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Calcination effect to the physical and optical properties of Zn <sub/>2</sub> SiO <sub/>4</sub> composite prepared by impregnation of ZnO on SiO <sub/>2</sub> amorphous nanoparticles
摘要： In this study, Zn2SiO4 composite-based ceramic was synthesised using amorphous SiO2 nanoparticles as a silicon source. The amorphous SiO2 nanoparticles which obtained from a simple precipitation process were mixed with aqueous zinc nitrate. Amorphous SiO2 nanoparticles were encapsulated by the zinc source in aqueous solution, dried, and subjected to calcination. The underwent calcination showed the changing of phases, morphology, and size with increased temperatures. During calcination, ZnO phase appeared at the beginning of heating temperature and Zn2SiO4 phase started to emerge at 800 °C onwards, as shown by XRD patterns. The optical band gap analysis of Zn2SiO4 composite was determined to be within the range of 3.12 to 3.19 eV. The diffusion of zinc ions into SiO2 nanoparticles with high surface area also reduced the phase formation temperature for Zn2SiO4, compared to a conventional solid state method. This optical characteristic is expected to be a potential candidate for phosphor materials in opto-electronic devices application.
关键词： optical properties,Zn2SiO4 composite,amorphous SiO2 nanoparticles,phosphor materials,calcination
更新于2025-09-10 09:29:36
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Structural Change in SrSiO <sub/>3</sub> Induced by Introduction of Nitrogen
摘要： SrSiO313xN2x with a single chain inosilicate structure, which has not been realized in Sr and Sr-rich metasilicates, has been synthesized by introduction of a small amount of nitrogen into SrSiO3. Its crystal structure was determined by a single-crystal X-ray analysis. Anion sites are severely distorted along b-axis, resulting in formation of the inosilicate structure. The present material activated with Eu2+ exhibits red emission under near ultraviolet and visible light irradiation. Our results suggest a new strategy for development of novel oxynitrides.
关键词： Phosphor,New compound,Oxynitride
更新于2025-09-10 09:29:36
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Leaching of Rare Earth Metals from Phosphor Coating of Waste Fluorescent Lamps
摘要： Phosphors made from compounds of rare earth metals (REMs) are very efficient. This material needs to be recycled for recovery of REMs after the fluorescent lamps (FLs) reach end of life. This work focuses on the leaching studies of REMs from phosphor. The phosphor was recovered from the spent linear FLs by end cut-push method. After detailed characterization of phosphor, effects of parameters viz. leachant, concentration, temperature, and pulp density were studied to determine the optimum leaching conditions. By using 9% (v/v) H2SO4, 98.6% (w/w) yttrium and 96.2% (w/w) europium could be leached out from phosphor at temperature, 70 °C, time, 4 h, and pulp density, 10% (w/v). The residue generated was treated with 54% (v/v) HCl to leach out 98.9% (w/w) lanthanum, 98.2% (w/w) cerium and 96.5% (w/w) terbium at temperature, 90 °C, time, 2 h, and pulp density, 10% (w/v). Kinetic studies of leaching reactions were also carried out.
关键词： Phosphor,Leaching,Waste recycling,Rare earth metals,Fluorescent lamps
更新于2025-09-09 09:28:46
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A novel Li <sub/>2</sub> CaSi <sub/>2</sub> N <sub/>4</sub> :Eu <sup>2+</sup> orange-red phosphor for field emission displays
摘要： The exploration of suitable phosphors with high efficiency, low saturation and good stability has always been a key issue for field emission displays (FEDs) development. In this work, a novel Li2CaSi2N4:Eu2+ orange-red phosphors were prepared by solid reaction process and the cathodoluminescence (CL) properties were investigated in detail to explore the potential application for FEDs. Under a low voltage electron-beam excitation, the phosphors show an intense orange-yellow emission in the range of 500-700 nm, which belongs to the 4f65d → 4f7 electron transition of Eu2+ ion. The influences of the Eu2+ doping concentration, filament current, accelerating voltage and bombardment time on the CL emission of Li2CaSi2N4:Eu2+ were investigated in detail. The results indicate that Li2CaSi2N4:Eu2+ phosphors exhibit an intense orange-red emission, no saturation effect, and excellent degradation property, which give the Li2CaSi2N4:Eu2+ phosphors potential application in full color FEDs.
关键词： Li2CaSi2N4:Eu2+,cathodoluminescence,phosphor,FED
更新于2025-09-09 09:28:46
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Color tunable emission from CaS:Cu+, Mn2+ rare-earth-free phosphors prepared by a simple carbon-thermal reduction method
摘要： Photoluminescence properties of CaS:Cu+, CaS:Mn2+ and CaS:Cu+, Mn2+ rare-earth-free phosphors prepared by a carbon-thermal reduction method were investigated. The emission spectrum of Cu+-doped CaS consists of two overlapped bands peaking at 415 nm (attributed to isolated Cu+ activator) and 475 nm (attributed to aggregated Cu+ center). The influence of Cu+ doping concentration on the emission spectrum is discussed. The emission spectrum of Mn2+-doped CaS exhibits a band emission peaking at 568 nm under 250 nm excitation. The emission spectra of the doubly activated CaS:Cu+, Mn2+ phosphors consist of Cu+ and Mn2+ emissions simultaneously, and their shapes depend strongly on the Mn2+ concentration. Based on the emission and excitation spectra of the CaS:0.15 mol%Cu+, xMn2+ phosphors, the energy transfer from Cu+ to Mn2+ takes place. The emitting colors of the doubly activated phosphors can also be tuned. In particular, the emitting color of CaS:0.15 mol% Cu+, 0.6 mol % Mn2+ sample is close to white light.
关键词： Carbon-thermal reduction method,Photoluminescence,CaS:Cu+, Mn2+,Rare-earth-free phosphor
更新于2025-09-09 09:28:46
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Crystal structure dependence of red to green light emission by LaOF : Yb3+/Er3+ up-conversion phosphor
摘要： Up-conversion (UC) is the conversion of electromagnetic waves from long to short wavelengths. In this study, near-infrared rays (with wavelengths of 980 nm) were upconverted to visible light rays (with wavelengths of 400–750 nm), and the UC luminescence characteristics of lanthanide-doped materials were measured and analyzed. LaOF : Yb3+/Er3+ UC phosphor samples were fabricated by using LaF3 (hexagonal), Yb2O3 (cubic), and Er2O3 (cubic) powders. The mole ratio of La : Yb : Er was 1 : 0.01 : 0.01, and LaOF : Yb3+/Er3+ was obtained by baking these materials. The UC emission of yellow to green light was confirmed by the overlapping of green and red light. The emitted light intensity was the highest for the sample baked at 1100 oC for 2 h. Furthermore, X-ray diffraction (XRD) results revealed that the photoluminescence emission intensity increased with increasing integrated intensity of the tetragonal LaOF crystal system.
关键词： Phosphor,Crystal structure,Up-conversion,Yb3+/Er3+,LaOF
更新于2025-09-09 09:28:46
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Mn <sup>4+</sup> -Doped Heterodialkaline Fluorogermanate Red Phosphor with High Quantum Yield and Spectral Luminous Efficacy for Warm-White-Light-Emitting Device Application
摘要： Narrow band red-emitting Mn4+-doped fluoride phosphor is an essential red component of modern white-light-emitting-diode (WLED) devices. Its luminescence has sensitivity to structure and influences the performance of WLED. In this paper, we report a high-performance Mn4+ phosphor based on a new heterodialkaline fluorogermanate, CsNaGeF6:Mn4+. As determined by the single-crystal X-ray diffraction analysis, the CsNaGeF6 compound crystallizes in the orthorhombic crystal system with space group Pbcm (No. 57). Under excitation by 360 and 470 nm photons, CsNaGeF6:Mn4+ emits intense red light near 630 nm with a high quantum yield of 95.6%. The electronic energy levels of the Mn4+ ion in Cs2GeF6, Na2GeF6, and CsNaGeF6 are calculated using the exchange charge model of crystal-field theory. The local Mn4+ environment inducing different zero-phonon-line emissions in the structures is probed by electron paramagnetic resonance. The Mn4+-doped heterodialkaline fluorogermanate CsNaGeF6:Mn4+ exhibits broader emission as a result of the lowest symmetry. It has higher quantum yield than Na2GeF6:Mn4+ and higher spectral luminous efficacy than Cs2GeF6:Mn4+. Given the good thermal stability and efficient luminescence, a prototype warm-WLED device with a color rendering index of 92.5, a correlated color temperature of 3783 K, and a luminous efficacy of 176.3 lm/W has been fabricated by employing the CsNaGeF6:Mn4+ phosphor as the red component. Our results not only reveal that a high-performance Mn4+ red phosphor is achieved through cationic substitutions but also construct a relationship of performance?structure to guide the design of Mn4+ phosphors in the future.
关键词： quantum yield,spectral luminous efficacy,Mn4+-doped fluoride phosphor,warm-white-light-emitting diode,heterodialkaline fluorogermanate
更新于2025-09-09 09:28:46
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Dy <sup>3+</sup> -doped Y <sub/>3</sub> Al <sub/>5</sub> O <sub/>12</sub> transparent ceramic for high efficiency ultraviolet excited single-phase white-emitting phosphor
摘要： A kind of Dy-doped yttrium aluminum garnet (YAG) transparent ceramic for ultraviolet excited single-phase white light emitting phosphor was investigated, which has high quantum efficiency (45%). The temperature field of Dy:YAG transparent ceramic was calculated by steady state thermal simulation. Moreover, by combining with 365 nm LED chip directly, the CIE coordinate (x=0.33, y=0.35) is close to the standard equal energy white light illumination. The Dy:YAG transparent ceramic, possessing of good optical and thermal properties, is promising for applications in high-power LEDs devices.
关键词： single-phase white-emitting phosphor,Dy-doped YAG,high-power LEDs,transparent ceramic
更新于2025-09-09 09:28:46
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Recovery of rare earths from waste cathode ray tube (crt) phosphor powder by selective sulfation roasting and water leaching
摘要： Until recently, most displays, such as television and computer screens, were based on cathode ray tubes (CRTs). With the introduction of new types of displays including liquid crystal displays, CRTs have been widely replaced, leading to a gradual build-up of hazardous CRT powder waste. In this paper, a new approach is introduced where the valuable rare-earth elements (REEs) (i.e. yttrium and europium) in the powder are selectively recovered, leaving behind a zinc-rich residue and glass for further recycling. The main rare-earth compound in the waste powder is Y2O2S:Eu3+ (YOS). The fine-grained CRT powder was mixed with zinc sulfate monohydrate (ZnSO4.H2O) and roasted at 600-900 °C for short periods of time. In this way, Y2O2S:Eu3+ was transformed into water-soluble rare-earth sulfates. Meanwhile, ZnS underwent a two-stage reaction with ZnSO4.H2O, where first a partially water-soluble intermediate (ZnO.2ZnSO4) and then the water-insoluble ZnO was formed. Addition of a sufficient amount of ZnSO4.H2O ensured the recovery of ≥ 95% of the rare earths in a subsequent water leaching step, but there was also co-dissolution of about 5% of the total amount of zinc present. Several purification methods were tested and compared to separate the REEs from the zinc impurity in the solutions. In addition to the conventional precipitation methods with sulfides and oxalic acid, Versatic Acid 10 was tested. Finally, a complete flow sheet is proposed for the (almost complete) valorization of REEs as well as the total zinc present.
关键词： CRT phosphor,zinc,water leaching,Versatic acid,rare earths,roasting
更新于2025-09-09 09:28:46
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Structural and photoluminescence properties of UV-excited Er3+ doped Ba2CaWO6 yellowish-green phosphors
摘要： Double perovskite Ba2CaWO6 phosphors doped with different concentrations of Er3+ have been synthesized by the conventional solid state reaction method in air at 1250 °C and are characterized by X-ray diffraction analysis (XRD), Energy Dispersive X-ray Spectrometer (EDS), Scanning electron microscope (SEM), Transmission electron microscope (TEM), Fourier transform infrared spectroscopy (FTIR) and Photoluminescence measurements. An intense green and weak red emissions are observed at 566 nm (4S3/2 →4I15/2), 680 nm (4F9/2 →4I15/2) under 314 nm, 378 nm corresponding to charge transfer band and rare earth excitations respectively. Under charge transfer excitation Ba2CaWO6:xEr3+ samples exhibit high intense emission peaks of Er3+ than the rare earth excitation. This is due to an efficient energy transfer from WO6 6- to Er3+. The maximum emission intensity was observed for 0.08 wt% concentration of Er3+ ions in Ba2CaWO6 phosphors. The critical energy transfer distance among Er3+ ions is calculated to be 15.18 ? and the quenching mechanism is due to dipole-dipole interaction. The energy transfer mechanism is discussed based on the energy level diagram of Er3+. The radiative lifetimes were determined from the fluorescence decay analysis. The CIE color coordinates were calculated from the emission spectra. The result shows that Ba2CaWO6:Er3+ phosphor can be considered as a potential candidate for UV excited yellowish-green phosphor for display applications.
关键词： Ba2CaWO6,phosphor,photoluminescence,Er3+,yellowish-green emission,energy transfer
更新于2025-09-09 09:28:46