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1.
2.
This paper reports on the photoluminescence (PL) and time-resolved properties of Ce3+, Eu3+, and Tb3+ in novel LiSr4(BO3)3 powder phosphors. Ce3+ shows an emission band peaking at 420 nm under 350-nm UV excitation. Energy transfer from Ce3+ to Mn2+ takes place in the co-doped samples. Eu3+ shows red emission under near UV excitation. LiSr4(BO3)3:Eu3+ phosphor could be a suitable candidate for phosphor-converted solid state lighting. The luminescence lifetime is 2.13 ms
for Eu3+ in LiSr4(BO3)3:0.001Eu3+. As Eu3+ concentration increasing, the decay curves deviate from exponential behavior. Tb3+ shows the strongest 5D4→7 F5 emission line at 540 nm. Decay curves of 5D4→7 F5 and 5D3→7 F5 emission with different Tb3+ concentrations were also measured. Cross-relaxation process is discussed based on the decay curves. 相似文献
3.
The high efficient antireflective down-conversion Y2O3:Bi, Yb films have been prepared successfully on Si(100) substrates by pulsed laser deposition (PLD) method, Upon excitation of ultraviolet photon varying from 300 to 400 nm, near-infrared emission of Yb3+ was observed for the film, can be efficiently absorbed by silicon (Si) solar cell. Most interestingly, there is a very low average reflectivity 1.46% for the incident light from 300 to 1100 nm. To the best of our knowledge, this is the lowest reflectance for the down-conversion thin films prepared by cost efficient method. The surface topography of the high efficient antireflective films can be controllably tuned through the substrate template regulation by optimizing process parameters. Besides, the results showed that there is a close relationship between luminescent property and morphology of the film. With the change of the surface morphology, the intensity of Bi3+ and Yb3+ emission peaks increase first and then decrease. The obtained results demonstrate that this film can enhance the Si solar cell efficiency through light trapping and spectrum shifting. 相似文献
4.
F.B. Xiong X.H. Gong Y.F. Lin Y.J. Chen Q.G. Tan Z.D. Luo Y.D. Huang 《Applied physics. B, Lasers and optics》2007,86(2):279-286
A Pr3+-doped La2(WO4)3 crystal grown by the Czochralski method has been investigated as a promising laser material. The principal axes of the optical
indicatrix and Pr3+ concentration of the crystal were determined. The polarized absorption, fluorescence spectra and fluorescence decay curves
of the main emission multiplets of the crystal were measured at room temperature. The spectroscopic parameters were obtained
by the modified Judd–Ofelt theory combined with the normalized method. The peak stimulated emission cross-sections of the
major emission lines were estimated. The good spectroscopic properties imply that the Pr3+:La2(WO4)3 crystal is a potential laser gain medium for solid-state laser and self-stimulated Raman laser applications.
PACS 78.20.-e; 42.70.Hj 相似文献
5.
Hemam Jenee Devi Wairokpam Rameshwor Singh Romeo Singh Loitongbam 《Journal of fluorescence》2016,26(3):875-889
Rare earth elements (RE = Eu3+& Dy3+)and Bi3+ doped Y2O3 nanoparticles were synthesized by urea hydrolysis method in ethylene glycol, which acts as reaction medium as well as a capping agent, at a low temperature of 140 °C,followed by calcination of the obtained product. Transmission electron microscope (TEM) images reveals that ovoid shaped Y2O3 nanoparticles of around 22–24 nm size range were obtained in this method. The respective RE and Bi3+ doped Y2O3 precursor nanoparticles when heated at 600 and 750 °C, retains the same shape as that of the as-synthesized Y2O3 precursor samples. From EDAX spectra, the incorporation of RE ions into the host has been studied. XRD pattern reveals the crystalline nature of the heated nanoparticles and indicate the absence of any impurity phase other than cubic Y2O3.However, the as-synthesized nanoparticles were highly amorphous without the presence of any sharp XRD peaks. Photoluminescence study suggests that the synthesized samples could be used as red (Eu3+), yellow (Dy3+), blue and green (Bi3+)emitting phosphors. 相似文献
6.
J.H. Huang X.H. Gong Y.J. Chen Y.F. Lin J.S. Liao X.Y. Chen Z.D. Luo Y.D. Huang 《Applied physics. B, Lasers and optics》2007,89(1):73-80
Polarized spectral properties of Er3+:NaGd(WO4)2 single crystal are reported. The crystal was grown by the Czochralski method. The Judd–Ofelt theory was applied to analyze
the polarized absorption spectra and then calculate the spontaneous emission probabilities, radiative lifetimes, and branching
ratios. Fluorescence decay curves of the 4
I
13/2, 4
I
11/2, and 4
S
3/2 multiplets for the Er3+ ions were measured. Stimulated emission cross-sections of the 4
I
13/2→4
I
15/2 transition obtained by the Fuchtbauer–Ladenberg formula and the reciprocity method were compared. Multi-phonon relaxation
rates of the crystal were estimated. Green up-conversion fluorescence around 531 and 552 nm was observed, and the possible
up-conversion mechanisms were proposed.
PACS 78.20.-e; 42.70.Hj 相似文献
7.
The crystal of Nd3+:Sr6YSc(BO3)6 with dimensions of O 19×42 mm3 was grown by the Czochralski method. It’s spectral and laser properties have been investigated. The absorption cross section
is 1.47×10-20 cm2 with a FWHM 12.0 nm at 807 nm, the emission cross section is 1.57×10-19 cm2 at 1060 nm, and the fluorescence lifetime is 76 μs at room temperature. The maximum laser output is 25.7 mJ at 1.06 μm pumped
by a single Xenon flash lamp and the overall and average slope efficiencies are 0.12% and 0.09%, respectively. The laser energy
threshold value is 1.28 J.
PACS 42.55.Rz; 42.70.Hj; 78.20.-e 相似文献
8.
9.
Yu. K. Voron’ko E. V. Zharikov D. A. Lis A. V. Popov V. A. Smirnov K. A. Subbotin 《Physics of the Solid State》2008,50(9):1605-1610
Single crystals of double sodium-containing lanthanum and gadolinium molybdates doped with Tm3+ ions were synthesized by the Czochralski method. The spectroscopic properties of these crystals were investigated from the viewpoint of their use as active media in diode-pumped lasers. The polarized spectra of absorption on the 3 H 4 and 3 F 4 levels and the polarized spectra of luminescence due to the 3 F 4-3 H 6 laser transition were recorded, and the lifetimes of the 3 H 4 and 3 F 4 excited states of the Tm3+ ions were determined. The luminescence cross sections were calculated using the Füchtbauer-Ladenburg formula. The simulation of the decay curve of the 3 H 4 excited state according to the Golubov-Konobeev-Sakun method revealed that, in the crystals under investigation, the interaction between Tm3+ ions predominantly occurs through the dipole-dipole mechanism. 相似文献
10.
A. D. Prokhorov M. T. Borowiec M. C. Pujol I. M. Krygin A. A. Prokhorov V. P. Dyakonov P. Aleshkevych T. Zayarnyuk H. Szymczak 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,55(4):389-395
The electron paramagnetic resonance (EPR) of Yb3+
ions in a KY(WO4)2 single crystal was investigated at T=4.2 K and
fixed frequency of 9.38 GHz. The resonance absorption observed on the lowest
Kramers doublet represents the complex superposition of three spectra,
corresponding to the ytterbium isotopes with different nuclear moments. The
EPR spectrum is characterized by a strong anisotropy of the g-factors. The
temperature dependence of the g-factors is shown to be caused by the strong
spin-orbital and orbital-lattice coupling. The resonance lines broaden with
increasing temperature due to the short spin-lattice relaxation times. 相似文献
11.
Shufang Wang Huiling Li Kun Zhao Songqing Zhao Mingjing Chen Jingchun Chen Jianglong Wang Guangsheng Fu 《Applied Physics A: Materials Science & Processing》2011,105(2):407-410
A heterojunction was fabricated by growing a layer of Bi2Sr2Co2O
y
thin film on the 0.7 wt% Nb-doped SrTiO3 substrate. Such heterojunction showed good rectifying characteristics over a wide temperature range, and its transport mechanism
under the forward bias can be attributed to a space charge limited conduction mechanism via defects near the interface of
the heterojunction. Photovoltaic properties of the heterojunction were studied by using both continuous-wave and pulsed irradiations
and the results can be well explained by the photovoltaic effect of a p–n junction. 相似文献
12.
Ph. V. Demekhin I. D. Petrov B. M. Lagutin V. L. Sukhorukov A. Neogi P. Yeates E. T. Kennedy M. W. D. Mansfield J. T. Costello 《Optics and Spectroscopy》2007,102(2):149-158
The photoionization cross sections for the 4p shell of ions of the Kr isoelectronic sequence Rb+, Sr2+, and Y3+ are calculated. The configuration interaction theory and the perturbation theory are used to describe the many-electron effects. The relativistic effects are taken into account in the Pauli-Fock approximation. The calculated resonance structure of photoionization cross sections for the 4p shell in the region below the 4s threshold associated with the autoionization of the 4s-np singly excited states and the 4p4p-nln′l′ doubly excited states reproduces the results of recent measurements of total photoabsorption cross sections for the Rb+, Sr2+, and Y3+ ions. It is found that, as the nuclear charge in the isoelectronic sequence increases, the ratio between the direct and correlation parts of amplitudes of the 4s-(n/?)p transition changes and, as the consequence, the minimum of the photoionization cross section of the 4s shell shifts from the continuous spectrum to the region of states of discrete spectrum. This accounts for the strong changes in the shape of the 4s-np resonances in the photoionization cross sections for the 4p shell of Rb+, Sr2+, and Y3+, as well as the distinction between the shapes of the 4s-6p 1/2 mirror resonance in the partial 4p 1/2 and 4p 3/2 photoionization cross sections for the Y3+ ion which do not suppress each other in the total photoionization cross section, as is the case for similar resonances in Rb+ and Sr2+. 相似文献
13.
Ren Chen Yihua Hu Yahong Jin Li Chen Xiaojuan Wang 《Applied Physics A: Materials Science & Processing》2014,116(2):823-830
MgO powders subjected to Q-switched laser pulses in water were characterized by X-ray/electron diffraction and optical spectroscopy to have a significant optical property change with accompanied transformation into the phase assemblages of periclase, brucite and liquid-crystalline lamella. The periclase nanoparticles tended to have {111} habit planes parallel to the basal layers of lamella and brucite flakes more or less rolled as fibers, ribbons or tubes. A significant internal compressive stress was built up for periclase and brucite but not the more flexible lamellar phase. The colloidal suspension containing the densified periclase nanoparticles within the rolled brucite/lamellae flakes showed UV–visible absorption corresponding to a minimum band gap of ca. 5 eV. 相似文献
14.
The Dy3+ and Eu3+ activated K3Al2 (PO4)3 phosphors were prepared by a combustion synthesis. From a powder X-ray diffraction (XRD) analysis the formation of K3Al2 (PO4)3 was confirmed. In the photoluminescence emission spectra, the K3Al2(PO4)3:Dy3+ phosphor emits two distinctive colors: blue and yellow whereas K3Al2(PO4)3:Eu3+ emits red color. Thus the combination of colors gives BYR (blue–yellow–red) emissions can produce white light. These phosphors
exhibit a strong absorption between 340 and 400 nm which suggest that present phosphor is a promising candidate for producing
white light-emitting diodes (LED). 相似文献
15.
L. Seetha Lakshmi K. Dörr K. Nenkov A. Handstein V. S. Sastry K.-H. Müller 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,58(2):115-121
We report the charge state modification effects at the Mn site on the ground
state properties of colossal magnetoresistive manganites. Ta5+
substitution results in an appreciable increase in the lattice parameters
and unit cell volume due to increased Mn3+ concentration. The
ferromagnetic-metallic ground state modifies to a cluster glass insulator
for
. The reduction in the transition temperatures with
increasing x is ∼39 K/at.%. Besides the modification of majority carrier concentration due to increased Mn3+ concentration and enhanced local structural effects, the local
electrostatic potential of the substituent seems to contribute to the
unusually strong reduction of the transition temperatures of the compounds.
Thermo magnetic irreversibility just below Curie temperature (Tc),
non-saturation of magnetization, two distinct magnetic transitions in ac
susceptibility in an appropriate static field: close to Tc and other at
low temperature (the spin freezing temperature (Tg)) and non-stationary
dynamics with a characteristic maximum in the magnetic viscosity close to
Tg confirm a cluster glass state for
. These results
find additional support from a linear low temperature magnetic specific heat
of x = 0.10 with a characteristic broad maximum close to Tg. 相似文献
16.
AC impedance spectroscopy technique has been used to study electrical properties of Bi3.25La0.75Ti3O12 (BLT) ceramic. Complex impedance plots were fitted with three depressed semicircles, which are attributed to crystalline
layer, plate boundary and grain boundary and all three were found to comprise of universal capacitance nature [C = C0w
n−1]. Grain boundary resistance and capacitance evaluated from complex impedance plots have larger values than that of plate
boundary and crystalline layer. The activation energies (E
a) for DC-conductance in grain boundary, plate boundary and crystalline layer are 0.68 eV, 0.89 eV and 0.89 eV, respectively.
Relaxation activation energies calculated from impedance plots showed similar values, 0.81 eV and 0.80 eV for crystalline
layer and plate boundary, respectively. These activation energy values are found to be consistent with the E
a value of oxygen vacancies in perovskite materials. A mechanism is offered to explain the generation of oxygen vacancies in
BLT ceramic and its role in temperature dependence of DC-conductance study.
相似文献
17.
Yb3+-Tm3+ co-doped up-conversion powder phosphors using Zn(AlxGa1-x)2O4 (ZAGO) as the host materials were synthesized via solid-state reaction successfully. In addition, the morphology, structural characterization and up-conversion luminescent properties were all investigated by scanning electron microscope (SEM), x-ray diffraction (XRD) and fluorescence spectrophotometer (F-7000), respectively. Under the excitation of a 980 nm laser, all as-prepared powders can carry out blue emission at about 477 nm (corresponding to 1G4 → 3H6 transition of Tm3+ ions), and red emission at about 691 nm (attributed to 3F3 → 3H6 transition of Tm3+ ions). Also, the influence of doping Al3+ ions were investigated. In brief, the doping of Al3+ ions has no effect on the position of emission peak. Howbeit the up-conversion efficiency and intensity of ZAGO:Yb,Tm phosphors are stronger than ZGO:Yb,Tm and ZAO:Yb,Tm phosphors, while the crystallinity is the opposite. More particularly, all as-prepared powder phosphors emit strong luminescence, which is observable by the naked eye, demonstrating the potential applications in luminous paint, luminescent dye, etc. 相似文献
18.
Chongfeng Guo Lin Luan Xu Ding Dexiu Huang 《Applied Physics A: Materials Science & Processing》2008,91(2):327-331
Eu2+ and Mn2+ co-doped SrMg2(PO4)2 phosphors with blue and red two emission bands were prepared by the high temperature solid state method and their luminescent
properties have been investigated as a function of activator and co-activator concentrations. Resonance-type energy transfers
from Eu2+ to Mn2+ were discovered by directly overlapping the Eu2+ emission spectrum and the excitation spectrum of Mn2+. Efficiencies of energy transfer were also calculated according to the changes of relative intensities of Eu2+ and Mn2+ emission. According to the principle of energy transfer, we demonstrated that the phosphor SrMg2(PO4)2:Eu2+,Mn2+ with double emission bands exhibited a great potential as a phosphor for ultraviolet light-emitting diodes and the relative
intensities of blue and red emission could be tuned by adjusting the contents of Eu2+ and Mn2+.
PACS 78.55.-m 相似文献
19.
The results of the ab initio FLAPW-GGA computations of the band structure of the recently synthesized layered tetragonal (space group I4/mmm) arsenide (Sr3Sc2O5)Fe2As2 as a possible basis phase of a new group of FeAs superconductors are presented. For (Sr3Sc2O5)Fe2As2, the energy bands, electron state density distributions, Fermi surface topology, low-temperature electron specific heat, molar Pauli paramagnetic susceptibility, and effective atomic charges have been determined. These results are discussed compared to similar data for the layered tetragonal crystals LaFeAsO, SrFeAsF, SrFe2As2, and LiFeAs that are the basis phases of the recently discovered high-temperature (T C ~ 26–56 K) 《1111》, 《122》, and 《111》 FeAs superconductors. 相似文献
20.
A. V. Sidorenko P. A. Rodnyi O. Guillot-Noel D. Gourier C. W. E. van Eijk 《Physics of the Solid State》2003,45(9):1676-1678
ESR spectra of Ce3+ ions in polycrystalline Sr2B5O9Br were studied, and the two crystallographic positions of the Ce3+ ion in this compound were identified on the basis of the data obtained. The ESR spectrum of Ce3+ ions with local charge compensation contains a broad line indicating the existence of several types of charge compensation. ESR spectra of Ce3+ ions in samples activated additionally by K+ ions are similar to those of the regular Ce3+ centers, which indicates that the effect of the univalent cation on Ce3+ is negligible. 相似文献