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Spectroscopic Studies of M??ssbauer, Infrared, and Laser-Induced Luminescence for Classifying Rare-Earth Minerals Enriched in Iron-Rich Deposits
摘要： Rare-earth (RE) phosphates often appear as an accessory phase in igneous or metamorphic rocks; however, these rocks are composed of myriad chemical elements and nuclides that interfere with the qualitative or quantitative analyses of the RE phosphates over a range of concentrations in the absence of a pretreatment. In addition, the limit of each analytical methodology constrains the approach as well as the usefulness of the results in geoscience applications. Here, we report the specific mineral characterization of RE-containing ores from Yen Phu mine, Vietnam, using a range of state-of-the-art spectroscopic techniques in conjunction with microscopy: M?ssbauer spectroscopy, infrared microspectroscopy, time-resolved laser-induced fluorescence spectroscopy (TRLFS), and scanning electron microscopy with energy-dispersive X-ray spectroscopy. Because the distribution of each element in the deposit differs, such combinatorial works are necessary and could lead to more plausible answers to questions surrounding the point of origin of RE elements. The results of our M?ssbauer spectroscopic analysis indicate that the three ores sampled at different locations all contain magnetite-like, hematite-like, and iron(III) salts other than hematite. In addition, we confirmed the presence of phosphate around the grain boundary in the magnetite-like mineral phase by infrared microspectroscopic analysis. The present analytical findings of trace amounts of europium(III) using TRLFS suggest that the europium ions generate identical luminescence spectra despite being embedded in three different matrices of iron minerals. This demonstration highlights the benefits of combinatorial spectroscopic analyses to gain insights into the effects of the environment of REs on their solid-state chemistry and shows the potential utility of TRLFS as a resource mining tool. Further applications of this approach in the analytical screening of rocks and minerals are feasible.
关键词： energy-dispersive X-ray spectroscopy,spectroscopic techniques,rare-earth phosphates,Yen Phu mine,infrared microspectroscopy,scanning electron microscopy,time-resolved laser-induced fluorescence spectroscopy,M?ssbauer spectroscopy,Vietnam
更新于2025-09-23 15:21:01
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Leaching Kinetics of Yttrium and Europium Oxides from Waste Phosphor Powder
摘要： Phosphor powder sample was characterized, and the leaching kinetics of yttrium, and europium in hydrochloric acid were investigated. Under optimized leaching conditions, 98% Y and 97% Eu were extracted, and a reaction curve was generated using the percentage of extraction as a function of time and temperature. Based on R2 values, shrinking spherical particle and shrinking core model were not applicable. SEM analysis also con?rmed shrinking core behavior was not applicable due to the lack of core–shells in the leach residue. The kinetic data were best ?tted by a logarithmic rate expression of the empirical model. Activation energy was calculated to be 77.49 kJ/mol for Y and 72.75 kJ/mol for Eu in the temperature range of 298–343 K.
关键词： Leaching,Phosphor powder,Rare earth elements,Waste ?uorescent lamp,Kinetics
更新于2025-09-23 15:21:01
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Magneto-optical properties of Rare Earth metals substituted Co-Zn spinel nanoferrites
摘要： Cobalt–zinc ferrite nanoparticles (NPs) substituted with three different metals, Co0.5Zn0.5RexFe2-xO4 (RE = Ce, Dy, and Y; 0.00 ≤ x ≤ 0.05) were prepared hydrothermally. Fourier Transform-Infrared (FT-IR) Spectroscopy, X-ray powder diffraction (XRD), Field-Emission Scanning Electron Microscope (FESEM) coupled with energy-dispersive X-ray spectroscopy (EDX) and Vibrating Sample Magnetometry (VSM) analyzed the products. The formation of cubic phase of spinel Co-Zn ferrite NPs were confirmed through XRD, FT-IR and FE-SEM techniques. The structural investigation of NPs by XRD revealed that the lattice parameter "a" decreases with the introduction of the RE in the ferrite structure by the substitution of Fe3+ by RE ions. The different magnetic parameters of Co0.5Zn0.5RexFe2-xO4 (RE = Ce, Dy, and Y; 0.00 ≤ x ≤ 0.05) NPs such as the saturation magnetization, coercivity, remanence, and magnetic moment were calculated and discussed in relation to structure and microstructure properties. M (H) hysteresis curves indicated that the samples exhibit superparamagnetic nature at room temperature. A slight improvement in the magnetization was obtained especially for the Ce- and Y-substituted Co0.5Zn0.5Fe2O4 (CZF) NPs at a certain RE level. However, the case Dy-substituted CZF products showed a sharp decrease in the magnetization with x > 0.01. The results are mostly ascribed to the substitution of smaller Fe3+ ions with larger RE3+ ions.
关键词： Spinel ferrites,Morphology,Rare earth substitution,Hydrothermal,Magnetic properties
更新于2025-09-23 15:21:01
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Laser Sources Based on Rare-Earth Ion Doped Tellurite Glass Fibers and Microspheres
摘要： In recent years, huge progress has been made in the development of rare-earth ion doped tellurite glass laser sources, ranging from watt- and multiwatt-level fiber lasers to nanowatt level microsphere lasers. Significant success has been achieved in extending the spectral range of tellurite fiber lasers generating at wavelengths beyond 2 μm as well as in theoretical understanding. This review is aimed at discussing the state of the art of neodymium-, erbium-, thulium-, and holmium-doped tellurite glass fiber and microsphere lasers.
关键词： microsphere laser,tellurite glass fiber,microlaser,rare-earth ions,tellurite fiber laser
更新于2025-09-23 15:21:01
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Energy transfer phenomenon of Gd3+ to excited ground state of Eu3+ ions in Li2O-BaO-Gd2O3-SiO2-Eu2O3 glasses
摘要： Li2O-BaO-Gd2O3-SiO2 glasses with different concentration of Eu3+ ions were developed by the traditional melt quenching technique and characterized via FTIR, absorption, excitation, emission and CIE color coordinates analysis for visible red emission application. The FTIR shows strong band at position 740 cm-1 which is attributed to Si-O-Si symmetric stretching mode. Density and molar volume of LBGSEu glasses increases with Eu3+ ions concentration. The covalent nature of bond between the Eu3+ ions and surrounding ligands was confirmed from the bonding parameter (δ). From absorption spectra JO-parameters and oscillator strength are evaluated for LBGSEu6 glass. From JO-parameters, Eu3+ ions have asymmetric coordination environment and stronger covalency. The phonon line PSB (22522 cm-1) confirm the phonon energy ≈ 971 cm-1, that corresponds to the energy of one phonon associated with maximum energy of the vibrational mode couple to Eu3+ ions. Under 275 nm and 393 nm excitation, intense red emission was observed at 613 nm, we observe efficient energy transfer phenomena from Gd3+ → Eu3+ in these glasses. Increasing trend of IR with increasing concentration of Eu2O3 indicates the asymmetric environment around Eu3+ ions in LBGS. Moreover from JO analysis, LBGS glasses have high capability for red laser device with high lasing power and energy extraction ratio. The fluorescence lifetimes show decreasing trend in lifetime with increasing concentration of Eu2O3 is due to radiative transition. From CIE color coordinate, the CIE color coordinates of LBGSEu6 glass fall in reddish region close to orange region and can be useful for optical display devices.
关键词： Judd-Ofelt analysis,Silicate glasses,Energy transfer,emission cross sections,Rare earth
更新于2025-09-23 15:21:01
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The long-wave infrared (8-12 μm) spectral features of selected rare earth element—Bearing carbonate, phosphate and silicate minerals
摘要： Rare earth elements (REEs) are a group of metals essential to high technology industries. This high demand, combined with a high supply risk, has led to an understanding that REEs are critical to society. Despite the potential that hyperspectral imaging (HSI) data offers for a fast and non-invasive characterization of the REEs, it is still poorly understood whether REEs have some information in the long-wave infrared (LWIR; 8–12 μm) wavelength range that can be used for their identification. To partially fill this gap, we have investigated the spectroscopy of twelve REE-bearing mineral samples using relatively high spatial and spectral resolution LWIR hyperspectral imaging data. These samples were formerly characterized using electron probe microanalysis (EPMA), scanning electron microscopy (SEM), and hyperspectral imaging data acquired in the 0.4–2.5 μm wavelength range. Results from these analyses were compared to and used to guide the analysis of the HSI data recorded in the LWIR range. This information was further compared to a reference spectral library of rare earth oxides. Our findings suggest that the spectral features of the samples can generally be traced to the asymmetric degenerate stretching and bending modes of the X-O (X = C, Si, P) groups. Moreover and contrary to what has been observed in the shorter wavelengths, there are no definitive spectral features in the LWIR wavelength region that could be assigned to any specific REE.
关键词： Imaging spectroscopy,Long-wave infrared,Rare earth element,Hyperspectral,Mineral
更新于2025-09-23 15:21:01
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Three-Layer Detection Pixel of Single-Photon Thermoelectric Detector Based on Rare-Earth Hexaborides
摘要： The results of computer simulation of heat propagation processes in the three-layer detection pixel of single-photon thermoelectric detector after the absorption of single photons with the energies 0.5–4.13 eV are presented. The various geometries of the detection pixel consisting of rare-earth hexaborides are considered. The lanthanum hexaboride (LaB6) is chosen as the absorber material, and for the materials of thermoelectric sensor the cerium (CeB6) and lanthanum–cerium (La0.99Ce0.01) B6 hexaborides are chosen. The problem is solved to achieve the high system efficiency of thermoelectric detector for the detection of photons in the wavelength range from the UV to the near IR. The computer modeling was carried out based on the equation of heat propagation from the limited volume with the use of three-dimensional matrix method for differential equations. It is shown that a single-photon thermoelectric detector with a three-layer detection pixel made only of hexaborides will have the gigahertz count rate, high-energy resolution, and detection efficiency exceeding 90%. Taking into account the advantages of the three-layer detection pixel compared to the single-layer it can be argued that the three-layer detection pixel of the thermoelectric detector has the great prospects to solve a number of single-photon detection tasks.
关键词： rare-earth hexaborides,thermoelectric detector,photon
更新于2025-09-23 15:21:01
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Dual-Emission and Two Charge Transfer States in Ytterbium-Doped Cesium Lead Halide Perovskite Solid Nanocrystals
摘要： Some unusual phenomena besides near-infrared emission of Yb3+ ions have been observed in ytterbium-doped perovskite solid nanocrystals. A systematic study on doping kinetic and energy transfer processes is presented. The observed unique dual-peak PL emission of perovskite nanocrystals in the visible region can be attributed to radiative recombination in the near-surface region and the interior region of perovskite nanocrystals respectively. Insight studies based on dual-peak PL emission clarify the kinetic process of doping in perovskite nanocrystals. After dopant concentration of rare earth ions in the near-surface region is more than a certain value, dopant ions are starting to be immersed into the interior region of host nanocrystals. The unusual excitation spectra of ytterbium-doped perovskite solid nanocrystals could be explained by the presences of two charge transfer (CT) states at ~24000 cm-1 (CT1) and ~21460 cm-1 (CT2), and both of them could be observed in the near-surface region of the perovskite host. Furthermore, the lifetime of near-infrared emission of Yb3+ ions through the CT2 state is three orders faster than that through CT1 state (in millisecond) which should be fixed on the surface of perovskite nanocrystals. The results provide essential insights into the dynamic carrier behaviors and surface effects of all inorganic perovskite nanocrystals doped with rare earth ions for expanded functionality.
关键词： dual-emission,kinetic process,rare earth,charge transfer states,Perovskite solid nanocrystals,energy transfer
更新于2025-09-23 15:21:01
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Highly selective antenna effect of graphene quantum dots (GQDs): A new fluorescent sensitizer for rare earth element terbium in aqueous media
摘要： This study focused on the fluorescence antenna-sensitizing effect of graphene quantum dots (GQDs) in a case on the detection of terbium ions. A simple one-step chemical oxidation method was applied for the preparation of GQDs starting from the regular multilayer graphene oxide (GO) via the refluxing in a concentrated mixture of strong acids. The as-prepared GQD were further evaluated as a fluorescent sensitizer to the terbium ion. An expanded in-deep mechanism study on the fluorescence phenomena during the interaction of the as-prepared GQDs and REEs was made. The highly selective antenna effect of GQD on one of REEs’ aqueous media, which was terbium (III), was identified. The excited terbium ion emitted its long-living fluorescence based on its own characteristic line-typed f-f transition, contrasting to a undetectable fluorescence in a very poor quantum yield in its aqueous solution induced by water collisions. This study, in the first place, identified the significant sensitization effect of the as-prepared GQD on the terbium ion in a high selectivity in aqueous media. The detectable linear range and the detection limit of the terbium ion was 0-30×10-6 mol L-1 (R2=0.9960) of 0.3 × 10-6 mol L-1, respectively. The excitation wavelength and the optimal fluorescence wavelength were 230 nm 546 nm, respectively. Further material characterizations, involving XPS, FTIR, Raman and the Zeta potential, verified the important participation of carboxyl function groups on the as-prepared GQD.
关键词： Fluorescence,Grapheme quantum dots,Rare earth elements,Terbium,Antenna-sensitizing effect
更新于2025-09-23 15:19:57
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Fast transformation of Rare-earth doped luminescent sub-microcrystal via plasmonic nanoislands
摘要： An efficient and fast transformation scheme for the matrix crystal of Rare-earth doped luminescent micro-nanomaterials is developed by using plasmonic gold/silver nanoislands. The transformation is realized through an oxidation reaction from polycrystalline sub-microcrystal to a single crystal, accompanied by an optimization of crystal structure and a significant increase in luminescence. The crystal transformation can be achieved in tens of milliseconds, and the rate is controlled not only by the laser illumination power and wavelength, but also by the size and nanogap of nanoislands. Particularly, single crystal transformation is also achieved even at very low temperature, which provides a new way to obtain single crystal materials in harsh environment. Moreover, the crystal transformation efficiency of the gold plasmonic islands is very stable in air over at least three months. This plasmon driven crystal transformation rapidly provides highly crystalline nanomaterials, which breaks the dependence of high temperature, long period and high energy consumption in the traditional annealing treatment.
关键词： luminescent,nanoislands,Rare-earth,crystal transformation,plasmonic
更新于2025-09-23 15:19:57