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1.
A series of magnesium borate phosphors MgB4O7:Dy, MgB4O7:Mn and MgB4O7:Dy,Mn were prepared and their ther-moluminescence (TL) emission spectra were measured. TL emission bands in 480, 575 and 660 nm at 200 and 360 oC were observed in the MgB4O7:Dy due to the transitions of the trivalent rare earth ions Dy3+. The glow peaks of broad wavelength band around~580 nm at 180 and~290 oC were observed in MgB4O7:Mn due to the emission of Mn2+ions. The main glow peak of MgB4O7 co-doped with Dy and Mn appeared in 580 nm at~360 oC. When MgB4O7 was co-doped with Dy (0.5 mol.%) and different concentrations of Mn (0.01 mol.%-1.0 mol.%), the peak in 580 nm at 360 °C was intensified and broadened as the concentration of Mn increased, while the peaks in 480, 680 and 750 nm below 300 °C remained the characteristic emission of Dy3+and were reduced in intensity. The emission spectra of the MgB4O7:Dy,Mn phosphor showed that the competitive de-excitation processes between Dy3+and Mn2+existed and the energy transfer occurred from Dy3+to Mn2+. These results meant that rare earth and Mn ions in MgB4O7:Dy,Mn might cause the formation of defects complex that dominated the traps and recombination.  相似文献   

2.
Rare earth borogermanates as a group of stable compounds provided various potential properties important for modern sciences. Among the properties of interests, luminescence was manifested due to the variability of rare earth elements and the compounds constituted an important group of potential candidate. In this work, novel phosphors of Eu3+, Tb3+ or Tm3+ doped LaBGeO5 with the stillwellite type structure were synthesized by the solid state reaction method. Their X-ray and UV excitation luminescent properties showed that LaBGeO5 was an excellent host lattice for the luminescence of Eu3+, Tb3+ and Tm3+. The LaBGeO5:Eu3+, LaBGeO5:Tb3+ and LaBGeO5:Tm3+ presented bright red, green and blue emission light for both UV and X-ray excitation.  相似文献   

3.
A novel white-light emitting single-phase phosphor La3Si6N11:Dy3+, exhibiting two emission peaks centering at 475 and 575 nm, was prepared via conventional solid-state reactions. The structure and morphology of La3Si6N11:Dy3+/Tb3+ were investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The emission colors can be tuned from white to yellow-green through increasing the Tb3+ concentration in La3Si6N11:Dy3+,Tb3+. The mechanism of energy transfer (ET) from Dy3+ to Tb3+ is confirmed according to the excitation, emission spectra and decay lifetimes curve. The temperature-dependent luminescence measurements of La2.83Si6N11:0.1Dy3+,0.07Tb3+ were also performed, and a good thermal stability is shown, suggesting superior properties for the application as white light-emitting diodes (w-LEDs) phosphor.  相似文献   

4.
The spectroscopic properties of a series of Dy~(3+) single-doped and Dy~(3+)/Nd~(3+),Dy~(3+)/Tb~(3+),and Dy~(3+)/Tm~(3+)co-doped YAlO_3(yttrium aluminum perovskite,YAP) phosphors were investigated and compared through the measurements of optical absorption,emission spectra,and fluorescence decay curves.For the Dy~(3+) ion single-doped samples,the intensity of each absorption band increases with an increment in Dy~(3+) ion doping concentration,and the identified strong absorption peak at 447 nm indicates that Dy~(3+):YAP phosphors are suitable to be pumped by a blue laser diode(LD).For all co-doped samples,absorption peaks of Dy~(3+) ion along with some of the absorption bands of Nd~(3+),Tb~(3+),and Tm~(3+) ions are observed.Under 351 and 447 nm excitation,a prominent emission peak at 572 nm was obtained in all the samples,corresponding to Dy~(3+):~4 F_(9/2)→~6 H_(13/2) transition.Here,2 at% Dy~(3+):YAP phosphor exhibits the highest yellow emission intensity under 447 nm pumping.Among the three kinds of Dy~(3+) co-doped phosphors,Dy~(3+)/Tb~(3+):YAP phosphor possesses the dominant yellow emission.The fluorescence decay curves show exponential behaviour and are fitted well.The Commission International de L'Eclairage(CIE)chromaticity coordinates were calculated following the respective emission spectra,and it is found that all the coordinates locate in the yellow region.The energy transfer(ET) processes were investigated and the concentration quenching mechanism was discussed.The obtained results suggest that Dy~(3+)-activated YAP phosphors are good candidates for yellow LED applications.  相似文献   

5.
In this paper, the Gd2O3:Eu3+,Tb3+phosphors with different doping concentrations of Eu3+and Tb3+ions were prepared by a hydrothermal method for nanocrystals and the solid-phase method for microcrystals. The interaction of the doped ions with different concentrations and the luminescent properties of the nanocrystals and microcrystals were studied systematically. Their structure and morphology of Gd2O3:Eu3+,Tb3+phosphors were analyzed by means of X-ray powder diffraction (XRD), transmission electron mi-croscopy (TEM) and scanning electron microscopy (SEM). The photoluminescence (PL) properties of Gd2O3:Eu3+,Tb3+phosphors were also systematically investigated. The results indicated that when the concentration of doped Eu3+was fixed at 1 mol.%, the emis-sion intensity of Eu3+ions was degenerating with Tb3+content increasing, while when the Tb3+content was fixed at 1 mol.%, the emission intensity of Tb3+ions reached a maximum when the concentration of Eu3+was 2 mol.%, implying that the energy transfer from Eu3+to Tb3+took place. In addition, Tb3+could inspire blue-green light and the Eu3+could inspire red light. Therefore co-doping systems by controlling the doping concentration and the hosts are the potential white emission materials.  相似文献   

6.
A series of Ln3+ (Ln3+ = Er3+/Dy3+) ions doped Na2NbAlO5 (NNAO) phosphors were synthesized by solid-state method. The Er3+ and Dy3+ ions doped phosphors were characterized by XRD, photoluminescence (PL) and decay profiles. The Ln3+-doped samples are consistent with the pure NNAO phase which is analyzed by the X-ray diffraction result. The PL graphs show that the intensity of luminescence increases with the increasing doping concentrations up to their critical certain values and then decreases at higher concentrations due to the concentration quenching effect of Er3+/Dy3+ ions. The energy level diagrams containing the positions of 4f and 5d energy levels of Er3+ and Dy3+ ions have been established and studied. In addition, under the ultraviolet light, the prepared NNAO:xLn3+ (Ln3+ = Er3+/Dy3+) phosphors show the characteristic green (Er3+), cyan (Dy3+) emission, respectively. Under the excitation of 365 nm, the quantum efficiencies of NNAO:0.01Er3+ and NNAO:0.03Dy3+ phosphors are measured to be 61.7% and 72.2%, respectively. The obtained results indicate that the new NNAO:xLn3+ (Ln3+ = Er3+/Dy3+) phosphors are promising applications in white-light emitting diodes field.  相似文献   

7.
Rare earth (RE) pentaborates, both α- and β-polymorphs, are good candidates for photoluminescent hosts suitable for various RE activators. Ce3+ acts not only as an activator itself, but also as a sensitizer to other rare earth activators, like in the case of commercial green phosphor CeMgAl11O19:Tb3+. In this work, two solid solutions of β-La0.9–xCe0.1TbxB5O9 (0 ≤ x ≤ 0.15) and β-La0.9–yCe0.1DyyB5O9 (0 ≤ y ≤ 0.07) were prepared by sol–gel method with high crystallinity, and the phase purity was confirmed with careful analyses on powder X-ray diffraction patterns. Energy transfers are expected due to the overlapping of Ce3+ emission with the Tb3+/Dy3+ excitation. Indeed, the steady photoluminescence spectra indicate the decrease of the Ce3+ emission and the increase of the Tb3+/Dy3+ emission, and the fluorescence decay curves exhibit the decrease of the average lifetime of Ce3+. The energy transfer efficiency is estimated to be 60% at x = 0.15 and 55% at y = 0.07, respectively. The mechanism is likely through the dipole–dipole electric interactions for both cases. With this rationale, the Tb3+ and Dy3+ emissions are greatly enhanced, in particular, the white emission of Dy3+ in β-La0.85Ce0.1Dy0.05B5O9 is enhanced by 20 times.  相似文献   

8.
Rare earth ions doped gadolinium oxybromide phosphors GdOBr:RE3+ (RE=Eu, Tb, Ce) were synthesized by the method of solid-state reaction at high temperature, and the VUV-VIS spectroscopic properties of the phosphors were systematically investigated. Under the excitation of VUV or UV source, the phosphors doped with Eu3+ and Tb3+ show a bright and sharp emission at around 620 nm corresponding to the forced electric dipole 5D07F2 transition of Eu3+, and at around 544 nm corresponding to the 5D47F5 transition of Tb3+, respectively. For GdOBr:Ce3+, a broader and intense emission spanned 370–500 nm corresponding to the d-f transition of Ce3+ was observed. The excitation spectra were also analyzed.  相似文献   

9.
CePO4:Tb3+ nanorods were successfully obtained via a simple hydrothermal method and combined with carbon dots (CDs) to obtain CDs@CePO4:Tb3+ nanorods. Due to the combination of CDs, the emission intensity of CDs@CePO4:Tb3+ nanorods increases about 92 times, compared with that of CePO4:Tb3+ nanorods. The combination of CDs and CePO4:Tb3+ nanorods was confirmed by Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and so on. The mechanism of luminescence enhancement may be attributed to some aspects: the formation of hexagonal phase results in the increase of crystal field symmetry, and the energy transfer among CDs, Ce3+ and Tb3+ ions, which causes the Tb3+ ions in CDs@CePO4:Tb3+ nanorods to obtain more excited energy and less non-radiative attenuation compared to CePO4: Tb3+ nanorods. The luminescence enhancement strategy through combination of CDs would provide a simple and effective approach for other rare earth ions doped luminescent materials.  相似文献   

10.
Due to the characteristic emission of phosphors,phosphor-converted LEDs have been employed to provide the requisite light sources for indoor plant growth in the optical agricultural industry.Herein,we prepared a series of Mn2+co-doped NaSrB5 O9:Dy3+phosphors via a solid-state reaction method.These phosphors have significant three-band emissions at 467 nm(blue region),606 nm(orange region),and765 nm(far-red region),ascribed to the4F9/2-6H15/2and 4 F9/2-6 H13/2 transitions of the Dy3+ions and the4T1g(G)-6A1g(S)spin-forbidden transition of the Mn2+ions,respectively,when excited by light of 376 nm(near-UV region).The co-dopant in the host material facilitates tunable photoluminescence(PL)due to energy transfer from the Dy3+ions to the Mn2+ions.The three emission peaks from the prepared phosphors well match with the absorption spectra of the photosynthesis pigments of plants,chlorophyll and phytochrome,which can absorb blue(400-500 nm),orange-red(550-700 nm),and infrared(IR)radiation,indicating that these phosphors have potential applications in the fabrication of plant-growth LEDs.Prior to the PL studies,the structure of the phosphors was determined by X-ray diffraction,refined by Rietveld method and chemically quantified by X-ray photoelectron spectroscopy.  相似文献   

11.
The long afterglow luminescent material SrAl2O4: Eu2+, Dy3+ was prepared by high temperature solid-state method. Effects of doped B on the luminescent properties of phosphors SrAl2O4: Eu2+, Dy3+ were investigated by means of excitation spectra, emission spectra and X-ray diffraction analysis. As the result, the addition of H3BO3 as flux promotes the growth of crystalline and reduces the synthesizing temperature, but the wavelength of emission peak of photoluminescent material did not change with the variation of H3BO3 content. The effect of Dy3+ concentration on the luminescent properties of material was investigated. It was found that the luminescence of phosphors prepared under the condition of the amount of H3BO3 5% and the mole ratio of Eu/Dy = 1/7(Eu = 0.02 mole) had better luminescent property and longer afterglow time.  相似文献   

12.
Nanosized terbium doped Lu2O3 phosphors were synthesized via a modified co-precipitation processing.The as-prepared Tb:Lu2O3 phosphors was consisted of well crystallized nanosized sphere particles with a diameter of about 30 nnx Local structure of Tb ions in Lu2O3 lattice was investigated by an analytical approach based on Fourier transformation of the extended X-ray absorption fine structure(EXAFS) data.X-ray near edge structure (XANES) spectra suggested that all Tb ions doped were tervalonce.EXAFS results indicated that Tb ions have entered the Lu2O3 cubic lattice by means of solid solution.The coordination number and first shell Tb-O distance dropped with the increasing of Tb concentration.Emission spectra of the phosphors was shown to be typical for Tb3+ with main components at 542,550 and 490 nm,derived from irradiative relaxation of 5D4 level.The emission intensity decreased severely with the increasing of Tb concentration from 1 mol.% to 15 tool.%,suggesting a significant concentration quenching above 1 mol.% Tb.The reduction of emission intensity was interpreted by higher distortion derived relaxation among the surface state resident Tb3+ ions.  相似文献   

13.
In this study, novel yellow-emitting fluorophosphate NaCa3Bi(PO4)3F phosphors doped with different concentrations of Dy3+ ions were first obtained via high-temperature solid-state reaction. The crystal structure, phase purity, particle morphology, photoluminescence (PL) properties, thermal stability, and luminescence decay curves of the resulting phosphors were then characterized in detail. Under the excitation of 349 nm, the three dominant peaks of the NaCa3Bi(PO4)3F:Dy3+ are centered at 480 nm (4F9/2-6H15/2), 577 nm (4F9/2-6H13/2), and 662 nm (4F9/2-6H11/2). The optimal doping concentration of Dy3+ ions in the NaCa3Bi(PO4)3F:xDy3+ phosphors is x = 5 mol%. The phosphors show excellent thermal stability with high activation energy (Ea = 0.32 eV). Eventually, the synthesized white light-emitting diode (w-LED) demonstrates the Commission International de L'Eclairage (CIE) chromaticity coordinates of (0.341, 0.334), a good correlated color temperature (CCT) of 5083 K, and a high color rendering index (Ra) of 92. Revealing its potential as yellow-emitting phosphors, the feasibility of the fabricated apatite-type NaCa3Bi(PO4)3F:Dy3+ fluorophosphate phosphors was confirmed for w-LEDs.  相似文献   

14.
Yttrium aluminium garnet(Y_3 Al_5 O_(12):YAG) singly doped with Dy3+ at different concentrations was prepared by solid state reactions using repeated heating cycles over the temperature range of 1300-1600 ℃. X-ray powder diffraction analysis confirms the presence of a well-crystallized YAG perovskite phase with cubic structure(by Rietveld refinement). The rare earth dopant is successfully integrated into the YAG host lattice without any major changes in the original structure. The temperature dependence,up to 250 ℃, of the conductivity, dielectric constant, dielectric loss, and loss tangent, at various frequencies of up to 5.0 MHz for undoped and doped crystals is compared to understand the electrical and structural characteristics. The experimental results reveal that Dy3+ dopants in YAG crystal significantly influence the conductivity, dielectric constant, and lossy mechanisms, which is probably due to the 3 d-AI ions and 4 f-Dy ions incorporated at different positions of both tetrahedral and octahedral symmetries in YAG:xDy3+ ceramics.  相似文献   

15.
The NaYF4:yb3+,Tb3+ (Xyb: 0.20, XTb: 0.04) materials were prepared using the co-precipitation method, lne as-preparea material was washed either with or without water in addition to ethanol and thereafter annealed for 5 h at 500℃. This resulted in materials with moderate or very high up-conversion luminescence intensity, respectively. The structural study carried out with X-ray powder diffraction revealed microstrains in the rare earth (R) sublattice that were relaxed for the material with very high up-conversion intensity thus decreasing energy losses. The local structural details were investigated with R LⅢ and Y K edge ex- tended X-ray absorption fine structure (EXAFS) using synchrotron radiation. Around 10 tool.% of the Yb3+ ions were found to occupy the Na site in the material with very high up-conversion intensity. These Yb species formed clusters with the Tb3+ ions occupying the regular Na/R sites. Such clustering enhanced the energy transfer between Yb3+ and Tb3+ thus intensifying the up-conversion emission.  相似文献   

16.
Novel yellow-emitting phosphors of Dy~(3+)-doped double perovskite Ca_2 MgTeO_6 were synthesized by using a conventional high-temperature solid-state reaction.The phase purity,particle morphology,size distribution,elemental composition,luminescence properties,and luminescence decay curves of the resulting products were then analyzed in detail.The Ca2 MgTeO_6:Dy~(3+),Na~+ phosphors show three emission peaks after near-ultraviolet excitation at 350 nm,which correspond to ~4 F_(9/2)→~6 H_(11/2),~4 F_(9/2)→~6 H_(13/2),and ~4 F_(9/2)→~6 H_(13/2) transitions,respectively.Among them,the strongest peak is observed at 573 nm.The best doping content of Dy~(3+)in Ca_2 MgTeO_6:xDy~(3+),xNa~+ phosphors is x=5 mol%.The calculated critical distance of energy transfer between Dy~(3+) ions is 1.6 nm.Luminescence quenching is confirmed to be due to dipole-dipole interactions among Dy~(3+) ions.The phosphors show excellent thermal stability with high activation energy(0.27 eV).The Commission Internationale de l'Eclairage(CIE) chromaticity coordinates of the Ca_2 MgTeO_6 Dy~(3+),Na~+ phosphors are located in the yellow region.White light-emitting diodes(w-LEDs) were fabricated with a high color rendering index(R_a) of 88 and a good correlated color temperature(CCT) of 5440 K.All observed properties indicate that Ca_2 MgTeO_6:Dy~(3+),Na~+ phosphors have potential applications in display and photonic devices.  相似文献   

17.
A series of CaMoO 4 :xTb 3+(x=0.01,0.03,0.05,0.07,0.09,0.15 and 0.20) phosphors in pure phase were prepared via high temperature solid-state reaction approach.The crystal structure of the phosphors was investigated by X-ray diffraction(XRD),and the optical properties were investigated by Fourier transform infrared spectroscopy(FT-IR),ultraviolet-visible spectroscopy(UV-Vis) and photoluminescence(PL) spectroscopy.The PL spectra illustrated that these phosphors could be efficiently excited by the charge transfer band of the host and the energy transfer efficiency from the host to the doped activator reached 60% when the doping concentration of the activator Tb 3+ was 20 mol.%.The concentration quenching occurred at x=10 mol.%,from which the critical distance of activator was calculated to be about 1.14 nm.The CIE coordinates were estimated to be close to the standard green value.The host sensitized samples had potential application as green phosphors.  相似文献   

18.
A series of Eu2+/Dy3+ single doped and co-doped Na3Sc2(PO4)3 phosphors were synthesized by the high-temperature solid-state method, and their phase, morphology, and luminescence properties were characterized. Under the excitation of 370 nm, the Na3Sc2(PO4)3:Eu2+,Dy3+ phosphor can emit white light whose spectrum is composed of a broad emission band centered at 460 nm and the other three peaks at 483, 577, and 672 nm, respectively. There is energy transfer from Eu2+ to Dy3+ ion in Na3Sc2(PO4)3:Eu2+,Dy3+ phosphor due to the good overlap between the emission spectrum of Na3Sc2(PO4)3:Eu2+ and the excitation spectrum of Na3Sc2(PO4)3:Dy3+, which is further confirmed by the fluorescence lifetime decrease of Eu2+ ion with the increase of Dy3+ concentration. The process of energy transfer is via dipole–quadruple interaction which is confirmed by applying Dexter's theory. By increasing the Dy3+ concentration, the color coordinates of the Na3Sc2(PO4)3:0.01Eu2+,xDy3+ phosphors can be adjusted from blue to white, and then to yellow. The optimized concentration of Dy3+ ions is 4.0 mol%, beyond which the concentration quenching will take place. The Na3Sc2(PO4)3:Eu2+,Dy3+ phosphor shows fairly good resistance to thermal quenching behavior, of which the emission intensity at 423 K can maintain 90.3% of the initial value (298 K). These results suggest that the Na3Sc2(PO4)3:0.01Eu2+,xDy3+ phosphors have potential applications as the color-tunable or a single-phase white emitting phosphor in white LEDs.  相似文献   

19.
At present,the rare earth(RE) ions doped phosphors have attracted more and more attention because of their excellent properties.In this paper,a series of novel blue-purple β-Ca_3(PO_4)_2:Ce~(3+) phosphors were synthesized by a high temperature solid phase method.The X-ray diffraction(XRD),infrared spectrum,energy dispersive spectroscopy(EDS),scanning electron microscopy(SEM),X-ray photoelectron spectroscopy(XPS),photoluminescence excitation and emission spectra were used to investigate the crystal structure,composition and the luminescent properties of the resulting samples.The phosphor shows a strong absorption in the ultraviolet band.Under the excitation of 269 nm,the phosphor emits a strong purple fluorescence ranging from 360 to 520 nm.When Ce~(3+) doping content is 0.07 mol,the strongest luminescence intensity is reached,and the concentration quenching mechanism is dipole-dipole(d-d)interaction for Ce~(3+) based on Dexter theory.  相似文献   

20.
Eu2+ and Dy3+ codoped(Ca,Sr)7(SiO3)6Cl2 yellow phosphors were successfully synthesized by self-flux method. The structure, morphology and photoluminescence properties were investigated by X-ray diffraction(XRD), scanning electron microscopy(SEM) and photoluminescence spectra. The as-prepared phosphor showed a broad emission spectrum centered at 550 nm for Eu2+single-doped phosphor, while located at 548–544 nm for the Eu2+, Dy3+ codoped samples under excitation at 380 nm light. The emission intensity was greatly improved when Dy3+ was doped into the(Ca,Sr)7(SiO3)6Cl2:Eu2+ system. The composition-optimized sample with 3 mol.% of Dy3+ and constant 10 mol.% of Eu2+ exhibited a 220% PL enhancement compared to the phosphor with 10 mol.% Eu2+ single-doped. Meanwhile, it was found that the quantum efficiency of phosphor namely(Ca,Sr)7(SiO3)6Cl2:3 mol.% Dy3+, 10 mol.% Eu2+ could get up to 24.6%. The synthesized yellow-emitting(Ca,Sr)7(SiO3)6Cl2:Dy3+,Eu2+ is a promising candidate as high-efficiency yellow phosphor for NUV-excited white LEDs.  相似文献   

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