Successful reproduction of two subspecies of Harting’s vole in monogamous pairs (monogamous groups, 35 pairs for each) was shown. The results obtained in modeling the experimental polygyny revealed a ...different attitude of females of the two subspecies to the formation of communal groups. In polygynous groups of
M. h. lydius
, regardless of the relationship of the females (35 groups consisting of sisters and 20 groups of unrelated females), the intensity of reproduction and the proportion of successfully reared pups decreased significantly compared to the monogamous groups. With high energy costs for reproduction, there were significantly fewer reared pups per mother giving birth than in the monogamous groups, thus suggesting the predominance of monogamy in this subspecies. On the contrary, related females of
M. h. hartingi
bred successfully in communal groups (35 groups of sisters), demonstrating a high tolerance, a tendency to co-rearing and feeding the pups, and low infant mortality. In polygynous groups consisting of unrelated females (20 groups), reproductive success decreased due to increased infant mortality. Possible benefits of communal reproduction in this subspecies are discussed, as well as the likely relationship with habitat fragmentation under such conditions and with a lack of vacancies for the dispersal of young animals, which may be an important adaptation for this subspecies of voles.
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.
This work presents our latest achievements in the development of advanced composite scintillators for simultaneous registration of α-particles and γ-quanta in mixed ionizing fluxes based on single ...crystalline films (SCFs) of Tb
3
Al
3
O
12
: Ce (TbAG : Ce) garnet and Gd
3
Al
2.5
Ga
2.5
O
12
: Ce (GAGG : Ce) single crystal (SC) substrates using the liquid phase epitaxy (LPE) growth method from a melt-solution based on a PbO-B
2
O
3
flux. The separation of the signals from the SCF and SC components of such composite scintillators can be realized by means of registration of the difference in the scintillation decay times of SCF and substrate scintillators and can be achieved at a large
K
=
t
(SCF)/
t
(SC) ratio, which is usually above 2. The TbAG : Ce SCFs exhibit relatively fast scintillation response under α-particle excitation with decay times of
t
1/e
= 344-380 ns and
t
1/100
= 3130-3770 ns. Meanwhile, the scintillation response of TbAG : Ce SCFs under α-particle excitation is significantly slower in the 500-4000 ns range than that of the GAGG : Ce crystals with decay times of
t
1/e
= 270-280 ns and
t
1/20
= 1280-1300 ns. We have found that for TbAG : Ce/GAGG : Ce composite scintillators, the optimal
K
ratio changes from 2.0 to 3.0 at the registration of scintillations with shaping times of 700-4000 ns. For this reason, TbAG : Ce/GAGG : Ce composite scintillators possess the best scintillation properties among all known LPE grown analogues for simultaneous registration of α-particles and γ-quanta in mixed fluxes.
The composite scintillators based on the single crystalline films of TbAG : Ce garnet and GAGG : Ce crystal substrates was developed using the LPE growth method for simultaneous registration of α-particles and γ-quanta in mixed ionizing fluxes.
The study is dedicated to the development of scintillating screens for microimaging applications based on the single crystalline films (SCFs) of Eu
3+
-doped (Y,Lu,Gd,Tb)AlO
3
-mixed perovskites ...grown onto YAlO
3
substrates using the liquid phase epitaxy (LPE) method with the objective to optimize their X-ray stopping power and light yield. We confirm that the Eu
3+
-doped YAlO
3
and TbAlO
3
SCFs and full set of Lu
1−
x
Gd
x
AlO
3
SCFs with
x
values in the
x
= 0-1.0 range can be crystallized on YAlO
3
substrates using the LPE technique. The structural quality of films was studied using X-ray diffraction. The optical properties of Lu
1−
x
Gd
x
AlO
3
:Eu (
x
= 0-1) SCFs and TbAlO
3
:Eu mixed perovskites were also studied in this work in comparison with YAlO
3
:Eu SCF counterpart using the absorption, cathodoluminescence, photoluminescence (PL) emission and excitation spectra and PL decay kinetics as well as light yield measurements under e-beam and α-particles excitation. The Gd
3+
→ Eu
3+
and Tb
3+
→ Eu
3+
energy transfer processes are observed in Lu
1−
x
Gd
x
AlO
3
and TbAlO
3
:Eu SCFs, respectively, increasing the efficiency of the Eu
3+
luminescence in the perovskite hosts. Meanwhile, the highest light yield of the cathodoluminescence (CL) and radioluminescence (RL) under excitation by α-particles is found only in YAlO
3
:Eu, Lu
0.5
Gd
0.5
AlO
3
:Eu and GdAlO
3
:Eu SCFs. The light yield of CL and RL of these SCFs is notably higher than that in TbAlO
3
:Eu and LuAlO
3
:Eu SCFs and they even slightly (9-11%) overcome the light yield of the conventional Gd
3
Ga
5
O
12
:Eu SCF screens that are used in the microimaging detectors.
The study is dedicated to the development of scintillating screens for microimaging applications based on the single crystalline films of Eu
3+
-doped (Y,Lu,Gd,Tb)AlO
3
-mixed perovskites using the liquid phase epitaxy method.
The luminescence, scintillation, and photoconversion properties of the single crystals of Ce3+ doped Tb3−xGdxAl5-yGayO12 (х = 0–1.5; у = 2–2.5) mixed garnets, grown by the micro-pulling-down (μ-PD) ...method, are investigated as a function of the Tb/Gd ratio with the aim of development of phosphor-convertors of white LED and scintillators. The partial Tb3+ substitution by Gd3+ cations leads to the suitable change of the crystal field splitting of the 5d energy levels of Ce3 ions due to different sizes of the Gd3+ and Tb3+ cations. For this reason, the cation engineering enables to improve the luminescence and scintillation characteristics of Tb3−xGdxAl3-2.5Ga2-2.5O12 crystals due to increasing the efficiency of Gd3+→ Tb3+→ Ce3+ cascade energy transfer observed in these solid solutions. We have shown that from all the crystals under study, the Tb3-xGdxAl2.5Ga2.5O12:Ce (х = 1–1.5) crystal is the best promising candidate for the photoconversion and scintillation applications.
•Single crystals of TbGdAGG:Ce grown by the micro-pulling-down method.•Tb3+/Gd3+ ratio control improving the color rendering and scintillation properties.•The best photoconversion properties are shown by Tb2-1.5Gd1-1.5Al2.5Ga2.5O12:Ce.
In this study, the structural, luminescence and photoconversion properties of novel composite color converters based on Tb1.5Gd1.5Al5O12:Ce (TGAG:Ce) single crystalline films, grown by the liquid ...phase epitaxy method onto Y3Al5O12:Ce (YAG:Ce) single crystal substrates, are investigated. The luminescence and chromaticity properties for the set of TGAG:Ce SCF/YAG:Ce composite color converters, including color coordinates, color rendering index (CRI), and luminous efficacy, were studied by varying the thickness of the TGAG:Ce film in the 12–48 μm range and the Ce3+ concentration in the 0.1–0.5% range in YAG:Ce substrates. Such combination of different YAG:Ce substrates with various TGAG:Ce films enables tuning the white light tones from cold white (correlated color temperature (CCT) > 6000 K) to neutral white (6000 K > CCT > 3300 K). The theoretical white light color coordinates on the chromaticity diagram were almost achieved for TGAG:Ce film/YAG:Ce (0.5 mm) crystal converters with a film thickness between 19 and 25 μm under 465 nm LED excitation, with the corresponding CRI values in the 79–74 range. The developed composite color converters allow the problem of a high color temperature and low color rendering index of conventional WLEDs based on conventional YAG:Ce phosphor converters to be solved.
The possibility of development of an efficient phosphor converters (PC) for white LED (WLED) based on single crystalline films (SCF) of Ce3+ doped Tb3Al5O12 garnet (TbAG:Ce), grown using liquid-phase ...epitaxy method onto Y3Al5O12 (YAG) substrates, is evidenced for the first time in this work. The detail investigation of the structural properties of the TbAG:Ce SCF/YAG epitaxial structures was performed. High-resolution scanning transmission electron microscopy and composition analysis revealed an interface with high structural quality including the formation of a transition layer with a 5–7 nm thickness between TAG:Ce SCF and YAG substrate. The transition layer consisted of solid solutions between Tb3Al5O12:Ce and Y3Al5O12 garnets gradually changing from undoped YAG in substrate towards TbAG:Ce in the film and allowed to reduce the mismatch-stress. The absorption, cathodoluminescence, photoluminescence properties of TbAG:Ce SCFs were investigated as well. Furthermore, the dependence of photoconversion properties on the film thicknesses was studied to construct the prototype of efficient warm white LEDs. The change in the crystal thickness enabled tuning of the white light tons from cold white/daylight to neutral white. These results can be useful for the development of a novel generation of phosphor converters for white LEDs.
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.
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.
