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1.
《Ceramics International》2016,42(15):16659-16665
In this paper, a series of Ce3+ doped Sr2MgAl22O36 (SMA) phosphors have been prepared by high temperature solid-state reaction method. The phase structure of prepared samples was checked by the powder X-ray diffraction (XRD). The morphology of the samples was inspected using a field-emission scanning electron microscope (SEM). Under different UV radiation, this phosphor exhibits different emission bands due to the Ce3+ ions located at different lattice sites. The corresponding luminescence and energy transfer mechanisms have been proposed in detail. The phosphor exhibits different concentration quenching mechanisms because the Ce3+ ions substitute two different crystallographic sites in the host. Moreover, the temperature dependent emission properties of SMA:Ce3+ were conducted from 30 °C to 200 °C, as much as 72.96% of the room-temperature emission intensity is retained at 150 °C. The SMA:Ce3+ phosphor exhibits bright blue emission with CIE coordinates (x=0.16, y=0.12) under UV excitation. The results indicate that SMA:Ce3+ phosphor has great potential applications in UV-pumped light emitting diodes.  相似文献   

2.
《Ceramics International》2017,43(13):9838-9845
The structural and luminescent properties of Eu3+ doped TiO2 nanophosphors synthesized by low cost combustion method were investigated. The X-ray diffraction analysis revealed that crystallite size decreases with doping concentration. Lattice volume expansion occurred due to the substitution of Ti4+ ions by larger ionic radii ions Eu3+. FESEM images showed prepared phosphors to be nano size spherical shaped particles. Energy band gap of 3 mol% Eu3+ doped samples decreased to 3.15 eV due to doping effect. The Eu3+ doped TiO2 nanophosphors exhibited main red emission peak centered at 616 nm under 395 nm UV light excitation. Concentration quenching was observed at 3 mol% doping, that has been ascribed to dipole-dipole interaction. The covalent nature of Eu-O bond and environment around Eu3+ ions were discussed using Judd-Ofelt (J-O) intensity parameters. Internal quantum efficiency was calculated using excited state lifetime 5D0 state of Eu3+ ion and J-O theory. The CIE colour coordinates and colour purity were calculated using the spectral energy distribution function. Low excited state life time indicated that Eu3+ doped TiO2 can be used as red emitting phosphor for white light emitting diode applications.  相似文献   

3.
《Ceramics International》2015,41(7):8801-8808
Gd2O3:Dy3+ Al3+ phosphors is synthesised by a wet-chemical method for various concentrations of Al3+ ion. X-ray diffraction, photoluminescence and impedance spectroscopy are used to understand the physio-chemical properties of the phosphors. The emission spectra of Dy3+ ion exhibit transition peaks centred at 572 nm (yellow), 486 nm (blue) and 669 nm (red). Energy transfer from Gd3+ to Dy3+ is also verified by exciting the phosphors at 274 nm. Some of the Dy3+ ions occupy both C2 and S6 site of Gd3+ ion in Gd2O3 matrix. It is also revealed that the enhancement of Dy3+ emission is strongly correlated to the surface morphology of the phosphors. Introducing Al3+ ions in Gd2O3:Dy3+ phosphor affect the emission properties of Dy3+ ions and its influence is explored at various concentration of Al3+ ions. The energy level diagram is presented to explain the cross-relaxation process among Dy3+ ions and the energy transfer from Gd3+ to Dy3+ ion.  相似文献   

4.
《Ceramics International》2017,43(18):16622-16627
Trivalent dysprosium (Dy3+) ions -doped calcium silicate (Ca2SiO4) phosphors have been synthesized by utilizing agricultural waste of egg shell and rice husk through solid-state reaction method. The synthesized Ca2SiO4 powders thus obtained are crystallized in monoclinic structure with unit cell parameters of a = 5.53 Å; b = 6.67 Å; c = 9.13 Å; β = 87.43° and irregular shape morphology. Luminescent properties of Dy3+:Ca2SiO4 phosphors were studied by varying active ion concentration. The phosphors emit characteristic blue and yellow emissions of Dy3+ ions corresponding to the 4F9/26H15/2 and 4F9/26H13/2 transitions, respectively. Color coordinates evaluated from emission spectra are found to fall in the white light region. Decay curves for the 4F9/2 level of Dy3+ ions exhibit single exponential nature and turn into non-exponential with shortening of lifetime from 739 µs to 510 µs when Dy3+ ion concentration is increased from 0.001 to 0.5 mol%. All these results confirm that Ca2SiO4:Dy3+ phosphors are suitable for the use as low cost white light emitting phosphors.  相似文献   

5.
Ce3+ and Tb3+ co-doped Sr2B2O5 phosphors were synthesized by the solid-state method. X-ray diffraction (XRD) was used to characterize the phase structure. The luminescent properties of Ce3+ and Tb3+ co-doped Sr2B2O5 phosphors were investigated by using the photoluminescence emission, excitation spectra and reflectance spectra, respectively. The excitation spectra indicate that this phosphor can be effectively excited by near ultraviolet (n-UV) light of 317 nm. Under the excitation of 317 nm, Sr2B2O5:Ce3+,Tb3+ phosphors exhibited blue emission corresponding to the fd transition of Ce3+ ions and green emission bands corresponding to the ff transition of Tb3+ ions, respectively. The Reflectance spectra of the Sr2B2O5:Ce3+,Tb3+ phosphors are noted that combine with Ce3+ and Tb3+ ion absorptions. Effective energy transfer occurred from Ce3+ to Tb3+ in Sr2B2O5 host due to the observed spectra overlap between the emission spectrum of Ce3+ ion and the excitation spectrum of Tb3+ ion. The energy transfer efficiency from Ce3+ ion to Tb3+ ion was also calculated to be 90%. The phosphor Sr2B2O5:Ce3+,Tb3+ could be considered as one of double emission phosphor for n-UV excited white light emitting diodes.  相似文献   

6.
《Ceramics International》2016,42(5):6115-6120
Ce3+ and Tb3+ singly doped and co-doped GdAl3(BO3)4 phosphors were synthesized by solid state reaction. The crystal structure, the luminescent properties, the lifetimes and the temperature-dependent luminescence characteristic of the phosphors were investigated. Through an effective energy transfer, the emission spectra of GdAl3(BO3)4:Ce3+, Tb3+ phosphor contains both a broad band in the range of 330–400 nm originated from Ce3+ ions and a series of sharp peaks at 484, 541, 583, and 623 nm due to Tb3+ ions. The energy transfer from Ce3+ to Tb3+ in GdAl3(BO3)4 host is demonstrated to be phonon assisted nonradiative energy transfer via a dipole–dipole interaction.  相似文献   

7.
《Ceramics International》2016,42(15):16626-16632
A series of Ce3+ doped and Ce3+/Mn2+ co-doped calcium zirconium silicate CaZrSi2O7 (CZS) phosphors have been synthesized via conventional high temperature solid state reactions. The luminescence properties, energy transfer between Ce3+ and Mn2+ have been investigated systematically. Under 320 nm excitation, the phosphor CZS: 0.05Ce3+ exhibit strong blue emission ranging from 330 nm to 500 nm, attributed to the spin-allowed 5d-4f transitions of Ce3+ ions. There are two different emission centers of Ce3+ ions, Ce3+(I) and Ce3+(II). The emission spectra of Ce3+, Mn2+ co-doped phosphors shows a broad emission around 550 nm corresponding to the 4T1(4G)-6A1(6S) spin-forbidden transition of Mn2+. The energy transfer between Ce3+ and Mn2+ is detected and the transfer efficiency of Ce3+(II) to Mn2+ is faster than that of Ce3+(I) to Mn2+. The resonant type is identified via dipole-dipole mechanism. Additionally, a blue-shift emission of Ce3+ and a red-shift emission of Mn2+ have been observed following the increase of Mn2+ content in relation to the energy transfer. Thermal quenching has been investigated and the emission spectra show a blue-shift with the temperature increases, which have been discussed in details. CZS: 0.05Ce3+, yMn2+ phosphors can be tuned from blue to white and even to yellow by adjusting the Mn2+ content. All the results indicate that CZS: Ce3+, Mn2+ phosphor have a potential application for near-UV LEDs.  相似文献   

8.
《Ceramics International》2017,43(15):12044-12056
Perovskite type titanate phosphors Sr0.97−xDy0.03LixTi1−xNbxO3, Sr0.9−xDyxLi0.1Ti0.9Nb0.1O3 and Sr0.87−yDy0.03EuyLi0.1Ti0.9Nb0.1O3 were prepared by conventional solid state method. Herein, white light emission from Sr0.9−xDyxLi0.1Ti0.9Nb0.1O3 phosphors and the lowering of its color temperature through codoping with Eu3+ ions are reported. Raman measurements have shown that the incorporation of dopants alters the vibrational properties of these phosphors significantly, indicating the reduction of the local symmetry in the crystal lattice. The addition of LiNbO3 in SrTiO3:Dy3+ phosphor enhances the luminescence intensity and the yellow to blue ratio resulting in emission of high quality white light with color coordinates corresponding to that of standard white. Life time measurements and data fits of Sr0.9−xDyxLi0.1Ti0.9Nb0.1O3 phosphors revealed the biexponential behaviour of luminescence decay profiles. From Judd-Ofelt analysis it is found that the intensity parameter Ω2 increases with Dy3+ concentration and a quantum efficiency of 90.4% was obtained for optimum concentration. In the case of Dy3+ and Eu3+ codoped phosphors, the color coordinates are found to be sensitive to the Eu3+ concentration and the highest energy transfer efficiency of 92% was obtained for the phosphor doped with 10 mol% Eu3+. The emission color changes from cold white to reddish orange when the wavelength of excitation alters from 452 to 388 nm, since the energy transfer mechanism alone take place under 452 nm excitation and both direct absorption and the energy transfer mechanism occurs under 388 nm excitation.  相似文献   

9.
In this work, we prepared CaSr1-xAl2SiO7:xCe3+ (0.03 ≤ x ≤ 0.12) and CaSr0.94Al2SiO7:0.03Ce3+,0.03 M+ (M+ = Li+ and Na+) phosphors via solid-state reaction method. Structural and photoluminescence (PL) properties of the phosphors were also investigated. The prepared phosphors formed an orthorhombic crystal structure with the P212121 space group. CaSr1-xAl2SiO7:xCe3+ phosphors were effectively excited by near-ultraviolet (UV) light (345 nm), which is suitable with the emission of near-UV light emitting diode chips. A broad blue emission (402 nm) was detected in CaSr1-xAl2SiO7:xCe3+ and CaSr0.94Al2SiO7:0.03Ce3+,0.03 M+ phosphors; this was attributed to the 4f05d1 → 4f1 transition of Ce3+. To maintain charge equilibrium, charge compensators, such as monovalent Li+ and Na+ ions, were doped into the CaSr0.97Al2SiO7:0.03Ce3+ phosphor, significantly improving its PL properties. The strongest emission intensity was achieved in CaSr0.94Al2SiO7:0.03Ce3+,0.03Li+ phosphor. Addition of Li+ charge compensator was highly effective in improving PL properties of CaSr0.97Al2SiO7:0.03Ce3+ phosphors.  相似文献   

10.
《Ceramics International》2015,41(7):8988-8995
A series of white-light-emitting phosphors of single-phase Ba2Mg(BO3)2:Ce3+, Na+, Tb3+, Eu2+ were synthesized by conventional solid-state reaction. The crystal structure of the host was characterized by X-ray diffraction and investigated by Rietveld refinement. Photoluminescence properties were studied in detail. The energy transfer from Ce3+ to Tb3+ in Ba2Mg(BO3)2 host was investigated and demonstrated to be a resonant type via a quadrupole–quadrupole mechanism. White light with wavelength tunable was realized by coupling the emission bands peaking at 417, 543 and 626 nm attributed to Ce3+, Tb3+ and Eu2+, respectively. By properly tuning the relative composition of Ce3+(Na+)/Tb3+/Eu2+, optimized Commission Internationale de l׳Eclairage (CIE) chromaticity coordinates (0.363, 0.295), high color rendering index (CRI) 90 and low correlated color temperature (CCT) 3793 K were obtained from the phosphor of Ba1.90Ce0.04Na0.04Eu0.02Mg0.94Tb0.06(BO3)2 upon the excitation of 296 nm UV radiation. These results indicate that Ba2Mg(BO3)2:Ce3+, Na+, Tb3+, Eu2+ phosphor has a potential application as an UV radiation down-converting phosphor in white-light-emitting diodes.  相似文献   

11.
Hexagonal Ho3+ doped NaYbF4 phosphors are synthesized via a hydrothermal method. The influence of Gd3+ and Ce3+ content on the phase structure and upconversion (UC) emission of NaYbF4 phosphors is investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM) and UC spectra. The results of XRD and TEM indicate that the solubility of Ce3+ in hexagonal NaYbF4 is low due to the large difference of ionic radius between Ce3+ and Yb3+. With help of Gd3+ co-doping (15 mol%), pure hexagonal NaYbF4 phosphors with high doping concentration of Ce3+ (15 mol%) and small crystal size are obtained. When excited by a 980 nm laser diode, Ho3+ doped hexagonal NaYb0.85Gd0.15F4 phosphors exhibit strong green UC emission at 540 nm and weak red one at 646 nm. UC luminescence tuning from green emission to red emission is observed in hexagonal Ho3+ doped NaYb0.85Gd0.15F4 phosphors by co-doping with Ce3+ ions. The UC luminescence tuning phenomenon is attributed to two resonant energy transfer processes of 5S2/5F4(Ho3+)+2F5/2(Ce3+)→5F5(Ho3+)+5F7/2(Ce3+) and 5I6(Ho3+)+2F5/2(Ce3+)→5I7(Ho3+)+5F7/2(Ce3+) between Ho3+ and Ce3+, which suppress the green emission at 540 nm, while promote the red one at 646 nm.  相似文献   

12.
《Ceramics International》2016,42(5):6094-6099
Dy3+/Tb3+ codoped CaMoO4 phosphors were synthesized by a simple sol–gel method and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and photoluminescence spectroscopy. The energy transfer process of Dy3+→Tb3+ was confirmed by excitation and emission spectra and luminescence decay curves, and the energy transfer efficiency was also estimated. The results verified that the efficient emission of Tb3+ was sensitized by Dy3+ under the excitation of 354 nm, realizing tunable emission in CaMoO4 phosphors. Furthermore, optical thermometry was achieved by the fluorescence intensity ratio between Tb3+: 5D47F5 (~546 nm) and Dy3+: 4F9/26H13/2 (~575 nm). It is expected that the investigated CaMoO4 nanograins doped with Dy3+/Tb3+ have prospective applications in display technology and optical thermometry.  相似文献   

13.
14.
Tunable full color emissive LiSr3.99?xDy0.01(BO3)3:xEu3+ (0≤x≤0.09) phosphors peaked at 481 nm (blue), 574 nm (yellow), 592 nm (orange), and 617 nm (red) were synthesized in air by high temperature solid-state reaction route. The as-synthesized phosphors were characterized by X-ray powder diffraction (XRD), photoluminescence excitation (PLE) and photoluminescence (PL) spectra. The PLE spectra in the range from 200 to 500 nm include an Eu–O charge transfer band (CTB) and several 4f–4f transition peaks of Dy3+ and Eu3+, indicating its potential application in white light emitting diodes (LEDs). The effect of Eu3+ concentration on the emission intensity of LiSr3.99?xDy0.01(BO3)3:xEu3+ phosphors was investigated in detail and the optical concentration is found to be x=0.005. The CIE chromaticity coordinates for LiSr3.99?xDy0.01(BO3)3:xEu3+ phosphors are simulated. With an increase in Eu3+ ion concentration, the chromaticity color coordinates can be tuned efficiently from the border of greenish white region to its equal-energy white light point, and eventually to red region. All the results imply that the studied LiSr3.99?xDy0.01(BO3)3:xEu3+ phosphors could be potentially used as white LEDs.  相似文献   

15.
Using the solid‐state reaction method, Ce3+,Tb3+‐coactivated Si5AlON7 (Si6?zAlzOzN8?z, = 1) phosphors were successfully synthesized. The obtained phosphors exhibit high absorption and strong excitation bands in the wavelength range of 240–440 nm, matching well with the light emitting‐diode (LED) chip. The ET from Ce3+ to Tb3+ ions in Si5AlON7:Ce3+,Tb3+ has been studied and demonstrated by the luminescence spectra and decay curves. Moreover, the phosphors show tunable emissions from blue to green by tuning the relative ratio of the Ce3+ to Tb3+ ions. Thermal quenching properties of Si5AlON7:Ce3+,Tb3+ had also been investigated and the quenching temperature is ~190°C. These results show that Si5AlON7:Ce3+,Tb3+ could be a promising candidate for a single‐phased color‐tunable phosphor applied in UV‐chip pumped LEDs.  相似文献   

16.
《Ceramics International》2017,43(11):8497-8501
Single-component white-emitting Sr3Y(PO4)3:Dy3+ phosphors were synthesized by a high-energy deformation process. X-ray diffraction patterns showed the resulting crystallized phase to be of cubic structure, space group I-43d (no. 220). The broad-band excitation spectra between 250 and 500 nm were observed by monitoring the emission wavelength at 576 nm, which matches well with commercial near-UV or blue LED chips. Under a 352 nm excitation, the emission peaks were observed at 483 nm (blue), 576 nm (yellow), and 666 nm (red), corresponding to the 4F9/26H15/2, 4F9/26H13/2, and 4F9/26H11/2 transitions of Dy3+ ions. The optimized doping concentration of Dy3+ ion was 8 mol%. By controlling the Dy3+ ion concentration, tunable colors from white to yellow were obtained in Sr3Y(PO4)3:Dy3+ phosphors. These results reveal that studied materials may be a promising candidate for white LED applications.  相似文献   

17.
《Ceramics International》2015,41(4):5830-5835
Trivalent dysprosium doped strontium aluminates (SrA12O4:Dy3+) were synthesized by firing the sol–gel at 600, 700 and 800 °C. The morphology, crystal structure, photoluminescence and long afterglow of the synthesized SrAl2O4:Dy3+ phosphors were characterized with scanning electron microscopy, X-ray diffraction, energy-dispersive X-ray spectroscopy and photoluminescence spectroscopy, respectively. It is found that SrA12O4:Dy3+ phosphors exhibit broadband afterglows with its peak at about 510 nm. As the sol–gel synthesis temperature increases from 600 to 800 °C, the green afterglow of the SrA12O4:Dy3+ phosphors becomes weaker in intensity and shorter in lifetime. The results are discussed in terms of thermally generated point defects in the host material.  相似文献   

18.
《Ceramics International》2016,42(12):13841-13848
A series of Eu3+- or Dy3+-doped and Eu3+/Dy3+ co-doped Y2WO6 in pure phase was synthesized via high-temperature solid-state reaction. X-ray diffraction, diffuse reflection spectra, photoluminescence excitation and emission spectra, the CIE chromaticity coordinates and temperature-dependent emission spectra were exploited to investigate the phosphors. Upon UV excitation at 310 nm, efficient energy transfer from the host Y2WO6 to dopant ions in Eu3+ or Dy3+ single-doped samples was demonstrated and those phosphors were suitable for the UV LED excitation. The intense red emission was observed in Y2WO6: Eu3+, and blue and yellow ones were observed in Y2WO6: Dy3+. Concentration quenching in Y2WO6: Dy3+ phosphors could be attributed to the electric dipole-dipole interaction. In Eu3+/Dy3+ co-doped Y2WO6 phosphors energy transfer process only took place from the host to Eu3+/Dy3+ ions and warm white-light emission can be obtained by adjusting the dopant concentrations. The temperature-dependent luminescence indicated Eu3+/Dy3+ co-doped Y2WO6 was thermally stable. Our overall results suggested that Y2WO6: Ln3+ (Ln3+=Eu3+, Dy3+) as warm white-light emitting host-sensitized phosphor might be potentially applied in WLEDs.  相似文献   

19.
《Ceramics International》2017,43(12):9158-9163
In this account, Bi4Si3O12:Sm3+ and (Bi4Si3O12:Sm3+, Pr3+) red phosphors were prepared by solution combustion method fueled by citric acid at 900 °C for 1 h. The effects of co-doping Pr3+ ions on red emission properties of Bi4Si3O12:Sm3+ phosphors, as well as the mechanism of interaction between Sm3+ and Pr3+ ions were investigated by various methods. X-ray diffraction (XRD) and Scanning electron microscopy (SEM) revealed that smaller amounts of doped rare earth ions did not change the crystal structure and particle morphology of the phosphors. The photoluminescence spectroscopy (PL) indicated that shape and position of the emission peaks of (Bi4Si3O12:Sm3+, Pr3+) phosphors excited at λex=403 nm were similar to those of Bi4Si3O12:Sm3+ phosphors. The strongest emission peak was recorded at 607 nm, which was attributed to the 4G5/26H7/2 transition of the Sm3+ ion. The photoluminescence intensities of Bi4Si3O12:Sm3+ phosphors were significantly improved by co-doping with Pr3+ ions and were maximized at Sm3+ and Pr3+ ions doping concentrations of 4 mol% and 0.1 mol%, respectively. The characteristic peaks of Sm3+ ions were displayed in the emission spectra of (Bi4Si3O12:Sm3+, Pr3+) phosphors excited at respectively λex=443 nm and λex=481 nm (Pr:3H43P2, 3H43P0). This indicated the existence of Pr3+→Sm3+ energy transfer in (Bi4Si3O12:Sm3+, Pr3+) phosphors.  相似文献   

20.
《Ceramics International》2017,43(16):13602-13611
K+ ions incorporated perovskite Ba(1−x)TiO3:x Eu3+ red emitting phosphors synthesized via facile solid -state reaction method has been investigated in the current study. The photoluminescence and decay time behavior of Ba(1−x−y)TiO3:x Eu3+,yK+ phosphors are investigated as a function of Eu3+, K+ concentration and temperature. An intense and sharp emission peak at 615 nm was exhibited by the phosphors upon excitation at 397 nm (7F05L6). It can be credited to the hypersensitive electric dipole transition 5D07F2, which confirms that Eu3+ ions are located at non-centrosymmetric site of the host. The incorporation of K+ ions in optimized Ba0.95TiO3:0.05 Eu3+ phosphor resulted in a remarkable enhancement of photoluminescence intensity by 2.33 times as compared to bare one. The Ba0.89TiO3:0.05 Eu3+, 0.06 K+ phosphors were found to observe good temperature sensing along with adequate thermal stability even at 427 K. Furthermore, the photometric parameters have been also studied which are strongly facilitate the prepared ceramic samples as suitable for potential application in lighting.  相似文献   

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