1,720,965 research outputs found
Optical spectroscopy of zinc metaphosphate glasses activated by Ce3+ and Tb3+ ions
No full textThe photoluminescence of Ce3+ and Tb3+ ions in zinc metaphosphate glasses is investigated. The blue and green emissions of Tb3+ ions are enhanced upon UV excitation through energy transfer from Ce3+ to Tb3+ ions. The efficiency of such an energy transfer was estimated based on spectroscopic data and resulted in being about 20-23%. Spectroscopic data revealed that the energy transfer occurs via a non-radiative process inside Ce3+-Tb3+ clusters formed in the glass. This ion clustering could be useful for the design of efficient conversion phosphors of ultraviolet to blue and green light
Blue-yellow photoluminescence from Ce3+ -> Dy3+ energy transfer in HfO2:Ce3+:Dy3+ films deposited by ultrasonic spray pyrolysis
No full textHfO2 films codoped with Ce3+ and several concentrations of Dy3+ have been processed by the ultrasonic spray pyrolysis technique. Emissions from Dy3+ ions centred at 480 and 575 nm associated with the 4F9/2 → 6H15/2 and 4F9/2 → 6H13/2 transitions, respectively, have been observed upon UV excitation via a non-radiative energy transfer from Ce3+ to Dy3+ ions. Such energy transfer via an electric dipole–quadrupole interaction appears to be the most probable transfer mechanism. The efficiency of this transfer increases up to 86 ± 3% for the film with the highest Dy3+ content (1.9 ± 0.1 at.% as measured from EDS). The possibility of achieving the coordinates of ideal white light with increasing the concentration of dysprosium is demonstrated
Energy transfer in Sr0.6Ba0.4Nb2O6 through its ferroelectric phase transition
No full textResonant Nd3+ -> Yb3+ energy-transfer in the Nd3+ and Yb3+ co-doped Sr0.6Ba0.4(NbO3)(2) (SBN) crystal is investigated by using pulsed and steady state laser spectroscopy. Spectroscopic data revealed that the energy transfer occurs via a non-radiative process. The efficiency of this energy transfer was estimated from spectral data in around 35%. Back energy transfer is not observed at the 295-415 K temperature range. A marked reduction in the luminescence intensity of Yb3+ ions directly excited into their F-2(7/2) -> F-2(5/2) transition, taking place at around 345 K, is due to the ferro to paraelectric phase transition in SBN. This thermal behavior, which is not clearly manifested when Yb3+ ions are excited via Nd3+ ions, has been explained in terms of structural changes taking place around the Yb3+ ions when the crystal becomes non-polar
Photoluminescence of Ce3+ and Mn2+ in zinc metaphosphate glasses
No full textThe spectroscopic characterization of zinc metaphosphate glasses, singly and doubly doped with Ce3+ and Mn2+ ions, is performed through excitation and emission spectra and decay time measurements. The weak yellow emission of Mn2+ is significantly enhanced by means of an efficient energy transfer from Ce3+ to Mn2+ ions. The efficiency of the energy transfer has been estimated based on spectroscopic data, and turned out to be about 53%. From spectroscopic data it can also be inferred that the energy transfer is nonradiative in nature and it takes place between Ce3+ and Mn2+ clusters formed in the glass through a short-range interaction mechanism. This impurity clustering appears to be a relevant finding for the design of efficient conversion phosphors of ultraviolet to visible light
Spectroscopic characterization and optical waveguide fabrication in Ce(3+), Tb(3+) and Ce(3+)/Tb(3+) doped zinc-sodium-aluminosilicate glasses
No full textA spectroscopy investigation of Ce3+ and Tb3+ ions in sodium-zinc-aluminosilicate glasses is performed using the photoluminescence technique. Blue-white light, with x = 0.24 and y = 0.24 CIE chromaticity coordinates, is obtained for the Tb3+ singly-doped glass excited at 351 nm. When the sodium-zinc-aluminosilicate glass is co-doped with Ce3+ and Tb3+ a non-radiative energy transfer from Ce3+ to Tb3+ ions is observed upon 320 nm excitation. From an analysis of the cerium emission decay curve, the Ce3+ -> Tb3+ energy transfer microscopic parameter and efficiency are obtained. Different concentrations of Ce3+ and Tb3+ ions in the glass host gives rise to blue and blue-green emissions, with different Ce3+ coordinates. Optical waveguides were produced in the samples by Ag+-Na+ ion-exchange, and their characterization is presented. (C) 2011 Elsevier B.V. All rights reserved
Lithium-aluminum-zinc phosphate glasses activated with Sm3+, Sm3+/Eu3+ and Sm3+/Tb3+ for reddish-orange and white light generation
No full textSpectroscopic evaluation of Sm3+, Sm3+/Eu3+ and Sm3+/Tb3+ doped lithium-aluminum-zinc phosphate glasses, based on excitation and emission spectra, and emission decay time measurements, were particularly focused on reddish-orange and white light emitting diode applications. The Sm3+ doped glass exhibits a reddish-orange emission tonality of 1676 K and a high color purity (CP) of 97.6% upon 408 nm excitation. The Sm3+/Eu3+ co-doped glass displays reddish-orange emission tonality of 1621 K (CP = 98.0%) and 2012 K (CP = 98.7%), upon 346 and 392 nm excitations, respectively. The Sm3+/Tb3+ co-doped glass emits neutral white light of 4946 and 4301 K upon 337 and 377 nm excitations, respectively, as well warm white light of 3504 K and reddish-orange light of 1758 K (CP = 91.5%) upon 370 and 396 nm excitations, respectively. The Sm3+/Tb3+ co-doped glass, excited at 337 and 396 nm, shows the highest values of luminous efficiency of radiation (LER = 444 lm/W) and color rendering index (CRI = 97), respectively. The Tb3+ and Sm3+ emission decay shortening in presence of Sm3+ and Eu3+, respectively, points out to Tb3+ -> Sm3+ and Sm3+ -> Eu3+ non-radiative energy transfers, with efficiencies of 8% and 21%, respectively. The Inokuti-Hirayama model suggests that such energy transfer processes might be dominated by an electric dipole-dipole interaction inside Tb3+-Sm3+ and Sm3+-Eu3+ clusters. (C) 2020 Elsevier B.V. All rights reserved
White light generation in Al2O3:Ce3+:Tb3+:Mn2+ films deposited by ultrasonic spray pyrolysis
No full textLi2O-Al2O3-ZnO-P2O5:Dy3+/Sm3+/Eu3+ glasses for solid-state yellow laser and color tunable phosphor applications
No full textLaser and optical properties (absorbance, excitation/emission and decay time data) of Dy3+, Dy3+/Sm3+, Dy3+/Sm3+/Eu3+-doped Li2O-Al2O3-ZnO-P2O5 glasses are investigated. Laser spectroscopic parameters of the dysprosium yellow emission show potentialities of the luminescent glass as yellow laser medium under excitation at 348 nm. The Dy3+/Sm3+-activated glass tonality can be shifted from neutral white of 4559 K under 350 nm excitation to yellowish-orange of 2033 K (85.3% color purity) upon 372 nm excitation. A shortening of the dysprosium F-4(9/2) level lifetime revealed that Sm3+ can be sensitized by Dy3+ by means of a non-radiative energy transfer that could be occurring into Dy3+-Sm3+ clusters with an efficiency of 0.13. The Dy3+/Sm3+/Eu3+-activated glass tonality can be shifted from warm white of 3387 K under 350 nm excitation to reddish-orange of 1638 K (92.1% color purity) upon 372 nm excitation. From lifetime data of the Dy3+ ion F-4(9/2) and Sm3+ ion (4)G(5/2) levels is inferred that non-radiative energy transfers from dysprosium to europium and/or samarium and from samarium to europium could be occurring into Dy3+-Sm3+-Eu3+ clusters with energy transfer efficiencies of 0.22 and 0.41, respectively
Phase transition in SrxBa1-xNb2O6 ferroelectric crystals probed by raman spectroscopy
No full textIn this paper the temperature evolution of the main Raman peak at about 630 cm(-1) has been studied in order to detect the ferroelectric to paraelectric phase transition in strontium barium niobate (SrxBa1-xNb2O6) crystals with different stoichiometries (x = 0.33, 0.5 and 0.61). Both its peak wavenumber and width have been shown to be strongly dependent on temperature and display clear anomalies around the Curie temperature. The obtained results manifest the usefulness of simple unpolarized Raman spectra to probe the changes in T-c as a result of modifications in the crystal composition
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