首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 435 毫秒
1.
In this study, Eu‐doped Li2(Ba1‐xSrx)SiO4 powders (x = 0, 0.2, 0.4, and 0.6) were synthesized at 850°C in a reduction atmosphere (5% H2 + 95% N2) for a duration of 1 h using a solid‐state reaction method. The reduction atmosphere was infused as the synthesis temperature reached 850°C, and was removed as the temperature dropped to 800–500°C. Li2(Ba1‐xSrx)SiO4 (or Li2BaSiO4), (Ba,Sr)2SiO4 (or BaSiO4), and Li4SiO4 phases co‐existed in the synthesized Eu‐doped Li2(Ba1‐xSrx)SiO4 powders. A new finding was that the reduction atmosphere removing (RAR) temperature of the Li2(Ba1‐xSrx)SiO4 phosphors had a large effect on their photoluminescence excitation (PLE) and PL properties. Except for the 800°C‐RAR‐treated Li2BaSiO4 phosphor, PLE spectra of all other Li2(Ba1‐xSrx)SiO4 phosphors had one broad emission band with two emission peaks centred at ~242 and ~283 nm; these PL spectra had one broad emission band with one emission peak centred at 502–514 nm. We showed that the 800°C‐RAR‐treated Li2BaSiO4 phosphor emitted a red light and all other Li2(Ba1‐xSrx)SiO4 phosphors emitted a green light. Reasons for these results are discussed thoroughly.  相似文献   

2.
Novel red‐emitting phosphors, Eu3+‐activated M7Sn(PO4)6 (M = Sr, Ba), were synthesized at 1200°C by conventional solid‐state reaction method. The luminescent properties of M7Sn(PO4)6:Eu3+ (M = Sr, Ba) phosphors were investigated, and the critical concentration of the activator (Eu3+) concentration were found to be 0.175 mol and 0.21 mol per formula unit for Sr7‐xSn(PO4)6:xEu3+ and Ba7‐xSn(PO4)6:xEu3+, respectively. These phosphors presented red luminescence under the excitation of 395 or 465 nm, perfectly matching with the emissions wavelength of near‐ultraviolet (UV) light‐emitting diodes (LEDs) and InGaN blue LED.  相似文献   

3.
Ce3+/Eu2+ co‐doped Na3Ca6(PO4)5 phosphors were prepared using a combustion‐assisted synthesis method. X‐Ray powder diffraction (XRD) analysis confirmed the formation of a Na3Ca6(PO4)5 crystal phase. Na3Ca6(PO4)5:Eu2+ phosphors have an efficient bluish‐green emission band that peaks at 489 nm, whereas Ce3+‐doped Na3Ca6(PO4)5 showed a bright emission band at 391 nm. Analysis of the experimental results suggests that enhancement of the Eu2+ emission intensity in co‐doped Na3Ca6(PO4)5:Eu2+,Ce3+ phosphors is due to a resonance‐type energy transfer from Ce3+ to Eu2+ ions, which is predominantly governed by an exchange interaction mechanism. These results indicate that Ce3+/Eu2+ co‐doped Na3Ca6(PO4)5 is potentially useful as a highly efficient, bluish‐green emitting, UV‐convertible phosphor for white‐light‐emitting diodes. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

4.
A series of red‐emitting phosphors Ca0.6Sr0.4–1.5x‐0.5yMo0.4 W0.6O4:EuxLiy (x = 0.02–0.12, y = 0–0.12) has been synthesized by a sol‐gel method. The effects of calcining temperature, concentrations of Li+ and Eu3+, and compensation ions on the luminescent properties were investigated. X‐ray diffraction and scanning electron microscopic results showed that as‐prepared phosphors were of single phase with several microns. The Li+ compensated compositions showed remarkably intense red emission at 619 nm. The emission intensity of the series reached maximum for compositions at x = 0.08 and y = 0.08 when the calcining temperature was 900 °C. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

5.
A series of blue phosphors Ca1.98–xMxPO4Cl:0.02Eu2+ (M = Mg and Sr) with different values of x were synthesized using a high‐temperature solid‐state reaction. X‐Ray diffraction and photoluminescence measurements were used to study the phase structure and luminescence properties. Ca2PO4Cl:0.02Eu2+ exhibits a tunable emission intensity and color due to the incorporation of Sr2+ or Mg2+. The incorporation of Sr2+ reduces the luminescence intensity and results in a slight red shift in the emission band. The incorporation of Mg2+ results in enhanced emission and a clear blue shift in the emission band along with a tunable chromatic coordination. Under excitation at λ = 334 nm, the emission intensity of the Mg2+‐doped Ca2PO4Cl:0.02Eu2+ is found to be 250% that of Ca2PO4Cl:0.02Eu2+. The luminescence behaviors of the as‐synthesized phosphors are discussed according to the host crystal structure and site occupancy of Eu2+. The results indicate that Mg2+‐doped Ca2PO4Cl:Eu2+ is more applicable as a near‐UV‐convertible blue phosphor for white light‐emitting diodes. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

6.
A series of Ce3+,Mn2+‐coactivated Ca3YNa(PO4)3F phosphors were synthesized via a traditional solid‐state reaction under a reductive atmosphere. X‐Ray powder diffraction was used to confirm that the crystal structure and diffraction peaks of Ce3+/Mn2+‐doped samples matched well with the standard data. A spectral overlap between the emission band of Ce3+ and the excitation band of Mn2+ suggested the occurrence of energy transfer from Ce3+ to Mn2+. With increasing Mn2+ content, the emission intensities and lifetime values of the Ce3+ emission for Ca3YNa(PO4)3F:Ce3+,Mn2+ phosphors linearly decrease, whereas the energy transfer efficiencies gradually increase to 89.35%. By adjusting the relative concentrations of Ce3+ and Mn2+, the emission hues are tuned from blue to white and eventually to yellow. These results suggest that Ca3YNa(PO4)3F:Ce3+,Mn2+ phosphors have promising application as white‐emitting phosphors for near‐ultraviolet light‐emitting diodes.  相似文献   

7.
Ca2Al2O5:Eu3+, Ca2Al2O5:Dy3+ and Ca2Al2O5:Tb3+ phosphors were synthesized using a combustion synthesis method. The prepared phosphors were characterized by X‐ray powder diffraction for phase purity, by scanning electron microscopy for morphology, and by photoluminescence for emission and excitation measurements. The Ca2Al2O5:Eu3+ phosphors could be efficiently excited at 396 nm and showed red emission at 594 nm and 616 nm due to 5D0 → 7F1 and 5D0 → 7F2 transitions. Dy3+‐doped phosphors showed blue emission at 482 nm and yellow emission at 573 nm. Ca2Al2O5:Tb3+ phosphors showed emission at 545 nm when excited at 352 nm. Concentration quenching occurred in both Eu3+ and Dy3+phosphors at 0.5 mol%. Photoluminescence results suggested that the aluminate‐based phosphor could be a potential candidate for application in environmentally friendly based lighting technologies.  相似文献   

8.
Energy storage phosphors with millisecond period afterglow that compensate for the diming time of alternating current light‐emitting diodes (AC‐LEDs) have promising application. To obtain a persistent luminescence (PersL) white colour in AC‐LEDs, we focussed on a red afterglow with short period phosphorescence. Ca4Ti3O10 forms a type of perovskite‐related Ruddlesden–Popper phase structure. Doping Pr3+ ions into Ca4Ti3O10, an ideal red PersL was obtained. X‐ray diffraction and element analysis demonstrated that our target samples were crystallized well. Steady‐state and afterglow luminescence properties were investigated in detail. Notably, the PersL intensity was dependent on various excitation wavelengths. By measuring three‐dimensional thermoluminescence spectra, we found that the trap depths showed a continuous distribution and that the shallowest trap contributed to the millisecond afterglow. Two PersL mechanism models were used to elucidate the electron charging and de‐trapping processes under UV or blue light activation.  相似文献   

9.
In this article, we report the synthesis of Na2Sr1‐x(PO4)F:Eux phosphor via a combustion method. The influence of different annealing temperatures on the photoluminescence properties was investigated. The phosphor was excited at both 254 and 393 nm. Na2Sr1‐x(PO4)F:Eux3+ phosphors emit strong orange and red color at 593 and 612 nm, respectively, under both excitation wavelengths. Na2Sr1‐x(PO4)F:Eux3+ phosphors annealed at 1050°C showed stronger emission intensity compared with 600, 900 and 1200°C. Moreover, Na2Sr1‐x(PO4)F:Eux3+ phosphor was found to be more intense when compared with commercial Y2O3:Eu3+ phosphor. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

10.
M5(PO4)3 F:Eu2+ (M = Ca and Ba) co‐doped with Ce3+ phosphors were successfully prepared by the combustion synthesis method. The introduction of co‐dopant (Ce3+) into the host enhanced the luminescent intensity of the M5(PO4)3 F:Eu2+ (M = Ca and Ba) efficiently. Previously, we have reported the synthesis and photoluminescence properties of same phosphors. The aim of this article is to report energy transfer mechanism between Ce3+?Eu2+ ions in M5(PO4)3 F:Eu2+ (M = Ca and Ba) phosphors, where Ce3+ ions act as sensitizers and Eu2+ ions act as activators. The M5(PO4)3 F:Eu2+ (M = Ca and Ba) co‐doped with Ce3+ phosphor exhibits great potential for use in white ultraviolet (UV) light‐emitting diode applications to serve as a single‐phased phosphor that can be pumped with near‐UV or UV light‐emitting diodes. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

11.
This work reports the photoluminescence properties of Ca3Mg3(PO4)4:Sm3+ phosphors that were synthesized by the combustion method. The phase formation and morphology of the prepared phosphors were analysed by X‐ray diffraction studies and scanning electron microscopy. Ca3Mg3(PO4)4:Sm3+ phosphors give orange light emission when excited by near‐ultraviolet (NUV) and blue light. The photoluminescence characteristics of the as‐prepared phosphors were investigated and their emission spectra showed three peaks due to 4G5/2 → 6H5/2, 4G5/2 → 6H7/2 and 4G5/2 → 6H9/2 transitions. The mechanism responsible for the concentration quenching of luminescence was found to be an electric dipole–dipole interaction. The CIE chromaticity coordinates suggested that the prepared phosphors are potential candidates for orange light‐emitting diodes (LEDs).  相似文献   

12.
The luminescent properties of europium (Eu)‐ and dysprosium (Dy)‐co‐doped K3Ca2(SO4)3Cl halosulfate phosphors were analyzed. This paper reports the photoluminescence (PL) properties of K3Ca2(SO4)3Cl microphosphor doped with Eu and Dy and synthesized using a cost‐effective wet chemical method. The phosphors were characterized by X‐ray diffraction and scanning electron microscopy. The CIE coordinates were calculated to display the color of the phosphor. PL emission of the prepared samples show peaks at 484 nm (blue), 575 nm (yellow), 594 nm (orange) and 617 nm (red). The emission color of the Eu,Dy‐co‐doped K3Ca2(SO4)3Cl halophosphor depends on the doping concentration and excitation wavelength. The addition of Eu in K3Ca2(SO4)3Cl:Dy greatly enhances the intensity of the blue and yellow peaks, which corresponds to the 4 F9/26H15/2 and 4 F9/26H13/2 transitions of Dy3+ ions (under 351 nm excitation). The Eu3+/Dy3+ co‐doping also produces white light emission for 1 mol% of Eu3+, 1 mol% of Dy3+ in the K3Ca2(SO4)3Cl lattice under 396 nm excitation, for which the calculated chromaticity coordinates are (0.35, 0.31). Thus, K3Ca2(SO4)3Cl co‐doped with Eu/Dy is a suitable candidate for NUV based white light‐emitting phosphors technology. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

13.
Peng Du  Jae Su Yu 《Luminescence》2017,32(8):1504-1510
A series of Sm3+‐activated Sr3La(VO4)3 phosphors were synthesized by a facile sol‐gel method. X‐ray diffraction patterns and photoluminescence (PL)/cathodoluminescence (CL) spectra as well as PL decay curves were employed to characterize the obtained samples. Upon 402 nm light excitation, the characteristic emissions of Sm3+ ions corresponding to 4G5/26HJ transitions were observed in all the as‐prepared products. The PL emission intensity was increased with increase in Sm3+ ion concentration, while concentration quenching occurred when the doping concentration was over 4 mol%. The non‐radiative energy transfer mechanism for concentration quenching of Sm3+ ions was dominated by dipole–dipole interaction and the critical distance was around 21.59 Å. Furthermore, temperature‐dependent PL emission spectra revealed that the obtained phosphors possessed good thermal stability with an activation energy of 0.19 eV. In addition, the CL spectra of the samples were almost the same as the PL spectra, and the CL emission intensity showed a tendency to increase with increase in accelerating voltage and filament current. These results suggest that the Sm3+‐activated Sr3La(VO4)3 phosphors with good color coordinates, high color purity and superior thermal stability may be a potential candidate for applications in white light‐emitting diodes and field‐emission displays as red‐emitting phosphors.  相似文献   

14.
In this study, a series of LaNbTiO6:RE3+ (RE = Tb, Dy, Ho) down‐converting phosphors were synthesized using a modified sol–gel combustion method, and their photoluminescence (PL) properties were investigated as a function of activator concentration and annealing temperature. The resultant particles were characterized using X‐ray diffraction, transmission electron microscopy, scanning electron microscopy, UV/Vis diffuse reflectance spectroscopy and PL spectra. The highly crystalline LaNbTiO6:RE3+ (RE = Tb, Dy, Ho) phosphors with an average size of 200–300 nm obtained at 1100°C have an orthorhombic aeschynite‐type structure and exhibit the highest luminescent intensity in our study range. The emission spectra of LaNbTiO6:RE3+ (RE = Tb, Dy, Ho) phosphors under excitations at UV/blue sources are mainly composed of characteristic peaks arising from the f–f transitions of RE3+, including 489 nm (5D47F6) and 545 nm (5D47F5) for Tb3+, 476 and 482 nm (4F9/26H15/2) and 571 nm (4F9/26H13/2) for Dy3+, and 545 nm (5F4 + 5S25I8) for Ho3+, respectively. The luminescent mechanisms were further investigated. It can be expected that these phosphors are of intense interest and potential importance for many optical applications. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

15.
Sr2CeO4 phosphors with different crystalline sizes were synthesized by the sol–gel method or the solid‐state reaction. Their crystalline size, luminescence intensity of O2??Ce4+ charge transfer and energy gaps were obtained through the characterization by X‐ray diffraction, photoluminescence spectra, as well as UV–visible diffuse reflectance measurements. An inverse relationship between photoluminescence (PL) spectra and crystalline size was observed when the heating temperature was from 1000°C to 1300°C. In addition, band energy calculated for all samples showed that a reaction temperature of 1200°C for the solid‐state method and 1100°C for sol–gel method gave the largest values, which corresponded with the smallest crystalline size. Correlation between PL intensity and crystalline size showed an inverse relationship. Band structure, density of states and partial density of states of the crystal were calculated to analyze the mechanism using the cambrige sequential total energy package (CASTEP) module integrated with Materials Studio software.  相似文献   

16.
Eu3+‐doped calcium titanate red phosphors, Ca1‐xZnxTiO3:Eu3+, were prepared by the sol‐gel method. The structure of prepared Ca1‐xZnxTiO3:Eu3+ phosphors were investigated by X‐ray diffraction and infrared spectra. Due to the 5D07F1–3 electron transitions of Eu3+ ions, photoluminescence spectra showed a red emission at about 619 nm under excitation of 397 nm and 465 nm, respectively. When zinc was added to the host, the luminescent intensity of Ca1‐xZnxTiO3:Eu3+ was markedly improved several fold compared with that of CaTiO3:Eu3+. Ca0.9Zn0.1TiO3:Eu3+ also had higher luminescence intensity than the commercially available Y2O3:Eu3+ phosphors under UV light excitation. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

17.
In this paper, europium‐doped strontium aluminate (SrAl2O4:Eu2+) phosphors were synthesized using a combustion method with urea as a fuel at 600°C. The phase structure, particle size, surface morphology and elemental analysis were studied using X‐ray diffractometry (XRD), transmission electron microscopy (TEM), energy‐dispersive X‐ray spectroscopy (EDX) and Fourier transform infrared (FTIR) spectra. The EDX and FTIR spectra confirm the elements present in the SrAl2O4:Eu2+ phosphor. The optical properties of SrAl2O4:Eu2+ phosphors were investigated by photoluminescence (PL) and mechanoluminescence (ML). The excitation and emission spectra showed a broad band with peaks at 337 and 515 nm, respectively. The ML intensities of SrAl2O4:Eu2+ phosphor increased proportionally with the increase in the height of the mechanical load, which suggests that this phosphor could be used in stress sensors. The CIE colour chromaticity diagram and ML spectra confirm that the SrAl2O4:Eu2+ phosphor emitted green coloured light. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

18.
The present study investigates the impact of the ligand environment on the luminescence and thermometric behavior of Sm3+ doped A3(PO4)2 (A = Sr, Ca) phosphors prepared by combustion synthesis. The structural and luminescent properties of Sm3+ ions in the phosphate lattices were investigated using powder X-ray diffraction (PXRD) and photoluminescence (PL) techniques. PXRD results of the synthesized phosphors exhibit the expected phases that are in agreement with their respective standards. Fourier-transform infrared (FTIR) spectroscopy confirms the presence of PO4 vibrational bands. Upon excitation with near ultraviolet light, the PL studies indicated that Sr3(PO4)2:Sm3+ phosphors exhibit a yellow light emission, whereas Ca3(PO4)2:Sm3+ phosphors exhibit an emission of orange light. The PL emission results are in accordance with the CIE coordinates, with the Sr3(PO4)2:Sm3+ phosphors showing coordinates of (0.56, 0.44), and the Ca3(PO4)2:Sm3+ phosphors displaying coordinates of (0.60, 0.40). Thermal analysis shows improved stability of Ca3(PO4)2:Sm3+ based on lower weight reduction in thermogravimetric analysis. The effect of temperature on the luminescence properties of the phosphor has been examined upon a 405 nm excitation. By using the fluorescence intensity ratio (FIR) method, the temperature responses of the emission ratios from the Sm3+: the 4F3/26H5/2 transition to the 4G5/26H7/2 and 4F3/26H5/2 transition to the 4G5/26H9/2 emissions are characterized. The Ca3(PO4)2:Sm3+ phosphors are more sensitive as compared with the Sr3(PO4)2:Sm3+ phosphors. The earlier research findings strongly indicate that these phosphors hold great promise as ideal candidates for applications in non-invasive optical thermometry and solid-state lighting devices.  相似文献   

19.
Triple whitlockite‐type structure‐based red phosphors Ca8MgBi1?x(PO4)7:xEu3+ (x = 0.10, 0.20, 0.30, 0.40, 0.50, 0.60, 0.70, 0.80 and 1.00) were synthesized by a conventional solid‐state reaction route and characterized by their X‐ray crystal structures. The X‐ray diffraction (XRD) patterns, Fourier transform infrared spectra, morphologies, photoluminescence spectra, UV/Vis reflectance spectra, decay times and the International Commission on Illumination (CIE) chromaticity coordinates of Ca8MgBi1?x(PO4)7:xEu3+ were analyzed. Eu‐doped Ca8MgBi(PO4)7 phosphors exhibited strong red luminescence with peaks at 616 nm due to the 5D07 F2 electric dipole transition of Eu3+ ions after excitation at 396 nm. The UV/Vis spectra indicated that the band gap of Ca8MgBi0.30(PO4)7:0.70Eu3+ is larger than that of Ca8MgBi(PO4)7. The phosphor developed in this study has great potential as a red‐light‐emitting phosphor for UV light‐emitting diodes. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

20.
Two series of red‐emitting phosphors Sr‐Ba‐Mo‐W‐O:Eu,Sm and Sr‐Ba‐Mo‐W‐O:Eu have been synthesized by a sol–gel method. The effects of the chemical composition, concentrations of Sm3+ and Eu3+, the Sr2+/Ba2+ ratio, and the W6+/Mo6+ ratio on the luminescent properties were investigated. The as‐prepared phosphors were characterized by X‐ray diffraction and Raman spectra. Results showed that single phases of the two series were prepared. The compositions of Sr0.6Ba0.13Mo0.8 W0.2O4:Eu0.10Sm0.08 and Sr0.75Ba0.1Mo0.8 W0.2O4:Eu0.10 had the strongest luminescent intensity. The excitation spectra of Sm3+, Eu3+ co‐doped phosphors were broader and the strongest peak moved to 404 nm when compared with that of Eu3+ single‐doped phosphors. The luminescent intensity of the Sr0.6Ba0.13Mo0.8 W0.2O4:Eu0.10Sm0.08 at 618 nm were 2.8 times greater than that of Sr0.75Ba0.1Mo0.8 W0.2O4:Eu0.10. The luminescent intensity of Sr0.6Ba0.13Mo0.8 W0.2O4:Eu0.10Sm0.08 and Sr0.75Ba0.1Mo0.8 W0.2O4:Eu0.10 at 150 °C decreased to 56.8% and 50.3% of the initial value at room temperature, respectively. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号