共查询到20条相似文献,搜索用时 62 毫秒
1.
Yanbo Qiao Ning Da Danping Chen Wenbo Ma Qinling Zhou Jianrong Qiu 《Journal of Materials Science》2009,44(15):4026-4030
The Nd3+, Yb3+-doped and Nd3+–Yb3+-codoped high silica glasses (HSGs) were fabricated by sintering porous glasses impregnated with Nd3+ and Yb3+ ions solutions. The Judd–Ofelt theory was used to study the spectroscopic properties of Nd3+-doped HSGs. Large parameter Ω2 of Nd3+-doped HSGs suggests a lower centrosymmetric coordination environment around the Nd3+ in HSG. The spontaneous emission probability and emission cross-section (σem) of Yb3+-doped HSGs are obtained. A broad emission band from 950 to 1,100 nm was detected when the Nd3+–Yb3+-codoped HSG was excited by 808 nm LD. The energy transfer process from Nd3+ to Yb3+ in HSG was described in this paper. 相似文献
2.
Subrata Das A. Amarnath Reddy S. Surendra Babu G. Vijaya Prakash 《Journal of Materials Science》2011,46(24):7770-7775
Potassium calcium borate, KCaBO3:Eu3+ phosphors with various Dy3+ concentrations (0–3 wt%) were synthesized by solid state reaction and studied for the first time. Under various UV–violet
excitations, the obtained single monoclinic phased Dy3+–Eu3+ co-doped KCaBO3 polycrystalline phosphors emit a combination of yellow–blue and red–orange wavelength giving intense white light, which can
easily be controlled by varying the concentration of Dy3+. The increase in white light emission with the increase of Dy3+ concentration indicates the efficient energy inter-ion transfer from Dy3+ to Eu3+ ions. Furthermore, the observed emission lifetimes and the intense white light emission are suggestive exploration for the
present phosphor for potential optoelectronic applications such as white light-emitting phosphor for blue LEDs chips. 相似文献
3.
Xing Gao Taiwen Li Jianfeng He Kexin Ye Xiaojiao Song Nengli Wang Jiangang Su Chunlong Hui Xiyan Zhang 《Journal of Materials Science: Materials in Electronics》2017,28(16):11644-11653
Well-crystalline β-NaYF4:Yb3+, Ho3+, Tm3+ nanoparticles were synthesized by sol–gel method using isopropyl alcohol [(CH3)2CHOH] as a complexing agent. The samples were characterized by X-ray diffraction, scanning electron microscopic analysis and fluorescence spectrum analysis methods. Under the excitation of 980 nm laser diode (LD), the samples displayed bright upconversion luminescence (UCL), which was generated from the energy level transition of Ho3+ and Tm3+ ions. With the increase of Tm3+, Ho3+ and Yb3+-doping concentration, the UCL intensity of blue, green and red light emission of the samples varied. Calculation of the CIE color coordinate of the β-NaYF4:Yb3+, Ho3+, Tm3+ nanoparticles revealed that with the adjustment of Tm3+, Ho3+ and Yb3+ doping concentration and the excitation power of 980 nm LD, the multi-color UCL can be realized. Approximately single red light output with the CIE color coordinate of x?=?0.545, y?=?0.306 and white light output with the CIE color coordinate of x?=?0.325, y?=?0.320 can be obtained in the synthesized β-NaYF4: Yb3+, Ho3+, Tm3+ nanoparticles. 相似文献
4.
Shumian Xu Sha-sha Liu Cong Zhao Tao Han Dachuan Zhu 《Journal of Materials Science: Materials in Electronics》2017,28(14):10061-10066
The Ba2P2O7:Tb3+, R (R?=?Eu2+, Ce3+) phosphors were synthesized by use of a co-precipitation method. Crystal phase, excitation and emission spectra of sample phosphors are analyzed by means of XRD and FL, respectively. The emission spectra of Ba2P2O7:Ce3+, Tb3+ phosphors exhibit four linear peaks attributed to the 5D4?→?7FJ (J?=?6–3) transition of Tb3+ while four broad emission bands are observed in the emission spectra of Ba2P2O7:Eu2+, Tb3+ phosphors. The effects of Eu2+ concentration on the luminescent properties of Ba2P2O7:Tb3+, R (R?=?Eu2+, Ce3+) are studied. Ce3+ affects the luminescent properties of Ba2P2O7:Ce3+, Tb3+ phosphors just as the sensitizer. However, Eu2+ is considered both as the sensitizer and the activator in Ba2P2O7:Eu2+, Tb3+ phosphors. The chromaticity coordinates of Eu2+ and Tb3+ co-doped phosphors gather around the white light field with the CCT approximate to 5000 K, indicating that the luminescent property of Ba2P2O7:Eu2+, Tb3+ phosphors may approach to a desired level needed for white LED application. 相似文献
5.
G. H. Mhlongo O. M. Ntwaeaborwa M. S. Dhlamini H. C. Swart K. T. Hillie 《Journal of Materials Science》2010,45(19):5228-5236
The successful incorporation of ZnO nanoparticles in Pr3+-doped SiO2 using a sol–gel process is reported. SiO2:Pr3+ gels, with or without ZnO nanoparticles, were dried at room temperature and annealed at 600 °C. On the basis of the X-ray
Diffraction (XRD) results, the SiO2 was amorphous regardless of the incorporation of Pr3+ and nanocrystalline ZnO or annealing at 600 °C. The particles were mostly spherical and agglomerated as confirmed by Field
Emission Scanning Electron Microscopy. Thermogravimetric analysis of dried gels performed in an N2 atmosphere indicated that stable phases were formed at ≥900 °C. Absorption bands ascribed to 3H4-3P(J = 0,1,2), 1I6 and 1D2 in the UV–VIS region were observed from SiO2:Pr3+ colloids. The red cathodoluminescent (CL) emission corresponding to the 3P0 → 3H6 transition of Pr3+ was observed at 614 nm from dried and annealed SiO2:Pr3+ powder samples. This emission was increased considerably when ZnO nanoparticles were incorporated. The CL intensity was measured
at an accelerating voltage of 1-5 keV and a fixed beam current of 8.5 μA. The effects of accelerating voltage on the CL intensity
and the CL degradation of SiO2:Pr3+ and ZnO·SiO2:Pr3+ were also investigated using Auger electron spectroscopy coupled with an Ocean Optics S2000 spectrometer. 相似文献
6.
Cyril Koughia Gokulakrishnan Soundararajan Safa Kasap Trevor Allen Chris Haugen Ray Decorby N. Ohrui Takeshi Aoki C. Fujihashi 《Journal of Materials Science: Materials in Electronics》2009,20(1):19-22
The positions of Stark levels have been determined, using a step-by-step procedure, in the 4I9/2 and 4F3/2 manifolds of Nd3+ ions from absorption and photoluminescence measurements in the 12–293 K temperature range. This data has been used to calculate the emission cross-section for which the maximum value turns out to be ~2.3 × 10?20 cm2. The radiative recombination time, calculated using Judd–Ofelt analysis, of the 4F3/2 manifold is in close vicinity to the experimentally determined times that were measured by the conventional decay of PL after interruption of excitation and by QFRS. Moreover, the peak time defined by QFRS is independent of temperature. Therefore, the dominant relaxation mechanism from the 4F3/2 excited manifold of Nd3+ ions in GaLaS glass is believed to be by radiative emission. 相似文献
7.
A. N. Georgobiani V. B. Gutan M. A. Kazaryan A. V. Krotov O. Ya. Manashirov Yu. P. Timofeev 《Inorganic Materials》2009,45(10):1166-1170
Ce3+ doping of Y2O2S:Er3+ can be used to suppress the visible anti-Stokes luminescence of the phosphor under excitation in the range 0.90–0.98 μm.
We take advantage of this effect to create a new, efficient “invisible” IR phosphor emitting in the range 1.5–1.6 μm. 相似文献
8.
Yu. A. Barbanel’ R. B. Dushin V. V. Kolin V. P. Kotlin L. G. Mashirov S. N. Nekhoroshkov 《Radiochemistry》2007,49(3):237-240
The absorption spectra of the NpO 2 + (5f 2) ion were examined in the region of the 3H 5 ← 3 H 4 magnetic dipole transition (1530–1760 nm) for series of melts with the UO 2 2+ concentration varied in the opposite directions: (1) NaCl-2CsCl eutectic melt with growing additions of the Cs2UO2Cl4 complex salt and (2) Cs2UO2Cl4 melt with growing additions of the NaCl-2CsCl mixture. Measurements of the integrated intensities of the bands belonging to the NpO 2 + ·UO 2 2+ complex and unbound NpO 2 + throughout the UO 2 2+ concentration range examined (up to 4.4 M in neat Cs2UO2Cl4 melt) and processing of the data obtained in terms of the mass action law showed that the formation-decomposition reaction of the cation-cation complex can be described adequately only using the equation of reaction in the form NpO2Cl 4 3? + UO2Cl 4 2? ? {Cl4ONpO?UO2Cl3}4? = Cl? (with the equilibrium constant of 1.3±0.1). Thus, the formation of the cationcation complex should be treated as replacement of chloride ion in the equatorial plane of uranyl(VI) by neptunyl(V), rather than as simple addition of UO 2 2+ to NpO 2 + . The reverse reaction, decomposition of the cation-cation complex, consists essentially in replacement of neptunyl(V) by chloride ion. 相似文献
9.
S. Y. Lee Y. L. Lu P. K. Liaw H. Choo S. A. Thompson J. W. Blust P. F. Browning A. K. Bhattacharya J. M. Aurrecoechea D. L. Klarstrom 《Mechanics of Time-Dependent Materials》2008,12(1):31-44
The creep–fatigue crack-growth tests of HASTELLOY® X alloy were carried out at the temperatures of 649°C, 816°C, and 927°C in laboratory air. The experiments were conducted under a constant stress-intensity-factor-range (ΔK) control mode with a R-ratio of 0.05. In the constant ΔK tests, a ΔK of 27.5 MPa\(\sqrt{\mathrm{m}}\) and a triangular waveform with a frequency of 0.333 Hz were used. Various tensile hold times at the maximum load were imposed to study fatigue and creep–fatigue interactions. Crack lengths were measured by a direct current potential drop method. In this paper, effects of hold time and temperature on the crack-growth rates are discussed. Furthermore, the crack-growth rates of the HASTELLOY® X alloy are compared to those of the HAYNES® 188 and HAYNES® 230® superalloys. 相似文献
10.
M. M. Kasumov 《Technical Physics Letters》2010,36(10):895-898
The mass spectrum of the products of arc discharge in helium between graphite electrodes has been studied for various values
of the gas flow rate. As the gas flow rate increases, the intensity of C60±, C70±, C84± and C90± fullerene peaks increases and that of the C2− and C3+ cluster radicals decreases, but the total decay in radicals amounts to only 21% of the total growth of fullerenes. From this
it follows that a contribution to the formation of fullerenes from the neutral clusters (which are taken into account for
the first time) significantly exceeds the contribution due to small radical species. 相似文献
11.
Glasses of the 0.5Er3+/2.5Yb3+ co-doped (40Bi2O3–20GeO2–(30 − x)PbO–xZnO–10Na2O system where x = 0.0, 5, 10, 15, 20, 25, and 30 mol%) have been characterized by FT-IR spectroscopy measurements to obtain information about
the influence of ZnO-substituted PbO on the local structure of the glass matrix. The density and the molar volume have been
determined. The influences of the ZnO-substituted PbO on the structure of glasses have been discussed. The dc conductivity
measured in the temperature range 475–700 K obeys Arrhenius law. The conductivity decreases while the activation energy for
conduction increases with increase ZnO content. The optical transmittance and reflectance spectrum of the glasses have been
recorded in the wavelength range 400–1100 nm. The values of the optical band gap E
opt for all types of electronic transitions and refractive index have been determined and discussed. The real and imaginary parts
ε1 and ε2 of dielectric constant have been determined. 相似文献
12.
O. P. Krivoruchko T. V. Larina V. F. Anufrienko I. Yu. Molina E. A. Paukshtis 《Inorganic Materials》2009,45(12):1355-1361
We have synthesized nanoparticulate cobalt(II) hydroxide containing Co2+ in tetrahedral oxygen coordination (Co Td 2+ ), atypical of such systems: nano- [Co(OH)2(H3O) δ + ]δ+. The (Co Td 2+ ) coordination in the hydroxide is inferred from its electronic diffuse reflectance spectrum, which shows a multiplet of strong absorption bands at 14500, 15000, and 16000 cm?1 (4 A 2(F)-4 T 1(P) transition). Nanoparticulate cobalt(II) hydroxide forms in a weakly acidic medium under essentially nonequilibrium conditions due to supersaturation (by three to four orders of magnitude) with the starting reagents (CoCl2 and LiOH) at the instant of the formation of the poorly soluble phase Co(OH)2. Presumably, colloidal particles of nanoparticulate cobalt(II) hydroxide in a weakly acidic aqueous medium have a positive surface charge, compensated by a counter-ion (Cl?) layer: nano-[Co(OH)2(H3O) δ + ]δ+ · δCl?. The XRD patterns of pastes (gels) containing this hydroxide show three broad-ened lines with d = 5.31 (2θ = 16.7°), 2.77 (2θ = 32.3°), and 2.32 Å (2θ = 38.8°). According to small-angle X-ray scattering data, nano-[Co(OH)2(H3O) δ + ]δ+ has a narrow particle size distribution (1.0–2.0 nm). Synthesis and storage conditions are identified which ensure stabilization of the electronic state and particle size of nano-[Co(OH)2(H3O) δ + ]δ+ for a long time. 相似文献
13.
The enthalpy stability of the LaCl 4 ? and LuCl 4 ? ions is assessed using high-temperature mass spectrometry. The enthalpy of Cl? detachment is determined to be ΔrH0(298.15 K) = 332 ± 10 kJ/mol for LaCl 4 ? and 359 ± 10 kJ/mol for LuCl 4 ? . 相似文献
14.
Qiguo Sheng Haiping Xia Qingyang Tang Shinan He Baojiu Chen 《Journal of Materials Science: Materials in Electronics》2018,29(10):7987-7992
This paper reported on optical spectra of Na5Lu9F32 single crystals co-doped with ~?0.91 mol% Ho3+ and various Yb3+ concentrations by using an improved Bridgman method. The emission spectra and fluorescence decay curves were measured to investigate the luminescent properties of the Ho3+/Yb3+ co-doped Na5Lu9F32 and the energy transfer process from Yb3+ to Ho3+ ion. Compared with the Ho3+ singly doped Na5Lu9F32 crystal, the Ho3+/Yb3+ co-doped crystal had an obviously enhanced emission at 2.0 µm via the 980 nm laser diode excitation because of the efficient energy transfer from Yb3+ to Ho3+ ion. The maximum emission intensity at 2.0 µm was obtained at about 6.99 mol% Yb3+ concentration when the concentration of Ho3+ ions is fixed at ~?0.91 mol% in the current research. The maximum emission cross section of the above sample at 2.0 µm was calculated to be 1.23?×?10?20 cm2 according to the measured emission spectrum. The energy transfer efficiency from Yb3+:2F5/2 to Ho3+:5I6 for the crystal was estimated up to 90.8% indicating that Yb3+ ions can efficiently sensitize the Ho3+ ions. 相似文献
15.
O. D. Maslov G. A. Bozhikov P. I. Ivanov M. V. Gustova A. G. Belov S. N. Dmitriev 《Radiochemistry》2010,52(1):87-89
237U was produced by the reaction 238U(γ, n) on an electron accelerator, MT-25 microtron, at the Flerov Laboratory of Nuclear Reactions. For the separation of 237U and [238U, the recoil nuclei were collected by a nanostructured material, hydrated manganese dioxide (of the cryptomelane type), in
the solid-solid system. From fission products, 237U was separated by ion exchange. The specific activity of the resulting 237U was 4.5 × 109 Bq (mg 238U)-1, with the content of radioactive impurities of ≤10-6 Bq Bq-1. The chemical yield of 237U was 80%. 相似文献
16.
Libei Huang Yongde Hao Jun Li Mingzhe Hu 《Journal of Superconductivity and Novel Magnetism》2017,30(10):2841-2847
Co-doped ZnO ceramic samples sintered at four different temperatures were prepared by solid-state reaction method and implanted by Al ions subsequently. The microstructural, defect, magnetic and electrical properties of the samples were systematically investigated by x-ray diffraction, micro-Raman spectroscope, vibrating sample magnetometer and Hall measurement, respectively. The results show that all the samples exhibit room-temperature ferromagnetism with a saturation magnetization of 0.02–0.03 emu g?1, the value of which is affected by the sintering temperature. The origin of room-temperature ferromagnetism is considered as the formation of Co2+– V O–Co2+ bound magnetic polarons. Even though the implantation of Al3+ slightly reduces the saturation magnetization because of the lattice damage, less V O and larger lattice spacing, however, an appropriate amount of Al3+ implantation and a proper sintering temperature can remarkably improve the electrical properties with the mobility of 200 ~300 cm2 Vs?1 and the resistivity of 20 ~40 Ω cm. In general, samples sintered at 1200°C present more excellent comprehensive performances. 相似文献
17.
Tomohito Kameda Toshiaki Yoshioka Fumiko Yabuuchi Miho Uchida Akitsugu Okuwaki 《Bulletin of Materials Science》2008,31(4):625-629
In this study, we confirmed that the characteristics of anion intercalation into the interlayer of a hydrotalcite-like compound
(HT) during synthesis are similar to those of the anion-exchange reaction of HTs as well as the reconstruction reaction of
HTs from Mg-Al oxide. We demonstrated that (i) Cl−, which has a higher charge density than NO3−, more easily reacted with Mg and Al species to form HT structure, resulting in greater intercalation of Cl− into the HT interlayer; and (ii) for HTs with lower Mg: Al molar ratios, OH−, which has a higher charge density than Cl− and NO3−, was more likely to interact with Mg and Al species to form HT structure, blocking the intercalation of Cl− and NO3−. Furthermore, we showed that high concentrations of Cl− and NO3− in solution regulated their intercalation into the HT interlayer. The high activity of Cl− and NO3− in solution would facilitate the anions’ reactions with Mg and Al species to form HTs, resulting in a high degree of anion
intercalation into the interlayer of HTs. 相似文献
18.
Evandro A. Morais Luis V. A. Scalvi Américo Tabata José B. B. De Oliveira Sidney J. L. Ribeiro 《Journal of Materials Science》2008,43(1):345-349
Photoluminescence data of Eu-doped SnO2 xerogels are presented, yielding information on the symmetry of Eu3+ luminescent centers, which can be related to their location in the matrix: at lattice sites, substituting to Sn4+, or segregated at particles surface. Influence of doping concentration and/or particle size on the photoluminescence spectra
obtained by energy transfer from the matrix to Eu3+ sites is investigated. Results show that a better efficiency in the energy transfer processes is obtained for high symmetry
Eu3+ sites and low doping levels. Emission intensity from 5D0→7F1 transition increases as the temperature is raised from 10 to 240 K, under excitation at 266 nm laser line, because in this
transition the multiphonon emission becomes significant only above 240 K. As an extension of this result, we predict high
effectiveness for room temperature operation of Eu-based optical communication devices. X-ray diffraction data show that the
impurity excess inhibits particle growth, which may influence the asymmetry ratio of luminescence spectra. 相似文献
19.
Boyd D Towler MR Wren A Clarkin OM 《Journal of materials science. Materials in medicine》2008,19(4):1745-1752
Conventional polymethylmethacrylate (PMMA) cements and more recently Bisphenol-a-glycidyl dimethacrylate (BIS-GMA) composite cements are employed in procedures such as vertebroplasty. Unfortunately, such materials have inherent drawbacks including, a high curing exotherm, the incorporation of toxic components in their formulations, and critically, exhibit a modulus mismatch between cement and bone. The literature suggests that aluminium free, zinc based glass polyalkenoate cements (Zn-GPC) may be suitable alternative materials for consideration in such applications as vertebroplasty. This paper, examines one formulation of Zn-GPC and compares its strengths, modulus, and biocompatibility with three commercially available bone cements, Spineplex, Simplex P and Cortoss. The setting times indicate that the current formulation of Zn-GPC sets in a time unsuitable for clinical deployment. However during setting, the peak exotherm was recorded to be 33 degrees C, the lowest of all cements examined, and well below the threshold level for tissue necrosis to occur. The data obtained from mechanical testing shows the Zn-GPC has strengths of 63 MPa in compression and 30 MPa in biaxial flexure. Importantly these strengths remain stable with maturation; similar long term stability was exhibited by both Spineplex and Simplex P. Conversely, the strengths of Cortoss were observed to rapidly diminish with time, a cause for clinical concern. In addition to strengths, the modulus of each material was determined. Only the Zn-GPC exhibited a modulus similar to vertebral trabecular bone, with all commercial materials exhibiting excessively high moduli. Such data indicates that the use of Zn-GPC may reduce adjacent fractures. The final investigation used the well established simulated body fluid (SBF) method to examine the ability of each material to bond with bone. The results indicate that the Zn-GPC is capable of producing a bone like apatite layer at its surface within 24 h which increased in coverage and density up to 7 days. Conversely, Spineplex, and Simplex P exhibit no apatite layer formation, while Cortoss exhibits only minimal formation of an apatite layer after 7 days incubation in SBF. This paper shows that Zn-GPC, with optimised setting times, are suitable candidate materials for further development as bone cements. 相似文献
20.
Distribution of 210Po in thalli of soil and wood (epiphytic) lichens was studied. Four fractions containing the corresponding 210Ро forms were obtained by sequential extraction: (1) intercellular, (2) extracellular, (3) intracellular, and (4) insoluble thallus residue. The 210Ро uptake by lichens is mainly passive, as the total content of the radionuclide in fractions 1, 2, and 4 reaches 88–97%. From 3 to 12% of 210Ро is taken up actively (fraction 3), and for soil lichens this parameter is approximately 2.75 times higher than for epiphytic lichens. Presumably, 210Ро is supplied into soil and epiphytic lichens in the form of different chemical compounds and is therefore characterized by different bioavailability. 相似文献