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1.
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   

2.
We present luminescence, luminescence excitation and luminescence time resolved spectra of La2Be2O5:Pr3+ system. We used high pressure spectroscopy approaches, with high pressure applied in diamond anvil cell (DAC) and sapphire anvil cell (SAC), for detailed analysis of luminescence related to the 4f5d → 4f2 and 4f2 → 4f2 transitions. We present effect of up-converted luminescence related to 4f5d → 4f2 transition excited with 488 nm. We also discussed possibility of existence of praseodymium trapped exciton (PTE) states in La2Be2O5:Pr3+ system. Lack of the PTE is attributed to high quantity of bulk modulus of this material.  相似文献   

3.
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   

4.
LiYbF4: Er3+ octahedral microcrystals have been successfully prepared through a facile hydrothermal method assisted with EDTA (ethylenediaminetetraacetic acid). X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), Fourier transform infrared spectroscopy (FTIR), thermogravimetric and differential scanning calorimeters (TG-DSC), photoluminescence (PL) spectra are used to characterize the samples. Under 976 nm excitation, the upconversion (UC) luminescence emission spectra of LiYbF4: Er3+ microcrystals show the characteristic Er3+ emissions. The results show that the infrared light emissions at 792 nm of 4I9/2 → 4I15/2 are dominantly strong unusually, while the green emissions at 526 and 545 nm assigned to 2H11/2 → 4I15/2 and 4S3/2 → 4I15/2, respectively, and the red emission at 667 nm of 4F9/24I15/2 are relatively weaker. Most importantly, the samples show more efficient luminescence with further heat treatment.  相似文献   

5.
Infrared to visible upconversion luminescence has been investigated in Er3+/Yb3+ co-doped CeO2 inverse opal. Under the excitation of 980 nm diode lasers, visible emissions centered at 525, 547, 561, 660 and 680 nm are observed, which are assigned to the Er3+ transitions of 2H11/2 → 4I15/2 (525 nm), 4S3/2 → 4I15/2 (547, 561 nm), 4F9/2 → 4I15/2 (660 and 680 nm), respectively. The effect of photonic band gap on the upconversion luminescence intensity was also obtained. Additionally, the upconversion luminescence mechanism was studied. The dependence of Er3+ upconversion emission intensity on pump power reveals that it is a two-photon excitation process.  相似文献   

6.
The Ba2TiSi2O8 is a well known piezoelectric, ferroelectric and non-linear crystal. Nanocrystals of Ba2TiSi2O8 doped with 1.5 Dy3+ have been obtained by thermal treatment of a precursor glass and their optical properties have been studied. X-ray diffraction patterns and optical measurements have been carried out on the precursor glass and glass ceramic samples. The emission spectra corresponding to the Dy3+: 4F9/2 → 6H13/2 (575 nm), 4F9/2 → 6H11/2 (670 nm) and 4F9/2 → 6H9/2 (757 nm) transitions have been obtained under laser excitation at 473 nm. These measurements confirm the incorporation of the Dy3+ ions into the Ba2TiSi2O8 nanocrystals which produces an enhancement of luminescence at 575 nm. At this wavelength has been demonstrated a maximum optical amplification around 1.9 cm−1 (∼8.2 dB/cm).  相似文献   

7.
C.W. Jia  J.G. Zhao  E.Q. Xie 《Materials Letters》2007,61(22):4389-4392
Er3+-doped TiO2 nanofibres were fabricated with electrospinning method followed by annealing in air at 420, 600, 800 and 1000 °C, respectively. The obtained nanofibres are relatively straight and have an average diameter of ∼ 75 nm. X-ray diffraction measurements showed that the crystal structure transforms from anatase to rutile phase with the increase of annealing temperature. Visible photoluminescence peaking at 528.1, 566.6 and 669.3 nm is detected which is ascribed to 2H11/2 → 4I15/2, 4S3/2 → 4I15/2 and 4F9/2 → 4I15/2 transitions of Er3+ ions and the PL intensities increase with the increase of annealing temperature. Meanwhile at high annealing temperatures, near-infrared photoluminescence peaking at 815 nm due to the defect states associated with Ti3+ ions is also found. The strong green photoluminescence of Er3+ ions may have potential applications in one-dimensional luminescent nanodevices.  相似文献   

8.
A novel reddish orange emitting long persistent phosphor CaO:Pr was prepared by a high temperature solid-state reaction method. All as-prepared phosphors were studied systematically by X-ray diffraction, photoluminescence (PL) spectra, decay curves, afterglow spectra and thermoluminescence (TL) glow curves. The intensity of PL and the performance of afterglow are dependent on the concentration of Pr3+ ions. The trap depth in the range between 0.5 and 0.7 eV is suitable for long afterglow (LAG). The optimal concentrations of Pr3+ ions for the best characteristic PL emission and afterglow were experimentally calculated to be 0.05 mol%. After irradiation by 273 nm for 3 min, the duration of reddish orange afterglow can last nearly 1 h. The decay processes and mechanism of LAG in CaO:Pr3+ were also discussed in detail.  相似文献   

9.
The photoluminescence and excitation spectra of Pr3+ activated LaPO4 has been investigated in the 1.6-300 K temperature region. At room temperature, the luminescence of LaPO4:Pr3+ is composed of the interconfigurational 4f15d1 → 4f2 emission transitions. However, in the 1.6-60 K temperature range, the emission spectrum also consists of the intraconfigurational emission transitions that emanate from the 1S0 state. A radiative lifetime of 145 ns is measured for the Pr3+1S0 → 1I6 emission transition in LaPO4. This is one of the shortest radiative lifetime observed for this transition in a solid. The energy position of the Pr3+1S0 state in LaPO4 is established by high-resolution emission spectrum at 46 375 ± 5 cm−1. A detailed analysis of the thermal quenching of the 1S0 lifetime and emission intensity is presented. It is proposed that the lowest energy state of the relaxed 4f15d1 configuration is situated energetically below that of the 1S0 state.  相似文献   

10.
11.
A high resolution luminescence study of NaLaF4: 1%Pr3+, 5%Yb3+ and NaLaF4: 1%Ce3+, 5%Yb3+ in the UV to NIR spectral range using a InGaAs detector and a fourier transform interferometer is reported. Although the Pr3+(3P0 → 1G4), Yb3+(2F7/2 → 2F5/2) energy transfer step takes place, significant Pr3+1G4 emission around 993, 1330 and 1850 nm is observed. No experimental proof for the second energy transfer step in the down-conversion process between Pr3+ and Yb3+ can be given. In the case of NaLaF4: Ce3+, Yb3+ it is concluded that the observed Yb3+ emission upon Ce3+ 5d excitation is the result of a charge transfer process instead of down-conversion.  相似文献   

12.
Synthesis and luminescence properties of Eu3+ and Tm3+-doped ZnNb2O6 nanocrystals by the sol–gel process were investigated. The products were characterized by differential thermal analysis (DTA), scanning electron microscopy (SEM), and photoluminescence spectroscopy (PL). ZnNb2O6:Eu3+ shows bright red luminescence with maximum peak at 613 nm attributed to 5D0 → 7F2 transition. The major blue emission peak of ZnNb2O6:Tm3+ was at 483 nm, corresponding to the transitions 1G4 → 3H6. The optimum concentration of Eu3+ and Tm3+ showing the maximum PL intensity was 4 mol% and 1 mol%, respectively.  相似文献   

13.
The fully concentrated Eu3+-based molybdenum borate Eu2MoB2O9 was synthesized by the solid-state reaction method. The photoluminescence excitation and emission spectra, the temperature dependent luminescence intensities and the decay curve were investigated. Photoluminescence spectra show that the phosphor can be efficiently excited by near-UV light and exhibits an intense red luminescence corresponding to the electric dipole transition 5D0 → 7F2 at 615 nm. The luminescence intensities and color purity were investigated by increasing the fired temperatures. The phosphor shows the stable luminescence and color purity at high temperature.  相似文献   

14.
Yb3+/Tm3+/Ho3+ tri-doped Gd2Mo3O9 phosphors were synthesized by the high-temperature solid-state method. Under 980 nm near-infrared excitation, the white-light emission can be observed, which is consists of the blue, green, and red UC emissions. The green and red emission at 547 nm and 660 nm originated from the transition of Ho3+ (5S2, 5F4 → 5I8 and 5F5 → 5I8) and the blue emission at 475 nm attributed to the transition of Tm3+ (5G4 → 5H6). In this experiment, we selected the optimum concentration ratio of the three rare earths for the bright white emission. The Commission internationale de L’Eclairage (CIE) coordinates for the samples were calculated, and chromaticity coordinates were very close to white light regions. We find that the calculated CIE color coordinates of the Yb3+/Tm3+/Ho3+ tri-doped Gd2Mo3O9 phosphors changed with the incident pump power from 400 mW/cm2 to 1000 mW/cm2. The upconversion luminescence mechanism of the samples was discussed on its spectral. The white light may be proved to be a candidate material for applications in various fields.  相似文献   

15.
NaGd(MoO4)2:Eu3+ (hereafter NGM:Eu) phosphors have been prepared by sol-gel method. The properties of the resulting phosphors are characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), photoluminescence (PL) spectra and decay curve. The excitation spectra of NGM:Eu phosphors are mainly attributed to O → Mo charge-transfer (CT) band at about 282 nm and some sharp lines of Eu3+ f-f transitions in near-UV and visible regions with two strong peaks at 395 and 465 nm, respectively. Under the 395 and 465 nm excitation, intense red emission peaked at 616 nm corresponding to 5D0 → 7F2 transition of Eu3+ are observed for 35 at.% NGM:Eu phosphors as the optimal doping concentration. The luminescence properties suggest that NGM:Eu phosphor may be regarded as a potential red phosphor candidate for near-UV and blue light-emitting diodes (LEDs).  相似文献   

16.
Trivalent thulium-doped K5Bi(MoO4)4 single crystals were grown by the Czochralski method. Its polarized absorption and fluorescence spectra and fluorescence decay curves were recorded at room temperature. On the basis of the Judd-Ofelt theory, the spectral parameters of the Tm3+:K5Bi(MoO4)4 crystal were calculated. The cross relaxations between Tm3+ ions were analyzed. The emission cross sections of the 3F4 → 3H6 transition were obtained by the Fuchtbauer-Ladenburg formula and then the gain cross sections around 1.9 μm were calculated. The peak emission cross section and width of emission band around 1.9 μm are comparable to those for Tm3+:YAG and the tunable range is about 280 nm for the potential ∼1.9 μm laser operation via the 3F4 → 3H6 transition.  相似文献   

17.
Yb3+/Er3+ codoped BaGd2(MoO4)4 phosphor powders were prepared by the Sol-gel method and the upconversion luminescence properties were investigated in detail. Under 980 nm semiconductor laser excitation, BaGd2(MoO4)4:Yb3+,Er3+ phosphor exhibits green upconversion luminescence with peaks at 530 and 550 nm, which are due to the transitions of Er3+ (2H11/2) → Er3+ (4I15/2) and Er3+ (4S3/2) → Er3+ (4I15/2), respectively. Both of the two green emission lines are produced by populating Er3+ ions to the excited state through a two-photon process. By monitoring the intensities of the green upconversion luminescence, the optimum conditions for the Sol-gel synthesis were determined when the molar ratio of citric acid to total chelate metal cations was 2:1 and the sintering temperature was at 1073 K. The concentration quenching effect for Er3+ was found at the optimum doping concentration of 6 mol%, and the critical distance for the neighboring Er3+ was determined to be about 21.5 Å.  相似文献   

18.
Sm3+-activated La2O2S phosphors with good crystallinity were prepared by solid-state reaction. The formation mechanism of La2O2S formation was assumed and the phase change with different temperatures was discussed. The luminescence properties of phosphors with different sintering temperatures and different doping concentrations of Sm3+were investigated. The emission peak at 605 nm showed a well intensity can be attributed to the 4G5/2 → 6H7/2 transition of Sm3+. The optical absorption of La2O2S phosphors showed a stronger intensity in UV-vis region comparing with the Y2O2S phosphors. The long afterglow properties were investigated after the phosphors were excited with a fluorescent lamp. Phosphorescence lasted for about 3 min in the limit of light perception of the dark-adapted human eye (0.32 mcdm−2).  相似文献   

19.
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   

20.
Near-infrared (NIR) quantum cutting luminescent materials Li2TeO4 doped with Pr3+ and Yb3+ were synthesized by solid-state reaction method. The dependence of Yb3+ doping concentration on the visible- and NIR-emissions, decay lifetime, and quantum efficiencies of the phosphors are investigated. Quantum cutting down-conversion involving 647 nm red emission and 960-1050 nm broadband near-infrared emission for each 487 nm blue photon absorbed is realized successfully in the resulting phosphors, of which the process of near-infrared quantum cutting could be expressed as 3P0(Pr3+) → 2F5/2(Yb3+) + 2F5/2(Yb3+). The maximum quantum cutting efficiency approaches up to 166.4% in Li2TeO4: 0.3 mol%Pr3+, 1.8 mol%Yb3+ sample corresponding to the 66.4% value of energy transfer efficiency.  相似文献   

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