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1.
Mg2+/Ga3+ doped Y3Al5O12:Ce3+ phosphors were synthesized through a solid state reaction. The phase and luminescent of the synthesized phosphors were investigated. For Ga3+ codoped Y2.96Ce0.04Al(5?x)GaxO12 phosphors, the emission intensity increases with the increase of Ga3+ concentration up to Y2.96Ce0.04Al4.80Ga0.20O12 and then decreases with a further increase of Ga3+ concentration, but the emission peak shifts to shorter wavelength continuously in the Ga3+ doping concentration range of 0.05–0.25. For Mg2+/Ga3+ codoped Y2.96Ce0.04Al(4.8?y)Ga0.20MgyO12 phosphors, the emission intensity decreases and the emission peak shifts to longer wavelength continuously in the Mg2+ doping concentration range of 0.02–0.12. The emission spectra of Y2.96Ce0.04Al(4.8?y)Ga0.20MgyO12 phosphors demonstrate that the codoped Mg2+/Ga3+ ions not only induce the enhancement of Y2.96Ce0.04Al5O12 emission intensity but also lead to the red shift of Y2.96Ce0.04Al5O12 emission peak. The decay lifetimes decrease in Mg2+/Ga3+ codoped Y2.96Ce0.04Al5O12 phosphors due to defects formed by substitutions of Y3+ by Mg2+/Ga3+.  相似文献   

2.
This article present the reports on optical study of Eu2+ and Ce3+ doped SrMg2Al6Si9O30 phosphors, which has been synthesized by combustion method at 550 °C. Here SrMg2Al6Si9O30:Eu2+ emission band observed at 425 nm by keeping the excitation wavelength constant at 342 nm, whereas SrMg2Al6Si9O30:Ce3+ ions shows the broad emission band at 383 nm, under 321 nm excitation wavelength, both the emission bands are assigned due to 5d–4f transition respectively. Further, phase purity, morphology and crystallite size are confirmed by XRD, SEM and TEM analysis. However, the TGA analysis is carried out to know the amount of weight lost during the thermal processing. The CIE coordinates of SrMg2Al6Si9O30:Eu2+ phosphor is observed at x?=?0.160, y?=?0.102 respectively, which may be used as a blue component for NUV-WLEDs. The critical distance of energy transfer between Ce3+ ions and host lattice is found to be 10.65 Å.  相似文献   

3.
Zn2GeO4, Zn2GeO4:Mn2+, Zn2GeO4:Pr3+ and Zn2GeO4:Mn2+/Pr3+ phosphors were fabricated by a solid state reaction. The phase and luminescent properties of the fabricated phosphors were investigated. The XRD patterns show that all of the fabricated phosphors have an orthorhombic structure. The fabricated Zn2GeO4 shows an emission band in the range of 350–550 nm. The fabricated Zn2GeO4:Mn2+ and Zn2GeO4:Pr3+ phosphors show emission bands corresponding to Mn2+ and Pr3+ ions, respectively. The fabricated Zn2GeO4:Mn2+/Pr3+ phosphor shows the emission band results from Mn2+ and the codoped Pr3+ enhances the emission intensity of Mn2+. Moreover, Zn2GeO4:Mn2+/Pr3+ phosphor exhibits longer decay time than that of Zn2GeO4:Mn2+. The higher intensity and longer lifetime of Mn2+ emission are induced by the energy transfer from Pr3+ of various vacancies to Mn2+ in Zn2GeO4:Mn2+/Pr3+ phosphors.  相似文献   

4.
Al3+/Mg2+ doped Y2O3:Eu phosphor was synthesized by the glycine-nitrate solution combustion method. In contrast to Y2O3:Eu which showed an irregular shape of agglomerated particles (the mean particle size >10 μm), the morphology of Al3+/Mg2+ doped Y2O3:Eu crystals was quite regular. Al3+/Mg2+ substituting Y3+ in Y2O3:Eu resulted in an obvious decrease of the particle size. Meanwhile, higher the Al3+/Mg2+ concentration, smaller the particle size. In particular, the introduction of Al3+ ion into Y2O3 lattice induced a remarkable increase of PL and CL intensity. While, for Mg2+ doped Y2O3:Eu samples, their PL and CL intensities decreased. The reason that causes the variation of PL and CL properties for Al3+ and Mg2+ doped Y2O3:Eu crystals was concluded to be related to sites of Al3+ and Mg2+ ions inclined to take and the difference of ion charge.  相似文献   

5.
A series of novel red-emitting Na2Ca3???x Si2O8:xEu3+ phosphors were synthesized by solid state reactions. The phosphors can strongly absorb 395 nm light, and show red emission with a good color purity. The excitation and emission spectra properties of Na2Ca3Si2O8:Eu3+ were characterized. Na2Ca3Si2O8:Eu3+ with self-compensated and alkali metal ions charge compensated approaches (2Ca2+→Eu3+ + M+, M?=?Li+, Na+, K+) have investigated, which found that the red emission of luminescent intensity can be greatly enhanced, and shows superior luminescent property to the commercial Y203S:Eu3+. The present work implies that the efficient charge compensated phosphors are promising candidates as red-emitting phosphor for w-LEDs.  相似文献   

6.
The Mn2+, Yb3+, Er3+: ZnWO4 green phosphors are synthesized successfully through the high temperature solid state reaction method. The micro-structure and morphology have been investigated by means of XRD and EDS. The doped concentrations of Mn2+, Yb3+, Er3+ are measured by ICP. The absorption spectra and emission spectra with different doped concentrations of Mn2+ are presented to reveal the influence of Mn2+ on the green up-conversion performance. Excited with 970 nm LED, the up-conversion emission peak at 547 nm is obtained and the CIE spectra as well as the green light photo are also presented. The results indicate that the Mn2+ ions play the role of the luminescence adjustment in the up-conversion process, which can improve the up-conversion green emission intensity effectively. The luminescence adjustment mechanism of Mn2+ ions in Mn2+, Yb3+, Er3+: ZnWO4 green phosphors has been discussed. The crystal parameters of Dq, B and C are calculated to evaluate the energy level split effect.  相似文献   

7.
A series of Sr3La(PO4)3:Eu2+/Mn2+ phosphors were synthesized by a solid state reaction. The phase and the optical properties of the synthesized phosphors were investigated. The XRD results indicate that the doped Eu2+ and Mn2+ ions do not change the phase of Sr3La(PO4)3. The peak wavelengths of Eu2+ single doped and Eu2+/Mn2+ codoped Sr3La(PO4)3 phosphors shift to longer wavelength due to the larger crystal field splitting for Eu2+ and Mn2+. The increases of crystal field splitting for Eu2+ and Mn2+ are induced by the substitution of Sr2+ by Eu2+ and Mn2+ in Sr3La(PO4)3 host. Due to energy transfer from Eu2+ to Mn2+ in Sr3La(PO4)3:Eu2+/Mn2+ phosphors, tunable luminescence was obtained by changing the concentration of Mn2+. And the white light was emitted by Sr3La(PO4)3:3.0 mol%Eu2+/4.0 mol%Mn2+ and Sr3La(PO4)3:3.0 mol%Eu2+/5.0 mol%Mn2+ phosphors.  相似文献   

8.
The polycrystalline Eu2+ and RE3+ co-doped strontium aluminates SrAl2O4:Eu2+, RE3+ were prepared by solid state reactions. The UV-excited photoluminescence, persistent luminescence and thermo-luminescence of the SrAl2O4:Eu2+, RE3+ phosphors with different composition and doping ions were studied and compared. The results showed that the doped Eu2+ ion in SrAl2O4:Eu2+, Dy3+ phosphors works as not only the UV-excited luminescent center but also the persistent luminescent center. The doped Dy3+ ion can hardly yield any luminescence under UV-excitation, but can form a electron trap with appropriate depth and greatly enhance the persistent luminescence and thermo-luminescence of SrAl2O4:Eu2+. Different co-doping RE3+ ions showed different effects on persistent luminescence. Only the RE3+ ion (e.g. Dy3+, Nd3+), which has a suitable optical electro-negativity, can form the appropriate electron trap and greatly improve the persistent luminescence of SrAl2O4:Eu2+. Based on above observations, a persistent luminescence mechanism, electron transfer model, was proposed and illustrated.  相似文献   

9.
Phase pure Ce3+ and Tb3+ singly doped and Ce3+/Tb3+ co-doped Ba3GdNa(PO4)3F samples have been synthesized via the high temperature solid-state reaction. The crystal structures, photoluminescence properties, fluorescence lifetimes, thermal properties and energy transfer of Ba3GdNa(PO4)3F:Ce3+,Tb3+ were systematically investigated. Rietveld structure refinement indicates that Ba3GdNa(PO4)3F crystallizes in a hexagonal crystal system with the space group P-6. For the co-doped Ba3GdNa(PO4)3F:Ce3+,Tb3+ samples, the emission color can be tuned from blue to green by varying the doping concentration of the Tb3+ ions. The intense green emission was realized in the Ba3GdNa(PO4)3F:Ce3+,Tb3+ phosphors on the basis of the highly efficient energy transfer from Ce3+ to Tb3+. Also the energy transfer mechanism has been confirmed to be quadrupole–quadrupole interaction, which can be validated via the agreement of critical distances obtained from the concentration quenching (13.84 Å). These results show that the developed phosphors may possess potential applications in near-ultraviolet pumped white light-emitting diodes.  相似文献   

10.
Lu3Al5O12:Ce3+ phosphor powder, which exhibits green emission band, was synthesized by the high-temperature solid-state reaction method with a flux BaF2. X-ray diffraction (XRD), photoluminescence (PL) spectra, and fluorescent lifetime spectra were used to characterize the structure and luminescent properties of the sample. The XRD patterns indicated that when prepared at 1550 °C for 3 h with 4 wt% flux, Lu3Al5O12:Ce3+ phosphors powder is the garnet cubic crystal system structure. Photoluminescence (PL) spectra showed that the Lu3Al5O12:Ce3+ phosphor powder can be effectively excited by near ultraviolet and blue light, emitting broad band peaking at 505 nm, which is attributed to 2F5/2?→?2D5/2 transition. The self-concentration quenching mechanism of Ce3+ is the dipole–dipole interaction. Small amount of Pr3+ increased red light emission at 610 nm. Photoluminescence (PL) spectra and fluorescent lifetime spectra indicated that there was an efficient energy transfer process between Ce3+ and Pr3+.  相似文献   

11.
The near-infrared (NIR) long persistent phosphors have gained considerable attention owing to the potential applications in in vivo imaging. A novel NIR long-persistent phosphors Zn3Al2Ge3O12:Cr3+ was successfully synthesized by a high temperature solid-state reaction. The luminescent properties and the afterglow behaviors of the Zn3Al2Ge3O12:Cr3+ were investigated in detail. On the basis of thermoluminescence analyses, the mechanism of the persistent afterglow of the phosphors was also discussed briefly. The afterglow duration of this phosphor can last more than 12 h with the 650–750 nm emission range after stoppage of 254 nm ultraviolet light irradiation. Specifically, the persistent luminescence intensity and duration were regulated by changing Cr3+ doping concentration. All the results indicate that the Cr3+ activated Zn3Al2Ge3O12 has promising potential of practical applications.  相似文献   

12.
A series of polycrystalline Na4Ca4(Si6O18):Eu3+ orange emitting phosphors were synthesized by a conventional high-temperature solid-state reaction. The phase formation was confirmed by X-ray power diffraction analysis. The excitation spectra show a strong host absorption indicating an efficient energy transfer process from O2? to Eu3+ ions. Upon NUV radiation, the phosphors showed strong red emission around 610 nm (5D0 → 7F2) and orange emission around 591 nm (5D0 → 7F1), but the 5D1,2,3 emission nearly can not be seen. Compared with the luminescence properties of Li+, Na+, and K+ co-doped samples, we deduced that Na+ ions probably prefer to dope into the intrinsic Na vacancies rather than Ca2+ ions vacancies in Na4Ca4(Si6O18) crystal. Thermal stability properties, quantum efficiency and chromaticity coordinates of the phosphors have been investigated for the potential application in white LEDs.  相似文献   

13.
The ultraviolet (UV)-emitting Sr3P4O13:Ce3+ phosphors were synthesized via the solid-state reaction method, and their structural, morphological and luminescence properties were characterized by X-ray diffraction analysis, scanning electron microscopy, photoluminescence spectroscopy. The obtained results indicate that these phosphors can be effectively excited by short-wavelength ultraviolet (<300 nm), and exhibit long-wavelength ultraviolet (300–380 nm) emission with nanosecond-level fluorescence lifetime corresponding to the parity-allowed 5d–4f transitions of Ce3+. The concentration-quenching phenomenon of Ce3+ in Sr3P4O13 host was also studied, in which the critical energy transfer distance between Ce3+ ions and concentration quenching mechanism were determined.  相似文献   

14.
The SrLa2?xO4:xEu3+ phosphors are synthesized through high-temperature solid-state reaction method at 1473 K with various doping concentration. Their phase structures, absorption spectra, and luminescence properties are investigated by X-ray diffraction (XRD), UV–Vis spectrophotometer and photoluminescence spectrometry. The intense absorption of SrLa2?xO4:xEu3+ phosphors have occurred around 400 nm. The prominent luminescence spectra of the prepared phosphors exhibited bright red emission at 626 nm. The doping concentration 0.12 mol% of Eu3+ is shown to be optimal for prominent red emission and chromaticity coordinates are x?=?0.692, y?=?0.3072. Considering the high colour purity and appropriate emission intensity of Eu3+ doped SrLa2O4 can be used as red phosphors for white light emitting diodes (WLEDs).  相似文献   

15.
The luminescent properties of CdI2, CdI2:Pb2+, CdI2:Mn2+, and CdI2:Pb2+,Mn2+) crystals have been studied at temperatures from 85 to 295 K under optical and x-ray excitation. Analysis of new and earlier spectroscopic data suggests that the 560-nm luminescence of CdI2:Pb2+ and CdI2:(Pb2+,Mn2+) crystals under excitation on the long-wavelength component of the A absorption band of Pb2+ centers is due to Pb2+-bound anion excitons. The 640-to 660-nm emission of these crystals is attributable to α centers. The manganese luminescence in the codoped material originates from both intracenter Mn2+ excitations and a sensitized process due to energy transfer from the host and Pb2+-related centers. The mechanisms of recombination and energy transfer processes in cadmium iodide crystals codoped with Pb2+ and Mn2+ are discussed.  相似文献   

16.
Polycrystalline Al5O6N samples have been prepared by sol–gel synthesis followed by carbothermal reduction and nitridation. X-ray luminescence (XRL) spectra and thermoluminescence (TL) curves of Ce3+- and Eu2+-doped aluminum oxynitride have been measured in the temperature range 5–380 K and analyzed. Working TL peaks have been detected in the range 150–250 K for the Al5O6N:Ce3+ sample and in the range 140–200 K for the Al5O6N:Eu2+ samples. There are also lower temperature peaks: in the ranges 10–60 and 20–100 K. The XRL spectra of the samples have been measured at temperatures of 8 (for the first time) and 300 K.  相似文献   

17.
Bluish green emitting phosphor, Ca3Al2O6:Ce3+, is prepared by low-temperature combustion method. X-ray diffraction, photoluminescence, scanning electron microscopy techniques are used to characterize the synthesized phosphor. The most efficient bluish green (483 nm) emission is observed under the excitation by near UV light. The emission characteristics are credited to 5d → 4f type transitions in Ce3+. The luminescence properties of Eu2+ are predicted for the first time from those of Ce3+. Also, photoluminescence of Eu3+ is studied in the same host. The emission spectrum of Ca3Al2O6:Eu3+ shows the peak at 592 (orange) and 614 nm (red) wavelengths. Ca3Al2O6:Ce3+phosphor can be a potential blue phosphor for field emission display, solid-state lighting and LED.  相似文献   

18.
The roentgenoluminescence spectra, temperature-dependent activator luminescence, optically stimulated luminescence, and the effect of IR irradiation on the yield and spectral composition of the low-temperature roentgenoluminescence and thermoluminescence curves of the Y3Al5O12:Ce3+ scintillator have been studied in the temperature range 85–295 K. The results, coupled with earlier data, suggest that the Ce3+ ions in the garnet crystal studied form Ce3+ p hole centers and increase the concentration of electronic F ?-centers responsible for the IR stimulation band at 940 nm. The reduction in roentgenoluminescence yield on cooling Y3Al5O12:Ce3+ to below 230 K is due to the significant localization of excited carriers at defects, which show up in thermoluminescence peaks and optical stimulation spectra. The low-temperature Ce3+ luminescence in Y3Al5O12:Ce3+ seems to result from the recombination of activator-bound excitons.  相似文献   

19.
Compound CaAl4O7 (CA4), SrAl4O7 (SA4), CaAl12O19 (CA12) and SrAl12O19 (SA12) have been synthesized by using single step combustion method. The phosphors have been characterized by XRD, SEM and PL techniques. Both CA4 and SA4 possess monoclinic crystal structure whereas CA12 and SA12 possess hexagonal structure. Effects of crystal symmetry on the emission spectrum have been studied by doping the samples with Ce3+ and Eu2+ ions. The luminescence properties of Ce3+ and Eu2+ in these hosts is discussed on the basis of their covalent character and the crystal field splitting of the d-orbital of dopant ions. The spectroscopic properties, crystal field splitting, centroid shift, red shift and stokes shift have been studied. Spectroscopic properties of Eu2+ ions have been accurately predicted from those of Ce3+ ions in the same host. Most importantly experimental results were matched excellently with the calculated results. The preferential substitution of Ce3+ and Eu2+ at different Ca2+, Sr2+ crystallographic sites have been discussed. The dependence of emission wavelengths of Ce3+ and Eu2+ on the local symmetry of different crystallographic sites was also studied by using Van Uitert’s empirical relation. Differences in the emission spectrum of these samples have been observed despite their similar crystal structures and space group. Possible reasons have been discussed.  相似文献   

20.
BaAl2O4:Eu2+,RE3+ (RE3+=Y, Pr) down conversion nanophosphors were prepared at 600 °C by a rapid gel combustion technique in presence of air using boron as flux and urea as a fuel. A comparative study of the prepared materials was carried out with and without the addition of boric acid. The boric acid was playing the important role of flux and reducer simultaneously. The peaks available in the XPS spectra of BaAl2O4:Eu2+ at 1126.5 and 1154.8 eV was ascribed to Eu2+(3d 5/2) and Eu2+(3d 3/2) respectively which confirmed the presence of Eu2+ ion in the prepared lattice. Morphology of phosphors was characterized by tunneling electron microscopy. XRD patterns revealed a dominant phase characteristics of hexagonal BaAl2O4 compound and the presence of dopants having unrecognizable effects on basic crystal structure of BaAl2O4. The addition of boric acid showed a remarkable change in luminescence properties and crystal size of nanophosphors. The emission spectra of phosphors had a broad band with maximum at 490–495 nm due to electron transition from 4f 65d 1 → 4f 7 of Eu2+ ion. The codoping of the rare earth (RE3+=Y, Pr) ions help in the enhancement of their luminescent properties. The prepared phosphors had brilliant optoelectronic properties that can be properly used for solid state display device applications.  相似文献   

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