Luminescence of europium(III) and manganese(II) in barium and zinc orthosilicate

The aim of this work is to report on the luminescence properties of BaZnSiO4 activated by Eu3+ and Mn2+ ions. Doped and undoped powder samples were prepared by solid-state reaction starting from oxides and carbonates or Ba2SiO4:Eu3+ and Zn2SiO4:Mn2+ precursors. X-ray diffraction powder data, IR vibrational, and UV-vis luminescence spectroscopies were carried out. Results showed that doped and undoped samples from both types of precursors have the same structure and crystallize with a superstructure of hexagonal kalsilite. Vibrational spectroscopy has confirmed the formation of a silicate group, which outlines differences between products and silicate precursors. The observed luminescence assigned to Eu3+ and Mn2+ transitions covered most parts of the visible spectrum, an important requirement for phosphors in fluorescent low-pressure mercury vapor lamps.

On epidote fission track dating

The use of epidote in fission track dating was abandoned since the beginning of the 1980s due to difficulties like absence of a standard etching procedure, obtainment of different closure temperatures and the percentage of the datable samples. The results become much more reproducible when restricting fission track analysis to a peculiar kind of track. We are also studying confined track length, what makes possible to obtain information about fossil track annealing. Fission tracks in epidote were successfully etched with 48% HF at 35 degrees C for 12.5 min. Dating samples by the external detector method was not possible due to problems in measuring the efficiency factor held between the number of fossil fission tracks and tracks induced in mica. Dating a sample from Brejui, RN, Brazil with the population method gave a corrected age of 510 +/- 69Ma, in agreement with published U/Th-Pb ages. From the fact that the fossil track length histogram was bimodal, we were able to infer that this sample registered a thermal episode during its history.These preliminary results indicate that epidote deserves further studies to establish whether it can be employed as a thermochronological tool. (c) 2005 Elsevier Ltd. All rights reserved.

Upconversion luminescence and thermal effects in terbium-ytterbium codoped fluorogermanate glass-ceramic

Cooperative energy transfer upconversion luminescence is investigated in Tb(3+)/Yb(3+)-codoped PbGeO(3)-PbF(2)-CdF(2) glass-ceramic and its precursor glass under resonant and off resonance infrared excitation. Bright UV-visible emission signals around 384, 415, 438 nm, and 473-490, 545, 587, and 623 nm are identified as due to the (5)D(3)((5)G(6))->(7)F(1) (J=6,5,4) and (5)D(4)->(7)F(1) (J=6,5,4,3) transitions, respectively, and readily observed. The results indicate that cooperative energy transfer between ytterbium and terbium. ions followed by excited state absorption are the dominant upconversion excitation mechanisms involved. Comparison of the upconversion process in a glass-ceramic sample and its glassy precursor revealed that the former present much higher upconversion efficiency. The dependence of the upconversion emission upon pump power, temperature, and doping content is also examined.

Effects of dispersion by Gd3+ upon europium diphenylphosphinate luminescence

A series of binary diphenylphosphinates with Eu3+ and Gd3+ were prepared. The compounds have the general formula Gd1-xEux(DPP)(3), where x ranges from 0 to 1. The spectroscopic measurements show interesting behavior. The intensity of the D-5(0) --> F-7(2) transitions decreases relative to D-5(0) --> F-7(1) With an increase in europium dispersion. Inside the temporal domain, the same decrease is observed with increasing delay after excitation. The lifetimes are also affected, which can be seen in the x = 1 compound, where the decay is a first-order process and lifetime values are 4.81 ms. In the binary compound, as an effect of dispersion, the lifetime of the D-5(0) level measured at the D-5(0) --> F-7(1) transition increases with europium dispersion, and the average along the series is 6.25 ms. The decay measured at the D-5(0) --> F-7(2) transitions reveals a second-order process with lifetimes ranging from 1.90 to 6.00 ms. (C) 2001 Elsevier B.V. B.V. All rights reserved.

Upconversion luminescence in Ho3+/Yb3+- and Tb3+/Yb3+-codoped fluorogermanate glass and glass ceramic

Energy-transfer excited upconversion luminescence in Ho3+/Yb3+- and Tb3+/Yb3+ -codoped PbGeO3-PbF2-CdF2 glass and glass-ceramic under infrared excitation is investigated. In Ho3+/Yb3+-codoped samples, green (545 nm), red (652 nm), and near-infrared (754 nm) upconversion emission corresponding to the S-5(2) (F-5(4)) -> I-5(8), F-5(5) -> I-5(8), and S-5(2)(F-5(4)) -> I-5(7) transitions, respectively, was observed. Blue (490 nm) emission assigned to the F-5(2,3) -> I-5(8) transition was also detected. In the Tb3+/Yb3+-codoped system, bright UV-visible emission around 384, 415, 438, 473-490, 545, 587, and 623 nm, identified as due to the D-5(3)((5)G(6)) -> F-7(J)(J = 6, 5, 4) and D-5(4) -> F-7(J)(J = 6, 5, 4, 3) transitions, was measured. The comparison of the upconversion process in glass ceramic and its glassy precursor revealed that the former samples present much higher upconversion efficiencies. The dependence of the upconversion emission upon pump power, and doping contents was also examined. The results indicated that successive energy-transfer between ytterbium and holmium ions and cooperative energy-transfer between ytterbium and terbium ions followed by excited-state absorption are the dominant upconversion excitation mechanisms herein involved. The viability of using the samples for three-dimensional solid-state color displays is also discussed. (c) 2007 Elsevier B.V. All rights reserved.

Cr3+ and Cr4+ luminescence in glass ceramic silica

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Effect of the ytterbium concentration on the upconversion luminescence of Yb3+/Er3+ co-doped PbO-GeO2-Ga2O3 glasses

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Chemical process to separate iron oxides particles in pottery sample for EPR dating

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Structural and Luminescence Properties of Silica-Based Hybrids Containing New Silylated-Diketonato Europium(III) Complex

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Luminescence properties of Eu(3+)- and Mg(2+)-doped LiTaO(3) obtained via the polymeric precursor method

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Luminescence of Tb(3+) doped TeO(2)-ZnO-Na(2)O-PbO glasses containing silver nanoparticles

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Frequency upconversion luminescence from Yb+3-Tm+3 codoped PbO-GeO2 glasses containing silver nanoparticles

Infrared-to-visible and infrared-to-infrared frequency upconversion processes in Yb3+-Tm3+ doped PbO-GeO2 glasses containing silver nanoparticles (NPs) were investigated. The experiments were performed by exciting the samples with a diode laser operating at 980 nm (in resonance with the Yb3+ transition F-2(7/2)-> F-2(5/2)) and observing the photoluminescence (PL) in the visible and infrared regions due to energy transfer from Yb3+ to Tm3+ ions followed by excited state absorption in the Tm3+ ions. The intensified local field in the vicinity of the metallic NPs contributes for enhancement in the PL intensity at 480 nm (Tm3+ :(1)G(4)-> H-3(6)) and at 800 nm (Tm3+ : H-3(4) -> H-3(6)). (C) 2009 American Institute of Physics. [doi:10.1063/1.3211300]

Optical spectroscopy and upconversion luminescence in Nd3+ doped Ga10Ge25S65 glass

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Stokes and anti-Stokes luminescence of Er3+ doped Ga10Ge25S65 glass excited at 980 and 532 nm

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Enhanced luminescence of Tb3+/Eu3+ doped tellurium oxide glass containing silver nanostructures

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)