The paper is dedicated to the comparative study of the luminescent properties of LuAG:Ce films, grown by pulse laser deposition (PLD) and liquid phase epitaxy (LPE) methods, using the time-resolved ...luminescent spectroscopy under excitation by synchrotron radiation in the fundamental absorption range and above the band gap of LuAG host. We have shown the similarities and differences in the luminescence properties of LuAG:Ce PLD and LPE grown films. Specifically, the luminescence of LuAl antisite defects is absent in the emission spectra of both films in the room temperature range. Meanwhile, the low intensive bands peaked at 350 and 400 nm, corresponding to the luminescence of excitons localized around and bound with F+ centers, respectively, are present in the emission spectra of LuAG:Ce PLD films at 12 K. The energy of formation of the excitons bound with the Ce3+ ions, being equal to 7.52 eV at 12 K, and the energy of the onset of interband transitions of LuAG host, being equal to 7.76 eV (at 300 K), have been found for LuAG:Ce LPE and PLD films, respectively. We have also found that the scintillation properties of LuAG:Ce PDL film are worse in comparison with LPE grown film analogue due to the significantly larger content of the slow emission component in the scintillation decay under high-energy excitation. Such differences between the optical and scintillation properties of PLD and LPE films are caused by the different conditions of their preparation (in vacuum and in air).
•LuAG:Ce films were grown by PLD and LPE methods.•Luminescent properties of LuAG:Ce PLD and LPE films were compared using synchrotron radiation.•Peculiarity of luminescence LuAG:Ce PLD film were determined with respect to the properties of LPE grown film.
Growth technologies of oxide crystals in W/Mo crucibles have been developed as a low-cost alternative to conventional processes involving Ir crucibles. Carbon-containing atmosphere needed to protect ...crucibles from oxidation leads to the introduction of carbon into the crystal lattice and creation of carbon-related defects, which affect the scintillation performance. Meanwhile, a search for fast scintillators for the new generation of positron-emission tomographs and high-energy physics experiments at colliders is under way. Codoping with divalent cations has become an efficient way to suppress long components of scintillation decay in Ce-doped scintillators. This work addresses Y 3 Al 5 O 12 (YAG) crystals codoped with carbon, cerium activator, and divalent cations. Optical and scintillation properties of YAG:Ce,C,<inline-formula> <tex-math notation="LaTeX">\text{A}^{2+} </tex-math></inline-formula> crystals (A = Ca<inline-formula> <tex-math notation="LaTeX">^{2+} </tex-math></inline-formula>, Mg<inline-formula> <tex-math notation="LaTeX">^{2+} </tex-math></inline-formula>, Ba<inline-formula> <tex-math notation="LaTeX">^{2+} </tex-math></inline-formula>, Sr<inline-formula> <tex-math notation="LaTeX">^{2+} </tex-math></inline-formula>) are systematically studied. Among all the studied garnet compounds, YAG:Ce,C,Ca<inline-formula> <tex-math notation="LaTeX">^{2+} </tex-math></inline-formula> crystals demonstrated the fastest scintillation decay times, which are promising for the mentioned applications. Mechanisms of scintillation process in the studied materials are discussed. The Ce<inline-formula> <tex-math notation="LaTeX">^{3+} </tex-math></inline-formula>/Ca<inline-formula> <tex-math notation="LaTeX">^{2+} </tex-math></inline-formula> ratio in YAG:Ce,C,Ca<inline-formula> <tex-math notation="LaTeX">^{2+} </tex-math></inline-formula> was optimized to minimize slow components in scintillation decay.
The paper is dedicated to the comparative study of the luminescent properties of Lu2O3:Eu (5%) nanopowders, ceramics and film samples using excitation by the synchrotron radiation in the range of the ...fundamental absorption edge of Lu2O3 host. The luminescence of F+ centers in the band peaked at 400 nm with a lifetime about of 1.4 ns was observed in Lu2O3:Eu nanopowder. We have also determined the energy of creation of excitons bound with the F+ centers in Lu2O3 host which is equal to 5.36 eV. The notable differences in the luminescence properties of Lu2O3:Eu nanopowder, ceramic and film samples were found which are caused by involvement of the F+ centers at the grain boundaries of ceramics and surface of nanoparticles in the excitation processes of the Eu3+ luminescence in Lu2O3 host. The positions of the high energy levels of the Eu3+ ions in Lu2O3 matrix ware determined in details. We have found also the energy of creation of excitons bound with Eu3+ in the Lu2O3 host which is equal to Eex(Eu) = 5.7 eV at 8 K. Meanwhile, the differences in the Eex(Eu) values in Lu2O3:Eu nanopowders, ceramics and films were also observed to be caused by participation of the host defects and flux impurities in the excitation processes of the Eu3+ luminescence in these samples.
This research deals with the luminescence and physical properties of Gd3(Ga,Al)5O12:Ce single crystal set and it is a complementary study to analogous (Y,Gd)3Al5O12:Ce and (Gd,Lu)3Al5O12:Ce single ...crystal sets. Those three groups of materials show similar luminescence and physical properties. In this research, the influence of substitution Ga for Al in Gd3(Ga,Al)5O12:Ce single crystals on the luminescence and scintillation characteristics as well as thermodynamical stability of the garnet phase is studied, and it is compared to (Y,Gd)3Al5O12:Ce and (Gd,Lu)3Al5O12:Ce single crystal sets. The unbalanced substitution Ga for Al makes garnet phase thermodynamically unstable and leads to the formation of the multiphase system with luminescence centers in UV and visible spectral ranges. The wavelength-dispersive X-ray spectroscopy, X-ray powder diffraction analysis, photoluminescence and decay kinetic measurements reviled all phase types within multiphase crystals. Temperature dependent measurements were applied to determine the quenching mechanism for Ce3+ luminescence. The timing characteristics are studied as the function of Ga content.
•Instability of the garnet phase and formation of the secondary phase inclusions discussed.•Temperature dependence of the decay time of Ce3+ emissions in garnet phase studied.•Energy transfer processes between secondary phase inclusion and target garnet phase discussed.
Thermal management poses a significant challenge for conventional phosphor-converted white LEDs (pc-WLEDs), thereby affecting their overall efficiency. Single crystal phosphors (SCPs), such as ...Y3Al5O12:Ce (YAG:Ce), exhibit enhanced efficiency and thermal stability in comparison to conventional powder phosphors. The garnet Lu3Al5O12:Ce (LuAG) has been characterized as a green phosphor with even higher than YAG:Ce temperature stability, making it suitable for use in high-power WLEDs. However, there are some difficulties in obtaining suitable components with longer emission wavelengths in LuAG:Ce phosphors. As a way to solve this issue, the article suggests the growth of LuAG:Ce single crystalline films onto YAG:Ce substrates, thereby producing a composite color converter that possesses adjustable parameters. This paper presents a comprehensive analysis of the fabrication process as well as the characteristics of a two-layered LuAG:Ce film/YAG:Ce substrate composite color converter. The results of investigations of the structural, luminescence and photoconversion characteristics of composite color converters were presented as well. This study includes also consideration of the effect of varying LuAG:Ce film thicknesses and concentrations of Ce3+ in YAG:Ce substrates on photoconversion characteristics of composite converters.
•The LPE growth technique was used to create a WLED composite converter.•The LuAG:Ce/YAG:Ce composite converter exhibits higher temperature stability compared to its YAG:Ce counterpart.•The photoconversion of LuAG:Ce/YAG:Ce structures with thicknesses were studied.
The study is dedicated to investigation of the structural, luminescent and photoconversion properties of epitaxial converters based on the single crystalline films of Ce3+ doped Ca3Sc2Si3O12 ...(CSSG:Ce) garnet. These SCFs with different thicknesses were grown using the liquid phase epitaxy method onto: (i) undoped Gd3Ga2.5Al2.5O12 (GAGG (2.5)) substrates; (ii) Ce3+ doped Gd3Ga2.5Al2.5O12 (GAGG:Ce (2.5) and Gd3Ga3Al2O12 (GAGG:Ce (3) substrates. For the first time, we have examined the phosphor conversion properties of the mentioned film and film-crystal converters under the excitation of a blue LED. We have established a trend line in the color coordinate diagram by systematically varying the film thickness in the 2–30 μm, 17–22 μm and 7–22 μm ranges for CSSG:Ce film/GAGG (2.5) crystal, CSSG:Ce film/GAGG:Ce (2.5) crystal and CSSG:Ce film/GAGG:Ce (3) crystal composite converters, respectively.
•Ca3Sc2Si3O12:Ce (CSSG:Ce) single-crystalline films (SCFs) grown onto Gd3Ga2.5Al2.5O12 (GAGG) crystal substrates by the liquid phase epitaxy (LPE) technique.•The optical behavior of the CSSG:Ce SCFs onto GAGG substrates was investigated using absorption and cathodoluminescence spectra.•Prototypes of a white LED based on the film and composite phosphor-converters and a blue LED were developed.
Alpha and gamma spectroscopy (pulse height spectra and scintillation decay time profiles) were used to study scintillating properties of composite scintillators systems consisting of single ...crystalline films (SCF) and single crystal (SC) substrate plates. α-particles of 241Am of energy 5.4857 MeV and γ-quanta of 137Cs of energy 661.66 keV are used as excitation sources of SCFs or SC substrates, respectively. As SC substrates mainly LuAG:Pr single crystal plates are used and these plates are characterized by light yield (LY) between 10-21 × 103 ph/MeV, Energy Resolution (ER) ~5% at 661.66 keV and good proportionality. LuAG:Ce, Lu2-xGdTbxAG:Ce and Lu3-xTbxAG:Ce SCFs at x = 0.15–2.285 were prepared by LPE method onto LuAG:Pr substrates and investigated. LY of LuAG:Ce SCF under α-particles excitation is about of 60% than that of LuAG:Pr SC substrate. The LY of Lu3-x TbxAG:Ce SCFs depend nonlinearly on Tb3+ concentration in the 0.15–2.285 range and changed from 60-62% to 106–109%, respectively, in comparison with LY of LuAG:Pr SC substrate. Detailed scintillation decay time profiles have shown that there are differences between the decay curves of composite scintillators under α-particles and γ-quanta excitations. Such differences are characterized using the tα/tγ ratio between the time of scintillation decay to 1/e, 0.1, 0,05 and 0.02 levels under α-particles excitation (tα) and γ-quanta excitation (tγ). From all studied types of composite scintillators, based on the LuAG:Pr substrates, the highest value of tα/tγ ratio can be reached for Lu3-xTbxAG:Ce SCF/LuAG:Pr SC substrate composite scintillators at Tb content x = 2.15–2.275, where this ratio is equal to 4.2–6.2 at scintillation decay level of 0.1.
•Pulsed height spectra under α- and γ-rays were used to study scintillating properties.•α-particles of 241Am allow to excite only single crystalline films as LuAG:Ce and LuAG:Ce,Tb.•Ratio of tα/tγ scintillation decay intensities should be the highest for new prepared Lu3-xTbxAG:Ce garnets.•Composite scintillators can to resolve various of parts ionizing radiation components as α-particles, ions or γ-quanta.
This article is directed on the creation of composite scintillators which are based on the films and crystals of R 2 Si 2 O 7 :Ce (R = Lu, Gd, La) pyrosilicates using the liquid phase epitaxy (LPE) ...growth method for application in the radiation monitoring of different components of mixed ionization fluxes. Such types of composite scintillators are epitaxial structures containing film scintillators grown by the LPE method onto the substrates of crystal scintillators. In this article, the film and crystal parts of the composite scintillators were fabricated from effective scintillation materials on the base of Ce 3+ doped Gd 2- x Lu x Si 2 O 7 and Gd 2- x La x Si 2 O 7 , and <inline-formula> <tex-math notation="LaTeX">x = {0} </tex-math></inline-formula> and 0.25 mixed pyrosilicates with various scintillation decay kinetics due to the different Lu/Gd/La cation content. We briefly report on the results of the LPE growth of the composite scintillators based on the Ce 3+ doped (Lu,Gd) 2 Si 2 O 7 films and (Gd,La) 2 Si 2 O 7 :Ce crystal substrates, as well as the results of investigation of their luminescent and scintillation properties.
The paper is dedicated to development of UV emitting scintillating screens for microimaging applications based on the single crystalline films (SCFs) of Ce doped Gd1−xLuxAlO3 and Pr1−xLuxAlO3 (x=0–1) ...multicomponent perovskites grown onto YAlO3 (YAP) substrates using the liquid phase epitaxy (LPE) method with the objective to improve the X-ray stopping power. Recently Riva et al. 1 have reported that the full set of GdxLu1−xAlO3 SCFs with x values in x=0−1.0 range can be crystallized on YAP substrates using this technique. We report here that PrxLu1−xAlO3 SCFs with x values in x=0–0.5 range can be grown also by the LPE method from PbO-B2O3 flux onto the same YAP substrates. The structural quality of the films was studied using X-ray diffraction. The optical properties of Ce3+ doped of Gd1−xLuxAlO3 and Pr1−xLuxAlO3 (x=0−1) multicomponent perovskite films, studied by traditional spectroscopic methods, such as absorption, cathodoluminescence, photoluminescence and light yield measurements under α–particles excitation, are also reported in this work. We have shown that Pb2+ flux related impurity has significantly larger influence on the light yield of Pr0.5Lu0.5AlO3:Ce, GdAlO3:Ce and Gd0.5Lu0.5AlO3:Ce SCFs in comparison with the YAP:Ce and LuAlO3:Ce counterparts grown onto YAP substrates.
•First time LPE growth of Gd1−xLuxAlO3:Ce and Pr1−xLuxAlO3:Ce single crystalline films at x=0–1.•Limitation conditions of LPE growth of perovskite films onto YAlO3 substrates were determined.•Relation between compositions engineering and luminescent properties of films were studied.•Gd3+–Ce3+ and Pr3+–Ce3+ energy transfer in perovskite films under study were investigated.•Large influence of Pb2+ flux related dopant on the light yield of perovskite films was found.
