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201 results on '"Spassky, D"'

31. Cathodoluminescence and Photoluminescence Studies of Undoped and Eu2+ Doped SrAl2O4 Phosphors Prepared by Combustion Method.

Author

Nazarov, M. and Spassky, D.

Abstract

Undoped and Eu2+ doped strontium aluminate (SrAl2O4) nanosized phosphorescent powders were prepared by urea-nitrate solution combustion method at 500°C for 5 minutes. The average particle size of the powders was about 60 nm. The photoluminescent properties have been studied using the synchrotron radiation and electron excitation. The broad photoluminescence bands were observed in SrAl2O4: Eu2+ peaking at λmax = 450 and 525 nm, which arise due to transitions from the 4 f65d1 to 4 f7 configuration of the Eu2+ ions situated in two sites with different symmetry. Three additional emission bands were also observed at 250, 370 and 403 nm in undoped as well as Eu-doped samples. The bands are attributed to the intrinsic emission of self-trapped excitons (band at 250 nm) and to extrinsic emission from complexes containing structural defects (bands at 370 and 403 nm). [ABSTRACT FROM AUTHOR]

Published
2023
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34. Defect Formation in Gd3AlxGa5–xO12 (x = 1–3) and Gd3Al2Ga3O12:Ce Crystals.

Author

Kasimova, V. M., Kozlova, N. S., Zabelina, E. V., Buzanov, O. A., Bykov, A. S., Skryleva, E. A., and Spassky, D. A.

Subjects
CERIUM oxides, X-ray spectroscopy, X-ray photoelectron spectroscopy, CRYSTALS, POINT defects, FLUORESCENCE spectroscopy
Abstract

We present results of a detailed study of defect formation processes and their effect on the optical properties of gadolinium aluminum gallium garnet crystals with partial aluminum substitution for gallium in the cation sublattice—Gd3Al1Ga4O12 (Al : Ga = 1 : 4), Gd3Al2Ga3O12 (Al : Ga = 2 : 3), and Gd3Al3Ga2O12 (Al : Ga = 3 : 2) and cerium-doped crystals: Gd3Al2Ga3O12:Сe3+ (GAGG:Ce). X-ray photoelectron spectroscopy and X-ray fluorescence analysis data demonstrate gallium deficiency relative to the stoichiometric composition in all of the crystals studied. The results obtained are used to analyze processes underlying the formation of structural growth point defects in gadolinium aluminum gallium garnet crystals. F-centers have been shown to be the predominant point defect species. We also have demonstrated the formation of Schottky defects and V-centers. The formation of additional F-centers in cerium-doped garnet crystals is happening. The refractive indices and attenuation coefficients of the crystals have been shown to depend on the Al : Ga ratio and doping with cerium. [ABSTRACT FROM AUTHOR]

Published
2023
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43. Intrinsic and [Ce.sup.3+]-related luminescence in single crystalline films and single crystals of LuAP and LuAP:Ce perovskites

Author

Zorenko, Yu, Gorbenko, V., Voznyak, T., Mikhailin, V., Kolobanov, V., Spassky, D., and Nikl, M.

Subjects
Luminescence -- Evaluation, Crystals -- Atomic properties, Crystals -- Optical properties, Perovskite -- Atomic properties, Perovskite -- Optical properties, Cerium -- Atomic properties, Business, Electronics, Electronics and electrical industries
Abstract

Intrinsic and Ce-related luminescence of LuAP:Ce single crystalline films (SCF) in comparison with their bulk single crystal (SC) analogs were analyzed for the first time using the time-resolved luminescence spectroscopy under synchrotron radiation excitation. Difference in luminescent properties of SCF and SC are due to the absence of the Lu-at-Al-site antisite defects (AD) and extremely low concentration of vacancy-type defects (VD) in SCF. SCF contamination by Pb ions from flux is noted, which gives rise to an additional emission band in UV range. In SCF, the absence of emission and trapping centers formed by the mentioned AD and VD can explain their favorable timing characteristics with respect to SC. The role of [Pb.sup.2+] trace impurities in LuAP-based SCF scintillators is considered as well. Index Terms--Antisite and vacancy type defects; intrinsic and Ce-related luminescence; LuAP:Ce single crystal and single crystalline films, scintillators.

Published
2008

48. Luminescent properties of solid solutions of yttrium-scandium phosphates doped with europium ions

Author

null Zadneprovsky B. I., null Nikiforov I. V., null Spassky D. A., null Arapova A. A., and null Wozniak-Levushkina V. S.

Abstract

The luminescent properties of solid solutions Y1-xScxPO4 : 0.5 mol.% Eu3+ (x=0,0.2, 0.4, 0.5, 0.6, 0.8, 1) under excitation by ultraviolet and vacuum-ultraviolet radiation were studied. The influence of disorder of the crystal structure in solid solutions on the structure of Eu3+ luminescence spectra is shown. A non-linear dependence of values of the optical band gap on solid solution composition was obtained and a model was suggested to explain this effect. Keywords: energy transfer, luminescence, solid solutions, ScPO4 : Eu3+, YPO4 : Eu3+.

Published
2022
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