properties of Trivalent Erbium-Doped CaY <sub/>2</sub> O <sub/>4</sub> Powders Under 980 nm Excitation
摘要： Nanocrystalline CaY2O4:Er3+ up-conversion phosphor was prepared by the sol–gel process. A homogeneous precursor sol was heated on a hot plate and then coagulated gel was pre?red at 300 °C for 4 hr in Ar, followed by ?nal annealing at 1,200 °C for 4 h in Ar. The crystallinity of the powders after annealing was con?rmed using an X-ray diffraction analysis. The shape and particle size of the powders were observed by ?eld emission-scanning electron microscope and transmission electron microscope. Up-conversion luminescence spectra were recorded with a ?uorescent spectrophotometer under a 980-nm excitation. The dependence of the up-converted intensities on pumping powers for powders was obtained by changing the excitation powers at room temperature. X-ray diffraction patterns con?rmed the presence of single orthorhombic crystalline CaY2O4 and no impurity peaks were identi?ed. Micrographical images of 3 mol%-doped CaY2O4 powder indicates that the particle size is uniform, and ranges from 100～200 nm. Up-conversion ef?ciency is the highest when the doping concentration of Er3+ is 3 mol%.
关键词： Up-Conversion Phosphor,Luminescence Spectra,CaY2O4
更新于2025-09-04 15:30:14
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Synthesis and luminescence properties of Eu3+-doped a novel double perovskite Sr2YTaO6 phosphor
摘要： A novel Sr2Y1?xTaO6:xEu3+ (x = 0.04–0.20) red-emitting phosphor was synthesized by using the conventional solid-state reaction method. The crystal structure, photoluminescence properties, thermal stability and decay lifetimes were investigated in detail. Upon near UV light excitation, this sample exhibited a strong red emission peak centered at 612?nm due to 5D0 → 7F2, which indicated that Eu3+ occupies low symmetry sites within the Sr2YTaO6 host lattice. The optimized doping concentration of Eu3+ ion is about 12?mol%. The excellent thermal stability of Sr2YTaO6:Eu3+ phosphor was tested according to the temperature dependent emission spectra. In addition, the Sr2Y1?xEuxTaO6 phosphors exhibited good color coordinate (0.6076, 0.3879) and high color purity about 84.55%. All results indicated that the Sr2Y1?xTaO6:xEu3+ phosphors can serve as an efficient red phosphor in the white light emitting diodes.
关键词： Sr2YTaO6:Eu3+,phosphor,luminescence,thermal stability,white light emitting diodes
更新于2025-09-04 15:30:14
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Effects of Al3+ substitution on the luminescence properties of LuNbO4 doped with Eu3+ and Tb3+ ions
摘要： The effect of Al3+ substitution on the enhancement of the luminescence of Lu1–xAlxNbO4:Eu3+ and Lu1–xAlxNbO4:Tb3+ was investigated. X-ray diffraction patterns confirmed that the Eu3+, Tb3+, and Al3+ ions were fully incorporated into the Lu3+ sites. In the case of Lu1–xAlxNbO4:Eu3+, the predominant red emission (614 nm) was assigned to the 5D0 → 7F2 transition of Eu3+ and for x = 0–0.05, its intensity increased up to ~125 and 108% under 395 nm (7F0 → 5L6) and a charge transfer band excitation, respectively. For Lu1–xAlxNbO4:Tb3+, the strongest emission band peaking at 551 nm was attained in the green region among multiple emission bands corresponding to the 5D4 → 7FJ transitions of Tb3+. Increasing the x values from 0 to 0.05 increased the green emission significantly by ~137%. These phenomena were explained by the local structural distortions and crystal field asymmetry surrounding Eu3+ and Tb3+, which were attributed to a large difference in the ionic radii of Al3+ and Lu3+.
关键词： Terbium,Luminescence,Europium,Phosphor,Lutetium niobate
更新于2025-09-04 15:30:14
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Synthesis, energy transfer, charge compensation and luminescence properties of CaZrO3:Eu3+, Bi3+, Li+ phosphor
摘要： A series of CaZrO3:Bi3+, CaZrO3:Eu3+, CaZrO3:Eu3+, Bi3+, and CaZrO3:Eu3+, Bi3+, Li+ phosphors are synthesized by high-temperature solid-state reaction method in air. Their luminescence properties are researched, compared, and analyzed. CaZrO3:Bi3+ phosphor under excitation at 310?nm emits deep-blue light with chromaticity coordinate (0.1612, 0.0254). CaZrO3:Eu3+ phosphor under excitation at 310 and 395?nm shows red-emitting with chromaticity coordinate (0.6386, 0.3611). CaZrO3:Eu3+, Bi3+ phosphor under excitation at 310?nm exhibits a systematically varied hue from deep-blue to red light by changing Eu3+ ion concentration, and that with excitation at 395?nm only emits red light with chromaticity coordinate (0.6386, 0.3611). The energy transfer process from Bi3+ to Eu3+ ions may be indicated by their spectral properties. The optimal Eu3+ and Bi3+ ions concentrations are 5?mol% and 0.9?mol%, respectively. The emission intensity CaZrO3:Eu3+, Bi3+ phosphor may be enhanced about 1.6 times due to the co-doping Li+ ion as charge compensator role. The luminous mechanism of CaZrO3:Eu3+, Bi3+ phosphor is explained by the simplified energy level diagrams of Bi3+ and Eu3+ ions.
关键词： energy transfer,CaZrO3,luminescence,charge compensation,phosphor
更新于2025-09-04 15:30:14