136 resultados para BAFBR-EU2
Resumo:
The absorption spectra of the undoped Y2SiO5 and Eu3+-doped Y2SiO5 crystals grown by the Czochralski technique were compared before and after annealing and, similarly, the unannealed and annealed crystals after gamma-ray irradiation. The absorption bands of Eu2+ ions with peaks at 300 and 390 nm were observed in the as-grown Y2SiO5:Eu3+ crystal. These peaks were more intense in H-2-annealed and irradiated Y2SiO5:Eu3+ crystals. The additional absorption peaks at 260 and 320-330 nm which were attributed to F color centers and O- hole centers were observed in irradiated undoped Y2SiO5 and Y2SiO5:Eu3+ crystals, respectively. (c) 2005 Elsevier B.V. All rights reserved.
Resumo:
Quasi-aligned Eu2+-doped wurtzite ZnS nanowires on Au-coated Si wafers have been successfully synthesized by a vapor deposition method under a weakly reducing atmosphere. Compared with the undoped counterpart, incorporation of the dopant gives a modulated composition and crystal structure, which leads to a preferred growth of the nanowires along the [0110] direction and a high density of defects in the nanowire hosts. The ion doping causes intense fluorescence and persistent phosphorescence in ZnS nanowires. The dopant Eu2+ ions form an isoelectronic acceptor level and yield a high density of bound excitions, which contribute to the appearance of the radiative recombination emission of the bound excitons and resonant Raman scattering at higher pumping intensity. Co-dopant Cl- ions can serve not only as donors, producing a donor-acceptor pair transition with the Eu2+ acceptor level, but can also form trap levels together with other defects, capture the photoionization electrons of Eu2+, and yield long-lasting (about 4 min), green phosphorescence. With decreasing synthesis time, the existence of more surface states in the nanowires forms a higher density of trap centers and changes the crystal-field strength around Eu2+. As a result, not only have an enhanced Eu2+ -4f(6)5d(1)-4f(7) intra-ion transition and a prolonged afterglow time been more effectively observed (by decreasing the nanowires' diameters), but also the Eu2+ related emissions are shifted to shorter wavelengths.
Resumo:
The pressure dependence of the photoluminescence from ZnS : Mn2+, ZnS : Cu2+, and ZnS : Eu2+ nanoparticles were investigated under hydrostatic pressure up to 6 GPa at room temperature. Both the orange emission from the T-4(1) - (6)A(1) transition of Mn2+ ions and the blue emission from the DA pair transition in the ZnS host were observed in the Mn-doped samples. The measured pressure coefficients are -34.3(8) meV/GPa for the Mn-related emission and -3(3) meV/GPa for the DA band, respectively. The emission corresponding to the 4f(6)5d(1) - 4f(7) transition of Eu2+ ions and the emission related to the transition from the conduction band of ZnS to the t(2) level of Cu2+ ions were observed in the Eu- and Cu-doped samples, respectively. The pressure coefficient of the Eu-related emission was found to be 24.1(5) meV/GPa, while that of the Cu-related emission is 63.2(9) meV/GPa. The size dependence of the pressure coefficients for the Mn-related emission was also investigated. The Mn emission shifts to lower energies with increasing pressure and the shift rate (the absolute value of the pressure coefficient) is larger in the ZnS : Mn2+ nanoparticles than in bulk. Moreover, the absolute pressure coefficient increases with the decrease of the particle size. The pressure coefficients calculated based on the crystal field theory are in agreement with the experimental results. (C) 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Resumo:
The photo- and thermo-stimulated luminescence (PSL and TSL) of BaFCl0.8Br0.2:Sm2+,Sm3+ phosphors were investigated. It is found that the stimulated luminescence intensity of Sm2+ is almost equal to that of Sm3+ even if the content of Sm2+ is much lower than that of Sm3+. Only the stimulated luminescence of Sm2+ is observed in the sample in which the content of Sm2+ is much higher than Sm3+, demonstrating that the PSL or TSL efficiency of Sm2+ is much higher than that of Sm3+. This is attributed to the effective overlap of the e-h emission with the absorption of Sm2+ centers which may make the energy transfer from the electron-hole pairs to Sm2+ effectively. In BaFCl0.8Br0.2:Sm2+,Sm3+ the stimulated luminescence is considered to be occurred via the recombination of photoreleased electrons with the [Sm2+ + h] or [Sm3+ + h] complex and the energy transfer from the electron-hole pairs to the luminescence centers (Sm2+ and Sm3+) is concerned to be the major step to determine the stimulated luminescence efficiency. The X-ray-induced stimulated luminescence is compared and connected to the photon gated hole burning. The net result of the two processes is quite similar and may be comparable. It is suggested from the observations of stimulated luminescence that electron migration between Sm2+ and Sm3+ is not the major process, color centers may play an important role in hole burning. The information from stimulated luminescence is helpful for the understanding of the hole burning mechanism. (C) 1999 Elsevier Science Ltd. All rights reserved.
Resumo:
LEDLEDLEDLEDLEDLEDYAG:CeUVLEDLED LED 1. LEDEu2+HTP-Ca3SiO4Cl2:Eu2+LEDHTP-Ca3SiO4Cl2 2. Eu2+LEDLTP-Ca3SiO4Cl2:Eu2+LED 3. LEDEu2+Li2CaSiO4:Eu2+LED 4. CaMoO4:Eu3+CaMoO4:Eu3+3LED
Resumo:
Eu2+Ce3+Eu2+Eu2+Eu2+Ce3+4f~(n+1) 4f ~n5d~1Eu2+Ce3+StokesStokesBa2MgB2O6, BaBe2B2O6 1 Ba2LiB5OjoSrB4O7Stokes shift vs FcSrA12B207BaLiBO3CaSiO3 1SrSiO3 , BaSiO3Sr2LiSiO4F, BasS1O4BrBaSSiO4ClStokes
Resumo:
srB4O7BO4MBPO5MCaSrBaPO404BaSO4SO4Eu3+Eu2+ Sr4Al14O25AIO4BaMgsiO4SiO4Eu3+Eu2+Eu3+Eu2+BaMgSiO4Eu2+Eu2+Ba3Eu2+398nmBa1Ba2Eu2+500nmBaMgSiO4Eu2+Eu2+500nmBlasseSAll4025SrAl2O4Sr3A12O6Sr4Al4O25SrAl2O4Eu3+Eu2+Sr3A12O6Eu3Eu2Sr4Al14O25BaMgSiO4Sr3Al2O6SAll 4025BaMgsi04Sr3Al2O6Ce4Ce3+Sr4Al14O25Ce3Tb3+Eu2+Ce3Tb3+Eu2Sr4Al14O25BaMgSiO4Sr3Al2O6CaYBO4Tb35D35D4254nmCaYBO4Eu3+609nmBaMgsio4Ce3371nm
Resumo:
MAIF5MCaSrBaLIMAIFaMCaSrCaAIFSrAIFBaAICaAIF6LrAISrAlF5LiSrAlF6llCoAIF6BaAlF5LiCaAlF6KMgF3:EuKMgFa:EU6P7/28S7/2420nml6P7/2-8S7/2Eu3+GdEuKMgFaBaLiF3BaY2F8Gd2+Eu2+Gd3+Eu2+Gd3+Eu2+Pr+ KMgF2LiYF4BaY2F8KMgFa:Pr3+352nmPr3+KMg1-xCaxF3Pr3+Ca2MgSi2O2EuEu3+Eu2+Ca2Eu8Si6O26X-ray
Resumo:
4fN-1n'l'4fN-1n'l'6604fN-1n'l'n'l'=5d6s6p4fN-1n'l'fN-15d4fN-15dfdhe[fciaiQi2]1/2Dy3+Tb3+fCe3+Eu2+4fN-15dheheCe3+Ey2+4fN-15dCe3+Eu2+4fN-15dFcEhQfi/NFc10Dq4fN-15dCe3+Eu2+heFc4fN-1n'l
Resumo:
Eu2+ab-Zn3(PO4)2:Mn2+-Zn3PO42:Mn2+Zn3B2O6:Mn2+Y2O3Eu3+Ca8MgSiO44Cl2:Eu2+Zn4B6O13:Mn2+-Zn3(PO4)2Mn2+Zn2SiO4:Mn2+Y2O2S:Eu3+caOEu3-Zn3(PO4)2:Mn2+Ga3+Zn2SiO4:Mn2+Al3+
Resumo:
Long lasting phosphorescence (LLP) was observed in Eu2+, Ce3+ co-doped strontium borate glasses prepared under the reducing atmosphere due to the emission of both Eu2+ and Ce3+. The methods of photoluminescence, thermoluminescence and phosphorescence were used to study the samples, and possible mechanism was suggested. The co-doping of Ce3+ ions poisoned the phosphorescence emission of Eu2+ because of the competition to obtain the trapped electron. The phosphorescence of Ce3+ in the sample decays more quickly than that of Eu2+, which is suggested for the reason that the emission energy of Ce3+ is higher or the distance between Ce3+ and electron traps of the glasses is longer.
Resumo:
In this study, KMgF3:Eu2+ luminescent nanocrystals (NCs) were prepared in water/cetyltrimethylammonium bromide (CTAB)/2-octanol microemulsions. The KMgF3:Eu2+ NCs were characterized by transmission electron microscopy (TEM), X-ray diffractometer (XRD), fluorescence spectrum, infrared spectroscopy (IR) and elementary analysis. The results showed that the size of the KMgF3:Eu2+ NCs was hardly affected by water content and surfactant (CTAB) concentration. The emission spectrum showed that the position of the 362 nm peak is due to the K+ sites substituted Eu2+. Two emission peaks located at 589 and 612 nm can be attributed to Eu3+, which exist at two different types of Eu3+ centers: one is Eu3+ at a K+ site, the other is clustering of Eu3+ ions in the interstices of KMgF3 host lattice.
Resumo:
M2B5O9X: Re(M = Ca, Sr, Ba; X = Cl, Br; Re = Eu, Th) phosphors were synthesized via solid state method. The products were characterized with X-ray powder diffraction and luminescence spectrometer. The luminescent properties as well. as the influences of the matrix composition and other doping ions on the luminescence of the rare earth ions of the co-doped phosphors were investigated. The coexistence of Eu3+, Eu2+ and Th3+ were observed in these matrices. The phenomenon may be explained by the electron transfer theory. The sensitization of Ce3+ ion improves the intensity of emission of Eu2+, and Tb3+. The competition between electron transfer among conjugate rare earth ions and energy migration might be the reasons for the observation. We predict a novel trichromatic phosphor co-doped with Eu3+ Tb3+ in M2B5O9X.
Resumo:
Europium-doped barium fluoride cubic nanocolumns were synthesized from the quaternary water in oil reverse microemulsions In this process, the aqueous cores of water/cetyl trimethyl ammonium bromide (CTAB)/n-butanol/n-octane reverse microemulsions were used as microreactors for the precipitation of europium doped barium fluoride. XRD analysis shows that under the dopant concentration of 0.06% (molar fraction), the products are single phase. The result products are cubic column-like with about 30 similar to 50 nm edge length of cross section, and about 200 nm of length obtained from the transmission electron microscopy (TEM), and atomic force microscopy (AFM). Under the 0.06 % (molar fraction) of dopant concentration I the fluorescence of Eu2+ and Eu3+ under the 589 of excitation wavelength is observed.
Resumo:
Ca BPO5 RE( RE=Eu,Tb) , , . , ,Eu3+ ,Tb3+ Eu2 + , Eu2 + 40 2 nm 42 8nm. Ce3+ ,Eu3+ ,Tb3+ Eu2 + , Ce3+ Eu3+
