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1.
LiSrBO 3:M (M = Eu 3+, Sm 3+, Tb 3+, Ce 3+, Dy 3+) phosphors which have been developed for white light-emitting diodes (LEDs) were synthesized by a normal solid-state reaction. The emission and excitation spectra indicate that these phosphors can be effectively excited by near-ultraviolet light-emitting diodes (UVLED), and exhibit satisfactory red, green and blue performances, respectively, nicely fitting in with the widely applied UV chip. Under the condition of doping charge compensation Li +, Na + and K +, the luminescence intensities of these phosphors were increased. 相似文献
2.
CaWO 4, CaWO 4:Sm 3+ and CaWO 4:(Sm 3+, Li +) nanoparticles were synthesized by the precipitation method with addition of PEG 200. The X-ray diffraction patterns show that the obtained samples have a pure tetragonal phase. The CaWO 4 sample shows an emission peak at 418 nm originating from the charge-transfer transitions within the WO 4 2? complex. CaWO 4:Sm 3+ and CaWO 4:(Sm 3+, Li +) samples show emission peaks originating from the f–f forbidden transitions of the 4f electrons of Sm 3+ ions. The charge compensator of Li + can enhance the emission intensity effectively. It is found that the emission intensity of CaWO 4:(3 mol% Sm 3+, 4 mol% Li +) phosphor is about double that of CaWO 4:3 mol% Sm 3+ phosphor. 相似文献
3.
LiSr 4?x (BO 3) 3: xSm 3+ and LiSr 3.985?x (BO 3) 3:0.015Sm 3+, xK + phosphors were prepared by solid-state reactions. The phases and luminescent properties of the obtained phosphors were characterized. The results demonstrate that the phosphors particles emit an intensive reddish orange light emission under excitation at 403 nm. LiSr 4?x (BO 3) 3: xSm 3+ phosphor can be efficiently excited by ultraviolet and blue light, and the emission spectrum consists of three emission peaks at 564, 601 and 647 nm. The introduction of the charge compensator K + into the LiSr 4?x (BO 3) 3: xSm 3+ phosphor matrix promotes the increase of the emission intensity, as well as the decrease of the E g value. Results suggest that LiSr 3.97(BO 3) 3:0.015Sm 3+, 0.015 K + is a promising orange–red emitting phosphor for UV LED applications. 相似文献
4.
One-dimensional Sm 3+ doped SrWO 4 with or without different charge compensation approaches (co-doping Li +, Na + and K +) nanofibers were prepared by electrospinning. The structure, morphology and luminescence properties of the obtained nanofiber phosphors were investigated. The X-ray diffraction, Fourier transformation infrared and thermogravimetric results show that the Sr (1?x)WO 4: Sm x 3+ samples crystallize at 700 °C. Scanning electron microscope results indicate that as prepared nanofibers before/after calcination present uniform fiberlike morphology. The luminescence results show that Sr (1?x)WO 4: Sm x 3+ phosphors can be excited efficiently by ultraviolet (UV) and near-UV light. The emission spectrum consists of three emission peaks at 561, 596 and 643 nm, corresponding to 4G 5/2 → 6H 5/2, 4G 5/2 → 6H 7/2 and 4G 5/2 → 6H 9/2 transitions of Sm 3+, respectively. The optimal doping concentration of Sm 3+ in SrWO 4 is experimentally ascertained to be 4 mol%. The introduction of charge compensator R + (R = Li, Na and K) can enhance the emission intensity of phosphors significantly. The co-doping of Li + has the best compensation effect. The present investigation indicates that Sm 3+ doped SrWO 4 is a promising orange phosphor for light-emitting diode based on UV chip technology. 相似文献
5.
ABO 4 (A = Ca, Sr; B = W, Mo):Er 3+/Yb 3+/Li + phosphors tri-doped with different concentrations of Li + ion ranging from 0 to 22.5 mol% were prepared by using a solid-state reaction method. And their upconversion (UC) luminescence properties were in estimated under a 975 nm laser-diode excitation. The four kinds of phosphors (CaWO 4, CaMoO 4, SrWO 4, and SrMoO 4) tri-doped with Er 3+, Yb 3+ and Li + ions showed strong green UC emission peaks at 530 nm and 550 nm and weak red UC emission. The intensity of green UC emission of Li + doped samples was several higher than that of Li + un-doped samples due to the reduction of lattice constant and the local crystal field distortion around rare-earth ions. The optimum doping concentration of Li + ions was investigated and the effects of Li + concentration for UC emission intensity were studied in detail. 相似文献
6.
High-saturated red aluminate phosphors SrMgAl 10O 17 doped with Mn 4+ ions were prepared by solid-state reaction at 1,400 °C. The crystal structure and particle morphology of SrMgAl 10O 17:Mn 4+ phosphors were investigated by X-ray diffraction, scanning electron microscopy and their photoluminescence were studied by the excitation and emission spectra. The excitation spectrum of samples showed two broad absorption bands ranging from 250 to 480 nm, which indicated that SrMgAl 10O 17:Mn 4+ could be effectively excited by both near-ultraviolet light and the commercially available blue light of light-emitting diode chips. Simultaneously, the emission spectrum exhibited two sharp peaks (651 and 662 nm) in the deep-red region. It was found that the quenching concentration of Mn 4+ in phosphor was 1.5 mol%. In the end, the effects of doping ions, M (Li +, Na +, K +, Cl ?) ions, on the luminescent properties of SrMgAl 10O 17:Mn 4+ were investigated, respectively. The results suggested that all of Li +, Na +, and Cl ? could significantly improve the luminescent properties of SrMgAl 10O 17:Mn 4+, and the phosphor SrMgAl 10O 17:Mn 4+, M (M = Li +, Na +, Cl ?) was expected to be used as a red phosphor in warm white light emitting diode. 相似文献
7.
A series of novel red-emitting Na 2Ca 3???x Si 2O 8: xEu 3+ 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 Na 2Ca 3Si 2O 8:Eu 3+ were characterized. Na 2Ca 3Si 2O 8:Eu 3+ with self-compensated and alkali metal ions charge compensated approaches (2Ca 2+→Eu 3+ + 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 Y 20 3S:Eu 3+. The present work implies that the efficient charge compensated phosphors are promising candidates as red-emitting phosphor for w-LEDs. 相似文献
8.
Y 2O 3:Eu 3+ phosphors were prepared by hydrothermal method. Effect of the doping concentration of Eu 3+ on the photoluminescence properties of Y 2O 3:Eu 3+ phosphor was studied in details. It was found that the strongest emission intensity is achieved as atomic ratio of Y 3+ to Eu 3+ is 8. As concentration of Eu 3+ exceeds the critical concentration, the emission intensity decreases dramatically due to the concentration quenching of Eu 3+. Also, the effect of Li + on the photoluminescence performance of the Y 2O 3:Eu 3+ phosphor is studied in this work. According to the results, the doping of Li + may greatly improve the PL performance of the Y 2O 3:Eu 3+ phosphors due to the flux effect and improved crystallinity caused by the doping of Li +. 相似文献
9.
A novel blue-emitting Sr 3Al 2O 5Cl 2:Ce 3+,Li + phosphor has been synthesized by solid state reaction. The excitation spectrum shows a broad band extending from 300 to 400 nm, and the emission spectrum shows a broad blue band peaking at 450 nm with a half width of about 100 nm. The emission intensity at 250 °C remains at about 50% of that at room temperature. The decay curve at the emission peak consists of fast and slow components. The Sr 3Al 2O 5Cl 2:Ce 3+,Li + should be a promising blue phosphor for near ultraviolet-based white-light-emitting diodes. 相似文献
10.
It has been found that charge compensated CaMoO 4:Eu 3+ phosphors show greatly enhanced red emission under 393 and 467 nm-excitation, compared with CaMoO 4:Eu 3+ without charge compensation. Two approaches to charge compensation, (a) 2Ca 2+ → Eu 3+ + M +, where M + is a monovalent cation like Li +, Na + and K + acting as a charge compensator; (b) 3Ca 2+ → 2Eu 3+ + vacancy, are investigated. The influence of sintering temperature and Eu 3+ concentration on the luminescent property of phosphor samples is also discussed. 相似文献
11.
Eu 3+ doped ZnB 2O 4 without or with different charge compensation (CC) approaches (co-doping Li +, Na +, K, decreasing the content of Zn 2+) were prepared by solid state reactions. The phosphors can strongly absorb 393 nm ultraviolet (UV) light which is coupled well with the emission of currently used InGaN-based near UV light emitting diodes (LEDs) and emit red light with a good color purity. The luminescent intensity of phosphors can be remarkably enhanced with any of CC methods. However, the shape and position of excitation and emission spectra keep unchanged. The introduction of Li + can enhance the red emission intensity of Eu 3+ by ∼4 times with the optimal effect. Red emission of Eu 3+ can also be enhanced with the other three CC approaches but the effects are not as good as Li + because the volume unbalance in Li + compensation approach is the smallest while net positive charge was offset. The results of this work suggest that volume compensation and equilibrium of mole number should also be taken into account when a CC approaches is selected. 相似文献
12.
A series of double-perovskite orange–red-emitting Ca(3?2x)SmxNaxTeO6 (x?=?0.01–0.25) phosphors have been synthesized via high-temperature method. The single-phase and orthorhombic structure of Ca3TeO6:Sm3+, Na+ phosphors was confirmed by X-ray powder diffraction. Under 405 nm excitation, Ca3TeO6:Sm3+, Na+ phosphors emitted a series of orange–red emission due to the transition of Sm3+ from 4G5/2 to 6HJ/2 (J?=?5, 7, 9, and 11). The optimal Sm3+-doping concentration of Ca(3?2x)SmxNaxTeO6 (x?=?0.01–0.25) was x?=?0.10. The thermal-quenching temperature of Ca3TeO6:0.10Sm3+, 0.10Na+ phosphor was above 480 K. A white light-emitting diode (w-LED) based on 410 nm UV chip was successfully fabricated, and it presented a good correlated color temperature and a high color-rendering index (Ra). Therefore, orange–red-emitting Ca3TeO6:Sm3+, Na+ phosphors have potential applications in UV-based w-LEDs. 相似文献
13.
The up-conversion (UC) emission of Ho 3+-Yb 3+ and Li + co-doped transparent glass ceramics 45SiO 2-15Al 2O 3-12Na 2CO 3-21BaF 2-7LaF 3-0.2HoF 3-1YbF 3-xLi 2CO 3 (x = 0, 0.5, 1, 2, 4 and 6 mol%) containing Ba 2LaF 7 nanocrystals were investigated. These glass ceramics samples were prepared using the conventional quenching techniques. The Ba 2LaF 7 nanocrystals precipitated from the glass matrix was confirmed by X-ray diffraction (XRD). Compared with the glass ceramics sample without Li +, the UC emission intensity of glass ceramics samples with Li + were enhanced. It can be proved that the Li + can affect the enhancement up-conversion (UC) emission. Particularly, the green UC emission intensity band centered at 546 nm was strongly increased twice with the concentration of Li + increasing up to 4 mol%. Through the comparison and analysis of the energy graph, it was shown that the 5F 4/ 5S 2→ 5I 8 transition of Ho 3+ ion obtained the green (546 nm) light. There are two weak fluorescences in the red (657 nm) region and near infrared (753 nm) region of spectrum, which is the 5F 4/ 5S 2→ 5I 7 and 5F 5→ 5I 8 transition of Ho 3+. Therefore, the emission results showed that the incorporation of Li + ions into the Ba 2LaF 7:Eu 3+ lattice could induce a remarkable change of the emission intensity in red region (R = I ED/I MD) with 393 nm excitation wavelength. It was indicated that the symmetry of the lattice was destroyed by Li + in glass ceramics. The possible mechanism responsible for the enhancement of UC emission in Ho-Yb co-doped was discussed. 相似文献
14.
A series of new green-emitting Ba 2?x?2ySiO 4:xEu 2+, yGd 3+, yR + (R = Li, Na or K) phosphors were synthesized by the solid-reaction method. X-ray diffraction (XRD) and fluorescence spectrophotometer are utilized to characterize the crystal structure and luminescence properties of the as-synthesized phosphors, respectively. The XRD patterns reveal that the doping of Gd 3+, Eu 2+ and R + ions have no significant influence on the Ba 2SiO 4 phase. The green emission of Eu 2+ ion associated with 4f 65d 1 → 4f 7 can be obtained by 396 nm UV excitation source, which match well with the emission wavelength of UV-LEDs chip (380–420 nm). Moreover, the effect of charge compensator ions (Li +, Na + or K +) on the luminescence intensity of (Ba, Gd) 2SiO 4:Eu 2+ phosphors were also investigated. When introducing the Li + ions into the (Ba, Gd) 2SiO 4 host lattices, the as-prepared phosphors show the strongest emission. The emission intensity of Ba 1.95SiO 4:0.04Eu 2+, 0.005Gd 3+, 0.005Li + is about 1.39 times than that of Ba 1.96SiO 4:0.04Eu 2+. Furthermore, the mechanism of energy transfer and concentration quenching of Ba 1.982?xSiO 4:xEu 2+, 0.009Gd 3+, 0.009Li + phosphors are also discussed. 相似文献
15.
Here the green-emitting highly luminescent Er3+ doped, Er3+-Li+ co-doped, Er3+-Na+ co-doped CaAl4O7 is synthesized by Pechini method at 1000°C. Photoluminescence (PL) of CaAl4O7: Er3+ studies have been compared with Li+ co-doped CaAl4O7: Er3+ and Na+ co-doped CaAl4O7: Er3+. Na+ co-doped CaAl4O7:Er3+ shows increases in luminescence intensity compared to Li+ co-doped CaAl4O7: Er3+ and Er3+ doped CaAl4O7. The results suggest that CaAl4O7:Er3+ phosphor can be used as efficient green-emitting phosphor in white LED. The resultant phosphor emits green color peaking at 549 nm upon 378 nm excitation. Powder X-ray diffraction (PXRD) and photoluminescence (PL) techniques have been studied to characterize the synthesized microparticles. Further, this phosphor has good thermal stability that implies its potential to act as green phosphor in white light-emitting diodes. The effect of activator (Er3+), Na+ co-doped CaAl4O7:Er3+, and Li+ co-doped CaAl4O7:Er3+ phosphors luminescence spectra as well as photoluminescence life time studies were studied in detail. The results show that as the concentration of Er3+ in CaAl4O7 increases, the symmetry around the Er3+ ion decreases due to the creation of lattice defects in the crystal. Addition of Na+ and Li+ ions in CaAl4O7: Er3+leads to a small distortion in the local symmetry of Er3+ ions, thereby significantly enhancing its luminescence property. Analysis of photoluminescence life time studies of the prepared samples shows a smaller concentration quenching of Er3+ luminescence in charge compensated Na+ and Li+ CaAl4O7 phosphor. 相似文献
16.
In this study, the synthesis and luminescence characterization of Samarium (Sm 3+) doped lithium metasilicate (Li 2SiO 3) phosphor ceramic were investigated. It was presented and discussed the results obtained on the luminescence and other optical studies such as X-ray diffraction (XRD), optical absorption and luminescence properties of Li 2SiO 3:Sm 3+ phosphor ceramic. The Li 2SiO 3 compound was shown a characteristic phase in XRD. The doping in the lithium compound was not having a significant effect on the basic crystal structure of the material. The maximum photoluminescence (PL) emission for Sm 3+ doped Li 2SiO 3 was observed at 554, 583, 641, 725 nm and bore resemblance to the visible region of the spectrum. The glow curves of all synthesized materials have a complex peak structure after being irradiated with a 90Sr– 90Y beta source. In addition, the peak between 400 and 600 nm was seen in the radioluminescence (RL) spectrum because of a wide peak thought to be caused by silicate. 相似文献
17.
Red phosphor of CaIn 2O 4:Eu 3+, Sm 3+ is synthesized by solid state reaction. The 5D 0 → 7F 2 transition of Eu 3+ is dominantly observed in the photoluminescence spectrum, leading to a red emission of the phosphor. The doped Sm 3+ is found to be efficient to sensitize the emission of Eu 3+ and be effective to extend and strengthen the absorption of near-UV light with wavelength of 400-405 nm, and the energy transfer from Sm 3+ to Eu 3+ occurs and is discussed. The effect of the molar concentration of Sm 3+ on the emission intensities of the phosphor CaIn 2O 4:Eu 3+, Sm 3+ is investigated. The temperature quenching effect is also measured from room temperature to 425 K, and the emission intensity of the phosphor at 425 K shows about 85% of that at room temperature. Furthermore, the chromaticity coordinates, the emission intensities and the conversion efficiencies of CaIn 2O 4:Eu 3+, Sm 3+ are compared to those of the conventional red phosphor of Y 2O 2S:Eu 3+. 相似文献
18.
The lithium solubility limit, photoluminescence (PL) and photoluminescence excitation (PLE) properties of lithium ion co-activated ZnGa 2O 4:Bi 3+,Li + phosphor have been investigated. A LiGaO 2 second phase began to appear from 3 mol% Li + ion co-activated ZnGa 2O 4:Bi 3+,Li + phosphor. The enhanced brightness of blue ( λex = 254 nm) and white ( λex = 315 nm) colors of bismuth ions doped ZnGa 2O 4:Bi 3+,Li + phosphor was assigned to the formation of LiGaO 2. Bi 3+ activated lithium zinc gallate phosphor showed a more enhanced PLE peak around 315 nm than that of lithium zinc gallate phosphor when λem = 520 nm. Thus, we observed that the PL intensity of ZnGa 2O 4:Bi 3+,Li + phosphor with λem = 520 nm was much greater than that of ZnGa 2O 4:Li + phosphor. Also, ZnGa 2O 4:Bi 3+,Li + phosphor exhibited a shorter decay time than that of ZnGa 2O 4:Li + phosphor by about a factor of about 2. 相似文献
19.
The effects of charge compensation on the luminescence behavior of a red-emitting phosphor, Ca 3Sr 3(VO 4) 4:Eu 3+, were investigated. It has been observed that charge compensated by monovalent ions, especially Na +, shows greatly enhanced red emission under ultraviolet excitation. It is found that Na 2CO 3 addition acts as a fluxing agent and plays a role in charge compensation, which clearly improves the emission intensity of Eu 3+-activated Ca 3Sr 3(VO 4) 4. Enhanced emission intensity of the corresponding charge compensated phosphors under ultraviolet radiation may find application in the production of red phosphors for white light-emitting diodes. 相似文献
20.
A novel green emitting phosphor, Tb 3+-doped Ca 2GeO 4 was prepared for the first time by a solid-state reaction. The phosphor showed prominent luminescence in green due to the magnetic dipole transition of 5D 4 → 7F 5. Structural characterization of the luminescent material was carried out with X-ray powder diffraction (XRD) analysis and field emission scanning electron microscopy (FE-SEM). Luminescence properties were analyzed by measuring the excitation and photoluminescence spectra. Photoluminescence measurements indicated that the phosphor exhibited bright green emission at about 541 and 550 nm under UV excitation. In addition, Al 3+ or Li + co-doping enhances the green emission from Ca 2GeO 4:Tb 3+ by about 18 and 4 times, respectively, under UV excitation. The excellent luminescence properties make it a possible candidate for flat panel display application. 相似文献
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