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1.
Hu Y  Yang JP  Liu JS 《Luminescence》2012,27(5):437-440
Mn‐doped willemite (Zn2SiO4:Mn) green phosphor were synthesized by sol–gel technology. The effect of the addition of sodium, as in the composition Zn(1.92 – X) NaXMn0.08SiO4, on the emission behavior was studied. FT–IR and EPR results revealed that sodium ion is incorporated into the lattice and results in the formation of isolated Mn2+ and Mn–Mn pairs. The maximum emission intensity of the sample under ultraviolet (UV) excitation occurred at the sodium concentration of x = ~0.03. The green emission at about 525 nm is assigned to Mn2+–Mn2+ pair centres on nearest neighbour Zn sites. The highest intensity of the green emission for x = ~0.03 is well close to the highest concentration of the Mn2+–Mn2+ pair. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

2.
A novel blue green‐emitting phosphor Ba2ZnSi2O7 : Eu2+ was prepared by combustion synthesis method and an efficient bluish green emission under from ultraviolet to visible light was observed. The emission spectrum shows a single intensive band centered at 503 nm, which corresponds to the 4f65d1 → 4f7 transition of Eu2+. The excitation spectrum is a broad band extending from 260 to 465 nm, which matches the emission of ultraviolet light‐emitting diodes (UV‐LEDs). The effect of doped Eu2+ concentration on the emission intensity of Ba2ZnSi2O7 : Eu2+ was also investigated. The result indicates that Ba2ZnSi2O7 : Eu2+ can be potentially useful as a UV radiation‐converting phosphor for white light‐emitting diodes. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

3.
We report the synthesis and structural characterization of Er3+,Yb3+‐doped Gd2O3 phosphor. The sample was prepared using the conventional solid‐state reaction method, which is the most suitable method for large‐scale production. The prepared phosphor sample was characterized using X‐ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), thermoluminescence (TL), photoluminescence (PL) and CIE techniques. For PL studies, the excitation and emission spectra of Gd2O3 phosphor doped with Er3+ and Yb3+ were recorded. The excitation spectrum was recorded at a wavelength of 551 nm and showed an intense peak at 276 nm. The emission spectrum was recorded at 276 nm excitation and showed peaks in all blue, green and red regions, which indicate that the prepared phosphor may act as a single host for white light‐emitting diode (WLED) applications, as verified by International de I'Eclairage (CIE) techniques. From the XRD data, the calculated average crystallite size of Er3+ and Yb3+‐doped Gd2O3 phosphor is ~ 38 nm. A TL study was carried out for the phosphor using UV irradiation. The TL glow curve was recorded for UV, beta and gamma irradiations, and the kinetic parameters were also calculated. In addition, the trap parameters of the prepared phosphor were also studied using computerized glow curve deconvolution (CGCD). Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

4.
Ca2MgSi2O7:Eu2+,Dy3+ phosphor was prepared by the solid‐state reaction method under a weak reducing atmosphere. The obtained phosphor was characterized using X‐ray diffraction (XRD), transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM), energy dispersive X‐ray spectroscopy (EDX) and Fourier transform infrared (FT‐IR) techniques. The phase structure of the Ca2MgSi2O7:Eu2+,Dy3+ phosphor was akermanite type, which is a member of the melilite group. The surface morphology of the sintered phosphor was not uniform and phosphors aggregated tightly. EDX and FT‐IR spectra confirm the elements present in the Ca2MgSi2O7:Eu2+,Dy3+ phosphor. Under UV excitation, a broadband emission spectrum was found. The emission spectra observed in the green region centered at 535 nm, which is due to the 4f–5d transition. The mechanoluminescence (ML) intensity of the prepared phosphor increased linearly with increases in the mechanical load. The ML spectra were similar to the photoluminescence (PL), which indicates that ML is emitted from the same emitting center of Eu2+ ions as PL. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

5.
Sr2MgSi2O7:Eu2+ and Sr2MgSi2O7:Eu2+,Dy3+ long afterglow phosphors were synthesized under a weak reducing atmosphere by the traditional high temperature solid state reaction method. The synthesized phosphors were characterized by powder X‐ray diffraction (XRD), energy dispersive X‐ray spectroscopy (EDX), and photo‐, thermo‐ and mechanoluminescence spectroscopic techniques. The phase structure of the sintered phosphor was an akermanite type structure, which belongs to tetragonal crystallography. The thermoluminescence properties of these phosphors were investigated and compared. Under ultraviolet light excitation, the emission spectra of both prepared phosphors were composed of a broad emission band peaking at 470 nm. When the Sr2MgSi2O7:Eu2+ phosphor was co‐doped with Dy3+, the photoluminescence (PL), afterglow and mechanoluminescence (ML) intensity were strongly enhanced. The decay graph indicated that both the sintered phosphors contained fast decay and slow decay processes. The ML intensities of Sr2MgSi2O7:Eu2+ and Sr2MgSi2O7:Eu2+,Dy3+ phosphors were increased proportionally with increasing impact velocity, a finding that suggests that these phosphors could be used as sensors to detect the stress of an object. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

6.
CaF2:Eu2+ is a well known phosphor having efficient excitation in the near ultraviolet (NUV) range. Phosphors with NUV excitation are required in newly emerging applications such as photoluminescence liquid crystal displays (PLLCD), solid‐state lighting (SSL), and down‐conversion for solar cells. However, emission of CaF2:Eu2+ is around 424 nm. Eye sensitivity drops considerably at these wavelengths. It is thus not useful for display applications for which emission in one of the primary colours (blue – 450 nm, green – 540 nm or red – 610 nm) is required. Efforts were made to modify the Photoluminescence (PL) spectra of CaF2:Eu2+ to meet these requirements using co‐dopants. A Ca0.49Sr0.50Eu0.01F2 phosphor showing better colour coordinates and having an emission maximum around 440 nm was discovered during these studies. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

7.
A series of Sr2P2O7:Dy3+, Sr2P2O7:Ce3+ and Sr2P2O7:Dy3+,Ce3+ phosphors was synthesized via the one‐step calcination process for the precursors prepared by co‐precipitation methods. The phases, morphology, quantum efficiency and photoluminescence properties of the obtained phosphors were characterized systematically. These results show that the near‐spherical particles prepared through calcining the precursors by means of ammonium dibasic phosphate co‐precipitation (method 3) have the smallest particle size and strongest emission intensity among the three methods in the paper. With Dy3+ concentration increasing in Sr2P2O7:Dy3+ phosphors, the luminescence intensity first increases, reaches maximum, and then decreases. A similar trend was followed by Sr2P2O7:Ce3+ with Ce3+concentration increasing. A successful attempt was made to initiate the energy transfer mechanism from Ce3+ to Dy3+ in the host lattice and an overlap between the emission band of Ce3+ and the excitation band of Dy3+ indicated that the Ce3+ → Dy3+ energy transfer may indeed exist. It is clear that the photoluminescence intensity of Dy3+ as well as the quantum efficiency of the phosphor can be enhanced markedly by co‐doping Ce3+. Sr2P2O7:Dy3+,Ce3+ has its (CIE) chromaticity coordinates in the bluish‐white‐light region, near the standard illuminant D65. The CIE 1913 chromaticity coordinates of Sr2P2O7:Dy3+ phosphors fall in the white‐light region, and are adjacent to the ideal white‐light coordinates. In addition, the colour temperature and colour tone of Sr2P2O7:Dy3+ could be adjusted by changing the relative concentration of Dy3+. In short, Sr2P2O7:Dy3+ can be a promising single‐phased white‐light emitting phosphor for near‐UV (NUV) w‐LEDs.  相似文献   

8.
Pyrophosphates K2AEP2O7 (AE = Ca, Sr) prepared by the classical solid‐state technique and activated with Ce3+ are described. Intense emission was observed in K2AEP2O7 (AE = Ca, Sr). The effect of Mn2+ co‐doping was studied. The broad emission peak of Mn2+ was observed at 534 nm in K2SrP2O7:Ce3+ and at 539 nm in K2CaP2O7:Ce3+, Mn2+. Mn2+ emission was greatly enhanced by addition of the sensitizer Ce3+ due to efficient energy transfer from Ce3+ to Mn2+. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

9.
A novel far-red emitting phosphor Sr2MgWO6: Mn4+ was fabricated using high-temperature solid-state reaction. X-ray diffraction patterns, scanning electron microscopy images, and photoluminescence excitation and photoluminescence spectra for this phosphor were analyzed in detail. The analysis revealed that its emission ranged from 600 to 800 nm and peaked at 699 nm, which was attributed to the 2Eg4A2g transition of Mn4+ under 314 nm excitation. Moreover, we introduced rare-earth Yb3+ ions into the Sr2MgWO6:Mn4+ to improve its far-red emitting intensity. The photoluminescence (PL) intensity of the Yb3+ co-doped phosphor was three times higher than that of the single-doped phosphor. Therefore charge compensation is an efficient approach to improving PL intensity. The phosphor emitted a far-red light that resembled the pigments essential for plant growth in terms of the absorption spectrum. Therefore, the obtained phosphor, Sr2MgWO6:0.006Mn4+,0.2Yb3+, had the potential to be a new type of far-red luminescent powder for indoor plant growth LEDs.  相似文献   

10.
In the recent few years, Eu2+- and Mn4+-activated phosphors are widely used as potential colour converters for indoor plant cultivation lighting application due to their marvellous luminescence characteristics as well as low cost. In this investigation, we synthesized novel red colour-emitting Ca(2−x)Mg2(SO4)3:xmol% Eu2+ (x = 0–1.0 mol%) phosphors via a solid-state reaction method in a reducing atmosphere. The photoluminescence (PL) excitation spectra of synthesized phosphors exhibited a broad excitation band with three excitation bands peaking at 349 nm, 494 nm, and 554 nm. Under these excitations, emission spectra exhibited a broad band in the red colour region at ~634 nm. The PL emission intensity was measured for different concentrations of Eu2+. The maximum Eu2+ doping concentration in the Ca2Mg2(SO4)3 host was observed for 0.5 mol%. According to Dexter theory, it was determined that dipole–dipole interaction was responsible for the concentration quenching. The luminous red colour emission of the sample was confirmed using Commission international de l'eclairage colour coordinates. The results of PL excitation and emission spectra of the prepared phosphors were well matched with excitation and emission wavelengths of phytochrome PR. Therefore, from the entire investigation and obtained results it was concluded that the synthesized Ca0.995Mg2(SO4)3:0.5mol%Eu2+ phosphor has huge potential for plant cultivation application.  相似文献   

11.
An intense green luminescent Na2Ca(PO4)F:Mn2+ phosphor has been prepared at high temperature by reduction treatment in a charcoal environment. The emission band of Mn2+ was obtained at around 522 nm (green) under 259 nm excitation. Enhancement in emission intensity arising from the thermal treatment is reported. The intense emission of the spectrum was assigned to electronic transitions 4T16A1 of Mn2+ ions. Intense PL emission suggested that temperature employed plays an important role in the present matrix. X‐ray diffraction pattern, photoluminescence and morphology by SEM of the host lattice of phosphors at different temperatures have been reported in this paper. The results obtained show that the present phosphor has potential for application in green emitting phosphors for the lamp industry. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

12.
Nanophosphors of (Sr0.98‐xMgxEu0.02)2SiO4 (x = 0, 0.18, 0.38, 0.58 and 0.78) were prepared through low temperature solution combustion method and their luminescence properties were studied. The emission peak for Eu2+ ?doped Sr2SiO4 nanophosphor is observed at ~490 nm and ~553 nm corresponding to two Sr2+ sites Sr(I) and Sr(II) respectively for 395 nm excitation. However the addition of Mg2+ dopant in Sr2SiO4 leads to suppression of ~553 nm emission peak due to absence of energy levels of Sr (II) sites which results in a single broad emission at ~460 nm. It was shown that the emission peak blue shifted with increase in Mg concentration which may be attributed to change in crystal field environment around Sr(I) sites. Therefore, the (Mg0.78Sr0.20Eu0.02)2SiO4 nanophosphor can be used for blue emission and the Sr2SiO4:Eu0.042+ for green–yellow emission at 395 nm excitations. The Commission International de L'Eclairage (CIE) chromaticity coordinates for mixed powders of (Mg0.78Sr0.20Eu0.02)2SiO4 and Sr2SiO4:Eu0.042+ (in a 1:1 ratio) fall in the white region demonstrating the possible use of the mixture in white light generation using near‐UV excitation source.  相似文献   

13.
Sr3MgSi2O8:Ce3+, Dy3+ phosphors were prepared by a solid‐state reaction technique and the photoluminescence properties were investigated. The emission spectra show not only a band due to Ce3+ ions (403 nm) but also as a band due to Dy3+ ions (480, 575 nm) (UV light excitation). The photoluminescence properties reveal that effective energy transfer occurs in Ce3+/Dy3+ co‐doped Sr3MgSi2O8 phosphors, and the co‐doping of Ce3+ could enhance the emission intensity of Dy3+ to a certain extent by transferring its energy to Dy3+. The Ce3+/Dy3+ energy transfer was investigated by emission/excitation spectra, and photoluminescence decay behaviors. In Sr2.94MgSi2O8:0.01Ce3+, 0.05Dy3+ phosphors, the fluorescence lifetime of Dy3+ (from 3.35 to 27.59 ns) is increased whereas that of Ce3+ is greatly decreased (from 43.59 to 13.55 ns), and this provides indirect evidence of the Ce3+ to Dy3+ energy transfer. The varied emitted color of Sr3MgSi2O8:Ce3+, Dy3+ phosphors from blue to white were achieved by altering the concentration ratio of Ce3+ and Dy3+. These results indicate Sr3MgSi2O8:Ce3+, Dy3+ may be as a candidate phosphor for white light‐emitting diodes. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

14.
Using a high‐temperature solid‐state reaction, the chlorine in Ba2YB2O6Cl is gradually replaced by F, and a new compound with the nominal chemical formula Ba2YB2O6F and two phosphors doped with Ce3+ and Eu3+, respectively, are obtained. X‐Ray diffraction and photoluminescence spectroscopy are used to characterize the as‐synthesized samples. The as‐synthesized Ba2YB2O6Cl exhibits bright blue emission in the spectral range ~ 330–410 nm with a maximum around 363 nm under X‐ray or UV excitation. Ba2YB2O6F:0.01Ce3+ exhibits blue emission in the range ~ 340–570 nm with a maximum around 383 nm. Ba2YB2O6F:0.01Eu3+ exhibits a predominantly 5D07 F2 emission (~610 nm) and the relative intensities of the 5D07 F0,1,2 emissions are tunable under different wavelength UV excitation. The luminescence behaviors of the two phosphors are explained simply in terms of the host composition and site occupancy probability of Ce3+ and Eu3+, respectively. The results indicate that these phosphors have potential application as a blue phosphor or as a red phosphor. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

15.
A series of Sr2ZnWO6 phosphors co‐doped with Eu3+, Bi3+ and Li+ were prepared using the Pechini method. The samples were tested using X‐ray diffraction and luminescence spectroscopy. The results show that the samples can be effectively excited by near‐ultraviolet (UV) and UV light. The introduction of Bi3+ and Li+ significantly enhances the fluorescence emission of Sr2ZnWO6:Eu3+ and changes the light emitted by the phosphors from bluish‐green to white. When excited at 371 nm, Sr2–x–zZn1–yWO6:xEu3+,yBi3+,zLi+ (x = 0.05, y = 0.05, z = 0.05, 0.1 and 0.15) samples emit high‐performance white light. Intense red–orange emission is also observed when excited by UV light. The obtained phosphor is a potential white‐emitting phosphor that could meet the needs of excitation sources with near‐UV chips. In addition, this phosphor might have promising application as a red–orange emitting phosphor for white light‐emitting diodes based on UV light‐emitting diodes. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

16.
Eu3+,Dy3+ co-doped Sr2LaZrO5.5-based phosphors were prepared through a sol–gel method. Through characterization, it was found that the Sr2LaZrO5.5-based fluorescent powder co-doped with Eu3+ and Dy3+ had a cubic structure. At an excitation wavelength of 290 nm, the substrate Sr2LaZrO5.5 exhibited strong blue emission at 468 nm, and the Sr2LaZrO5.5:18%Eu3+ phosphor exhibited a strong red emission peak at 612 nm. When the doping amount of Dy3+ was 5, 8, 12, 15, or 18%, the Sr2LaZrO5.5:18%Eu3+ phosphor changed from an orange-red light, to a warm white light, and to a cold white light. According to the emission spectra, the emission intensities of the substrates Sr2LaZrO5.5 and Sr2LaZrO5.5:Eu3+ decreased with increasing Dy3+ concentration, confirming the energy transfer between the host Sr2LaZrO5.5-Eu3+,Dy3+, and resulting in a lower CCT value, with significantly improved white light emission.  相似文献   

17.
The structural and photoluminescence properties of CaYAl3O7 phosphor material doped with varying concentration of Mn2+ have been studied. The phosphor material was synthesized by the combustion method at 500 °C and was characterized using X‐ray diffraction, Fourier transform infrared spectroscopy and photoluminescence spectroscopy (PL). X‐ray diffraction showed that the crystallites have average sizes in the range of ~58–70 nm. Corresponding Fourier transform infrared spectroscopy investigations confirm the phase formation and the presence of aluminate group (Al‐O bands) in CaYAl3O7:Mn2+ phosphor. Under the excitation at 356 nm wavelength, the PL spectra show the occurrence of two emission peaks obtained in the blue region at 389 nm and 412 nm, which is attributed to the 4 T1(G) → 6A1 transition of Mn2+ ion. Upon increasing Mn2+ concentration, the relative PL intensity shows an initial decrement followed by an increase displaying the effect of concentration quenching. Overall the results suggest the possibility of using this material in white lighting devices and plasma display panels. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

18.
The afterglow properties of long afterglow luminescent materials are greatly affected by their defects, which are distributed on the grain surface. Increasing the exposed surface area is an important method to improve the afterglow performance. In this research, long rod-shaped long afterglow materials Sr2MgSi2O7:Eu2+,Dy3+ were prepared using the hydrothermal-coprecipitation method. When the reaction time reached 96 h, the length of the afterglow materials could grow to 2 mm, and the sintering temperature was just 1150°C. The emission spectra of all obtained samples upon excitation at 397 nm had a maximum of 465 nm, which belonged to the representative transition of Eu2+. The initial brightness was 1.35 cd/m2. The afterglow time could reach 19 h, giving a good afterglow performance. The research on this kind of material has essential significance in the exploration of luminescence mechanisms and their applications.  相似文献   

19.
Sr4Al2O7:Eu3+ and Sr4Al2O7:Dy3+ phosphors with alkali metal substitution were prepared using a sol–gel method. The effects of a charge compensator R on the structure and luminescence of Sr4Al2O7:Re3+,R+ (Re = Eu and Dy; R = Li, Na and K) phosphors were investigated in detail. Upon heating to 1400°C, the structure of the prepared samples was that of the standard phase of Sr4Al2O7. Under ultraviolet excitation, all Sr4Al2O7:Eu3+,R+ samples exhibited several narrow emission peaks ranging from 550 to 700 nm due to the 4f → 4f transition of Eu3+ ions. All Sr4Al2O7:Dy3+,R+ phosphors showed two emission peaks at 492 and 582 nm, due to the 4F9/2 → 6H15/2 and 4F9/2 → 6H13/2 transitions of Dy3+ ions, respectively. The luminescence intensity of Sr4Al2O7:Re3+,R+ (Re = Eu and Dy; R = Li, Na and K) phosphors improved markedly upon the addition of charge compensators, promoting their application in white light‐emitting diodes with a near‐ultraviolet chip.  相似文献   

20.
Yongfu Teng 《Luminescence》2019,34(4):432-436
In the Ba9Lu2Si6O24 (BLS) host, Ce3+ shows cyan emissions peaking at 490 nm under 400 nm excitations. BLS:Tb3+ only can be effectively excited by 254 nm light and gives rise to green emissions at 553 nm. However, both the cyan and green emissions can be obtained in BLS:Ce3+,Tb3+ under 400 nm excitations due to effective energy transfers from Ce3+ to Tb3+. BLS:Mn2+ shows red emissions peaking at 610 nm under 414 nm excitations. By co‐doping Ce3+, Tb3+ and Mn2+, tunable full‐color emissions were obtained. The BLS:0.3Ce3+,0.6Tb3+,0.15Mn2+ single phosphor exhibits a white light with a high color rendering index of 85 and a correlated color temperature of 5480 K under 400 nm excitation.  相似文献   

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