1,721,147 research outputs found
Tb3+→Eu3+ energy transfer processes in eulytite A3Tb(PO4)3 (A=Sr, Ba) and silico-carnotite Ca3Tb2Z3O12 (Z=Si, Ge) materials doped with Eu3+
No full textIn this study the optical spectroscopy, the excited state dynamics and in particular the Tb3+-> Eu3+ energy transfer, have been investigated in detail in eulytite double phosphate and silico-carnotite silicate or germanate hosts based on the Tb3+ ion and doped with Eu3+. It has been found that the energy transfer rates and efficiencies depend significantly on the nature of the divalent elements present in the two different structural families, opening the way to the control of the energy transfer rate and efficiency, on the basis of chemical and structural properties
Tunable emission from silico-carnotite type double silicates doped with Tb^3+ and Eu^3+
Full text linkDouble silicates with the silico-carnotite orthorhombic structure and co-doped with Tb3+ and Eu3+ have been prepared by solid-state reaction. Room temperature luminescence spectra and decay kinetics have been measured and analysed. Upon UV excitation at 378 nm, the emission colour varies from red to pinkish, depending on the doping level. The resulting colour can be adjusted by controlling the Tb3+/Eu3+ concentration ratio. Control of the doping leads to close-to-white emission in some of the analysed samples upon excitation in the wavelength region useful for LED lightin
Crystal structure and optical spectroscopy of Ca3Ln2Si3O12 (Ln = Gd and Lu) doped with Eu3+
No full textThe luminescence of Eu3+ introduced as impurity in Ca3Gd2Si3O12, and Ca3Lu2Si3O12 has been investigated. According to the crystallographic evidences, three sites for the dopant ion are available with different occupation in the two hosts. In both matrixes, the dominant 5D0 → 7F2 emission line reveals a low symmetry of the Eu3+ crystal sites. In the excitation spectrum of Eu doped Ca3Gd2Si3O12 a Gd3+ → Eu3+ ET process is clearly visible
Structural investigation of the new Ca(3)Ln(2)Ge(3)O(12) (Ln=Pr, Nd, Sm, Gd and Dy) compounds and luminescence spectroscopy of Ca3Gd2Ge3O12 doped with the Eu3+ ion
No full textThe crystal structures of new rare earth-based germanate compounds (Ca3Pr2Ge3O12, Ca3Nd2Ge3O12, Ca3Sm2Ge3O12, Ca3Gd2Ge3O12 and Ca3Dy2Ge3O12) have been determined by Rietveld refinement calculations on the collected synchrotron X-ray diffraction powder patterns. A different distribution of the rare earth ions in the three available crystal sites was observed, as the main structural feature. The reasons of the instability of the silico-carnotite structure for lanthanide ions out of the range Pr-Dy have been proposed. Finally, the luminescence spectroscopy of the Eu3+ dopant ion in Ca3Gd2Ge3O12 was presented and analyzed taking into account the observed structural characteristics. The Eu3+ luminescence spectroscopy was also compared with the one of Eu3+ doped Ca3Gd2Si3O12 and Ca3Lu2Si3O12 isostructural material
White light emission and energy transfer processes in LaInO3 doped with Bi3+, Tb3+ and Eu3+
No full textA series of LaInO3 bulk materials doped with Bi3+, Tb3+ and Eu3+ ions have been synthesized via a flux solidstate reaction technique, characterized by powder X-ray diffraction (PXRD) and investigated by luminescence spectroscopy. The compounds exhibit the pure crystal phase of LaInO3 (JCPDS No. 08-0148), and the structure is not affected by the presence of the dopants. The Bi3+ -> Tb3+ and Tb3+ -> Eu3+ energy transfer phenomena have been studied by means of luminescence spectroscopy and decay kinetics of Bi3+ excited state and of the 5D4 excited state of Tb3+. White light emission is attained via altering the concentration of dopant, and the obtained color coordinate (0.3248, 0.3030) is close to standard white light (0.313, 0.329). The energy transfer process is crucial, in order to tune the color of the emitted light
Luminescence of Tb-based materials doped with Eu3+: case studies for energy transfer processes
No full textThis review addresses the energy transfer processes involving lanthanide ions, analysing in particular the case of the Tb3+→Eu3+ energy transfer processes in terbium-based materials containing Eu3+ as a dopant. These examples are used as case studies for the processes and mechanisms concerning energy transfer generally involving Ln3+ ions, pointing out the differences caused by the structural characteristics of the host. The review introduces the theoretical background of the energy transfer processes, providing a brief description of the possible regimes for the donor-acceptor transfer depending on the donor concentration, together with the general considerations on the specific case of Tb3+→Eu3+ transfer. The review is completed by a brief survey of the literature published on this topic from the 60s to date, including some of the most recent papers
Metrological analysis of a virtual flowmeter-based transducer for cryogenic helium
No full textThe metrological performance of a virtual flowmeter-based transducer for monitoring helium under
cryogenic conditions is assessed. At this aim, an uncertainty model of the transducer, mainly based
on a valve model, exploiting finite-element approach, and a virtual flowmeter model, based on the
Sereg-Schlumberger method, are presented. The models are validated experimentally on a case study
for helium monitoring in cryogenic systems at the European Organization for Nuclear Research
(CERN). The impact of uncertainty sources on the transducer metrological performance is assessed
by a sensitivity analysis, based on statistical experiment design and analysis of variance. In this way,
the uncertainty sources most influencing metrological performance of the transducer are singled out
over the input range as a whole, at varying operating and setting conditions. This analysis turns out
to be important for CERN cryogenics operation because the metrological design of the transducer
is validated, and its components and working conditions with critical specifications for future
improvements are identified
Energy Transfer Processes in NaBiF4 Nanocrystals Co‐Doped with Tb3+ and Eu3+ Dispersed in Aqueous Solution
No full textThe synthesis of hexagonal NaBiF4 co-doped with Tb3+ and Eu3+(NaBi0.75-xTb0.25EuxF4; with x=0, 5, 10, 20 and 30) was achieved via a facile and fast precipitation route at 35 degrees C. Powder X-ray diffraction (PXRD) and luminescence spectroscopy have been employed to characterize and investigate the materials. The study of luminescence spectroscopy and decay kinetics of the D-5(4) excited state of Tb3+ provides the evidence of a Tb3+-> Eu3+ energy transfer process. Sodium citrate has been adopted as capping agent to promote a homogeneous dispersion of the materials into water and to protect the inorganic host, which is water sensitive, from direct contact with this molecule. The comparison of luminescence properties between bare and citrate-capped samples of NaBiF4 co-doped with Tb3+ and Eu3+ reveals a marked difference in the Tb3+-> Eu3+ energy transfer efficiency, which has been tentatively explained on the basis of a different environment surrounding the lanthanide ions in the two families of compounds
Sensitivity of a solid Eu(III) complex towards acetonitrile vapor: Structural and spectroscopic characterization
No full textThe Eu(III) nitrate complex of the meso- N,N'-bis(2-pyridylmethylene)-1,2-(R,S)-cyclohexanediamine ligand was synthesized and characterized by single crystal and powder X-ray diffraction. The crystal lattice of the complex is capable of absorbing and desorbing selectively acetonitrile molecules, at 293 K upon an acetonitrile vapor pressure of similar to 0.1 x 10(5) Pa. This process, which is partially reversible, can be easily followed by both powder X-ray diffraction (P-XRD) and Eu(III) luminescence spectroscopy. The acetonitrile molecule, located in the outer coordination sphere of the metal ion, does not affect the radiative transition probability of D-5(0) level of Eu(III) and also it does not activate further non-radiative channels from this level. On the other hand, this molecule is capable of affecting the energy position and intensities of the crystal field components of the D-5(0) -> F-7(2) transition. The complex in solid form can be considered a promising material for the optical sensing of acetonitrile vapors
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