Eu3+离子在微晶玻璃研究中的探针作用

制备出单掺Eu³⁺离子的氟氧化物玻璃陶瓷系列样品，利用Eu³⁺离子作为荧光探针，通过热处理前后Eu³⁺离子发射光谱中电偶极子跃迁与磁偶极子跃迁强度比值的变化表征在玻璃材料中微晶是否形成，分析了Eu³⁺离子荧光发射谱中电偶极子跃迁与晶体场对称性的关系，进一步表征了稀土离子所处微晶晶格场的变化. 关键词： 微晶玻璃 探针 3+离子')" href="#">Eu³⁺离子     

Blue light emission from Eu ions in sol-gel-derived Al2O3-SiO2 glasses

Blue light-emitting glasses were successfully prepared by doping Eu²⁺ ions in the system Al₂O₃-SiO₂. The Al₂O₃-SiO₂ glasses doped with Eu³⁺ ions were synthesized using a sol-gel method, followed by heating in hydrogen gas atmosphere to reduce into the Eu²⁺ ions. The obtained glasses exhibited emission spectra with peak at ∼450 nm due to 4f⁶5d→4f⁷ (⁸S_7/2) transition, the intensities of which strongly changed depending on their glass composition and heating conditions. The emission quantum efficiency of 48% was achieved by heating the glass with the ratio of Al³⁺ to Eu³⁺ at about 6 at 1000 °C in hydrogen gas atmosphere. It was found that the Al₂O₃-SiO₂ glasses were appropriate not only for homogeneously doping the Eu³⁺ ions in glass structure but also reducing to Eu²⁺ ions, resulting in enhanced blue light-emission properties.     

Luminescence studies on ZnO-P2O5 glasses doped with Gd2O3:Eu nanoparticles and Eu2O3

Zinc phosphate glasses doped with Gd₂O₃:Eu nanoparticles and Eu₂O₃ were prepared by conventional melt-quench method and characterized for their luminescence properties. Binary ZnO-P₂O₅ glass is characterized by an intrinsic defect centre emission around 324 nm. Strong energy transfer from these defect centres to Eu³⁺ ions has been observed when Eu₂O₃ is incorporated in ZnO-P₂O₅ glasses. Lack of energy transfer from these defect centres to Eu³⁺ in Gd₂O₃:Eu nanoparticles doped ZnO-P₂O₅ glass has been attributed to effective shielding of Eu³⁺ ions from the luminescence centre by Gd-O-P type of linkages, leading to an increased distance between the luminescent centre and Eu³⁺ ions. Both doped and undoped glasses have the same glass transition temperature, suggesting that the phosphate network is not significantly affected by the Gd₂O₃:Eu nanoparticles or Eu₂O₃ incorporation.     

Optical properties of (ZnO)0.5(P2O5)0.5 glasses doped with Gd2O3:Eu nanoparticles and Eu2O3

Binary (ZnO)_0.5(P₂O₅)_0.5 glasses doped with Eu₂O₃ and nanoparticles of Gd₂O₃:Eu were prepared by conventional melt-quench method and their luminescence properties were compared. Undoped (ZnO)_0.5(P₂O₅)_0.5 glass is characterized by a luminescent defect centre (similar to L-centre present in Na₂O-SiO₂ glasses) with emission around 324 nm and having an excited state lifetime of 18 ns. Such defect centres can transfer the energy to Eu³⁺ ions leading to improved Eu³⁺ luminescence from such glasses. Based on the decay curves corresponding to the ⁵D₀ level of Eu³⁺ ions in both Gd₂O₃:Eu nanoparticles incorporated as well as Eu₂O₃ incorporated glasses, a significant clustering of Eu³⁺ ions taking place with the latter sample is confirmed. From the lifetime studies of the excited state of L-centre emission from (ZnO)_0.5(P₂O₅)_0.5 glass doped with Gd₂O₃:Eu nanoparticles, it is established that there exists weak energy transfer from L-centres to Eu³⁺ ions. Poor energy transfer from the defect centres to Eu³⁺ ions in Gd₂O₃:Eu nanoparticles doped (ZnO)_0.5(P₂O₅)_0.5 glass has been attributed to effective shielding of Eu³⁺ ions from the luminescence centre by Gd-O-P type of linkages, leading to an increased distance between luminescent centre and Eu³⁺ ions.     

Effect of induced crystallization in rare-earth doped lithium borate glass

Rare-earth doped borate glasses and glass ceramics are investigated for their potential as photon converters. Thermal processing of the as-made glass results in the formation of nanocrystals therein. For optical activation, the glasses are doped with Eu³⁺ and Tb³⁺, both enabling an intense emission under ultraviolet excitation. Differential scanning calorimetry and X-ray diffraction are applied to analyze the crystallization behavior. Compared to the undoped glass, the glass transition temperature as well as the crystallization temperature are increased with Eu³⁺ doping. Upon thermal processing of the as-made glasses, the transmittance is significantly reduced. Preliminary photoluminescence quantum efficiency measurements yield lower values for the glass ceramics.     

Role of Al2O3 in upconversion and NIR emission in Tm and Er codoped calcium fluoro phosphorous silicate glass system

In this study, the principal role of Al₂O₃ on the features of the photoluminescence spectra of Tm³⁺ ion and upconversion phenomenon in Tm³⁺ and Er³⁺ codoped CaF₂−Al₂O₃−P₂O₅−SiO₂ glass system has been investigated. The concentration of Al₂O₃ is varied from 2 to 10 mol% while that of Er³⁺ and Tm³⁺ is fixed. IR and Raman spectral studies have indicated that there is a gradual increase in the degree of disorder in the glass network with increase in the concentration of Al₂O₃ up to 6.0 mol%. This is attributed to the presence of Al³⁺ ions in octahedral positions in larger proportions. When the glasses are doped with Tm³⁺ ions, the blue and red emissions were observed, whereas in Er³⁺ doped glasses blue, green and red emissions were observed. When the glasses are codoped with Tm³⁺ and Er³⁺ ions and excited at 790 nm, all the three emission lines were observed to be reinforced, especially in the glasses mixed with 6.0 mol% of Al₂O₃. The IR emission band detected at about 1.8 μm due to ³F₄→³H₆ transition of Tm³⁺ ions is also observed to be strengthened due to codoping. The reasons for enhancement in the intensity of various emission bands due to codoping have been identified and discussed with the help of rate equations for various emission transitions.     

Assessment of role of iron ions on the physical and spectroscopic properties of multi-component Na2O−PbO−Bi2O3−SiO2 glass ceramics

Multi-component glass ceramics composition Na₂O?PbO?Bi₂O₃?SiO₂ doped with different concentrations of Fe₂O₃ as nucleating agent were characterised by XRD, SEM (scanning electron microscope) and DTA (differential thermal analysis) techniques. Optical absorption, EPR, FTIR and Raman studies are also carried out on these glass ceramics. Absorption bands observed at about 457, 489, 678 and 820 nm are the characteristics of Fe³⁺ ions whereas the band observed at about 964 nm is due to Fe²⁺ ions. EPR studies suggested that Fe³⁺ ions entered in the lattice as tetragonally distorted octahedral symmetry or rhombic sites at low concentration of Fe₂O₃, whereas at higher concentration of Fe₂O₃ (beyond 1 mol%), the super exchange type of interactions between multivalency iron ions begin to dominate. FTIR and Raman spectra have revealed the behaviour of various structural units in the glass ceramic matrix. The analysis of these spectroscopic studies indicates that iron ions do exist in Fe³⁺ and Fe²⁺ state.     

OH-对磷酸盐铒玻璃光谱性质的影响

本文系统研究了Yb³⁺、Er³⁺共掺磷酸盐铒玻璃中OH^-含量与铒玻璃荧光寿命和光谱性质的关系.结果表明OH^-基团的存在使得Er³⁺离子的荧光强度显著降低,荧光寿命大大缩短.比较了三种不同Al₂O₃含量(5mol%,8mol%和13mol%)的铒玻璃在2.9μm波长处的红外吸收系数与铒离子荧光寿命的关系,发现玻璃中OH^-在2.9μm的吸收系数和Er³⁺的⁴Ⅰ_13/2能级离子衰减速率成线性关系,不同Al₂O₃含量的玻璃具有不同Er³⁺和OH^-基团的相互作用参量和不同的荧光寿命值及量子效率.并从玻璃结构上解释了Al₂O₃含量对除水机制和光谱性质的影响.经过充分除水后的铒玻璃荧光寿命可达到9.1ms.     

Luminescence and energy transfer in La2O3–Nb2O5–B2O3:M3+ (M=Bi,Eu, Dy) glasses

The luminescence and energy transfer processes in La₂O₃–Nb₂O₅–B₂O₃:M³⁺ (M=Bi, Eu, Dy) glasses were investigated using luminescence spectroscopy (excitation and emission, down to 4.2 K) and decay time measurements at room temperature. The observation of niobate luminescence implies a considerable degree of short- and intermediate-range order in these glasses. Energy transfer from the niobate groups to the lanthanide ions was observed for Eu³⁺, but not for Dy³⁺, suggesting that the energy transfer process occurs to the charge-transfer state of the Eu³⁺ ion, rather than to its f-levels. Inter-Eu³⁺ energy transfer was negligible in the concentration range investigated (up to 3 mol%). In contrast, cross-relaxation processes between Dy³⁺ ions were active at concentrations as low as 0.5 mol%. In the Bi³⁺ doped glasses the energy transfer was observed from the Bi³⁺ excited levels to the oxygen deficient niobate groups.     

Optical properties of Eu-doped zinc borate glasses

Photoluminescence, absorption and optical excitation spectra of undoped and Eu³⁺-doped binary zinc borate glasses of varied composition prepared by the melt quenching technique in air atmosphere were investigated. From photoluminescence measurements it was found that growing Eu³⁺ concentration leads to gradual disappearance of the broadband glass emission in the near-UV spectral range, while the red Eu³⁺ emission at 613 nm shows a considerable increase. This result together with excitation spectra suggests that the Eu³⁺ ions are excited via energy transfer from the initially excited glassy host. The glass composition strongly affects the position of the excitation maximum in the UV energy range.     

白光LED用LiBaBO3:Eu2+材料发光特性研究

采用高温固相法制备了LiBaBO₃:Eu²⁺绿色发光材料.测量了Eu²⁺浓度为1mol%时样品的激发与发射光谱,其发射光谱为双峰宽谱,主峰分别为482和507nm,与理论计算值符合很好;监测482nm发射峰时,对应激发光谱的峰值为287和365nm,监测507nm发射峰时,对应的激发峰为365和405nm.研究了Eu²⁺浓度对材料发射光谱的影响,结果显示,随Eu²⁺浓度的增大,蓝、绿发射峰均发生了     

Lead−barium fluoroborate glass ceramics doped with Nd<Superscript>3+</Superscript> or Er<Superscript>3+</Superscript>

Lead?barium fluoroborate glasses in the PbF₂–BaF₂–B₂O₃, PbF₂–BaO–B₂O₃, and PbO_– BaF₂–B₂O₃ systems doped with rare-earth ions (Nd³⁺ or Er³⁺) are synthesized and studied. It is shown that, based on these glasses, it is possible to produce transparent glass ceramics with fluoride crystalline phases, including ceramics with one crystalline phase of the fluorite structure. The spectral and luminescent properties of the doped glasses, glass ceramics, and polycrystalline complex fluorides containing Pb, Ba, and rare ions are studied.     

Role of Al coordination in barium phosphate glasses on the emission features of Ho ion in the visible and IR spectral ranges

The glasses of the composition (39−x)BaO-xAl₂O₃-60P₂O₅:1.0Ho₂O₃ (in mol%) with x value ranging from 1.0 to 4.0 have been synthesized. The IR spectral studies of these glasses have indicated that there is a gradual transformation of Al³⁺ ions from tetrahedral to octahedral with increase in the concentration of Al₂O₃ up to 3.0 mol%. Optical absorption and fluorescence spectra (in the visible and NIR regions) of these glasses have been recorded at room temperature. The Judd-Ofelt theory could successfully be applied to characterize the absorption and luminescence spectra of Ho³⁺ ions in these glasses. From the luminescence spectra, various radiative properties like transition probability A, branching ratio β_r, the radiative lifetime τ_r and emission cross-section σ^E for various emission levels of these glasses have been evaluated. The radiative lifetime of the ⁵S₂→⁵I₈ (green emission) transition has also been measured. The variations observed in these parameters have been discussed in the light of varying co-ordinations (tetrahedral and octahedral positions) of Al³⁺ ions in the glass network. The influence of hydroxyl groups on the luminescence efficiency of the transition ⁵S₂→⁵I₈ has also been discussed. Finally the optimum concentration of Al₂O₃ for getting maximum luminescence output has also been identified and reported.     

The crystallinity and the photoluminescent properties of spray pyrolized ZnO phosphor containing Eu and Eu ions

A europium doped ZnO (ZnO:Eu) particle was directly synthesized by the spray pyrolysis method. The crystal structure of samples was designated by the europium ion and the synthesis temperature. We identified the coexistence of Eu²⁺ and Eu³⁺ ions in the as prepared ZnO, which was strongly influenced by the doping concentration and the synthesis temperature. With addition of a 0.5 mol% concentration of europium ions, only the Eu²⁺ ion existed in particles, while both Eu²⁺ and Eu³⁺ ions existed in sample using 1 mol% or higher concentration of europium ions. Changing the wavelength of the excitation source, we also found that both the blue and red luminescence can be obtained.     

Synthesis and characterization of Ce doped silica (SiO2) nanoparticles

A series of silica doped with different mol percentages of Ce³⁺ concentration was synthesized using a sol-gel method to determine the dependence of photoluminescence wavelengths and intensity on the concentrations of the dopants. Sol-gel glasses are porous networks that have been densified through chemical processing and heat treatment. Rare-earths (REs) are insoluble in silica; due to this insolubility RE ions in silicate glasses enter as network modifiers and compete for non-bridging oxygen in order to complete their coordination. The morphological, structural, thermal and optical properties of the phosphors were characterized by X-ray diffraction, scanning electron microscopy, UV-vis absorption, photoluminescence, thermogravimetric analyses and differential scanning calorimeter. Silica (SiO₂) gel containing Ce³⁺ ions was sputter coated with Au (gold) in order to monitor surface morphology of the samples. The highest emission intensity was found for the sample with a composition of 0.5 mol% Ce³⁺. Cerium doped silica glasses had broad blue emission corresponding to the ²D_3/2-²F_J transition at 448 nm but exhibited apparent concentration quenching above concentrations of 0.5 mol% Ce³⁺.     

Spectroscopic and magnetic studies of manganese ions in ZnO-Sb2O3-B2O3 glass system

ZnO-Sb₂O₃-B₂O₃ glasses containing different concentrations of MnO ranging from 0 to 1.0 mol% were prepared. A number of studies, viz. optical absorption, infrared and ESR spectra and magnetic susceptibility, were carried out as a function of manganese ion concentration. The analysis of the results indicate that manganese ions mostly exist in Mn²⁺ state in these glasses when the concentration of MnO≤0.6 mol% and above this concentration, these ions seem to exist in Mn³⁺ state in the glass network.     

Energy transfer from the host to Er<Superscript>3+</Superscript> dopants in semiconductor SnO<Subscript>2</Subscript> nanocrystals segregated in sol–gel silica glasses

Undoped and Er³⁺-doped glass–ceramics of composition (100−x)SiO₂–xSnO₂, with x = 5 or 10 and with 0.4 or 0.8 mol% of Er³⁺ ions, were synthesised by thermal treatment of precursor sol–gel glasses. Structural studies were developed by X-Ray Diffraction. Wide band gap SnO₂ semiconductor quantum-dots embedded in the insulator SiO₂ glass are obtained. The mean radius of the SnO₂ nanocrystals, ranging from 2 to 3.2 nm, is comparable to the exciton Bohr radius. The luminescence properties have been analysed as a function of sample composition and thermal treatment. The results show that Er³⁺ ions are partially partitioned into the nanocrystalline phase. An efficient UV excitation of the Er³⁺ ions by energy transfer from the SnO₂ nanocrystal host is observed. The Er³⁺ ions located in the SnO₂ nanocrystals are selectively excited by this energy transfer mechanism. On the other hand, emission from the Er³⁺ ions remaining in the silica glassy phase is obtained by direct excitation of these ions.     

Rare-Earth Doped Sol-Gel Silicate Glasses for Scintillator Applications

Radio-, photo- and thermally stimulated—luminescence (RL, PL, TSL) measurements have been performed on SiO₂ sol-gel glasses doped by 0.1 mol% Ce and 3 mol% Gd, and on (0.1 mol% Ce, 3 mol% Gd) co-doped samples. Ce^3? 5d-4f emission peaking at about 2.7 eV has been observed in the RL of SiO₂: 0.1 mol% Ce, while the typical ⁶P-⁸S emission of Gd^3? centred at 3.97 eV has been detected in SiO₂: 3 mol% Gd. The co-doped sample displays both 5d-4f Ce^3? and ⁶P-⁸S Gd^3? emissions with reduced intensities with respect to those observed in the singly doped glasses. Moreover, in co-doped glasses the PL time decay patterns of both rare earth ions show a non exponential dependence and are significantly shortened. To explain such an effect non radiative de-excitation of both RE ions excited states involving energy transfers to defect levels is suggested. Bidirectional Gd^3? ? Ce^3? energy transfers could also occur. Complementary TSL measurements put in evidence the existence of broad glow peaks at about 100 K and 220 K. The TSL spectra feature the RE ions emissions.     

Luminescence properties of the Eu-doped porous glass and spontaneous reduction of Eu to Eu

The luminescent properties of Eu³⁺-doped porous glass were investigated and reduction of Eu³⁺ to Eu²⁺ was observed when the Eu³⁺-doped porous glasses were heat treated in air. The absorption, emission and excitation spectra of Eu³⁺-doped porous glasses were measured and the results significantly depended on the treating temperature. The integral intensity of Eu³⁺ and Eu²⁺ ions at different temperatures was also investigated to investigate this reduction process. Electron spin resonance (ESR) spectra of the samples were also measured, which also confirmed the reduction effect. A possible mechanism was discussed to explain this process.     

Frequency-conversion properties of Eu doped chlorophosphate glass ceramics containing CaCl2 nanocrystals

Eu³⁺ ion doped chlorophosphate glass ceramics containing nanocrystals were successfully prepared, and their spectroscopic characterizations were done using absorption, excitation and emission spectra. For the crystallized samples, X-ray diffraction (XRD) and transmission electron microscopy (TEM) experiments evidenced the formation of CaCl₂ nanocrystals. The absorption and emission spectra investigations indicate that a considerable amount of Eu³⁺ ions was trapped in CaCl₂ nanocrystals, and therefore an efficient up- and down-frequency conversion was observed. The comparative spectroscopic studies of Eu³⁺ doped samples suggest that the investigated glass ceramics systems are potentially applicable as frequency-conversion photonics devices.