Search

The investigation of the structural, luminescent and photoconversion properties (color coordinates, correlated color temperature, color rendering index and luminous efficacy) of the single-crystalline films of Ce3+-doped Tb1.5Gd1.5Al5O12:Ce mixed garnet with variable film thickness was performed in this work. These film converters were grown on undoped Y3Al5O12 substrates using the liquid phase epitaxy technique. When combined directly with blue LEDs that were commercially available in the market, the developed garnet film converters were responsible for producing white light. The trend line on the color coordinate diagram was obtained for the first time for the Tb1.5Gd1.5Al5O12:Ce converters with the systematic variation in film thickness in the range of 45–82 µm. Under 464 nm blue LED excitation, the investigated converters with a thickness of 55 µm resulted in an ideal white color. [ABSTRACT FROM AUTHOR]

In this study, the infrared optically stimulated luminescence (IRSL) of single crystals of Ce3+ doped yttrium aluminum garnet (YAG) was investigated for the first time. It was found that infrared stimulation of these crystals, following previous exposure to beta radiation, produces a strong luminescence signal. The highest luminescence efficiency was exhibited by the YAG crystal with 0.1% of Ce. With this crystal, it was possible to measure as low doses as 0.1 mGy. Moreover, IRSL is mainly related to the TL peak at a relatively high temperature of c.a. 175 °C, which leads to quite good stability of the signal in time. These properties create good prospects for potential applications of YAG:Ce in dosimetric radiation measurements [ABSTRACT FROM AUTHOR]

The crystals of (Lu,Gd)3(Ga,Al)5O12 multicomponent garnets with high density ρ and effective atomic number Zeff are characterized by high scintillation efficiency and a light yield value up to 50,000 ph/MeV. During recent years, single-crystalline films and composite film/crystal scintillators were developed on the basis of these multicomponent garnets. These film/crystal composites are potentially applicable for particle identification by pulse shape discrimination due to the fact that α-particles excite only the film response, γ-radiation excites only the substrate response, and β-particles excite both to some extent. Here, we present new results regarding scintillating properties of selected (Lu,Gd)3(Ga,Al)5O12:Ce single-crystalline films under excitation by alpha and beta particles and gamma ray photons. We conclude that some of studied compositions are indeed suitable for testing in the proposed application, most notably Lu1.5Gd1.5Al3Ga2O12:Ce film on the GAGG:Ce substrate, exhibiting an α-particle-excited light yield of 1790–2720 ph/MeV and significantly different decay curves excited by α- and γ-radiation. [ABSTRACT FROM AUTHOR]

The paper addresses the development of composite scintillation materials providing simultaneous real-time monitoring of different types of ionizing radiation (α-, β-particles, γ-rays) in mixed fluxes of particles and quanta. The detectors are based on composite heavy oxide scintillators consisting of a thin single-crystalline film and a bulk single-crystal substrate. The film and substrate respond to certain types of ionizing particles, forming together an all-in-one composite scintillator capable of distinguishing the type of radiation through the different time characteristics of the scintillation response. Here, we report the structure, composition, and scintillation properties under different ionizing radiations of (Lu,Gd,Tb)3(Al,Ga)5O12:Ce films deposited using liquid phase epitaxy onto Gd3(Al1−xGax)5O12:Ce (GAGG:Ce) single-crystal substrates. The most promising compositions with the highest light yields and the largest differences in scintillation decay timing under irradiation with α-, β-particles, and γ-rays were selected. Such detectors are promising for environmental security purposes, medical tomography, and other radiation detection applications. [ABSTRACT FROM AUTHOR]

This work is dedicated to the crystallization and luminescent properties of a prospective Ca2YMgScSi3O12:Ce (CYMSSG:Ce) micropowder (MP) phosphor converter (pc) for a white light–emitting LED (WLED). The set of MP samples was obtained by conventional solid-phase synthesis using different amounts of B2O3 flux in the 1–5 mole percentage range. The luminescent properties of the CYMSSG:Ce MPs were investigated at different Ce3+ concentrations in the 1–5 atomic percentage range. The formation of several Ce3+ multicenters in the CYMSSG:Ce MPs was detected in the emission and excitation spectra as well as the decay kinetics of the Ce3+ luminescence. The creation of the Ce3+ multicenters in CYMSSG:Ce garnet results from: (i) the substitution by the Ce3+ ions of the heterovalent Ca2+ and Y3+ cations in the dodecahedral position of the garnet host; (ii) the inhomogeneous local environment of the Ce3+ ions when the octahedral positions of the garnet are replaced by heterovalent Mg2+ and Sc3+ cations and the tetrahedral positions are replaced by Si4+ cations. The presence of Ce3+ multicenters significantly enhances the Ce3+ emission band in the red range in comparison with conventional YAG:Ce phosphor. Prototypes of the WLEDs were also created in this work by using CYMSSG:Ce MP films as phosphor converters. Furthermore, the dependence of the photoconversion properties on the layer thickness of the CYMSSG:Ce MP was studied as well. The changes in the MP layer thickness enable the tuning of the white light thons from cold white/daylight to neutral white. The obtained results are encouraging and can be useful for the development of a novel generation of pcs for WLEDs. [ABSTRACT FROM AUTHOR]

Intrinsic emission of undoped and [Ce.sup.3+] doped single crystal (SC) and single crystalline films (SCF) of YAl[O.sub.3] (YAP) was studied using the time-resolved luminescence spectroscopy under excitation by pulsed X-ray and synchrotron radiation. In contrast to YAP SCF, the YAP bulk SC are characterized by the presence of Y-in-Al-positions antisite defects (AD) and large concentration of vacancy-type defects (VD) of different types, which contribute to the intrinsic emission of YAP SC. Such type defects are centers of the luminescence in the UV (6.0-4.75 eV) and near UV (4.75-2.2 eV) ranges, overlapping with the Ce absorption and emission bands. Furthermore, they can give rise to shallow trapping centers as well. For this reason the AD and VD can strongly influence the scintillation properties of YAP:Ce SC. Specifically, the decay kinetics of the Ce emission in YAP:Ce SC, besides the fast component (23.3 [+ or -] 3.5 ns) related to radiative 5d-4f transition of Ce ions, contains also two slow components in the hundred ns and [mu]s ranges, which are due to the AD and VD-related traps. The advantages of scintillators based on YAP:Ce SCF, namely faster scintillation decay and lower contribution of slow components in the total light yield, can be achieved due to the absence of above mentioned bulk crystal defects. Index Terms--Antisite and vacancy type defects, intrinsic luminescence, scintillators, YAP single crystals and single crystalline films.

The aim of this work is to investigate the influence of shallow traps on scintillating properties of YAl[O.sub.3] : Ce. Wavelength-resolved thermally stimulated luminescence measurements following X-ray irradiation at 10 K have been performed on both undoped and Ce-doped crystals. Different and composite glow curves and emission spectra were obtained. Following glow peaks analysis of YAl[O.sub.3] : Ce, their room temperature decay time was evaluated to be of the order of [10.sup.-4] s. The presence of an athermal tunneling recombination process between traps and [Ce.sup.3+] ions below 100 K has been evidenced by phosphorescence decays. Index Terms--Perovskites, scintillators, thermally stimulated luminescence, YAP.

The development of a novel composite phosphor converter based on single‐crystalline films of Tb3Al5O12:Ce garnet and Y3Al5O12:Ce single‐crystal substrate is reported. The liquid phase epitaxy growth method is chosen for the fabrication of the Tb3Al5O12:Ce/Y3Al5O12:Ce epitaxial structures with excellent photoconversion properties for application in white light‐emitting diodes (LEDs). The influence of Ce3+ concentration and thickness of Y3Al5O12:Ce substrate as well as the thickness of Tb3Al5O12:Ce films on the photoconversion properties is investigated for the construction of warm white LEDs prototypes based on the developed composite phosphor converters. [ABSTRACT FROM AUTHOR]

This research deals with a novel approach for the self‐flux growth of Tb3Al5O12:Ce single crystal using the micro‐pulling‐down method. The self‐flux method enables the fabrication of the crystals with excellent photoconversion and scintillation properties. Tb3Al5O12:Ce (TbAG:Ce) efficiently converts the blue light‐emitting diode (LED) radiation into bright white light. The gradual change of crystal thicknesses (0.2–1 mm) allows for tuning white light temperature from cold to neutral white. The scintillation response is comparable with that of a high‐quality single crystalline film counterpart with a light yield value of around 4500 photons MeV−1 under α particle excitation from 239 Pu radioisotope. This is the highest value obtained for the TbAG:Ce crystal yet. [ABSTRACT FROM AUTHOR]

Herein, the development of phosphor‐converted white light‐emitting diodes (pc‐WLED) and scintillators based on the crystals of Ce3+‐doped multicomponent garnets, grown by the micro‐pulling‐down (MPD) method is studied. The combined technique of the "bandgap engineering" and "positioning of Ce3+ 5d‐levels" is applied to the crystals of Gd3−xLuxAl5−yGayO12 (x = 0–1.5 and y = 2–3) mixed garnets for improving their color‐rending properties in pc‐WLEDs application as well as their scintillation figure of merit. The absorption, cathodoluminescence, photoluminescence, photoconversion (PC), and also the scintillation light yield and scintillation decay time measurements under excitation by α‐particles of 239Pu radioisotope are used for the characterization of the crystals. Among all the investigated garnet compounds, the best photoconverting properties are observed in Gd3−1.5Lu0−1.5Al5−yGayO12:Ce crystals at x = 0–1.5 and y = 2.5–3. Meanwhile, the best scintillation characteristics are found in Gd3−xLuxAl5−yGayO12 crystals at x = 0–1.5 and y = 2–2.5. [ABSTRACT FROM AUTHOR]

In this work we show the influence of material preparation technology on the thermoluminescent properties of single crystalline films (SCFs) of Ce3+-doped Lu2SiO5 (LSO) and Y2SiO5 (YSO) orthosilicates. LSO:Ce and YSO:Ce SCFs were grown by the liquid phase epitaxy method from two different melt-solutions based on PbO-B2O3 and Bi2O3 fluxes. Absorption, cathodoluminescence, and thermoluminescent properties of LSO:Ce and YSO:Ce SCFs grown from the two previously mentioned types of fluxes were compared, and results of spectrally resolved thermoluminescence measurements and thermoluminescent glow curves of SCFs recorded in different spectral ranges were presented. We have found that the observed differences in thermoluminescent properties of the SCFs under study can be caused by the domination of Ce4+ and Pb2+ emission centers in LSO:Ce and YSO:Ce SCFs grown using PbO-B2O3 flux, and Ce3+ and Bi3+ emission centers in the SCFs grown from BiO3 flux. [ABSTRACT FROM AUTHOR]

The growth of single crystalline films (SCFs) with excellent scintillation properties based on the Tb1.5Gd1.5Al5-yGayO12:Ce mixed garnet at y = 2-3.85 by Liquid Phase Epitaxy (LPE) method onto Gd3Al2.5Ga2.5O12 (GAGG) substrates from BaO based flux is reported in this work. We have found that the best scintillation properties are shown by Tb1.5Gd1.5Al3Ga2O12:Ce SCFs. These SCFs possess the highest light yield (LY) ever obtained in our group for LPE grown garnet SCF scintillators exceeding by at least 10% the LY of previously reported Lu1.5Gd1.5Al2.75Ga2.25O12:Ce and Gd3Al2-2.75 Ga3-2.25O12:Ce SCF scintillators, grown from BaO based flux. Under a-particles excitation, the Tb1.5Gd1.5 Al3Ga2O12:Ce SCF show LY comparable with that of high-quality Gd3Al2.5Ga2.5O12:Ce single crystal (SC) scintillator with the LY above 10,000 photons/MeV but faster (at least by 2 times) scintillation decay times t1/e and t1/20 of 230 and 730 ns, respectively. The LY of Tb1.5Gd1.5Al2.5Ga2.5O12:Ce SCFs, grown from PbO flux, is comparable with the LY of their counterparts grown from BaO flux, but these SCFs possess slightly slower scintillation response with decay times t1/e and t1/20 of 330 and 990 ns, respectively. Taking into account that the SCFs of the Tb1.5Gd1.5Al3-2.25Ga2-2.75O12:Ce garnet can also be grown onto Ce3+ doped GAGG substrates, the LPE method can also be used for the creation of the hybrid film-substrate scintillators for simultaneous registration of the different components of ionization fluxes. [ABSTRACT FROM AUTHOR]

The paper is dedicated to development of scintillators based on single crystalline films of Ce doped (Gd,Y)3(Al,Ga,Sc)5O12 multi-component garnets onto Gd3Ga5O12 substrates using the liquid phase epitaxy method. [ABSTRACT FROM AUTHOR]

The paper presents the results of systematic research directed on the development of scintillating screens based on single crystalline films of Ce and Ce-Tb doped (Y,Lu,Gd)2SiO5 orthosilicates using the liquid phase epitaxy method. [ABSTRACT FROM AUTHOR]

The paper is dedicated to development of the novel scintillating screens based on single crystalline films of Ce doped multi-component (Gd,Y,Lu)3(Al,Sc)5O12 garnets onto Gd3Ga5O12 substrates using the liquid phase epitaxy method. [ABSTRACT FROM PUBLISHER]

This research is directed on creating by liquid phase epitaxy the single crystalline film scintillators based on undoped and Bi doped \CdWO4 compounds as well as the phoswich detector based on “\CdWO4\!\!:\!\!{\Bi} or \CdWO4 films/\CdWO4 or \CdWO4\!\!:\!\!{\Bi} crystals” epitaxial structures. The luminescent and scintillation properties of the undoped and \Bi^3+ doped (in a concentration range of 0.04–0.25 at. %) \CdWO4 films, grown by LPE method from \Na2{\WO}4 flux, were compared with the properties of \CdWO4 bulk crystal analogs, grown from melts by the Czochralski method. Using the traditional luminescence spectroscopy and the luminescence spectroscopy under excitation by pulsed synchrotron radiation with energy in the fundamental absorption range of \CdWO4 host, we have also examined the nature of different emission centers and studied energy transfer processes from tungstate hosts to \Bi^3+ ions and defect centers in \CdWO4 and \CdWO4\!\!:\!\!{\Bi} films and their crystal analogs. [ABSTRACT FROM PUBLISHER]

Intrinsic emission of undoped and Ce3+ doped single crystal (SC) and single crystalline films (SCF) of YAlO3 (YAP) was studied using the time-resolved luminescence spectroscopy under excitation by pulsed X-ray and synchrotron radiation. In contrast to YAP SCF, the YAP bulk SC are characterized by the presence of Y-in-Al-positions antisite defects (AD) and large concentration of vacancy-type defects (VD) of different types, which contribute to the intrinsic emission of YAP SC. Such type defects are centers of the luminescence in the UV (6.0-4.75 eV) and near UV (4.75-2.2 eV) ranges, overlapping with the Ce absorption and emission bands. Furthermore, they can give rise to shallow trapping centers as well. For this reason the AD and VD can strongly influence the scintillation properties of YAP:Ce SC. Specifically, the decay kinetics of the Ce emission in YAP:Ce SC, besides the fast component (23.3 ± 3.5 ns) related to radiative 5d-4f transition of Ce ions, contains also two slow components in the hundred ns and µs ranges, which are due to the AD and VD-related traps. The advantages of scintillators based on YAP:Ce SCF, namely faster scintillation decay and lower contribution of slow components in the total light yield, can be achieved due to the absence of above mentioned bulk crystal defects. [ABSTRACT FROM AUTHOR]