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1.
Long afterglow phosphors (Ca1−xEux)2MgSi2O7 (0.002 ≤ x ≤ 0.02) were prepared by solid-state reactions under a weak reductive atmosphere. X-ray diffraction pattern, photoluminescence spectra, decay curve, afterglow spectra and thermoluminescence curves were investigated. The phosphors showed two emission peaks when they were excited by 343 nm, due to two types of Eu2+ centers existing in the Ca2MgSi2O7 lattice. However, only one emission peak can be found in their afterglow spectra. Energy transfer between Eu2+ ions in inequivalent sites was found. A possible mechanism was presented and discussed. The afterglow decay time of Ca1.998MgSi2O7:Eu0.002 was nearly 12.5 h which means it was a good long lasting phosphor.  相似文献   

2.
Lead borate glass samples doped with the tripositive lanthanide ions Pr3+ and Yb3+ were synthesized by the conventional melting-quenching method. The luminescence properties and energy transfer process from Pr3+ to Yb3+ were investigated. Upon ultraviolet excitation, the room temperature luminescence decay curve of a sample containing only a low concentration of Pr3+ exhibited monoexponential decay from 1D2 with the lifetime 37 μs, without emission from 3P0. The room temperature Pr3+ emission intensity decreased with the increase of Yb3+ mole ratio in the glass. Under the excitation of 454.5 nm at 10 K, a broad red emission band centered at 605 nm, and an NIR emission band at 995 nm were observed in the co-doped lead borate glass, originating from Pr3+ and Yb3+ ions, respectively. The decay curves of the 1D2 emission from Pr3+ with addition of Yb3+ in lead borate glass show non-monoexponential character, and are best described by a stretched exponential function. The average 1D2 decay time decreases considerably with the addition of Yb3+ in the glass. Decay curve fitting using a modified Inokuti-Hirayama expression indicates dipole-dipole energy transfer from Pr3+ to Yb3+, which is consistent with the expected cross-relaxation scheme. There is a good agreement of the estimated overall energy transfer efficiency obtained from the integrals under the normalized decay curves, or from the lifetimes fitted by the stretched exponential function, or from the average decay times.  相似文献   

3.
Pr3+-doped La2(WO4)3 single crystal with dimensions up to Ø 20 mm × 35 mm has been grown by the Czochralski method. The structure of the Pr3+:La2(WO4)3 crystal was determined by the X-ray powder diffraction and the Pr3+ concentration in this crystal was determined. The absorption and fluorescence spectra of Pr3+:La2(WO4)3 crystal were measured at room temperature, and the fluorescence lifetime of main emission multiplets were estimated from the recorded decay curves. The spectral properties related to laser performance of the crystal were evaluated.  相似文献   

4.
A white-emitting phosphor Sr2SiO4: Pr3+ was synthesized through a solid-state reaction, and characterized by XRD, scanning electron microscopy (SEM), fluorescence spectrophotometer and thermo luminescence (TL) meter. Its emission spectra is composed of bluish purple (peaking at 390 nm), green (peaking at 535 nm) and red (peaking at 604 nm) light emission. They originate from the transitions of 4f → 5d, 3P0 → 3H5 and 1D2 → 3H4 of Pr3+. The afterglow emission spectrum is similar to the emission spectra. And the afterglow can last over 40 min in darkness. The TL curve shows that there is only one thermo luminescence band peak at about 376.480 K, which is responsible for the long-lasting emission.  相似文献   

5.
An investigation of spectroscopic properties of (SrTiO3-TiO2):Pr3+ eutectic and, for comparison, of bulk SrTiO3:Pr3+ and TiO2:Pr3+crystals is presented. Luminescence spectra have been measured under both 450 nm and 350 nm excitation wavelength. For UV excitation they are characterized by a dominant red luminescence corresponding to transition from the 1D2 level of Pr3+ ions. The mechanism responsible for quenching of blue (from 3P0 state) and intensification of red luminescence is proposed to be thermally-induced radiationless relaxation involving a low-lying Pr3+-Ti4+ intervalence charge transfer state. Measured decay constants of 1D2 excited state of Pr3+ are compared with values obtained for other praseodymium doped titanate hosts.  相似文献   

6.
The Tb3+ doped CaWO4 phosphors are synthesized via high temperature solid state reaction. The X-ray diffraction shows that small amount of Tb3+ does not have a significant influence on the structure of CaWO4. A broad absorption band of the WO42− group is observed from photoluminescence and the energy transfer from WO42− group to Tb3+ ions induces the f-f transition. The cross-relaxation between two adjacent Tb3+ ions weakens 5D3-7Fj transitions and enhances the 5D4-7Fj transitions, leading to a green long afterglow of the phosphors. The thermoluminescence curves centered around 75 °C reveal the trap depth for afterglow generation is about 0.74-0.77 eV. The optimum Tb3+ concentration for afterglow properties is about 1%. A deep hole trap is induced when Tb3+ concentration exceeds 1% and it suppresses the thermoluminescence and the decay properties.  相似文献   

7.
Mn2+ and RE3+ (RE = Tb, Eu, Nd) co-doped CdSiO3 orange phosphors were prepared at 1050 °C by a sol–gel method. The phase and crystallinity of the synthesized materials were investigated by X-ray powder diffraction (XRD) and scanning electron microscopy (SEM). The luminescence characteristics were analyzed using photoluminescence (PL) spectra, afterglow decay curves, long-lasting phosphorescence spectra, and thermoluminescence (TL) spectra. Due to the difference in co-doped rare earth ionic radii, it varied greatly in trap density and trap depth caused by the different defects deriving from RE3+ ions co-doping into the CdSiO3: Mn2+ host. The afterglow intensity and time for these samples increased as follows: CdSiO3: Mn2+0.2%, Nd3+0.8% < CdSiO3: Mn2+0.4%, Tb3+0.8% < CdSiO3: Mn2+0.4%, Eu3+0.3%. CdSiO3: Mn2+0.4%, Eu3+0.3% had the best afterglow properties, which could be due to the proper traps formed by Eu3+ ions co-doping into the host. The role of RE3+ co-doped into the CdSiO3: Mn2+ matrix and the possible long-lasting phosphorescence process was also discussed in this paper.  相似文献   

8.
Luminescence spectra and time resolved luminescence spectra of GGG crystal doped with Pr3+ were measured at high hydrostatic pressure from ambient to 220 kbar. Effect of pressure results in the red shift of all luminescence lines related to Pr3+ ion emission equals from −0.32 to −1.02 cm−1/kbar and in the diminishing of the luminescence lifetimes. The luminescence decay related to emission from 3P0 state was single-exponential and diminished with pressure from 23 μs at ambient pressure to 6.5 μs at 165 kbar. Luminescence decay related to transition form 1D2 state was two-exponential with longer decay equal to 162 μs at ambient pressure and 120 μs at 165 kbar. We discussed effect of pressure on the 1D2 → 3H4 luminescence and emission from 3P0 state in the context of non-radiative processes that depopulate the 3P0 and populate the 1D2 state, considering mainly multiphonon relaxation processes and depopulation via the praseodymium trapped exciton state.  相似文献   

9.
K. Wei  Chang Du  Na Zhao  Xiang Li 《Materials Letters》2009,63(21):1781-1784
We prepared PrxZn1 − xO nanopowder using a combustion method. The sample was characterized by XRD, TEM, XPS, UV-visible and PL spectroscopy. The prepared PrxZn1 − xO nanopowder had a good photon absorption performance in the range of 200-800 nm wavelength. Moreover, the 4f2 electronic configuration of trivalent Pr3+ ions was revealed from the diffuse reflectance spectra. The single crystalline particle size was about 20-70 nm based on the TEM observation. A quantum size effect of the PrxZn1 − xO nanopowder was also noted.  相似文献   

10.
Bi3+ and Tb3+ ions co-doped GdAlO3 (GAP) nanophosphors have been synthesized by means of solvothermal reaction method. The XRD pattern of GAP phosphor confirms their orthorhombic phase. The luminescence properties of these phosphors have been explored by analyzing their excitation and emission spectra along with their decay curves. The excitation spectra of GAP:Tb3+, Bi3+ phosphors consist of a broad band in the shorter wavelength region due to the 4f8 → 4f75d1 transition of Tb3+ ions overlapped with the 6s2 → 6s16p1 (1S0 → 3P1) transition of Bi3+ ions and some sharp peaks in the longer wavelength region due to f → f transitions of Tb3+ ions. The present phosphors exhibit green color due to strong 5D4 → 7F5 transition of Tb3+ ions. The emission intensity was enhanced by co-doping with Bi3+ ions under 292 nm excitation, which indicate that the efficient energy transfer occurred from Bi3+ to Tb3+ ions.  相似文献   

11.
Homogeneous precipitation method for synthesizing (Gd0.99,Pr0.01)2O2S sub-microphosphor was developed, using the commercially available Gd2O3, Pr6O11, H2SO4 and (NH2)2CO (urea) as the starting materials. It was found that the as-synthesized precursor is mainly composed of (Gd0.99,Pr0.01)2(OH)2(CO3)(SO4nH2O. Pure quasi-spherical shaped (Gd0.99,Pr0.01)2O2S particles can be synthesized by calcining the precursor at a temperature higher than 700 °C for 1 h in flowing hydrogen. The (Gd0.99,Pr0.01)2O2S particles have a narrow size distribution with a mean grain size of about 300-400 nm. Photoluminescence spectra of (Gd0.99,Pr0.01)2O2S under 303 nm UV excitation show a green emission at 515 nm as the most prominent peak, which corresponds to the 3P0 → 3H4 transition of Pr3+ ions. Decay study reveals that the 3P0 → 3H4 transition of Pr3+ ions in Gd2O2S host lattice has a single exponential decay behavior.  相似文献   

12.
Temperature dependent radioluminescence under X-ray excitation (XRL) and luminescence decay time measurements following 430 nm laser excitation have been performed in the 10-775 K range on Gd2O2S:Pr3+,Ce3+ scintillating ceramics. From 200 K to both low and high temperature, XRL light yield decreases by 60%. High temperature luminescence quenching has been revisited. Temperature dependent lifetime measurements imply non-radiative de-excitation mechanism at electronic defects spatially correlated to Pr3+ emitting ions. At low temperatures, decreasing XRL light yield with irradiation time is linked to very intense thermoluminescence (TL) peak around 120 K ascribed to sulfur vacancies. These traps cause efficient electron trapping which competes with the prompt recombination mechanism.  相似文献   

13.
In the search for new scintillator materials, Ce3+ doped chlorides are a promising class of materials, combining a high efficiency and fast response time. Even shorter response times may be achieved by replacing Ce3+ by Pr3+ or Nd3+ as the lifetime of the d-f emission is substantially shorter for these ions. Here we report on the luminescence properties of Ce3+, Pr3+ and Nd3+ in RbCl and investigate the potential as a scintillator material. Under UV excitation Ce3+ shows d-f emission between 325 and 425 nm. The emission originates from multiple (differently charge compensated) Ce3+ sites. The luminescence lifetime varies with wavelength and is ∼40 ns for the longer wavelength emission. For RbCl:Pr3+ three d-f emission band are observed between 250 and 350 nm which can be assigned to transitions from the lowest energy fd state to different 3HJ (J = 4-6) states within the 4f2 configuration of Pr3+. The decay time is ∼17 ns. For the Nd3+ activated sample a weak emission band around 220 nm is observed only at 8 K which may be due to d-f emission. The very short lifetime (4 ns) is faster than the radiative lifetime, indicating that the d-f emission is quenched by relaxation to lower lying 4f3 states or by the process of photoionization. Under VUV excitation at wavelengths below 175 nm (the bandgap of RbCl) the d-f emission is very weak for Ce3+, Pr3+ and Nd3+ doped RbCl and the emission spectra are dominated by defect related emission. This indicates that energy transfer from the host lattice to the fd states is inefficient which prevents application as a scintillator material.  相似文献   

14.
The red afterglow phosphors of CaWO4 doped with Eu3+, Zn2+ or (and) Si4+ were prepared by solid state reaction. All crystalline phases were identified by the X-ray powder diffraction (XRD). The photoluminescence spectra and decay curves as well as thermoluminecence (TL) curves of all samples were also investigated. In comparison to CaWO4:Eu3+ phosphor, the luminescence and afterglow properties could be improved greatly after being doped with Zn2+ or (and) Si4+ ions.  相似文献   

15.
Undoped and Mn-doped ZnS nanoclusters have been synthesized by a hydrothermal approach. Various samples of the ZnS:Mn with 0.5, 1, 3, 10 and 20 at.% Mn dopant have been prepared and characterized using X-ray diffraction, energy-dispersive analysis of X-ray, high resolution electron microscopy, UV-vis diffusion reflection, photoluminescence (PL) and photoluminescence excitation (PLE) measurements. All the prepared ZnS nanoclusters possess cubic sphalerite crystal structure with lattice constant = 5.408 ± 0.011 ?. The PL spectra of Mn-doped ZnS nanoclusters at room temperature exhibit both the 495 nm blue defect-related emission and the 587 nm orange Mn2+ emission. Furthermore, the blue emission is dominant at low temperatures; meanwhile the orange emission is dominant at room temperature. The Mn2+ ion-related PL can be excited both at energies near the band-edge of ZnS host (the UV region) and at energies corresponding to the Mn2+ ion own excited states (the visible region). An energy schema for the Mn-doped ZnS nanoclusters is proposed to interpret the photoluminescence behaviour.  相似文献   

16.
Absorption and circular-dichroism spectra of LaBGeO5 crystal doped with Pr3+ and Ho3+ ions were investigated at 8 K in the range 300-900 nm. Electronic transitions of these ions, which substitute La3+ ions in positions with a local symmetry C1 are observed in the spectra. All transitions are active in both absorption and circular-dichroism spectra. Values of the dipole strengths Dom, rotation strengths Rom and anisotropy factors g are calculated for some well-separated bands.  相似文献   

17.
Different concentrations of Li-doped YBO3:Eu3+ phosphors have been prepared by the conventional solid state reaction method and were characterized by X-ray diffraction, field emission scanning electron microscopy, photoluminescence excitation and emission measurements. An intense reddish orange emission is observed under UV excitation and the emitted radiation was dominated by an orange peak at 594 nm resulted from the 5D0 → 7F1 transitions of Eu3+ ions. The brightness of the YBO3:Eu3+ phosphor was found greatly improved with Li-doping accompanied by slight improvement in the purity of the color which might be attributed to improvement in crystallinity, grain sizes and creation of oxygen vacancies with Li-doping. The observed results have been discussed in comparison with similar reported works.  相似文献   

18.
Optical properties of Bi3+ doped SrS nanophosphors synthesized by solid state diffusion method in the presence of sodium thiosulfate as a flux have been reported. UV-vis absorption and photoluminescence (PL) spectra of SrS phosphors doped with trivalent Bi3+ ions either alone or in combination with charge compensating ions, were also studied. These studies reflect that the incorporation of Bi3+ into host lattice is facilitated by the charge compensating Na+ ions. PL emission for SrS:Bi shows a peak at 481 nm at an excitation wavelength of 430 nm, which is attributed to the transition from the 3P1 to 1S0 states of Bi3+. We have also investigated the effect of different dopant concentrations on PL emission intensity.  相似文献   

19.
Eu-doped ZnO microrods, with wurtzite structure and [0 0 0 1] growth direction have been successfully synthesized on Si (1 0 0) substrates by a simple hydrothermal method. The samples were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), lifetime decay curves, photoluminescence (PL) and photoluminescence excitation (PLE) spectra, respectively. These results indicate that Eu3+ ions are located in the distorted lattice sites near the surface of the ZnO microrods. Additionally, it is also suggested that the surface defects may act as a step in the process of energy transfer from ZnO to Eu3+ ions.  相似文献   

20.
Rare-earth ions (Eu3+, Tb3+, Dy3+) doped SrMoO4 nanoparticles were prepared by solvothermal route using oleic acid as surfactant to control the particle shape and size. X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectra (XPS), photoluminescence spectra (PL) and the kinetic decay times were applied to characterize the obtained samples. The XRD patterns reveal that all the doped samples are assigned to the scheelite-type tetragonal structure of SrMoO4 phase. In addition, the as-synthesized SrMoO4:Ln (Ln = Eu3+, Tb3+, Dy3+) particles are high purity well crystallized and with the average size of 30-50 nm. The possible formation process of SrMoO4:Ln (Ln = Eu3+, Tb3+, Dy3+) nanoparticles have been discussed as well. Upon excitation by ultraviolet radiation, the as-synthesized SrMoO4:Ln (Ln = Eu3+, Tb3+, Dy3+) nanoparticles exhibit the characteristic emission lines of corresponding Eu3+, Tb3+, Dy3+, respectively.  相似文献   

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