Luminescence of excitons and antisite defects in Lu3Al5O12:Ce single crystals and single-crystal films

Zorenko, Yu.; Gorbenko, V.; Stryganyuk, G.; Kolobanov, V. N.; Spasskii, D. A.; Blažek, K.; Nikl, M.

doi:10.1134/1.2149417

Cited by 27 publications

(34 citation statements)

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“…The position of this band at 4.95 eV (250 nm), determined from the spectra of the fast and slow luminescence components (Fig. 1a, curves 2f , 2s ), coincides with the position of the luminescence band due to selftrapped excitons (STEs) in LuAG:Ce single crystals and single-crystal films [2,3]. Hence, this luminescence band is due to the radiative relaxation of STEs in regular, unperturbed by the presence of defects or impurities, lattice sites in LuAG single crystals.…”

Section: Resultsmentioning

confidence: 99%

“…It can be seen that the structure of the luminescence spectra of LuAG single crystals measured is similar in measurements of the integral ( 2i ), slow ( 2s ), and fast ( 2f ) luminescence components. The luminescence spectrum of LuAG single crystals at 8 K upon synchrotron radiation excitation with an energy of 7.155 eV in the maximum of the excitation band in the exciton region (curve 2 ) is a superposition of two dominant bands, peaking at 4.36 (284 nm) and 3.76 eV (329 nm), which are, respectively, due to the exciton luminescence and recombination luminescence of Lu Al ADs [2][3][4]. It should be noted that the band at 4.36 eV in the spectra of LuAG single crystals (Fig.…”

Section: Resultsmentioning

confidence: 99%

“…The Lu 3 Al 5 O 12 (LuAG) garnet has been investigated much less thoroughly [9]. At the same time, the results of the investigation of LuAG:Ce single crystals and single-crystal films as promising high-speed scintillators, reported by us previously [2,3], indicate a significant difference in their…”

Section: Introductionmentioning

confidence: 91%

“…As a result, single-crystal phosphor films contain no channels of excitation energy dissipation that are related to the above-mentioned types of defects (which compete with the luminescence of Ce 3+ ions [3][4][5]). That is why single-crystal films are also a convenient model object of studying the processes of relaxation of low-energy excitations in complex oxides with several cation sublattices, in particular, luminescence of excitons [1][2][3][4][5].…”

Section: Introductionmentioning

confidence: 99%

“…In this context, comparative analysis of the timeresolved luminescence spectra of garnet single crystals and single-crystal films upon excitation by synchrotron radiation is an extremely informative method, because it makes it possible to localize excitation only in the bulk of single-crystal films, both near the fundamental absorption edge and in the range of interband transitions in garnets [1][2][3][4][5]. This circumstance allows one to investigate the intrinsic luminescence of the chosen types of garnets by the example of single-crystal, excluding the corresponding luminescence of centers related to ADs and vacancy-type defects, as this generally occurs in single crystals of the same composition [6][7][8][9].…”

Section: Introductionmentioning

confidence: 99%

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Luminescence spectroscopy of excitons and antisite defects in Lu3Al5O12 single crystals and single-crystal films

et al. 2008

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-The nature of the intrinsic luminescence of the lutetium aluminum garnet Lu 3 Al 5 O 12 (LuAG) has been analyzed on the basis of time-resolved spectral kinetic investigations upon excitation of two model objects, LuAG single crystals and single-crystal films, by pulsed X-ray and synchrotron radiations. Due to the differences in the mechanisms and methods of crystallization, these objects are characterized by significantly different concentrations of Lu Al antisite defects. The energy structure of luminescence centers in LuAG single crystals (self-trapped excitons (STEs), excitons localized near antisite defects, and Lu Al antisite defects) has been established. For single-crystal LuAG films, grown by liquid-phase epitaxy from a Pb-containing flux, the energy parameters of the following luminescence centers have been determined: STEs in regular (unperturbed by the presence of antisite defects) sites of the garnet lattice and excitons localized near Pb 2+ ions. The structure of the luminescence centers, related to the background emission of impurity Pb 2+ ions, has also been established in the UV and visible ranges. It is suggested that, in contrast to the two-halide hole self-trapping, a self-trapped state similar to STEs in simple oxides ( Al 2 O 3 , Y 2 O 3 ) is formed in LuAG; this state is formed by self-trapped holes in the form of singly charged O -ions and electrons localized at excited levels of Lu 3+ cations. PACS numbers: 78.55.-m

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 91%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Luminescence spectroscopy of excitons and antisite defects in Lu3Al5O12 single crystals and single-crystal films

et al. 2008

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High Efficiency Green‐Emitting LuAG:Ce Ceramic Phosphors for Laser Diode Lighting

Liu

et al. 2021

Advanced Optical Materials

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CP because it can be achieved white light directly combined with blue LDs. [19][20][21][22][23] Recently, yellow/green/red CPs were discovered to rich spectral components and modify the color quality for white LD lighting. [24][25][26][27][28] Lu 3 Al 5 O 12 :Ce (LuAG:Ce) is a well-known green color converter due to its high thermal stability and high efficiency. [29][30][31] LuAG:Ce CPs are regarded as the best type that is robust irradiated by high-power LD light (15-25 W, up to 49 W mm −2 ). [32][33][34][35][36] The luminous efficacy (LE) of LuAG:Ce CPs in LD lighting has been greatly enhanced from about 54 to 205 lm W −1 by designing geometric structures and introducing scattering centers. [32][33][34][35][36][37] However, LuAG CPs are usually sintered higher than 1700 °C, SiO 2 or TEOS is commonly added as sintering aid. [32][33][34] SiO 2 begins to react with the garnets at about 1400 °C, [38] and defects are inevitable due to the size and charge mismatches between Si 4+ and Lu 3+ /Al 3+ . [39] The defects decline the thermal stability that is directly related with the performance of LuAG:Ce in LD lighting. [19] Thus, how to depress the defect and maintain the high thermal stability is the hardest challenge in fabricating LuAG CPs and achieving high LE value.As we know, heavy atom can depress lattice relaxation and improve thermal stability. [40,41] Considering valence state, in this work, we design the Ba 2+ -Si 4+ pair to substitute the Lu 3+ -Al 3+ pair to keep charge balance. SiO 2 powder are used as sintering aid and BaCO 3 provides the Ba 2+ to control defects and adjust thermal stability. Combining annealing process in air to eliminate oxygen vacancies, LuAG:Ce CPs manifest high LE of 213.7-216.9 lm W −1 in LD lighting, which is the best performance up to date. These results demonstrate that suitable strategies further improve LuAG:Ce CPs properties, thus in turn making great contributions to high-brightness and efficient white LD lighting. The tunable thermal stability by Ba 2+ -Si 4+ pairs and relationships with performance of LuAG:Ce CPs in LD lighting are detailed in present report. Results and DiscussionNominal compositions of Lu 2.995−x Ba x Al 5−x Si x O 12 :0.005Ce (LuAG:0.5%Ce+xBS, x = 0, 0.005, 0.01, 0.015, and 0.02) CPs sintered in vacuum are dark yellow (unannealed samples in Figure 1a), especial for x = 0, due to a lot of color centers Lu 3 Al 5 O 12 :Ce 3+ (LuAG:Ce 3+ ) ceramic phosphors (CPs) are regarded as the most promising green color converter and play a key role in high quality white light in the next-generation laser diode (LD) lighting. High efficient LuAG:Ce 3+ CPs are still urgent for high luminous efficacy (LE) LD lighting devices. By designing the Ba 2+ -Si 4+ pair to keep charge balance and annealing in air to remove oxygen vacancy defects, the luminescent properties of LuAG:Ce CPs are greatly enhanced. The LE is promoted to 216.9 lm W −1 , which is the best performance of LuAG:Ce in LD lighting so far. Strategies for optimizing LuAG:Ce 3+ CPs are detailed. It is believed ...

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Overview of S(T)EMelectron detectors with garnet scintillators: Some potentials and limits

Schauer

Lalinský

Kučera

2020

Microscopy Res & Technique

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The paper is focused on a complete configuration and design of a scintillation electron detector in scanning electron and/or scanning transmission electron microscopes (S(T)EM) with garnet scintillators. All processes related to the scintillator and light guide were analyzed. In more detail, excitation electron trajectories and absorbed energy distributions, efficiencies and kinetics of scintillators, as well as the influence of their anti-charging coatings and their substrates, assigned optical properties, and light guide efficiencies of different configurations were presented and discussed. The results indicate problems with low-energy detection below 1 keV when the scandium conductive coating with a thickness of only 3 nm must be used to allow electron penetration without significant losses. It was shown that the short rise and decay time and low afterglow of LuGdGaAG:Ce liquid-phase epitaxy garnet film scintillators guarantee a strong modulation transfer function of the entire imaging system resulting in a contrast transfer ability up to 0.6 lp/pixel. Small film scintillator thicknesses were found to be an advantage due to the low signal self-absorption. The optical absorption coefficients, refractive indices, and the mirror optical reflectance of materials involved in the light transport to the photomultiplier tube photocathode were investigated. The computer-optimized design SCIUNI application was used to configure the optimized light guide system. It was shown that nonoptimized edgeguided systems possess very poor light guiding efficiency as low as 1%, while even very complex optimized ones can achieve more than 20%.

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Luminescence of excitons and antisite defects in Lu3Al5O12:Ce single crystals and single-crystal films

Cited by 27 publications

References 5 publications

Luminescence spectroscopy of excitons and antisite defects in Lu3Al5O12 single crystals and single-crystal films

Luminescence spectroscopy of excitons and antisite defects in Lu3Al5O12 single crystals and single-crystal films

High Efficiency Green‐Emitting LuAG:Ce Ceramic Phosphors for Laser Diode Lighting

Overview of S(T)EMelectron detectors with garnet scintillators: Some potentials and limits

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