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1.
A series of LiGd(MO4)2: Sm3+, Tb3+ (M = Mo, W) phosphors was prepared by a conventional solid state reaction method. Powder X-Ray diffraction (XRD) analysis reveals that the compounds are of the same structure type. Their luminescent properties have been studied. The optimal doping concentrations are 8% for Sm3+ and 18% for Tb3+ in the LiGd(MoO4)2 host. Sm3+ and Tb3+ have different sensitivity to the Mo/W ratio. For LiGd(MoO4)2-X(WO4)X: Sm3+ (X = 0, 0.4, 0.8, 1.2, 1.6, 2.0), the strongest emission intensity is 1.766 times than that of the weakest, while 171 times for LiGd(MoO4)2-X(WO4)X: Tb3+. The experimental results show that Mo/W ratio strong influences on the properties of LiGd(MoO4)2-X(WO4)X: Tb3+. With the increasing of WO42− groups concentration, the shape of characteristic excitation peaks of Tb3+ is almost the same and the excitation intensity gradually increase. Moreover, the energy transfer from Tb3+ to Sm3+ has been realized in the co-doped phosphors. The experimental analysis and theoretical calculations reveal that the quadrupole–quadrupole interaction is the dominant mechanism for the Tb3+→Sm3+ energy transfer. Therefore, luminous intensity can be adjusted by different sensitivities to matrix composition and energy transfer from Tb3+→Sm3+. By this tuning color method, white-light-emitting phosphor has been prepared. The excitation wavelength is 378 nm, and this indicates that the white-light-emitting phosphor could be pumped by near-UV light.  相似文献   

2.
A series of Tm3+ and Dy3+ codoped BaWO4 phosphors with tunable shapes were controllably synthesized by a facile solvothermal method. The effects of ratio of ethylene glycol (EG) and water on the morphologies of BaWO4 structures are systematically studied. It was discovered that the reason for these morphological changes is based on the reaction speed of the kinetic control, which relates to the strong chelating abilities of ethylene glycol. And when the solvent is pure ethylene glycol, the peanut-like BaWO4:Dy3+ has the strongest emission intensity. Moreover, the emission color of the phosphors varied from blue (0.232, 0.180) to white (0.268, 0.250) by controlling Dy3+ ions content with a fixed Tm3+ concentration. The energy transfer mechanism was investigated in detail. With increasing the doped concentration of Dy3+ ions, the energy transfer efficiency of BaWO4:0.005Tm3+,yDy3+ increased gradually and reached as high as 63% when the Dy3+ doped concentration is 0.03. The critical distance RC calculated by the spectral overlap method is about 19.93 Å, and it is in good agreement with that obtained using the concentration quenching method (19.70 Å), indicating that the electric dipole-dipole interaction is the main energy transfer mechanism for BaWO4:Tm3+,Dy3+ phosphors.  相似文献   

3.
Eu3+, Dy3+ and Dy3+/Eu3+ doped CdO-GeO2-TeO2 glasses were prepared using the melt-quenching process and analyzed by X-diffraction, Raman spectroscopy, excitation and emission spectra, and emission decay time profiles. The lack of X ray diffraction peaks revealed that all samples are amorphous. Vibrational modes associated with TeOTe and GeOGe related bonds and molecular oxygen were detected by Raman spectroscopy. The luminescence characteristics were studied upon excitations that correspond with the emission of InGaN (370–420 nm) based LEDs. The Eu3+ singly doped glass displayed reddish-orange global emission, with x = 0.601 and y = 0.349 CIE1931 chromaticity coordinates, upon 393 nm excitation. Neutral emission with x = 0.373 and y = 0.412 CIE1931 chromaticity coordinates and correlated color temperature (CCT) of 4400 K, was achieved in the Dy3+ singly doped glass excited at 388 nm. The Dy3+/Eu3+ co-doped glass exhibited warm, neutral and soft warm white emissions with CCT values of 3435, 4153 and 2740 K, under excitations at 382, 388 and 393 nm, respectively, depending mainly on the Dy3+ and Eu3+ relative excitation. The Dy3+ excitation bands observed in the Dy3+/Eu3+ glass by monitoring the 611 nm Eu3+ emission, suggest that Dy3+ → Eu3+ energy transfer takes place, despite the fact that the Dy3+ emission decays in the Dy3+ and Dy3+/Eu3+ doped glass, remain without changes. The shortening of Eu3+ decay in presence of Dy3+ was attributed to an Eu3+ → Dy3+ non-radiative energy transfer process, which according with the Inokuti-Hirayama model might be dominated through an electric quadrupole-quadrupole interaction, with efficiency and probability of 5.5% and 51.6 s−1, respectively.  相似文献   

4.
MY2(MoO4)4:Sm3+ and MY2(MoO4)4:xSm3+,yEu3+ (M=Ca, Sr and Ba) phosphors were successfully prepared using solid-state reaction route, and their luminescent properties and energy transfer process from Sm3+ to Eu3+ were systematically investigated. The results indicate that MY2(MoO4)4:Sm3+ phosphors can be effectively excited by 407 nm near UV light originating from the 6H5/2 → 4F7/2 transition of Sm3+, and exhibit a satisfactory red emission at 646 nm attributed to the 4G5/2 → 6H9/2 transition of Sm3+, in which the emission intensity of SrY2(MoO4)4:Sm3+ is the strongest among the MY2(MoO4)4:Sm3+ (M=Ca, Sr and Ba) phosphors. For Eu3+ co-doped MY2(MoO4)4:Sm3+ samples, with increasing Eu3+ doping content, the main emission peaks of Sm3+ (approximately 646 nm) are decreased, but the emission peaks and intensity of Eu3+ are increased while the maximum intensity of luminescence at the Eu3+ concentration 0.9. The introduction of Eu3+ in the MY2(MoO4)4:Sm3+ phosphors can remarkably generate a strong emission line at 616 nm, originating from the 5D07F2 transition of Eu3+ and Sm3+ (4G5/2) → Eu3+ (5D0) effective energy transfer process. The energy transfer mechanism from Sm3+ to Eu3+ was discussed in detail.  相似文献   

5.
Vacuum ultraviolet (VUV) spectroscopic properties of rare-earth RE3+- activated (RE3+ = Sm3+, Eu3+, Tb3+ and Dy3+) Ba6Gd9B79O138 borates (BGBO) are investigated. The strong absorption bands in the VUV range of un-doped and RE3+-activated BGBO were observed. The band range from 140 to 200 nm with a peak at about 173 nm results from the host lattice absorption. For Sm3+-activated BGBO, the charge transfer transition from O2- to Sm3+ was observed at 202 nm. In addition, it exhibits bright red emission originating from the Sm3+ f-f transitions of 4G5/26HJ (J = 5/2, 7/2 and 9/2). The O2--Eu3+ charge transfer (CT) at 249 nm is observed in the excitation spectrum for Eu3+-doped BGBO. For Tb3+-activated BGBO, the broad bands around 208 and 230 nm are due to the spin-allowed and spin-forbidden f-d transitions of Tb3+, respectively. In addition, the absence of the f-d transitions of Sm3+ and Dy3+ in the excitation spectra probably due to the photo-ionization effect. It is demonstrated that there are energy transfers from the BGBO host lattice to the luminescent activators depending on the activators.  相似文献   

6.
采用微波固相法制备了CaWO4xEu3+,ySm3+,zLi+红色荧光粉。测量样品的XRD图、激发谱、发射谱及发光衰减曲线,研究并分析了Eu3+、Sm3+、Li+的掺杂浓度,对样品微结构、光致发光特性、能量传递及能级寿命的影响。结果表明,Eu3+、Sm3+、Li+掺杂并未引起合成粉体改变晶相,仍为CaWO4单一四方晶系结构。Eu3+、Sm3+共掺样品中,Sm3+掺杂为3%时,Sm3+对Eu3+的能量传递最有效。Li+掺杂起到了助熔剂和敏化剂的作用,使样品发光更强。在394 nm激发下,与CaWO4:3%Eu3+样品比较,3%Eu3+、3%Sm3+共掺CaWO4及3%Eu3+、3%Sm3+、1%Li+共掺CaWO4样品的发光分别增强2倍及2.4倍。同一激发波长下,单掺Eu3+样品寿命最短,Sm3+、Eu3+共掺样品随Sm3+浓度增加,寿命先减小后增加,且掺杂了Li+的样品比不掺Li+的样品5D0能级寿命有所增加。  相似文献   

7.
Energy transfer from UO22+ to Sm3+ is described. The transfer efficiencies are calculated from the decrease of donor luminescence and lifetimes and from the increase of the acceptor fluorescence. It is shown that the transfer is nonradiative. The energy transfer efficiencies are greater when the donor is excited at higher energy levels due to stronger overlap between electronic levels of donor UO22+ and acceptor Sm3+. From the comparison of energy transfer efficiencies from UO22+ to Sm3+ and Eu3+ it is deduced that the overlap between excitation levels of donor and acceptor is a sufficient condition for the transfer.  相似文献   

8.
A series of Ca9Ga(PO4)7:Ce3+/Tb3+/Dy3+/Mn2+ phosphors with tunable color, in which Ce3+ acts as the sensitizer, was synthesized. Energy transfer (ET) from Ce3+ to Tb3+/Dy3+/Mn2+ was investigated in detail. Tb3+/Dy3+/Mn2+ single-doped Ca9Ga(PO4)7 can exhibit green, yellow, and red emission, respectively. Incorporating Ce3+ into a Tb3+/Dy3+/Mn2+ single-doped Ca9Ga(PO4)7 phosphor can remarkably promote the luminous efficiency of the Tb3+/Dy3+/Mn2+ ions. This enhancement originates from an efficient ET from Ce3+ to Tb3+/Dy3+/Mn2+. The ET was validated by luminescence spectra, decay dynamics, and schematic energy levels. Moreover, the intensity ratio of red emission of Mn2+ to violet emission of Ce3+ was analyzed based on energy-transfer and lifetime measurements. In Ce3+-Tb3+, Ce3+-Dy3+, and Ce3+-Mn2+ doped Ca9Ga(PO4)7, the emitting color changed from violet to green, yellow, and red, respectively, which indicates the potential use of this new tunable phosphor in UV light-emitting diodes.  相似文献   

9.
In this study, a series of Sr1-xZrO3:xSm (x = 0.01 ≤ x ≤ 0.11) samples were synthesized using the sol-gel process. X-ray diffraction (XRD), scanning electron microscope (SEM), UV–visible and photoluminescence (PL) spectroscopy were employed to analyze these phosphors. The reporting of the bandgap energies (Eg), for which the diffuse-reflectance spectra of the Sr0.97ZrO3:Sm0.03 phosphor was used, is based on the Kubelka–Munk (K–M) function. Under the 406 nm excitation, the three Sm3+-emission transitions 4G5/26H5/2 (562 nm), 4G5/26H7/2 (599 nm), and 4G5/26H9/2 (644 nm) were observed for all the samples. The diminishing Sm3+-emission intensity that was observed was analyzed in the evaluation of the critical transfer rate (Rc) and the energy-transfer interaction parameter (Q). The CIE-chromaticity color coordinates of the Sm3+-doped SrZrO3 indicate that the prepared phosphors may act as an orange-emitting-light converter for the white LED.  相似文献   

10.
A series of phosphors SrBPO5:Dy3+ and SrBPO5:Dy3+,Tm3+ was synthesized by traditional solid-state high-temperature method and was characterized by X-ray diffraction (XRD) and fluorescence spectrophotometry. For SrBPO5:Dy3+ material, the f-f transitions of Dy3+ ions were assigned and discussed, and the optimal doping concentration of Dy3+ was found. As a result of co-doping SrBPO5:Dy3+ with Tm3+, the phosphors SrBPO5:Dy3+,Tm3+ can be effectively excited by 360 nm ultraviolet (UV), and exhibit color-tunable emission from blue to yellowish-white region with different doping concentration. The present study can pave the way for the creation of efficient UV phosphors using Dy3+,Tm3+ co-doped systems for near-UV InGaN-based light emitting diodes (LEDs).  相似文献   

11.
The Sr3Y(PO4)3:0.05Sm3+, Sr3Y(PO4)3:0.005Tb3+, and Sr3Y(PO4)3:0.005Tb3+, 0.05Sm3+ phosphors were synthesized using a conventional solid-state reaction technique at high temperature and their photoluminescence properties under ultraviolet (UV) excitation were studied. We observed the UV sensitization of Sm3+ emission (565, 600, and 648 nm) by Tb3+ in Sr3Y(PO4)3:0.005Tb3+, 0.05Sm3+, that leads to a white light emission with the CIE coordinate (0.367, 0.312) of Sr3Y(PO4)3:0.005Tb3+, 0.05Sm3+ phosphor under UV excitation. The emission is a result of partial energy transfer from Tb3+ to Sm3+, which is discussed in detail in terms of the corresponding excitation and emission spectra.  相似文献   

12.
Samarium and nitrogen co‐doped Bi2WO6 nanosheets were successfully synthesized by using a hydrothermal method. The crystal structures, morphology, elemental compositions, and optical properties of the prepared samples were investigated. The incorporation of samarium and nitrogen ions into Bi2WO6 was proved by X‐ray diffraction, energy dispersive X‐ray spectroscopy, and X‐ray photoelectron spectroscopy. UV/Vis diffuse reflectance spectroscopy indicated that the samarium and nitrogen co‐doped Bi2WO6 possessed strong visible‐light absorption. Remarkably, the samarium and nitrogen co‐doped Bi2WO6 exhibited higher photocatalytic activity than single‐doped and pure Bi2WO6 under visible‐light irradiation. Radical trapping experiments indicated that holes (h+) and superoxide radicals ( . O2?) were the main active species. The results of photoluminescence spectroscopy and photocurrent measurements demonstrated that the recombination rate of the photogenerated electrons and holes pairs was greatly depressed. The enhanced activity was attributed to the synergistic effect of the in‐built Sm3+/Sm2+ redox pair centers and the N‐doped level. The mechanism of the excellent photocatalytic activity of Sm‐N‐Bi2WO6 is also discussed.  相似文献   

13.
The Sr4Al14O25:M and doped Sr4Al14O25:M+Sm3+ (M=Mn4+, Cr3+) phosphors were syn-thesized by a solid-state reaction method and their luminescent properties were investi-gated. The results showed that the co-doping of Sm ions did not change the positions of excitation band and emission band but signi cantly improved the luminescent properties of Sr4Al14O25:Cr3+ phosphors; whereas, the emission intensity of Sr4Al14O25:Mn4+ was re-dueced remarkably when Sm ions were co-doped. In addtion, a radiative-form energy transfer from Sm3+ to Cr3+ was observed for the first time in the Cr, Sm co-doped Sr4Al14O25 phos-phors. The results indicated that Sm ions could signi cantly improve the emission intensity of Sr4Al14O25:Cr3+, making the Sm3+co-doped Sr4Al14O25:Cr3+ phosphor a promising can-didate for the applications in display and solid state lightening.  相似文献   

14.
采用高温固相法制备了Sr_3Y(BO_3)_3:xTm~(3+),yDy~(3+)荧光粉,并通过XRD、SEM和荧光光谱仪对样品的物相、微观形貌、发光性能、能量传递机制和CIE色坐标进行了分析。结果表明:Sr_3Y(BO_3)_3:xTm~(3+)荧光粉在监测波长为359 nm时发射蓝光,Tm~(3+)的浓度淬灭点为x=0.08;在Sr_3Y(BO_3)_3:0.08Tm~(3+),yDy~(3+)荧光粉中,随着Dy~(3+)掺杂浓度的增加,Tm~(3+)的发光强度降低而Dy~(3+)发光强度却先增加后降低,Dy~(3+)的浓度淬灭点为y=0.1;通过改变Dy~(3+)掺杂浓度或改变激发光的波长,均可实现发射光的颜色可调;在Tm~(3+)-Dy~(3+)离子之间存在能量传递。当Dy~(3+)掺杂浓度(物质的量分数)为0.15时能量传递效率达75.14%,能量传递机制为电偶极-电偶极相互作用。  相似文献   

15.
Samples of POCl3-SnCl4-235UO2-Dy3+ solutions have been prepared to investigate conversion of energy of heavy charged particles into optical radiation. Experimental data on radioluminescent characteristics of Dy3+ upon homogenous excitation of solutions by uranium α-radiation have been obtained. The efficiency of conversion of the energy of uranium α-particles into light energy depends on the Dy3+ concentration and the Dy3+ luminescence lifetime τ. At [Dy3+] = 0.2 mol/L and τ = 550 μs, the conversion efficiency is 0.12 ± 0.01% for the luminescent transition 4F 9/2 → 6H 13/2 (λmax = 574 nm) or 0.20 ± 0.01% for the visible and near IR regions of Dy3+ luminescence.  相似文献   

16.
The structural characteristics and optical spectra of Y(P,V)O4:Dy3+phosphors obtained by solid state reaction, sol-gel and hydrothermal routes have been investigated and compared. The luminescence features of these materials show a complicate dependence on the composition, synthetic method and excitation conditions. The emission performance depends on different effects: host luminescence, energy transfer to the doping ions and host dependence of the Dy3+ emission properties. These effects have been rationalized in order to provide useful information for the development of a suitable material for the white light emitting phosphors technology.  相似文献   

17.
In this study, lithium yttrium borate (LYBO) phosphor was doped with various concentrations of trivalent dysprosium ions. To produce these phosphors, the raw materials were sintered. The phase conformation, crystallinity, grain size, and overall morphology of the synthesized phosphors were studied with X-ray diffraction and scanning electron microscopy. The optimized LYBO phosphor, i.e., the LYBO phosphor that exhibited the highest X-ray- and ultraviolet (UV)-induced photoluminescent intensities, had a Dy3+ concentration of 4 mol%. Photoluminescence analysis showed that this phosphor could be easily excited with near-UV light (300–400 nm). The dominant photoluminescence bands were found in the blue (480 nm) and yellow (577 nm) regions of the visible spectrum. The light yield of the X-ray-induced luminescence of the optimized Li6Y(BO3)3:Dy3+ was found to be 66% of that of the commercially available X-ray imaging material, Gd2O2S:Tb3+ (GOS). The chromaticity coordinates of the Li6Y(BO3)3:Dy3+ phosphor were x = 0.34 and y = 0.32, which agree well with achromatic white (x = 0.33, y = 0.33). The results of this study show that the synthesized Li6Y(BO3)3:Dy3+ phosphor could be used as X-ray imaging material.  相似文献   

18.
The novel orange-red light emitting La7Ta3W4O30:xSm3+ (x = 0.005–0.20) phosphors were synthesized via the solid-state reaction method. The crystal structure, photoluminescence (PL) properties, optimum concentration, color purity, decay life, and thermal stability of the samples were systematically studied. Under the excitation of 404 nm, La7Ta3W4O30:Sm3+ emits intense orange-red light at 597 nm. The PL spectra of La7Ta3W4O30:Sm3+ phosphors are ascribed to the 4G5/2 to 6HJ (J = 5/2, 7/2, 9/2, and 11/2) transitions of Sm3+ ions. The concentration quenching occurs at the doping level of 1 mol%. The quenching temperature is higher than 500 K. Finally, a white LED (w-LED) with the Commission Internationale de L'Eclairage (CIE) chromaticity coordinates of (0.312, 0.296) and good color rendering index (Ra) of 86 was fabricated. As a consequence, all the results suggest that the orange-red phosphors La7Ta3W4O30:Sm3+ have potential applications in w-LEDs structures.  相似文献   

19.
The luminescent characteristics of RE (RE3+ = Eu, Tb, Dy, Sm and Tm)-doped K2GdZr(PO4)3 have been investigated. The band in the range of 130–157 nm in the VUV excitation spectra of these compounds is attributed to the host lattice or PO43? group absorption and the band from 157 nm to 215 nm with the maximum at 188 nm is due to the O–Zr charge transfer transition. For Eu3+-doped sample, the relatively weak band of O2?–Eu3+ charge transfer (CTB) at 222 nm is observed and for Tb3+-doped sample, the band at 223 nm is related to the 4f–5d spin-allowed transition of Tb3+. For Dy3+- and Sm3+-doped samples, the O2?–Dy3+ and O2?–Sm3+ CTBs have not been observed, probably due to the 2p electrons of oxygen tightly bound to the zirconium ion in the host lattice. In Tm3+-doped sample, the weak O2?–Tm3+ CTB is located at 170 nm. It is observed that there is energy transfer between the host and the luminescent activators (e.g. Eu3+, Tb3+ and Sm3+) except for Tm3+.  相似文献   

20.
采用高温固相反应合成了M5-2xSmxNax(PO4)3F(M=Ca,Sr,Ba)荧光体,研究了其在真空紫外-可见光范围的发光特性。发现在Ca5(PO4)3F中Sm3+的电荷迁移带约在191 nm,在Sr5(PO4)3F中约在199 nm,而在Ba5(PO4)3F中约在204 nm,随着被取代碱土离子半径的增大电荷迁移能量逐渐减小。比较了M5(PO4)3F (M=Ca,Sr,Ba)中Sm3+和Eu3+电荷迁移能量的关系。  相似文献   

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