The nature of luminescence centers created by La3+ isoelectronic impurities (IIs) in Y3Al5O12 (YAG) crystals has been considered. The La3+ dopant in YAG crystals gives rise to intensive UV ...luminescence in the complex band peaked at 4.28 eV at 300 K with a decay time of the main component of 575 ns. It has been shown that the complex UV emission band in YAG:La crystals in the 10–300 K range is a superposition of the luminescence of excitons localized near La dopants (LE(La) centers), the recombination luminescence of La3+ ions in the positions of Y3+ cations (LaY centers) and the low-intensive recombination luminescence of YAl antisite defects in the bands peaked at 4.65–4.62, 4.29–4.25 and 3.86–3.84 eV, respectively. In the visible range the emission spectra of YAG:La crystals also consist of the luminescence of F+ and F-centers in the bands peaked at 3.1 and 2.69 eV with a decay time of the main components of 2.3 ns and in the μs-ms range, respectively. It has been shown that the luminescence of F+ and F-centers in YAG:La crystals can be excited by emission of LE(LaY) and LaY centers.
Time evolution of luminescence of Sr2SiO4:Eu2 Barzowska, J; Szczodrowski, K; Grinberg, M ...
Journal of physics. Condensed matter,
10/2013, Letnik:
25, Številka:
42
Journal Article
Recenzirano
In this contribution, the photoluminescence, time-resolved luminescence and luminescence kinetics of α′-Sr2SiO4:Eu2+ are studied. The luminescence of Sr2SiO4:Eu2+ consists of two broad bands, peaked ...at 490 nm (blue-green) and 570 nm (yellow-orange), which originate from two luminescence centers, related to Eu2+ in ten-coordinated SI and nine-coordinated SII sites, respectively. Based on spectroscopic data the energetic structure of Sr2SiO4:Eu2+ has been developed, which includes the bands edges, energies of Eu2+ in the SI and SII sites and energies of strontium and oxygen vacancies. To investigate the long-lasting luminescence phenomenon in Sr2SiO4:Eu2+ the temperature influence on the time evolution of luminescence was analyzed. It has been found that the long-lasting luminescence is related to the Eu2+ in SII site. The shallowest traps responsible for emission decaying within a few seconds are tentatively attributed to the Eu3+(SII)- centers. The depth of traps responsible for the long-lasting luminescence observed at room temperature has been estimated as equal 0.73 eV.
The absorption, cathodoluminescence, excitation spectra of photoluminescence (PL) and PL decay kinetics were studied at 300K for the double Bi3+–Ce3+-doped and separately Bi3+- and Ce3+-doped ...Y3Al5O12 (YAG) and Lu3Al5O12 (LuAG) single crystalline film phosphors grown by liquid phase epitaxy method. Emission bands in the UV range arising from the intrinsic radiative transitions of Bi3+-based centers, and emission bands in the visible range related to the luminescence of excitons localized around Bi-based centers, were identified in both Bi–Ce and Bi-doped YAG and LuAG SCF. Energy transfers from the host lattice to Bi3+ and Ce3+ ions and from Bi3+ to Ce3+ ions were investigated. Competition between Bi3+ and Ce3+ ions in the energy transfer from the YAG and LuAG hosts was evidenced. A strong decrease of intensity of the Ce3+ luminescence both in YAG:Ce and LuAG:Ce SCF phosphors, grown from a Bi2O3 flux, is observed due to the quenching influence of Bi3+ flux related impurity. Due to overlap of the visible emission band of Bi3+ centers with the absorption band of Ce3+ ions peaking at around 450–460nm, an effective energy transfer from Bi3+ ions to Ce3+ ions takes place, resulting in the appearance of a slower component in the Ce3+ luminescence decay kinetics.
► Bi- and Ce-doped single crystalline film phosphor grown by liquid phase epitaxy method from Bi2O3 flux. ► Energy transfer from Bi3+ to Ce3+ ions. ► Strong quenching of the Ce3+ luminescence by the Bi3+ co-dopant.
The work is dedicated to the development of scintillating screens based on the single crystalline films (SCF) of Ce,Tb doped Lu-based silicates, perovskites and garnets grown by the liquid phase ...epitaxy method. We confirm in this work the presence of the Ce → Tb energy transfer in LSO and LuAP hosts. We also show that in Ce–Tb doped LuAG SCF, the effective Tb → Ce energy transfer is observed. This results in increasing the light yield of the luminescence of double doped LuAG:Ce,Tb SCF up to 25–30% with respect to single Ce doped (Y,Lu)AG SCF counterparts at optimal ratio of Ce/Tb ions.
► Growth of LSO, LuAP and LuAG films by LPE method. ► Effective Ce → Tb energy transfer in LSO, LuAP and LuAG hosts. ► Higher light yield of Ce,Tb doped LSO, LuAP and LuAG film screens.
This paper presents comparative analysis of thermally (TL) and optically (OSL) stimulated luminescence of a number of lutetium orthosilicates (LSO) single crystals and single crystalline films. ...Samples under study were prepared with two techniques: Czochralski method for single crystals and liquid phase epitaxy method for single crystalline films. This work describes in particular similarities and differences in OSL and TL response for alpha and beta particles between samples with different crystal form. The emission spectrum of LSO was found to extend from 350 nm to 500 nm, with a maximum near 430 nm. Intensity of TL and OSL of some samples to beta radiation was found to be quite high, indicating a potential of LSO for applications in dosimetry.
► TSL and OSL properties of Lu2SiO5 (LSO) in various crystalline forms were studied. ► The LSO emission spectrum exhibits maximum near 430 nm. ► Intense TSL/OSL of some samples indicates a potential for dosimetric applications.
Luminescent properties and the energy transfer from host to
Ce
3
+
ions are analyzed in single crystalline films (SCF) of YAlO
3:Ce (YAP:Ce),
Y
1
-
x
Lu
x
AP
:Ce (YLuAP:Ce) and LuAlO
3:Ce (LuAP:Ce) ...perovskites in comparison with their single crystal (SC) analogues using the time-resolved luminescence spectroscopy under synchrotron radiation excitation. It is shown that the main peculiarity of luminescent properties of YAP:Ce, YLuAP:Ce and LuAG:Ce SCF is determined by the extremely low concentration of
Y
Al
and
Lu
Al
antisite defects and vacancy-type defects in SCF as compared to SC. The advantages of phosphors based on (Y-Lu)AP:Ce SCF are due to the absence of emission and trapping centers in these SCF which are connected with the above mentioned bulk crystal defects.
The work is dedicated to the development of scintillating screens based on single crystalline films (SCF) of Ce doped Lu–Y–Al perovskites grown by the liquid phase epitaxy method. We show in this ...work that Lu1−xYxAP:Ce SCF with very good structural and optical perfection can be grown from the PbO-based flux onto YAP substrates in all range of x-values. We also found the Lu1−xYxAP:Ce SCF can be crystallized by LPE method from the lead free BaO–B2O3–BaF2 flux onto YAP substrates in the range of x values up to 0.4 formula units.
► Growth of Lu1−xYxAlO3:Ce films by LPE method from PbO and BaO based fluxes. ► Comparison of the luminescent and scintillation properties of Lu1−xYxAP:Ce films. ► Advantages of Lu1−xYxAlO3:Ce films scintillators grown from BaO based flux.
Bi-doped Lu3Al5O12 (LuAG) single crystalline films (SCFs) of thickness within 8-31 mum were grown by the liquid-phase epitaxy method onto Y3Al5O12 (YAG) single crystal substrates using a melt ...solution based on a Bi2O3 flux. Their characteristics were compared with YAG : Bi SCFs grown at the same conditions. The concentration of Bi3+ ions in LuAG : Bi and YAG : Bi SCFs was varied by changing the growth temperature in the ranges 0.05-0.18 at% and 0.13-0.57 at%, respectively. The absorption, luminescence and scintillation properties of these SCFs noticeably depend on the Bi3+ concentration. Luminescence spectra of both LuAG : Bi and YAG : Bi SCF consist of two broad emission bands in the UV and visible (VIS) spectral ranges peaking at 4.155-4.085 eV and 2.45-2.66 eV, respectively. Both the UV and VIS luminescence show complex non-exponential decays. Under 241Am alpha-particle excitation the photoelectron yield of the best performing LuAG : Bi (0.18 at%) and YAG : Bi (0.13 at%) SCFs is about 15% and 21%, respectively, of that of the reference YAP : Ce single crystal.
Intrinsic emission (excitons, anti-site defects (AD)) of oxides with garnet structure has been analysed by means of investigation of the time resolved luminescence and decay kinetic spectra under ...excitation by the synchrotron and X-ray radiation at 10–300K of the model objects: undoped single crystals and single crystalline films of Y3Al5O12 and Lu3Al5O12 garnets which are characterised by the significant differences in concentrations of AD YAl3+ and LuAl3+-types as analogs of cation isoelectronic impurities.
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