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1.
Peng-Fei Ai Ying-Liang Liu Li-Yuan Xiao Hou-Jin Wang Jian-Xin Meng 《Science and Technology of Advanced Materials》2010,11(3)
A phosphorescent material in the form of Y2O2S:Eu3+, Mg2+, Ti4+ hollow microspheres was prepared by homogeneous precipitation using monodispersed carbon spheres as hard templates. Y2O3:Eu3+ hollow microspheres were first synthesized to serve as the precursor. Y2O2S:Eu3+, Mg2+, Ti4+ powders were obtained by calcinating the precursor in a CS2 atmosphere. The crystal structure, morphology and optical properties of the composites were characterized. X-ray diffraction measurements confirmed the purity of the Y2O2S phase. Electron microscopy observations revealed that the Y2O2S:Eu3+, Mg2+, Ti4+ particles inherited the hollow spherical shape from the precursor after being calcined in a CS2 atmosphere and that they had a diameter of 350–450 nm and a wall thickness of about 50–80 nm. After ultraviolet radiation at 265 or 325 nm for 5 min, the particles emitted strong red long-lifetime phosphorescence originating from Eu3+ ions. This phosphorescence is associated with the trapping of charge carriers by Ti4+ and Mg2+ ions. 相似文献
2.
G. Aka E. Reino P. Loiseau D. Vivien B. Ferrand L. Fulbert D. Pelenc G. Lucas-Leclin Patrick Georges 《Optical Materials》2004,26(4):431-436
We have taken advantage of congruent melting behavior of the nonlinear rare-earth oxoborate Ca4REO(BO3)3 family to perfect a process of collective fabrication of self-frequency doubling microchip laser based on Nd:GdCOB (Ca4Gd1−xNdxO(BO3)3) crystals. The process goes from Czochralski boule to 1 × 3 mm2 chips perfectly oriented (better than 0.1°) to the phase matching direction (θ=90°, φ=46°) in the XY principal plane, with dielectric mirrors directly deposited on both faces of the chips. 20 mW of self-frequency doubling output power at 530 nm was performed under 800 mW of diode laser as incident pump power at 812 nm. In addition, new compositions from the solid solution Ca4Gd1−xYxO(BO3)3 (Gd1−xYxCOB) (x=0.13, 0.16, 0.44) have been grown by the Czochralski pulling method, in order to achieve noncritical phase matching (NCPM) second harmonic generation of 4F3/2 → 4I9/2 Nd3+ doped laser hosts. Three types of laser wavelengths have been chosen: Nd:YAP (YAlO3) at 930 nm, Nd:YAG (Y3Al5O12) at 946 nm, and Nd:ASL (NdySr1−x Lax−yMgx Al12−xO19) at 900 nm. Angular acceptance measurements of these three types of compositions present very large values, compared to pure GdCOB or YCOB oriented in critical phase matching configurations. 相似文献
3.
Luminescence properties of Y2−xGdxO3:Eu3+ (x = 0 to 2.0) thin films are investigated by site-selective laser excitation spectroscopy. The films were grown by pulsed laser deposition method on SiO2 (100) substrates. Cubic phase Y2O3 and Gd2O3 and monoclinic phase Gd2O3 are identified in the excitation spectrum of the 7F0 → 5D0 transition of Eu3+. The emission spectra of the 5D0 → 7FJ (J = 1 and 2) transition from individual Eu3+ centers were obtained by tuning the laser to resonance with each excitation line. The excitation line at around 580.60 nm corresponds to the line from Eu3+ with C2 site symmetry of cubic phase. New lines at 578.65 and 582.02 nm for the CS sites of Gd2O3 with monoclinic phase are observed by the incorporation of Gd in Y2O3 lattice. Energy transfer occurs between Eu3+ ions at the CS sites and from Eu3+ ions at the CS sites to those at the C2 site in Y2−xGdxO3. 相似文献
4.
Yuan Qiang Li Naoto Hirosaki Rong-Jun Xie Mamoru Mitomo 《Science and Technology of Advanced Materials》2007,8(7-8):607
The crystal and electronic structures, as well as the luminescence properties of Sr2Al2−xSi1+xO7−xNx:Eu2+ are reported. First-principles calculations energetically confirm that the Al and Si atoms are in partial ordering in the 2a and 4e sites in Sr2Al2SiO7. In addition, the band structure calculation shows that Sr2Al2SiO7 has an indirect band gap with an energy gap of about 4.07 eV, which is in good agreement with the experimental data (5.3 eV) obtained from the diffuse reflection spectrum. The crystal structure of Sr2Al2SiO7 can be modified by Si–N substitution for Al–O in the lattice with a maximum solubility of about x=0.6. The average bond length of EuSr-(O,N) slightly increases although the lattice parameters decrease with the incorporation of Si–N in Sr2Al2SiO7:Eu2+. Under excitation in the visible spectral region, Sr2Al2−xSi1+xO7−xNx:Eu2+ emits blue to yellow light with a broad emission band in the range of 480–570 nm, varying with both the Eu concentration and the x value. The red shift of the emission band of Eu2+ is associated with an increase in the crystal-field splitting and the covalency, which arise from the incorporation of nitrogen as well as the energy transfer between the Eu ions at high Eu concentrations. Moreover, the Eu ions have a strong effect on both the concentration quenching and the thermal quenching in Sr2Al2−xSi1+xO7−xNx. The temperature dependence of photoluminescence indicates that Sr2Al2−xSi1+xO7−xNx:Eu2+ shows strong thermal quenching due to the dominant nonradiative process at room temperature. 相似文献
5.
AbstractA phosphorescent material in the form of Y2O2S:Eu3+, Mg2+, Ti4+ hollow microspheres was prepared by homogeneous precipitation using monodispersed carbon spheres as hard templates. Y2O3:Eu3+ hollow microspheres were first synthesized to serve as the precursor. Y2O2S:Eu3+, Mg2+, Ti4+ powders were obtained by calcinating the precursor in a CS2 atmosphere. The crystal structure, morphology and optical properties of the composites were characterized. X-ray diffraction measurements confirmed the purity of the Y2O2S phase. Electron microscopy observations revealed that the Y2O2S:Eu3+, Mg2+, Ti4+ particles inherited the hollow spherical shape from the precursor after being calcined in a CS2 atmosphere and that they had a diameter of 350–450 nm and a wall thickness of about 50–80 nm. After ultraviolet radiation at 265 or 325 nm for 5 min, the particles emitted strong red long-lifetime phosphorescence originating from Eu3+ ions. This phosphorescence is associated with the trapping of charge carriers by Ti4+ and Mg2+ ions. 相似文献
6.
Iko Hyppnen Jorma Hls Jouko Kankare Mika Lastusaari Laura Pihlgren 《Optical Materials》2009,31(12):1787
Up-converting yttrium oxysulfide nanomaterials doped with ytterbium and erbium (Y2O2S:Yb3+,Er3+) were prepared with the flux method. The precursor oxide materials were prepared using the combustion synthesis. The morphology of the oxysulfides was characterized with transmission electron microscopy (TEM). The particle size distribution was 10–110 nm, depending on the heating temperature. According to the X-ray powder diffraction (XPD), the crystal structure was found hexagonal and the particle sizes estimated with the Scherrer equation agreeded with the TEM images. Upon the 970 nm infrared (IR) laser excitation, the materials yield moderate green ((2H11/2, 4S3/2) → 4I15/2 transition) and strong red (4F9/2 → 4I15/2) luminescence. The green luminescence was enhanced with respect to the red one by an increase in both the crystallite size and erbium concentration due to the cross-relaxation (CR) processes. The most intense up-conversion luminescence was achieved with xYb and xEr equal to 0.10 and 0.005, respectively. Above these concentrations, concentration quenching occurred. 相似文献
7.
Zhi-Jun Zhang Shuang Chen Jiao Wang Hao-Hong Chen Xin-Xin Yang Jing-Tai Zhao Ye Tao Yan Huang 《Optical Materials》2009,32(1):99-103
The VUV excited luminescent properties of Ce3+, Eu3+ and Tb3+ in the matrices of KMLn(PO4)2 (M2+ = Ca, Sr; Ln3+ = Y, La, Lu) were investigated. The bands at about 155 nm in the VUV–UV excitation spectra are attributed to the host lattice absorption, which indicates that the optical band gap of KMLn(PO4)2 is about 8.0 eV. Ce3+-doped samples show typical Ce3+ emission in the range of 300–450 nm, and the energy transfer from host lattice to Ce3+ is efficient. For Eu3+-doped samples, the O2−–Eu3+ CTBs are observed to be at about 228 nm except KSrLu(PO4)2:Eu3+ (247 nm). As for Tb3+-doped samples, typical 4f → 5d absorption bands in the region of 175–250 nm were observed. 相似文献
8.
Congbing Tan Yunxin Liu Wenbin LiYutao Zhang Yunan Han 《Materials Science and Engineering: B》2011,176(16):1251-1256
Lanthanide-doped uniform pure cubic phase Y2O3 hollow microspheres have been successfully synthesized via a facile, high yield urea-based coprecipitation route with assistant of carbon spheres templates. The diameter and shell thickness of the microspheres can be manipulated by adjusting carbon sphere templates. Under a 980 nm excitation, Yb3+/Er3+, Er3+, Yb3+/Tm3+-doped Y2O3 hollow microspheres emit bright upconversion red, green, blue light with high purity, respectively, while Eu3+, Eu3+/Tb3+-doped Y2O3 hollow microspheres exhibit intense downconversion red light under the excitation of 254 nm ultraviolet light. Especially, the 610 nm emission intensity of Eu3+ in the Eu3+/Tb3+-codoped Y2O3 hollow microspheres is almost 5 times of that in the Y2O3:Eu3+ hollow microspheres indicating the occurring of the energy transfer from Tb3+ to Eu3+ ions. 相似文献
9.
Wangdong Liu Hanchao Wang Shiping Zhan Wenbin Li 《Journal of Materials Science》2011,46(23):7620-7625
Although Eu3+ ion-doped Y2O3 has been extensively used as red phosphors, their color rendering needs to be improved for high-quality illumination and
displaying. Here, we show that the emission spectra of Y2O3:Eu3+ red phosphors can be broadened by the doping of Nd3+ ion so that the color rendering capability of Y2O3:Eu3+ was remarkably enhanced. Y2O3:Eu3+ and Y2O3:Eu3+,Nd3+ colloidal spheres were synthesized by wet chemical procedure and high-temperature treatment. The fluorescence measurement
under the 254 and 380 nm ultraviolet excitation indicates that the 612 nm red emission peak of Eu3+ can be splitted into two ones by the doping of Nd3+ ion, of which the full width at half maximum (FWHM) is broadened from 4.2 nm to 9.6 nm. By varying the concentration of Nd3+ ion, it was determined that the optimal doping concentration of Nd3+ ion is of 3 mol% for realizing the strongest emission intensity. The further increase of Nd3+ ion exceeding 3 mol% would lead to a concentration quenching phenomenon. The analysis based on XRD spectra and the simplified
energy diagram suggested that the doped Nd3+ ion not only monitored the growth dynamics, but also took an efficient energy transfer and a cross relaxation process to
generate intense emission from Eu3+ ion in both of C2 and S6 sites, instead of preferable one type of Eu3+ site (C2 or S6) in the Nd3+ undoped sample. 相似文献
10.
The detailed preparation process of Eu2+ and Dy3+ ion co-doped Sr3Al2O6 phosphor powders with red long afterglow by sol–gel-combustion method in the reducing atmosphere is reported. X-ray diffraction, scanning electron microscopy and photoluminescence spectroscopy are used to investigate the effects of synthesis temperature on the crystal characteristics, morphology and luminescent properties of the as-synthesized Sr3Al2O6:Eu2+, Dy3+ phosphors. The results reveal that Sr3Al2O6 crystallizes completely when the combustion ash is sintered at 1200 °C. The excitation and the emission spectra indicate that the excitation broad-band lies chiefly in visible range and the phosphor powders emit strong light at 618 nm under the excitation of 472 nm. The light intensity and the light-lasting time of Sr3Al2O6:Eu2+, Dy3+ phosphors are increased when increasing the calcination temperatures from 1050 to 1200 °C. The afterglow of Sr3Al2O6:Eu2+, Dy3+ phosphors sintered at 1200 °C lasts for over 600 s when the excited source is cut off. The red emission mechanism is discussed according to the effect of nephelauxetic and crystal field on the 4f65d1 → 4f7 transition of the Eu2+ ions. 相似文献
11.
Xiaoyun Hu Jun Fan Jing Pan Jianhua Gao Ting Li Dekai Zhang Xinliang Zheng Dong Jiang Enzhou Liu 《Optical Materials》2009,31(11):1707-1710
A Eu, Dy co-doped SiO2 matrix xerogel with blue emission was prepared by the sol–gel method. Strong blue emission located between 425 nm and 525 nm with a peak at 486 nm is observed under UV laser excitation at room temperature, which is related to a 4f → 5d energy transition of Eu2+. Such techniques as FT-IR and TGA–DSC were used to measure the microstructure of the luminescent materials. The influence of Dy3+ ions on the luminescent property of Eu2+ was investigated. The emission intensity of Eu, Dy-codoped samples is stronger than that of Eu doped samples. The emission enhancement mechanism relating to Eu2+ is attributed to an energy transfer involving Dy3+ → Eu2+. Using energy transition theory, we speculate that the mechanism may be one of the resonance transfers via multi-polar interactions, and present a possible energy transfer model. The Eu2+ blue emission intensity reaches the maximum when the Dy3+ concentration is 0.1 mol%. When the concentration of Dy3+ is 0.3 mol%, a fluorescence quenching appears which might be related to the overlap part of Eu2+ excitation and emission levels, and also suggests the existence of Eu2+ → Eu2+ energy transfer. 相似文献
12.
Phosphate glasses in the compositions of 70P2O5–15Al2O3–14Na2O–1RE3+ (RE = Sm, Dy, and Tm) (mol%) were prepared by melt-quenching technique and characterized optically. The differential thermal analysis (DTA) profile of the host glass was carried out to confirm its thermal stability. For all the glasses absorption, photoluminescence and decay measurements have also been carried out. These glasses have shown strong emission and absorption bands in visible and near-infrared (NIR) region. From the measured absorption spectra, Judd–Ofelt (J–O) intensity parameters (Ω2, Ω4 and Ω6) have been calculated for all the studied ions. For Sm3+ doped glass, four emission bands centered at 562 nm (4G5/2 → 6H5/2), 598 nm (4G5/2 → 6H7/2), 644 nm (4G5/2 → 6H9/2), and 704 nm (4G5/2 → 6H11/2) have been observed with 402 nm (6H5/2 → 4F7/2) excitation wavelength. Of them, 598 nm (4G5/2 → 6H7/2) has shown a bright orange emission. With regard to Dy3+ doped glass, a blue emission band centered at 486 nm (4F9/2 → 6H15/2) and a bright yellow emission at 575 nm (4F9/2 → 6H13/2) have been observed, apart from 662 nm (4F9/2 → 6H11/2) emission transition with an excitation at 388 nm (6H15/2 → 4I13/2,4F7/2) wavelength. Emission bands of 650 nm (1G4 → 3F4) and 785 nm (1G4 → 3H5) transitions for the Tm3+ doped glass, with an excitation wavelength at 466 nm (3H6 → 1G4), have also been observed. The stimulated emission cross-sections of all the emission bands of RE3+ glasses (RE = Sm, Dy, and Tm) have been computed based on their measured full-width at half maximum (FWHM, Δλ) and measured lifetimes (τm). 相似文献
13.
We report an effective method to synthesize Y2O2S:Eu3+, Mg2+, Ti4+ nanoparticles. Tube-like Y(OH)3 were firstly synthesized by hydrothermal method to serve as the precursor. Nanocrystalline long-lasting phosphor Y2O2S:Eu3+, Mg2+, Ti4+ was obtained by calcinating the precursor with co-activators and S powder. XRD investigation shows a pure phase of Y2O2S, indicating no other impurity phase appeared. SEM and TEM observation reveals that the precursor synthesized via a hydrothermal routine has tube-like structure and the final phosphor reveals a hexagonal shape. The fine nanoparticles which have the particle size ranging from 30 to 50 nm show uniform size and well-dispersed distribution. From the spectrum, the main emission peaks are ascribed to Eu3+ ions transition from 5DJ (J = 0, 1, 2) to 7FJ (J = 0, 1, 2, 3, 4). After irradiation by 325 nm for 10 min, the Y2O2S:Eu3+, Mg2+, Ti4+ long-lasting phosphor shows very bright red afterglow and the longest could last for more than 1 h even after the irradiation source had been removed. It is considered that the long-lasting phosphorescence is due to the contribution from the electron traps with suitable trap depth. 相似文献
14.
Xinguo Zhang 《Materials Letters》2009,63(11):852-854
Sr4Si3O8Cl4:Eu2+ and Sr3.5Mg0.5Si3O8Cl4:Eu2+ phosphors were prepared by a conventional solid state reaction (SS). Excited by 370 nm near-ultraviolet light, the phosphors show an efficient bluish-green wide-band emission centering at 484 nm, which originates from the 4f5d1 → 4f7 transition of Eu2+ ion. The excitation spectra of the phosphors are a broad band extending from 250 nm to 400 nm. Mg2+-codoping greatly enhances the bluish-green emission of the phosphors. An LED was fabricated by coating the Sr3.5Mg0.5Si3O8Cl4:0.08Eu2+ phosphor onto an ~ 370 nm-emitting InGaN chip. The LED exhibits bright bluish-green emission under a forward bias of 20 mA. The results indicate that Sr3.5Mg0.5Si3O8Cl4:0.08Eu2+ is a candidate as a bluish-green component for fabrication of NUV-based white LEDs. 相似文献
15.
SiO2–SrB4O7:Eu2+ glass–ceramic thin films were fabricated for possible application in near ultraviolet (NUV) emitting devices. Nano-sized SrB4O7:Eu2+ powders were prepared by a Pechini-type sol–gel method and a subsequent ball-milling treatment. The powders showed NUV emissions centered at 367 nm, upon irradiation with UV of shorter wavelengths, due to an allowed 4f65d1 → 4f7 electronic transition of Eu2+ ions. The glass–ceramic thin films were prepared by dip-coating of tetraethylorthosilicate (TEOS) solutions dispersed with the nano-sized SrB4O7:Eu2+ powders and a subsequent heat-treatment. It was found that the glass–ceramic thin films had relatively high thermal stability up to 800 °C in terms of the Eu2+ emissions. SiO2 layers surrounding SrB4O7:Eu2+ appeared to be effective for the surface passivation of the phosphor particles. 相似文献
16.
Y2O3:Eu3+ red phosphors were prepared by surfactant assisted co-precipitation-molten salt synthesis method. The effects of surfactant content and annealing temperature on the structure and luminescence were investigated by X-ray diffraction and fluorescence spectrophotometer. The use of surfactant reduces the impurities on the surface of particles and promotes the reaction. The color purity of as-prepared Y2O3:Eu3+ red phosphors is improved with the presence of surfactant. In the excitation spectra, two strong bands at 394 and 466 nm are attributed to 7F0,1-5L6, 7F0,1-5D2 transitions of Eu3+ ions respectively. With the excitation of 394 or 466 nm, the as-fabricated samples reveal excellent red emission as high as that of samples monitored by 254 nm. Thus, the Y2O3:Eu3+ is a promising red phosphor for ultraviolet-visible light-emitting diodes. 相似文献
17.
Liya Zhou Wallace C.H. Choy Jianxin Shi Menglian Gong Hongbin Liang 《Materials Chemistry and Physics》2006,100(2-3):372-374
Vacuum ultraviolet (VUV) excitation and emission properties of Tb3+ ion doped silico-aluminate phosphor Ca1.5Y1.5Al3.5Si1.5O12:Tb3+ was studied. Upon excitation with vacuum ultraviolet (VUV) and near UV light excitation, the phosphor showed strong green-emission peaked at 545 nm corresponding to the 5D4 → 7F5 transition of Tb3+, and the highest PL intensity at 545 nm was found at a content of about 14 mol% Tb3+. The 4f–5d transition absorption of Tb3+ is in the range from 150 nm to 260 nm, and there is an energy transfer from the host to the rare earth ions. Field emission scanning electron microscopy (FE-SEM) images showed the particle size of the phosphor was less than 3 μm. 相似文献
18.
The luminescent properties of Na3Y1−xSi3O9:xEu3+ (0.05 ≦ x ≦ 0.80) powder crystals were investigated in UV-VUV region. The Eu3+-O2− charge transfer band (CTB) was observed to be located at around 233 nm and the environmental parameter (he) was estimated to be about 0.730. The excitation spectrum monitoring the 613 nm red emission from Eu3+ ions reveals the host absorption band (HAB) to be around 145 nm. The calculated Commission Internationale de l’Eclairage (CIE) chromaticity coordinates indicate the emission by 233 nm rather than by 147 nm excitation has the better color purity and the possible mechanisms have been proposed. The Eu3+-emission showed high quenching concentration due to the isolated YO6 octahedra in the host and the small he for the Eu3+ ions and the optimum concentration was determined to be as high as x = 0.65 and 0.30 with 233 and 147 nm excitation, respectively. 相似文献
19.
Li-Ya Zhou Jian-She Wei Ling-Hong Yi Fu-Zhong Gong Jun-Li Huang Wei Wang 《Materials Research Bulletin》2009,44(6):1411-1414
Motivated by the need for new red phosphors for solid-state lighting applications Eu3+-doped MgMoO4 was prepared by solid-state reaction and its excitation and emission spectra were measured at room temperature. In addition, the effects of firing temperature and Eu3+ doping concentration on the PL intensities were also investigated. Compared with Y2O2S:0.05Eu3+, the obtained Mg0.80MoO4:Eu3+0.20 phosphor shows a stronger excitation band near 400 nm and intensely red-emission lines at 616 nm correspond to the forced electric dipole 5D0 → 7F2 transitions on Eu3+ under 394 nm light excitation. The CIE chromaticity coordinates (x = 0.651, y = 0.348) of Mg0.80MoO4:Eu3+0.20 close to the NTSC (National Television Standard Committee) standard values, and therefore may find application on near UV InGaN chip-based white light emitting diodes. 相似文献
20.
Effects of Ho2O3 addition on defects of BaTiO3 ceramic have been studied in terms of electrical conductivity at 1200 °C as a function of oxygen partial pressure (PO2°) and oxygen vacancy concentration. The substitution of Ho3+ for the Ti site in Ba(Ti1−xHox)O3−0.5x resulted in a significant shift of conductivity minimum toward lower oxygen pressures and showed an acceptor-doped behavior. The solubility limit of Ho on Ti sites was confirmed less than 3.0 mol% by measuring the electrical conductivity and the lattice constant. Oxygen vacancy concentrations were calculated from the positions of PO2° in the conductivity minima and were in good agreement with theoretically estimated values within the solubility limit. The Curie point moved to lower temperatures with increasing the oxygen vacancy concentration and Ho contents. 相似文献