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1.
The polycrystalline Eu2+ and RE3+ co-doped strontium aluminates SrAl2O4:Eu2+, RE3+ were prepared by solid state reactions. The UV-excited photoluminescence, persistent luminescence and thermo-luminescence of the SrAl2O4:Eu2+, RE3+ phosphors with different composition and doping ions were studied and compared. The results showed that the doped Eu2+ ion in SrAl2O4:Eu2+, Dy3+ phosphors works as not only the UV-excited luminescent center but also the persistent luminescent center. The doped Dy3+ ion can hardly yield any luminescence under UV-excitation, but can form a electron trap with appropriate depth and greatly enhance the persistent luminescence and thermo-luminescence of SrAl2O4:Eu2+. Different co-doping RE3+ ions showed different effects on persistent luminescence. Only the RE3+ ion (e.g. Dy3+, Nd3+), which has a suitable optical electro-negativity, can form the appropriate electron trap and greatly improve the persistent luminescence of SrAl2O4:Eu2+. Based on above observations, a persistent luminescence mechanism, electron transfer model, was proposed and illustrated.  相似文献   

2.
《Materials Letters》2004,58(3-4):352-356
Eu2+,Dy3+ co-doped strontium aluminate (SrAl2O4) phosphor nanoparticles with high brightness and long afterglow were prepared by glycine–nitrate solution combustion synthesis at 500 °C, followed by heating the resultant combustion ash at 1100 °C in a weak reductive atmosphere of active carbon. The average particle size of the SrAl2O4:Eu,Dy phosphor nanoparticles ranges from 15 to 45 nm as indicated by transmission electron microscopy (TEM). The broad-band UV-excited luminescence of the SrAl2O4:Eu,Dy phosphor nanoparticles was observed at λmax=513 nm due to transitions from the 4f65d1 to the 4f7 configuration of the Eu2+ ion. The results indicated that the main peaks in the emission and excitation spectrum of phosphor nanoparticles shifted to the short wavelength compared with the phosphor obtained by the solid-state reaction synthesis method. The decay speed of the afterglow for phosphor nanoparticles was faster than that obtained by the solid-state reaction method.  相似文献   

3.
Pb2+ doped SrAl2B2O7 was prepared by solution combustion synthesis. The synthesized material was determined by powder XRD. The photoluminescence properties of the synthesized phosphor were investigated at room temperature using a spectrofluorometer. The emission peak of Pb2+ doped SrAl2B2O7 was observed at 420 nm upon excitation at 277 nm. The Stokes shift of SrAl2B2O7:Pb2+ was calculated to be 12 292 cm−1. The luminescence behavior of Pb2+ in both SrAl2B2O7 and CaAl2B2O7 was discussed. The text was submitted by the authors in English.  相似文献   

4.
This article present the reports on optical study of Eu2+ and Ce3+ doped SrMg2Al6Si9O30 phosphors, which has been synthesized by combustion method at 550 °C. Here SrMg2Al6Si9O30:Eu2+ emission band observed at 425 nm by keeping the excitation wavelength constant at 342 nm, whereas SrMg2Al6Si9O30:Ce3+ ions shows the broad emission band at 383 nm, under 321 nm excitation wavelength, both the emission bands are assigned due to 5d–4f transition respectively. Further, phase purity, morphology and crystallite size are confirmed by XRD, SEM and TEM analysis. However, the TGA analysis is carried out to know the amount of weight lost during the thermal processing. The CIE coordinates of SrMg2Al6Si9O30:Eu2+ phosphor is observed at x?=?0.160, y?=?0.102 respectively, which may be used as a blue component for NUV-WLEDs. The critical distance of energy transfer between Ce3+ ions and host lattice is found to be 10.65 Å.  相似文献   

5.
The novel Ca4?x(PO4)2O: xDy3+ and Ca4?x?y(PO4)2O: xDy3+, yEu2+ multi-color phosphors were synthesized by traditional solid-state reaction. The crystal structure, particle morphology, photoluminescence properties and energy transfer process were investigated in detail. The X-ray diffraction (XRD) results demonstrate that the products showed pure monoclinic phase of Ca4(PO4)2O when x < 0.1. The scanning electron microscopy (SEM) indicated that the phosphors were grain-like morphologies with diameters of ~ 3.7–7.0 μm. Under excitation of 345 nm, Dy3+-doped Ca4(PO4)2O phosphors showed multi-color emission bands at 410, 481 and 580 nm originated from oxygen vacancies and Dy3+. Interestingly, Ca4(PO4)2O: Dy3+, Eu2+ phosphors exhibited blue emission band at 481 nm and broad emission band from 530 to 670 nm covering green to red regions. The energy transfer process from Dy3+ to Eu2+ was observed for the co-doped samples, and the energy transfer efficiency reached to 60% when Eu2+ molar concentration was 8%. In particular, warm/cool/day white light with adjustable CCT (2800–6700 K) and high CRI (Ra > 85) can be obtained by changing the Eu2+ co-doping contents in Ca4(PO4)2O: Dy3+, Eu2+ phosphors. The optimized Ca3.952(PO4)2O: 0.04Dy3+, 0.008Eu2+ phosphor can achieve the typical white light with CCT of 4735 K and CRI of 87.  相似文献   

6.
Bluish green emitting phosphor, Ca3Al2O6:Ce3+, is prepared by low-temperature combustion method. X-ray diffraction, photoluminescence, scanning electron microscopy techniques are used to characterize the synthesized phosphor. The most efficient bluish green (483 nm) emission is observed under the excitation by near UV light. The emission characteristics are credited to 5d → 4f type transitions in Ce3+. The luminescence properties of Eu2+ are predicted for the first time from those of Ce3+. Also, photoluminescence of Eu3+ is studied in the same host. The emission spectrum of Ca3Al2O6:Eu3+ shows the peak at 592 (orange) and 614 nm (red) wavelengths. Ca3Al2O6:Ce3+phosphor can be a potential blue phosphor for field emission display, solid-state lighting and LED.  相似文献   

7.
LiEu1−x (W2−y Mo y )O8:xBi3+ series red-emitting phosphors were synthesized by solid state reaction. The structure, morphology, and photoluminescent properties of phosphors were studied by X-ray powder diffraction, scanning electron microscopy, and photoluminescence spectrum, respectively. X-ray powder diffraction analysis showed that the as-obtained phosphors belong to the scheelite structure. The average particle size of the investigated phosphor was about 8 μm. The excitation spectrum exhibits a charge-transfer broad band along with some sharp peaks from the typical 4f–4f transitions of Eu3+. Under excitation of UV, near-UV, or blue light, these phosphors showed strong red emission at 615 nm due to 5D07F2 transition of Eu3+. The incorporation of Mo6+ into LiEuW2O8:Bi3+ could induce red-shift of the charge-transfer broad band and a remarkable increase of photoluminescence. The highest red-emission intensity was observed with LiEu0.80Mo2O8:0.20Bi3+. Compared with the commercial red-emitting phosphor, Y2O2S:Eu3+, the emission intensity of LiEu0.80Mo2O8:0.20Bi3+ phosphor is much stronger than that of Y2O2S:Eu3+ and its chromaticity coordinates are closer to the standard values than that of the commercial phosphor. The optical properties of LiEu0.80Mo2O8:0.20Bi3+ phosphor make it attractive for the application in white-light-emitting diodes (LEDs), in particular for near-UV InGaN-based white-LEDs.  相似文献   

8.
SrAl2O4 phosphor nano-powders activated with heavy elements such as Eu and Dy were prepared by microwave synthesis method. Using this method led to the reduction of processing time. Various calcinations times have been employed to produce pure SrAl2O4:Eu2+, Dy3+ phosphor materials. It was found out that microwave synthesis technique led to reduction of optimum calcinations time to 9 min. XRD analysis showed that the powders were nearly pure SrAl2O4 phase, in which the SrAl2O4 host phase has the maximum fraction of monoclinic SrAl2O4 phase. The critical pH to achieve pure SrAl2O4 phase determined to be equal to 4. For the synthesized SrAl2O4:Eu2+, Dy3+, the properties of photoluminescence such as emission, excitation and decay time were examined. Fluorescent spectrophotometer results revealed that two excitation peaks are appeared at 280 and 339 nm and an emission peak at 515 nm. The crystallite size of these pigments is about 58.22 nm after calcinations for 9 min in microwave as determined by Scherrer’s formula. SEM was used to study the morphology and shape of powders.  相似文献   

9.
Compound CaAl4O7 (CA4), SrAl4O7 (SA4), CaAl12O19 (CA12) and SrAl12O19 (SA12) have been synthesized by using single step combustion method. The phosphors have been characterized by XRD, SEM and PL techniques. Both CA4 and SA4 possess monoclinic crystal structure whereas CA12 and SA12 possess hexagonal structure. Effects of crystal symmetry on the emission spectrum have been studied by doping the samples with Ce3+ and Eu2+ ions. The luminescence properties of Ce3+ and Eu2+ in these hosts is discussed on the basis of their covalent character and the crystal field splitting of the d-orbital of dopant ions. The spectroscopic properties, crystal field splitting, centroid shift, red shift and stokes shift have been studied. Spectroscopic properties of Eu2+ ions have been accurately predicted from those of Ce3+ ions in the same host. Most importantly experimental results were matched excellently with the calculated results. The preferential substitution of Ce3+ and Eu2+ at different Ca2+, Sr2+ crystallographic sites have been discussed. The dependence of emission wavelengths of Ce3+ and Eu2+ on the local symmetry of different crystallographic sites was also studied by using Van Uitert’s empirical relation. Differences in the emission spectrum of these samples have been observed despite their similar crystal structures and space group. Possible reasons have been discussed.  相似文献   

10.
BaAl2O4:Eu2+,RE3+ (RE3+=Y, Pr) down conversion nanophosphors were prepared at 600 °C by a rapid gel combustion technique in presence of air using boron as flux and urea as a fuel. A comparative study of the prepared materials was carried out with and without the addition of boric acid. The boric acid was playing the important role of flux and reducer simultaneously. The peaks available in the XPS spectra of BaAl2O4:Eu2+ at 1126.5 and 1154.8 eV was ascribed to Eu2+(3d 5/2) and Eu2+(3d 3/2) respectively which confirmed the presence of Eu2+ ion in the prepared lattice. Morphology of phosphors was characterized by tunneling electron microscopy. XRD patterns revealed a dominant phase characteristics of hexagonal BaAl2O4 compound and the presence of dopants having unrecognizable effects on basic crystal structure of BaAl2O4. The addition of boric acid showed a remarkable change in luminescence properties and crystal size of nanophosphors. The emission spectra of phosphors had a broad band with maximum at 490–495 nm due to electron transition from 4f 65d 1 → 4f 7 of Eu2+ ion. The codoping of the rare earth (RE3+=Y, Pr) ions help in the enhancement of their luminescent properties. The prepared phosphors had brilliant optoelectronic properties that can be properly used for solid state display device applications.  相似文献   

11.
A new efficient phosphor, Eu2+/Eu3+ and Ce3+ activated Na2Zn5(PO4)4 has been synthesized by solid-state reaction technique at high temperature. X-ray powder diffraction analysis confirmed the formation of Na2Zn5(PO4)4 host lattice. Scanning electron microscopy indicated that the microstructure of the phosphor consisted of irregular fine grains with a size of about 0·5–2 μm. Photoluminescence excitation spectrum measurements of Ce3+ activated Na2Zn5(PO4)4 show that the phosphor can be efficiently excited by UV-Vis light from 280 to 310 nm to realize emission in the visible (blue) range due to the 5d-4f transition of Ce3+ ions which is applicable for scintillation purpose, whereas Eu2+/Eu3+ activated Na2Zn5(PO4)4 phosphor emits blue, green and red emission spectrum shows at 487 nm, 546 nm with a dominant peak at 611 nm respectively, due to Eu2+/Eu3+ ions which is promising candidate for solid state lighting. Therefore, newly synthesised, by low cost and easy technique prepared, novel phosphors may be useful as RGB phosphor for solid state lighting application.  相似文献   

12.
Y2O3:Eu3+ phosphors were prepared by hydrothermal method. Effect of the doping concentration of Eu3+ on the photoluminescence properties of Y2O3:Eu3+ phosphor was studied in details. It was found that the strongest emission intensity is achieved as atomic ratio of Y3+ to Eu3+ is 8. As concentration of Eu3+ exceeds the critical concentration, the emission intensity decreases dramatically due to the concentration quenching of Eu3+. Also, the effect of Li+ on the photoluminescence performance of the Y2O3:Eu3+ phosphor is studied in this work. According to the results, the doping of Li+ may greatly improve the PL performance of the Y2O3:Eu3+ phosphors due to the flux effect and improved crystallinity caused by the doping of Li+.  相似文献   

13.
This paper reports the comparison of photoluminescence and afterglow behavior of Dy3+ in CaSnO3 and Ca2SnO4 phosphors. The samples containing CaSnO3 and Ca2SnO4 were prepared via solid-state reaction. The properties have been characterized and analyzed by utilizing X-ray diffraction (XRD), photoluminescence spectroscope (PLS), X-ray photoelectron spectroscopy (XPS), afterglow spectroscopy (AS) and thermal luminescence spectroscope (TLS). The emission spectra revealed that CaSnO3:Dy3+ and Ca2SnO4:Dy3+ phosphors showed different photoluminescence. The Ca2SnO4:Dy3+ phosphor showed a typical 4F9/2 to 6Hj energy transition of Dy3+ ions, with three significant emissions centering around 482, 572 and 670 nm. However, the CaSnO3:Dy3+ phosphor revealed a broad T1 → S0 transitions of Sn2+ ions. The XPS demonstrate the existence of Sn2+ ions in CaSnO3 phosphor caused by the doping of Dy3+ ions. Both the CaSnO3:Dy3+ and Ca2SnO4:Dy3+ phosphors showed a typical triple-exponential afterglow when the UV source switched off. Thermal simulated luminescence study indicated that the persistent afterglow of CaSnO3:Dy3+ and Ca2SnO4:Dy3+ phosphors was generated by the suitable electron or hole traps which were resulted from the doping the calcium stannate host with rare-earth ions (Dy3+).  相似文献   

14.
This article presents the synthesis and photoluminescence (PL) properties of Y2Zr2O7:Tb3+. The Tb3+-doped Y2Zr2O7 zirconates were successfully synthesized by a hydrothermal process at 200 °C for 20 h. X-ray diffractometer (XRD) patterns revealed that all of the products were phase-pure with the fluorite structure. PL study showed that the Y2Zr2O7:Tb3+ phosphors exhibited obvious PL emission peaks which located at 490, 545, 585, and 623 nm; the dominant emission located at 545 nm is assigned to 5D4 → 7F5 transition. Furthermore, Tb3+-doping concentration strongly affected the PL properties, and the quenching concentration is 5 at.%.  相似文献   

15.
Homogeneous Y2O3:Eu3+ nanorods with the lengths of several micrometres were successfully synthesised on a large scale by using a urea-assisted hydrothermal method and a post-calcining process. In this study, the influences of urea content and NaOH concentration on the oriented growth, photoluminescence (PL) and electroluminescence (EL) intensity enhancement of Y2O3:Eu3+ were investigated. As a precipitant for isotropic growth, urea can counteract the effect of NaOH on oriented growth along the c-axis during hydrothermal treatment. The Y2O3:Eu3+ powders exhibited a strong red emission centred at 613 nm under either 245 nm UV excitation or the direct current high electric field. The PL intensity of the Y2O3:Eu3+ phosphor prepared with 0.3 g of urea reached 141 % that of the sample prepared under the same conditions but without urea. The strategy for controlling the oriented growth, PL and EL enhancement of Y2O3:Eu3+ can be extended to the synthesis of other inorganic nano/micromaterials.  相似文献   

16.
The detailed preparation process of Eu2+ and Dy3+ ion co-doped Sr3Al2O6 phosphor powders with red long afterglow by sol–gel-combustion method in the reducing atmosphere is reported. X-ray diffraction, scanning electron microscopy and photoluminescence spectroscopy are used to investigate the effects of synthesis temperature on the crystal characteristics, morphology and luminescent properties of the as-synthesized Sr3Al2O6:Eu2+, Dy3+ phosphors. The results reveal that Sr3Al2O6 crystallizes completely when the combustion ash is sintered at 1200 °C. The excitation and the emission spectra indicate that the excitation broad-band lies chiefly in visible range and the phosphor powders emit strong light at 618 nm under the excitation of 472 nm. The light intensity and the light-lasting time of Sr3Al2O6:Eu2+, Dy3+ phosphors are increased when increasing the calcination temperatures from 1050 to 1200 °C. The afterglow of Sr3Al2O6:Eu2+, Dy3+ phosphors sintered at 1200 °C lasts for over 600 s when the excited source is cut off. The red emission mechanism is discussed according to the effect of nephelauxetic and crystal field on the 4f65d1 → 4f7 transition of the Eu2+ ions.  相似文献   

17.
《Advanced Powder Technology》2021,32(8):2806-2815
A series of white-emitting K2CaP2O7:Dy3+ and K2CaP2O7:Dy3+, Eu3+ phosphors were synthesized via a solid-state method, and Eu3+ was co-doped in K2CaP2O7:Dy3+ to improve its white light performance. The influences of preparation temperature and Dy3+/Eu3+ concentration on the crystal structure and photoluminescence characteristics were investigated. XRD results indicate that K2CaP2O7:Dy3+ samples prepared above 700 °C matches the standard K2CaP2O7 phase. Under excitation of 349 nm, K2CaP2O7:Dy3+ phosphor exhibited characteristic emission peaks at 487 nm (blue) and 579 nm (yellow), and white emission was realized through combining these blue and yellow emissions. After co-doping Eu3+ ions, the co-luminescence of Dy3+/Eu3+ with energy transfer between Dy3+and Eu3+ were demonstrated. The chromaticity of white light was controlled by changing the ratio of Dy3+/Eu3+ concentrations, which lead to a warm white light. Therefore, the results indicate that K2CaP2O7:Dy3+, Eu3+ powders have a potential application in w-LEDs as single-component white-emitting phosphor.  相似文献   

18.
A series of novel red-emitting Na2Ca3???x Si2O8:xEu3+ 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 Na2Ca3Si2O8:Eu3+ were characterized. Na2Ca3Si2O8:Eu3+ with self-compensated and alkali metal ions charge compensated approaches (2Ca2+→Eu3+ + 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 Y203S:Eu3+. The present work implies that the efficient charge compensated phosphors are promising candidates as red-emitting phosphor for w-LEDs.  相似文献   

19.
Glassy-crystalline samples of compositions (B2O3-Al2O3-SiO2):Eu2+ (3 at %) and (B2O3-2SiO2):Eu2+ (3 at %) were obtained by sintering the initial powdered mixtures at 1300°C in air. Being excited by laser radiation at a wavelength of 325 nm, the former samples exhibit intense blue photoluminescence with a maximum at 434–448 nm, while the latter samples emit in the violet spectral interval with a maximum at 409 nm. An increase in the content of B2O3 leads to a shift of the emission maximum toward a shorter wavelength, while additional annealing at 1300°C C in vacuum shifts the spectrum toward longer wavelengths.  相似文献   

20.
Ba2LaV3O11:Eu3+ phosphors were firstly synthesized by the traditional solid-state reaction method at 1100 °C. Their luminescence properties were investigated by photoluminescence excitation and emission spectra. The excitation spectrum shows a broad band centered at about 275 nm in the region from 200 to 370 nm, which is attributed to an overlap of the charge transfer transitions of O2??→?V5+ and O2??→?Eu3+. The phosphors exhibit the red emissions of Eu3+ and the emission intensity ratio of 5D0?→?7F2 to 5D0?→?7F1 is dependent on the Eu3+ concentration due to an environment change about Eu3+ ions. Concentration quenching occurs at 30 mol% in the phosphors and exchange interaction is its main mechanism. Ba2LaV3O11:Eu3+ displays tunable CIE color coordinates from yellow orange to red depended on Eu3+ content, which may have a potential application for illuminating and display devices.  相似文献   

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