174 resultados para BAFBR-EU2
Resumo:
The doped Eu3+ ions can be partly reduced to Eu2+ in a series of MO-B2O3: Eu (M=Ba, Sr, Ca) glasses synthesized in air atmosphere, but not in the 12CaO-7Al(2)O(3): Eu glass. The different redox-behavior of Eu ions in these two glass systems is attributed to the different host optical basicity. It is found that a lower valence state of Eu2+ is more favorable in acidic glasses, which have lower optical basicities. A notion of the critical value of optical basicity is introduced empirically, which can be used as a guide for the selection of glass composition suitable to incorporate Eu2+ for luminescence. (C) 2006 Elsevier B.V. All rights reserved.
Resumo:
Compounds of Sr3Al2O6: Eu, Sr4Al14O25: Eu, and BaZnSiO4: Eu were synthesized by high-temperature solid state reactions. The doping Eu3+ ions were partially reduced to Eu2+ in Sr4Al14O25: Eu and BaZnSiO4: Eu prepared in an oxidizing atmosphere, N-2 + O-2. However, such an abnormal reduction process could not be performed in Sr3Al2O6: Eu, which was also prepared in an atmosphere of N-2 + O-2. Moreover, even though Sr3Al2O6: Eu was synthesized in a reducing condition CO, only part of the Eu3+ ions was reduced to Eu2+. The existence of trivalent and divalent europium ions was confirmed by photoluminescent spectra. The different valence-change behaviors of europium ions in the hosts were attributed to the difference in host crystal structures. The higher the crystal structure stiffness, the easier the reduction process from Eu3+ to Eu2+.
Resumo:
Eu2+-doped high silica glass (HSG) is fabricated by sintering porous glass which is impregnated with europium ions. Eu2+-doped HSG is revealed to yield intense blue emission excited by ultraviolet (UV) light and near-infrared femtosecond laser. The emission profile obtained by UV excitation can be well traced by near-infrared femtosecond laser. The upconversion emission excited by 800 nm femtosecond laser is considered to be related to a two-photon absorption process from the relationship between the integrated intensity and the pump power. A tentative scheme of upconverted blue emission from Eu2+-doped HSG was also proposed. The HSG materials presented herein are expected to find applications in high density optical storage and three-dimensional color displays. (c) 2008 American Institute of Physics.
Resumo:
KMgF3F EuEu^3Eu^2100029KMgFX1h100hKMgF3Eu^2X360nmKMgF310^3Gy30dKMgF3Eu^2360nm
Resumo:
-Y2SiO5Eu^3Y2SiO5Y2SiO5260-270nm320nmFO^-YSOEu^3Y2SiO5FOEu^2300nm390nmEu^3Y2SiO5
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+
