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1.
Eu3+, Dy3+ and Dy3+/Eu3+ doped CdO-GeO2-TeO2 glasses were prepared using the melt-quenching process and analyzed by X-diffraction, Raman spectroscopy, excitation and emission spectra, and emission decay time profiles. The lack of X ray diffraction peaks revealed that all samples are amorphous. Vibrational modes associated with TeOTe and GeOGe related bonds and molecular oxygen were detected by Raman spectroscopy. The luminescence characteristics were studied upon excitations that correspond with the emission of InGaN (370–420 nm) based LEDs. The Eu3+ singly doped glass displayed reddish-orange global emission, with x = 0.601 and y = 0.349 CIE1931 chromaticity coordinates, upon 393 nm excitation. Neutral emission with x = 0.373 and y = 0.412 CIE1931 chromaticity coordinates and correlated color temperature (CCT) of 4400 K, was achieved in the Dy3+ singly doped glass excited at 388 nm. The Dy3+/Eu3+ co-doped glass exhibited warm, neutral and soft warm white emissions with CCT values of 3435, 4153 and 2740 K, under excitations at 382, 388 and 393 nm, respectively, depending mainly on the Dy3+ and Eu3+ relative excitation. The Dy3+ excitation bands observed in the Dy3+/Eu3+ glass by monitoring the 611 nm Eu3+ emission, suggest that Dy3+ → Eu3+ energy transfer takes place, despite the fact that the Dy3+ emission decays in the Dy3+ and Dy3+/Eu3+ doped glass, remain without changes. The shortening of Eu3+ decay in presence of Dy3+ was attributed to an Eu3+ → Dy3+ non-radiative energy transfer process, which according with the Inokuti-Hirayama model might be dominated through an electric quadrupole-quadrupole interaction, with efficiency and probability of 5.5% and 51.6 s−1, respectively. 相似文献
2.
In this article the physical, thermal structural and optical properties of Dy3+ doped lithium borate glasses have been studied for white LED application. The emission spectra shows two intense emission bands at around 483 nm and 574 nm corresponds to the 4F9/2 → 6H15/2 and 4F9/2 → 6H13/2 transitions along with one feeble band at 663 nm corresponds to 4F9/2 → 6H11/2 transition. The average lifetime <τ> of Dy3+ were found to be about 2.95 and 4.94 ns for blue and yellow emission bands respectively. CIE chromaticity diagram shows glass LBD-4 containing 0.5 mol% Dy2O3 with colour co-ordinates x = 0.33 and y = 0.37 have highest emission intensity. These glasses having emission in the white region and thus can be used for bright white LED's and modern white LED bulbs. 相似文献
3.
Dy-doped Y2O3 nanoparticles were synthesized by solution combustion route with urea as fuel, and their microstructural features were analyzed by X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM). The XRD study confirms the formation of a pure cubic phase of Y2O3, with the maximum textural coefficient along the (2 2 2) plane for the Dy-doped samples. The lattice fringes in the HRTEM image and the bright spotty rings in the selected area electron diffraction (SAED) pattern reveal the highly crystalline nature of the nanoparticles. From the diffuse reflectance spectroscopy, using Kubelka-Monk theory, the direct bandgap energy is estimated to be 5.61 eV for the undoped Y2O3, which is found to decrease upon Dy3+ doping. The room-temperature excitation spectra of the nanoparticles recorded at 575 nm emission wavelength comprise several excitation bands corresponding to the f-f transitions of Dy3+ ions in the host lattice. The photoluminescence spectra of the nanoparticles excited at the wavelength of 350 nm comprise three visible emission peaks at 477 nm (blue), 573 nm (yellow), and 666 nm (red). It has been concluded that the 0.5 mol% Dy-doped Y2O3 nanoparticles are the potential candidate to be used for solid-state luminescent device applications. 相似文献
4.
Realizing the ubiquitous presence of rare-earth orthoborates in various applications involving their optical properties, the current investigation is directed towards the exploration of epoxide mediated rapid synthesis to make YBO3. Highly crystalline orthoborate with disordered vaterite structure resulted on calcining xerogel from the reaction of yttrium chloride, boric acid and propylene oxide at 900 °C as verified from diffraction, vibration spectroscopic and microscopic techniques. Following this approach, orthoborate containing 50 mol% of Y and Gd was obtained and characterized. Dissolution limit of Ce3+ in Y0.50Gd0.50BO3 has been determined. Cerium doping resulted in the reduction in the optical band gap of these samples and appended photocatalytic ability in terms of degradation of aqueous rhodamine-6G (Rh-6G) dye solution. The intensity of 4f → 5d transition of Ce3+ increased monotonously with increase in cerium content. The role of distortion on the blue emission from Ce3+ and photocatalytic properties of these samples were comprehended by characterizing Li+, Ca2+ and Al3+-doped samples (up to 10 mol%) for yttrium. The distortion of Y0.50?xMxGd0.45Ce0.05BO3 lattice decreased in the order, RCa2+ > RY3+ > RLi+ > RAl3+, with the emission intensity (5d → 4f transitions) from Ce3+ increasing in the reverse order. Optical band gap was found to decrease for the Li+, Ca2+ and Al3+ doped samples as compared to undoped one. These doped samples retained their catalytic ability as verified from their use in the photo degradation of rhodamine-B (Rh-B) dye. An insight in to possible mechanism operative in the present photo catalytic degradation experiments has been attempted by carrying out trapping experiments. 相似文献
5.
Phosphate glasses with compositions of 44P2O5 + 17K2O + 9Al2O3 + (30 − x)CaF2 + xDy2O3 (x = 0.05, 0.1, 0.5, 1.0, 2.0, 3.0 and 4.0 mol %) were prepared and characterized by X-ray diffraction (XRD), differential thermal analysis (DTA), Fourier transform infrared (FTIR), optical absorption, emission and decay measurements. The observed absorption bands were analyzed by using the free-ion Hamiltonian (HFI) model. The Judd–Ofelt (JO) analysis has been performed and the intensity parameters (Ωλ, λ = 2, 4, 6) were evaluated in order to predict the radiative properties of the excited states. From the emission spectra, the effective band widths (Δλeff), stimulated emission cross-sections (σ(λp)), yellow to blue (Y/B) intensity ratios and chromaticity color coordinates (x, y) have been determined. The fluorescence decays from the 4F9/2 level of Dy3+ ions were measured by monitoring the intense 4F9/2 → 6H15/2 transition (486 nm). The experimental lifetimes (τexp) are found to decrease with the increase of Dy3+ ions concentration due to the quenching process. The decay curves are perfectly single exponential at lower concentrations and gradually changes to non-exponential for higher concentrations. The non-exponential decay curves are well fitted to the Inokuti–Hirayama (IH) model for S = 6, which indicates that the energy transfer between the donor and acceptor is of dipole–dipole type. The systematic analysis of revealed that the energy transfer mechanism strongly depends on Dy3+ ions concentration and the host glass composition. 相似文献
6.
Nd3+-doped precursor glass in the K2O–SiO2–Y2O3–Al2O3 (KSYA) system was prepared by the melt-quench technique. The transparent Y3Al5O12 (YAG) glass–ceramics were derived from this glass by a controlled crystallization process at 750 °C for 5–100 h. The formation of YAG crystal phase, size and morphology with progress of heat-treatment was examined by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM) and Fourier transformed infrared reflectance spectroscopy (FT-IRRS). The crystallite sizes obtained from XRD are found to increase with heat-treatment time and vary in the range 25–40 nm. The measured photoluminescence spectra have exhibited emission transitions of 4F3/2 → 4IJ (J = 9/2, 11/2 and 13/2) from Nd3+ ions upon excitation at 829 nm. It is observed that the photoluminescence intensity and excited state lifetime of Nd3+ ions decrease with increase in heat-treatment time. The present study indicates that the incorporation of Nd3+ ions into YAG crystal lattice enhance the fluorescence performance of the glass–ceramic nanocomposites. 相似文献
7.
Synthesis,Persistent Luminescence,and Thermoluminescence Properties of Yellow Sr3SiO5:Eu2+,RE3+ (RE=Ce,Nd, Dy,Ho, Er,Tm, Yb) and Orange‐Red Sr3−xBaxSiO5:Eu2+, Dy3+ Phosphor
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Dr. Ye Li Baohong Li Chenchen Ni Shuxia Yuan Jing Wang Prof. Qiang Tang Prof. Qiang Su 《化学:亚洲杂志》2014,9(2):494-499
Sunlight‐excitable orange or red persistent oxide phosphors with excellent performance are still in great need. Herein, an intense orange‐red Sr3?xBaxSiO5:Eu2+,Dy3+ persistent luminescence phosphor was successfully developed by a two‐step design strategy. The XRD patterns, photoluminescence excitation and emission spectra, and the thermoluminescence spectra were investigated in detail. By adding non‐equivalent trivalent rare earth co‐dopants to introduce foreign trapping centers, the persistent luminescence performance of Eu2+ in Sr3SiO5 was significantly modified. The yellow persistent emission intensity of Eu2+ was greatly enhanced by a factor of 4.5 in Sr3SiO5:Eu2+,Nd3+ compared with the previously reported Sr3SiO5:Eu2+, Dy3+. Furthermore, Sr ions were replaced with equivalent Ba to give Sr3?xBaxSiO5:Eu2+,Dy3+ phosphor, which shows yellow‐to‐orange‐red tunable persistent emissions from λ=570 to 591 nm as x is increased from 0 to 0.6. Additionally, the persistent emission intensity of Eu2+ is significantly improved by a factor of 2.7 in Sr3?xBaxSiO5:Eu2+,Dy3+ (x=0.2) compared with Sr3SiO5:Eu2+,Dy3+. A possible mechanism for enhanced and tunable persistent luminescence behavior of Eu2+ in Sr3?xBaxSiO5:Eu2+,RE3+ (RE=rare earth) is also proposed and discussed. 相似文献
8.
《Solid State Sciences》2004,6(4):349-355
X2–Y2SiO5:A (A=Eu3+, Tb3+, Ce3+) phosphor films and their patterning were fabricated by a sol–gel process combined with a soft lithography. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), atomic force microscopy (AFM), scanning electron microscopy (SEM) optical microscopy and photoluminescence (PL) were used to characterize the resulting films. The results of XRD indicated that the films began to crystallize at 900 °C with X1–Y2SiO5, which transformed completely to X2–Y2SiO5 at 1250 °C. Patterned thin films with different band widths (5 μm spaced by 5 μm and 16 μm spaced by 24 μm) were obtained by a soft lithography technique (micromoulding in capillaries, MIMIC). The SEM and AFM study revealed that the nonpatterned phosphor films were uniform and crack free, and the films mainly consisted of closely packed grains with an average size of 350 nm. The doped rare earth ions (A) showed their characteristic emissions in X2–Y2SiO5 phosphor films, i.e., 5D0–7FJ (J=0,1,2,3,4) for Eu3+, 5D3, 4–7FJ (J=6,5,4,3) for Tb3+ and 5d (2D)–4f (2F2/5, 2/7) for Ce3+, respectively. The optimum doping concentrations for Eu3+, Tb3+ were determined to be 13 and 8 mol% of Y3+ in X2–Y2SiO5 films, respectively. 相似文献
9.
Yanlin Huang Wanxue Zhao Kiwan Jang Ho Sueb Lee Soung-Soo Yi 《Journal of solid state chemistry》2008,181(9):2161-2164
Eu3+-doped triple phosphate Ca8MgR(PO4)7 (R=La, Gd, Y) was synthesized by the general high-temperature solid-state reaction. Excitation and emission spectra as well as luminescence decay were used to characterize the phosphors. Photoluminescence excitation and emission spectra showed that the phosphor could be efficiently excited by UV-vis light from 260 to 450 nm to give bright red emission assigned to the transition (5D0→7F2) at 612 nm. The richness of the red color has been verified by determining their color coordinates (X, Y) from the CIE standard. 相似文献
10.
Broadband amplifier emission near the second telecommunication window in Ho3+ doped 76TeO2·10ZnO·9.0PbO·1.0PbF2·3.0Na2O was studied. The optical transition properties and radiative lifetimes of several excited states of Ho3+ have been predicted using intensity Judd–Ofelt parameters. The emission cross section for Ho3+ in this glass, around 2 μm, was calculated according to McCumber theory. The maximum stimulated emission cross section was calculated to be 0.9 × 10−20 cm2 for 2046 nm emissions. The theoretical gain cross sections was evaluated and positive gain bands was anticipated. Furthermore, the peak Raman gain coefficient in the present glass was around 250 times larger than that of SiO2. 相似文献
11.
A detailed investigation on 1.06 μm spectroscopic properties as a function of Nd3+ ions concentration in bismuth silicate glasses is reported. Judd–Ofelt analysis indicated that Nd2O3 has no substantial influence on glass structure. Based on the Judd–Ofelt intensity parameters, several radiative properties such as radiative transition probability, radiative lifetime, branching ratio and emission cross-section of Nd3+ ions have been derived. The 1.06 μm emission intensity increases firstly and then attains maximum at 0.5 mol% Nd2O3 and decreases with further increase of dopant concentration. The luminescence quenching behavior at higher Nd3+ concentration has been ascribed to the hopping migration assisted cross relaxation mechanism. The high emission cross section (2.33 × 10−20 cm2) and large quantum efficiency (90.7%) suggests their potential for compact 1.06 μm lasers applications. 相似文献
12.
The polycrystalline powder samples of Eu3+ activated; mixed metal yttrium borate phosphors M3Y2(BO3)4 (M = Ba, Sr) with improved color purity of red emission for plasma display panels (PDPs) were prepared by solution combustion technique. The synthesis is based up on the exothermic reaction between the fuel (Urea) and oxidizer (Ammonium nitrate) .The heat generated in the reaction is utilized for auto combustion of ingredients. The formation of desired product and crystal structure was confirmed by powder XRD technique; while particle morphology was studied using FE-SEM. Samples under 254 and 147 nm excitation showed intense and pure red emission around 613 nm corresponding to the electric dipole 5D0 → 7F2 transition of Eu3+, CIE chromaticity coordinates of synthesized phosphors was found to be (x = 0.67, y = 0.32) close to National Television Standard Committee (NTSC) for red color; found suitable to employ in plasma display panels (PDPs) applications. 相似文献
13.
The Dy3+ or/and Sm3+ doped LiLa(WO4)2 phosphors are synthesized by a facile solid state reaction method. The phase and luminescence properties of the phosphors are investigated. The powder X-ray diffraction (XRD) results show that the phosphor has a tetragonal phase crystal structure. The quenching concentration of single doped Dy3+ and Sm3+ in the LiLa(WO4)2 are determined to be 6% and 3%, respectively. Under the excitation of 404 nm, warm white light is obtained in the co-doped phosphors. With the concentration of Sm3+ increasing, the correlated color temperature (CCT) gradually decreases from 3090 to 2453 K. Two kinds of energy transfer may exist at the same time. The overlap between the emission spectrum of Dy3+ and the excitation spectrum of Sm3+ reveals that the energy of Dy3+ can transfer to Sm3+ via radiation. Another way of energy transfer, that is non-radiative energy transfer, is attributed to the excited state of Dy3+ (4F9/2) slightly higher than that of Sm3+ (4I19/2). The calculation results show that non-radiative energy transfer process from Dy3+ to Sm3+ ions is predominated by quadrupole–quadrupole interaction. 相似文献
14.
Zongjie Zhang Balaji Devakumar Shaoying Wang Liangling Sun Nan Ma Wei Li Xiaoyong Huang 《Materials Today Chemistry》2021
White light-emitting diodes (LEDs) with high color rendering index (CRI) and low correlated color temperature (CCT) are desirable for next-generation solid-state lighting. In this work, we demonstrated an efficient near-UV-excited cyan-emitting phosphor based on Ce3+-doped Ca2LuHf2Al3O12 (CLHAO) garnet, which could be used to cover the cyan gap for fabricating high-CRI warm-white LEDs. We found that the CLHAO:Ce3+ samples exhibited a broad excitation band in the 300–450 nm wavelength range peaking at 400 nm, and upon 400 nm excitation they showed broad cyan emission bands in the 420–600 nm spectral region with peak positions ranging from 477 to 493 nm. The optimal CLHAO:0.02Ce3+ sample had CIE color coordinates of (0.160, 0.255), and its internal and external quantum efficiencies were measured to be 84.3% and 60.8%, respectively. Impressively, the luminescence intensity of CLHAO:0.02Ce3+ sample at 423 K still remained at 62% of the initial value at 303 K, and the chromaticity shift was calculated to be as low as 1.7 × 10?2, revealing its high thermal stability and color stability at a higher temperature. Finally, a warm-white LED device (CCT = 3,194 K) was fabricated by combining CLHAO:0.02Ce3+ cyan phosphors with commercial blue/green/red tricolor phosphors, showing bright white-light emission with a high CRI of 89.4, which was superior to that of another warm-white LED device (CRI = 83.2) fabricated without CLHAO:0.02Ce3+ cyan phosphors. These outstanding luminescence properties of CLHAO:Ce3+ cyan phosphors illustrated that they offer a new feasible approach for the production of high-CRI warm-white LEDs toward high-color-quality solid-state lighting. 相似文献
15.
《Journal of solid state chemistry》2004,177(4-5):1292-1296
The monodisperse array and nanowires of Y2O3:Eu3+ phosphor were synthesized using anodic aluminum oxide (AAO) template by sol–gel method. Scanning electron microscope (SEM) images indicated that Y2O3:Eu3+ nanowires are parallelly arranged, all of which are in uniform diameter of about 50 nm. The high-magnification SEM image showed that each nanowire is composed of a lot of agglutinating particles. The patterns of selected-area electron diffraction confirmed that Y2O3:Eu3+ nanowires mainly consist of polycrystalline materials. Excitation and emission spectra of Y2O3:Eu3+/AAO composite films were measured. The characteristic red emission peak of Eu3+ ion attributed to 5D0→7F2 transition in Y2O3:Eu3+/AAO nanowires broadened its halfwidth. 相似文献
16.
《Comptes Rendus Chimie》2002,5(11):739-749
Spectroscopic properties and local structure of rare-earth ions in Ge–Ga–S glasses with the addition of alkali halides were investigated. The intensity of the 1.31-μm emission from Dy3+ (6F11/2·6H9/2 → 6H15/2) increased sharply when the appropriate amount of alkali halides was added, at the expense of the 1.75-μm emission intensity (6H11/2 →6H15/2). The lifetimes of the 1.31-μm emission level also increased as much as 35 times from 38 μs for Ge–Ga–S glass (0.1 at.% Dy3+) to 1320 μs for glass containing 10 mol% of CsBr. These enhancements occurred only when the ratio of MX(M = K,Cs and X = Br, I)/Ga was equal to or larger than unity. Phonon side band (PSB) showed that the several local phonon modes, with the frequencies around 100 cm–1, were coupled to 4f electrons of Eu3+. The nearest neighbors of Eu3+ ions are composed of halogen ions that are part of well-structured complex such as EuCl3, tetrahedral 〚GaS3/2Cl〛– subunit and/or Ga2Cl6. A small amount of As was added to increase the resistivity against the recrystallization during re-heating. The best composition for practical usage was 0.7 〚Ge0.25As0.10S0.65〛–0.15 GaS3/2–0.15 CsBr. This glass also exhibited high resistance against the attack of liquid water and is therefore a potential material for efficient fiber-optic amplifiers. 相似文献
17.
Yiqiang Shen 《Journal of solid state chemistry》2010,183(12):3093-3099
The crystal structure and photoluminescent properties of europium doped silicate Sr2Y8(SiO4)6O2:Eu3+ are reported. The Sr2Y8−xEux(SiO4)6O2 compounds have typical apatite crystal structures with the P63/m space group. The distributions of Eu3+ between the two crystallographic sites 4f and 6h in the apatite structure are investigated by the powder X-ray diffraction and Rietveld refinement. Results show that Eu3+ ions only occupy the 4f sites when the Eu doping concentration is low (x=0-0.5 in Sr2Y8−xEux(SiO4)6O2). However, in higher concentrations, Eu3+ ions begin to enter the 6h sites as well. The distributions of the Eu3+ are also reflected in photoluminescent spectra. The CIE coordinates for Sr2Y6Eu2(SiO4)6O2 are (0.63, 0.37), which is close to the pure red color. 相似文献
18.
Yellow emitting β-Zn2SiO4:Mn2+ and green emitting α-Zn2SiO4:Mn2+ nanoparticles are synthesized by nucleation applying a zinc-containing ionic liquid. As-prepared material is non-agglomerated and very uniform with a mean diameter of 32 nm. According to X-ray diffraction (XRD) two crystallographic different modifications of Zn2SiO4 can be realized by annealing of as-prepared and non-crystalline nanomaterial at 750 and 1000 °C. Surprisingly, these crystalline materials are still nanosized, non-agglomerated and redispersible. Scanning electron microscopy (SEM) and dynamic light scattering (DLS) confirm particle diameters of 18 nm (β-Zn2SiO4:Mn2+) and 14 nm (α-Zn2SiO4:Mn2+). Photoluminescence indicates Mn2+-related emission at an average wavelength of 579 nm and 528 nm, and a quantum yield of 7% and 12% for β-Zn2SiO4:Mn2+ and α-Zn2SiO4:Mn2+, respectively. 相似文献
19.
H. Wang 《Journal of solid state chemistry》2009,182(10):2716-171
Spherical SiO2 particles have been coated with rare earth oxide layers by a Pechini sol-gel process, leading to the formation of core-shell structured SiO2@RE2O3 (RE=rare earth elements) and SiO2@Gd2O3:Ln3+ (Ln=Eu, Tb, Dy, Sm, Er, Ho) particles. X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), photoluminescence (PL), and cathodoluminescence spectra as well as lifetimes were used to characterize the resulting SiO2@RE2O3 (RE=rare earth elements) and SiO2@Gd2O3:Ln3+ (Eu3+, Tb3+, Dy3+, Sm3+, Er3+, Ho3+) samples. The obtained core-shell phosphors have perfect spherical shape with narrow size distribution (average size ca. 380 nm), smooth surface and non-agglomeration. The thickness of shells could be easily controlled by changing the number of deposition cycles (40 nm for two deposition cycles). Under the excitation of ultraviolet, the Ln3+ ion mainly shows its characteristic emissions in the core-shell particles from Gd2O3:Ln3+ (Eu3+, Tb3+, Sm3+, Dy3+, Er3+, Ho3+) shells. 相似文献
20.
F. Xiao Y.N. Xue Q.Y. Zhang 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2009,74(2):498-501
Y4MgSi3O13:Bi3+, Eu3+ nanophosphors have been prepared by a facile sol–gel method. The products have been characterized by X-ray diffraction, field-emission scanning electron microscopy and fluorescence measurements. The results show that the nanophosphors are of single phase hexagonal Y4MgSi3O13 with size-distribution of 50–90 nm in diameter. White-light emission has been obtained from Bi3+ and Eu3+ co-doped Y4MgSi3O13 nanophosphors upon excitation of 350 nm ultraviolet light. It is noted that Bi3+ ions can occupy two different Y3+ sites and generate different emissions from the 3p1 → 1s0 transition. Warm white light has been obtained from Y4MgSi3O13:Bi3+, Eu3+ nanophosphors according to Commission International de I’Eclairage (CIE) chromaticity coordinates and color temperature (Tc) with appropriately adjusted contents of Bi3+ and Eu3+. The results indicate that Y4MgSi3O13:0.08Bi3+, 0.04Eu3+ (x = 0.31, y = 0.31, Tc = 6907 K) are potential nanophosphors for white light-emitting diodes (LEDs) applications. 相似文献