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A set of samples based on InGaN/GaN multiple quantum well (QW) structures with an extremely thick active region and high QW numbers was prepared on different substrates by metal organic vapor phase epitaxy. Their morphology was studied by SEM images, and their optical properties, including photoluminescence (PL) excitation, PL emission spectra, and PL decay curves, were measured by means of time-resolved luminescence spectroscopy. The obtained spectral features were tentatively explained by using the band scheme, which is commonly used for the description of InGaN/GaN multiple QW (MQW) structures. The application potential in the field of nanoscintillators used for fast timing of studied structures is discussed as well.

We report the study of the fast rise time and decay time in the ps time scale of the excitonic luminescence of a multiple quantum well (MQW) heterostructure of InGaN/GaN, including the excitation density effect. These structures were proposed as ultrafast scintillators for soft X-ray detectors and particle beam diagnostics. Measurements were carried out with a Hadland Imacon 500 streak camera following excitation of the sample by laser pulses of few tens of µJ at 266 nm and 400 nm, with pulse duration less than 200 fs. The rise time of the detected MWQ luminescence was less than 10 ps, with a possible contribution from the detection system and signal collection geometry. The calibration and the signal processing techniques employed to fully exploit the time resolution of the detection system are also described.

Ce,Mg:LuAG scintillation ceramics with Ce dopant content ranging from 0.025 at.% to 0.3 at.% and constant 0.2 at.% Mg codoping were fabricated by solid-state reaction. The effects of Ce concentration and annealing conditions on the microstructure, optical quality and scintillation properties are studied in great details. Lattice parameters as well as the absorption, photoluminescence, radioluminescence and thermoluminescence characteristics are investigated as a function of Ce content. Both the photoluminescence and scintillation decays are measured as well in order to study re-absorption and concentration quenching processes. In addition, an enhanced positive effect of air annealing on radioluminescence intensity and light yield is put in evidence. Moreover, the role of the charge transfer absorption of Ce^(4+) is investigated. Thermoluminescence measurements are performed to investigate the influence of both air annealing and Ce concentration on defects acting as traps. Finally, the correlations among steady state scintillation efficiency, light yield, thermoluminescence and Ce^(3+) concentration are found and discussed.

The indirect photochemical synthesis for the preparation of bandgap- or defect-engineered multicomponent garnet powders from aqueous solutions was investigated. Gd3(Ga,Al)5O12 (GGAG) doped with Ce or Ce + Eu and Lu3(Al,Sb)5O12 doped with Eu were produced by calcination of the prepared solid precursors at various conditions and their structural and luminescence properties including decay curves were thoroughly studied. In GGAG:Ce, the content of Ga was shown to have strong impact on the lattice parameter and position of the Ce3+ 5 d - $4f$ emission. To induce the formation of Ce4+ ions as defects competing with electron traps, Mg2+ ions were added into the solutions and calcination in air was examined. Both factors were shown to cause the decrease of Ce3+ emission intensity and acceleration of luminescence decay in a similar way. The doping with Sb(III) required calcination of solid precursors in inert atmosphere to prevent formation of an unknown pyrochlore-type phase containing Sb(V). Low temperatures were needed to limit Sb2O3 evaporation during calcination.

The In-doped LiCaAlF6 [In:LiCAF] single crystals were grown by the micro-pulling-down (μ-PD) method, and the phases, chemical compositions, transmittance and radioluminescence spectra were investigated. All the grown crystals showed high transparency and single phase of LiCAF without visible cracks and inclusions except for the end part of In2%:LiCAF crystal which included the impurity phase. In the radioluminescence spectra of the In:LiCAF crystals under X-ray irradiation, the emission peak around 750 nm was revealed.

International audience; A significant enhancement in the light attenuation length in 22 cm long YAG:Ce and YAG:Ce,Mg fibers grown by the micro-pulling-down method has been reported. This progress has been achieved by the introduction of Al excess into the melt, optimization of thermal conditions of crystallization and post growth annealing. Attenuation length clearly correlates with surface roughness of the fibers. Al excess addition over the stoichiometric composition enhances the fiber surface smoothness. An increase in axial thermal gradient and melt pressure in the crucible capillary die improves the crystallization process stability. Mg codoping provides a Ce3+ scintillation decay time decrease down to 80 ns.

(Gd 0.75 ,Ce 0.015 ,La 0.235 ) 2 Si 2 O 7 (Ce:La-GPS) single crystals co-doped with 0, 100, 200, 500 and 1000 ppm Zr were grown by the Czochralski process, and their scintillation properties were investigated. We investigated the co-doping effect of a stable tetravalent ion in Ce:La-GPS for the first time. The scintillation decay times in the faster component were shortened with increasing the Zr concentration. While the non-co-doped sample showed ∼63 ns day time, the Zr 100, 200, 500 and 1000 ppm co-doped samples showed ∼61, ∼59, ∼57, ∼54 ns, respectively. Additionally, light output, photon nonproportional response (PNR) and other optical properties were investigated.

The ns2-type metal elements (Pb and Sn) doped LiCaAlF6 single crystals were grown by a micro-pulling-down (μ-PD) method. Pb doped LiCaAlF6 [Pb:LiCAF] crystals showed high transparency and single phase of the LiCAF structure. However, we could not obtain Sn:LiCAF crystals due to the evaporation of SnF2 during the crystal growth. There was an absorption peak around 193 nm in the transmittance spectrum of Pb:LiCAF crystal. In the radioluminescence spectrum of the Pb:LiCAF crystal under X-ray irradiation, two emission peaks around 200 and 830 nm were observed.

This paper reports on the preparation and growth of Eu-doped strontium iodide ( ${\rm SrI}_{2}$ ) single crystals by modified micro-pulling-down method. Influence of the ${\rm Eu}^{2 + }$ and ${\rm Eu}^{3 + }$ (introduced in form of ${\rm EuI}_{2}$ and ${\rm EuCl}_{3}$ ) on the luminescence and scintillation properties is analyzed. Sufficient optical quality of prepared single crystals was obtained allowing further characterization of their absorption, radio- and photoluminescence spectra. Photoluminescence and scintillation decay time of grown ${\rm SrI}_{2}$ crystals irradiated under $\gamma $ -ray source were evaluated as well.

The 14th International Conference on Inorganic Scintillators and Their Applications (SCINT 2017) was organized by CERN, and held on September 17–22, 2017, in Chamonix, France. This was a particular event in the series of SCINT conferences, since we celebrated the 25th anniversary of its birth in 1992. Intentionally, it has also been held at the place of its origin. The conference was dedicated to the late Marvin Weber, one of the fathers of scintillator research. The 273 colleagues from 35 different countries finally participated at the conference. The scientific program was introduced by a memorial lecture about 25 years of history of the SCINT conference given by Bill Moses. The program consisted of nine invited lectures, and 79 oral and 119 poster contributions. As a part of the program, one session was devoted to an Industrial Event organized by the COST Action TD1401 with two invited lectures, presentation of six companies, and a round table discussion at the end. Extended exhibition with altogether 18 exhibitor stands provided another link to the market applications behind the research. An intense and structured research and development in this field was represented by 13 sessions oriented toward various material technologies including nanomaterials, metamaterials, classical bulk single crystals, and optical ceramics. Their characterization, modeling, and underlying physical mechanisms constituted the subject of major part of conference contributions. Finally, also various applications of inorganic scintillators were presented and discussed.

Time and cost effective methods are highly desirable in research and development of new scintillators. Modern techniques like micro-pulling down (μ-PD) are suitable for material screening but are unfit for the growth of some crystals. These crystals must be grown by different methods that are usually very time demanding. Modification of halide μ-PD apparatus by custom made elements allowed us to grow cesium hafnium chloride (Cs2HfCl6) by vertical Bridgman method (VB) with significantly reduced growth time. Structural and optical properties of samples prepared from as-grown crystals were studied and compared to crystals grown by standard VB method. The X-ray diffraction confirmed the formation of cesium hafnium chloride single-phase and natural cleavage of the crystals along the (1 1 1) crystallographic plane. Photoluminescence emission, excitation, absorption, and radioluminescence spectroscopy revealed that the optical quality of the crystals grown by modified VB method was comparable to the quality of the crystals grown by standard VB method. Therefore we can use samples prepared by modified VB to estimate and optimize the performance of Cs2HfCl6 based crystals in scintillation detectors. This setup allows the time and cost-effective material screening and it is a powerful tool for the development of new halide based single crystal scintillators.

We study Ce3+ luminescence and scintillation characteristics in novel, high performing hosts among the oxide single crystal scintillators, the La-admixed Gd2Si2O7. Obtained characteristics are systematically compared with the earlier studied Lu2Si2O7 host. We determine the barrier height of the thermal ionization of the Ce3+ excited center, we address the effect of La-admixture on the physical characteristics, and we construct an energy level diagram of the material system. High scintillation efficiency, low afterglow, and the onset of Ce3+ excited state ionization appearing well above room temperature indicate a large potential of La-admixed Gd2Si2O7 in a variety of scintillating material applications.

In this work, a group of Lu 2 SiO 5 :Tb (LSO:Tb) scintillating layers with a Tb concentration between 8% and 19% were investigated by means of synchrotron and laboratory techniques. The scintillation efficiency measurements proved that the highest light yield is obtained for a Tb concentration equal to 15%. At higher concentration, quenching processes occur which lower the light emission. The analysis of the reciprocal space maps of the (082) (280) and (040) Bragg reflections showed that LSO:Tb epilayers are well adapted on YbSO substrates for all the investigated concentrations. The spatial resolution tests demonstrated the possibility to achieve a resolution of 1 μm with a 6 μm thick scintillating layer.

Rare-earth ( RE=Sm, Pr, Tb, Tm) doped ternary sulfides having the general formula KLn0.995RE0.005S2 ( Ln=La, Gd, Lu) and undoped KLnS2 were synthesized in the form of crystalline hexagonal platelets by a chemical reaction in an electric resistance furnace under the flow of hydrogen sulfide. X-ray powder diffraction confirmed only a single phase of the rhombohedral lattice system (space group R-3 m). Time-resolved luminescence spectroscopy was employed to investigate radioluminescence, photoluminescence, decay kinetics and absorption spectra. The KLnS 2 band edge at 300-330 nm was found and characteristic Pr3+, Sm3+, Tb3+ and Tm3+ 4 f -4 f emission lines in the visible spectral range were observed. The charge transfer transitions in the Pr3+- and Sm3+-related excitation spectra in the range 330-370 nm are described and the eficient energy transfer from the host to the emission centers is revealed. We discuss the potential for application of these materials in white LED solid-state lighting and X-ray phosphors.

We study the low temperature contribution to delayed recombination decay in several complex oxide scintillating crystals. We experimentally test the previously suggested hypothesis that the losses of fast scintillation light even at the lowest temperatures can be due to quantum effects. The results obtained for several material systems confirm that quantum tunneling between the luminescence center and a nearby defect is a good candidate for the origin of the observed phenomena.

The transparent single crystals of high-melting strontium hafnate (SHO) and strontium zirconate (SZO) have been grown by the floating zone method with vertical mirror arrangement. The X-ray diffraction analysis revealed orthorhombic perovskite structures for both compounds. Evaporation of Sr-containing species during the growth was proved by micro x-ray fluorescence analysis and led to slightly Sr-poor composition in the studied materials. The overall scintillation efficiency of SHO was found to be comparable with that of Bi4Ge3O12 standard scintillator, while that of SZO was considerably lower. The emission spectrum of both compounds was red-shifted when compared to the previously intensively studied powder counterparts and the photoluminescence decay curves became accelerated with pronounced nonexponentiality. The phenomenological model applied to the temperature dependences of the luminescence data revealed that in single crystals the leading luminescence process is either strongly modified with respect to powders or is of a different origin. The scintillation light yield of both materials was determined to be only several tens of photons per MeV under alpha-ray excitation due to strong afterglow, most probably related to ionization of excited state of the luminescence center.

Journal of luminescence 141, 137-143 (2013). doi:10.1016/j.jlumin.2013.03.036, Absorption, cathodoluminescence, excitation spectra of photoluminescence (PL) and PL decay kinetics were studied at 300 K for the double doped with Bi3+–Pr3+ and separately doped with Bi3+ and Pr3+ Lu3Al5O12 (LuAG) and Y3Al5O12 (YAG) single crystalline film (SCF) phosphors grown by the liquid phase epitaxy method. The emission bands in the UV range arising from the intrinsic radiative transitions of Bi3+ based centers, and emission bands in the visible range, related to the luminescence of excitons localized around Bi3+ based centers, were identified both in Bi–Pr and Bi-doped LuAG and YAG SCFs. The energy transfer processes from the host lattice simultaneously to Bi3+ and Pr3+ ions and from Bi3+ to Pr3+ ions were investigated. Competition between Pr3+ and Bi3+ ions in the energy transfer processes from the LuAG and YAG hosts was evidenced. The strong decrease of the intensity of Pr3+ luminescence both in LuAG:Pr and YAG:Pr SCFs phosphors, grown from Bi2O3 flux, is observed due to the quenching influence of Bi3+ flux related impurity. Due to overlap of the UV emission band of Bi3+ centers with the f–d absorption bands of Pr3+ ions in the UV range and the luminescence of excitons localized around Bi ions with the f–f absorption bands of Pr3+ ions in the visible range, an effective energy transfer from Bi3+ ions to Pr3+ ions takes place in LuAG:Bi,Pr and YAG:Bi,Pr SCFs, resulting in the appearance of slower component in the decay kinetics of the Pr3+ d–f luminescence., Published by Elsevier, New York, NY [u.a.]

We studied the processes occurring in the 5d1 excited state of Ce3+ in Gd3Ga3Al2O12 (GGAG) host. Energy transfer from Gd3+ to Ce3+ was evidenced by photoluminescence excitation spectra of Ce3+ emission. We measured temperature dependences of prompt nanosecond decays and millisecond delayed recombination decays of Ce3+ in GGAG host. The decrease of nanosecond decay times above approximately 200 K is due to thermally induced ionization of the 5d1 excited state of Ce3+. Thermal stimulated luminescence glow curve measurements after X-ray or UV (within 4f–5d1 absorption of Ce3+) irradiation at RT provide another support for the ionization effect around this temperature.

We investigate the luminescence and scintillation characteristics of highly efficient cerium-doped scintillators, lutetium-(yttrium) orthosilicate (Lu2(1-x)Y2xSiO5:Ce, x=0-1). The radioluminescence, photoluminescence excitation (PLE) and emission (PL) spectra of the Ce1, Ce2 centres as well as the decay curves and their temperature dependences are measured in the 80-500 K range. Light yield values are provided as well. The influence of yttrium concentration on the Ce1, Ce2 luminescence characteristics is demonstrated. With increasing yttrium content the onset of the Ce1 and Ce2 decay time decrease as well as the Ce1, Ce2 delayed recombination integrals increase shift to higher temperatures. The 5d1 thermally induced excited-state ionization of both Ce1 and Ce2 centres is confirmed and studied by purely optical methods.

Non-stoichiometric undoped zirconates of Ca, Sr and Ba were prepared and studied for their luminescence and scintillation characteristics in a broad range of compositions. Powder samples were prepared by solid state reaction method. Based on phase analysis the zirconate phases compositions in the sintered samples have been determined. Dominant emission band of these materials is situated in near UV-blue spectral range. The highest scintillation efficiency was found at the samples of the strontium zirconate containing surplus of ZrO2.

We analyze thermally stimulated luminescence (TSL) above room temperature in Ce-doped Y2SiO5 oxyorthosilicate single crystal. We perform detailed TSL glow peak analysis based on the initial rise technique to evaluate trap depths and other characteristics associated with TSL peaks. The tunneling process previously proposed to be at work in recombination mechanism of Ce-doped lutetium oxyothosilicate was not confirmed in presently studied isostructural yttrium silicate. The charge carrier transfer between traps and Ce recombination centers is rather accomplished via conduction band.

To examine scintillation response of piezoelectric crystals the 241 Am 5.5 MeV α -ray excited emission spectra of langasite family crystals, LGS (La 3 Ga 5 SiO 14 ), LNGA (La 3 Nb 0.5 Ga 5.3 Al 0.2 O 14 ) and LTGA (La 3 Ta 0.5 Ga 5.3 Al 0.2 O 14 ) were measured. Dominating emission bands were observed at 378 nm for LGS, 556 nm for LNGA and 425 nm for LTGA. X-ray excited radioluminescence intensity of these crystals was quantitatively compared with BGO standard scintillator. Photoluminescence 2D-spectra were measured as well and compared with radioluminescence ones. In LTGA also photoluminescence decays were measured for two dominant contributing emission centers. Observed emission bands within 300–360 nm and beyond 400 nm most probably belong to self-trapped or trapped excitons and lattice defects, respectively.

The optical absorption, temperature dependence of emission spectra, prompt nanosecond decays and millisecond delayed recombination decays for Pr^(3+) center in Lu_(0.8)Sc_(0.2)BO_3 host were studied. The photoluminescence decay time decreases from 16 ns (80 K) to 11 ns (300 K), but its steady-state emission intensity at 300 K is stronger than that at 80 K and towards higher temperatures is further decreasing comparatively much less with respect to the decay time shortening, which was proved to be associated with the thermal ionization processes occurring from 5d_1 relaxed state of Pr^(3+). The quantitative parameters governing the ionization processes were calculated.

Structural and optical properties of sol–gel silica based glassceramics doped with 0.1 mol% Ce and codoped with Gd at high concentrations, from 5 mol% up to 40 mol%, are investigated and compared to those of analogous samples doped only with Ce. Raman scattering, transmission electron microscopy, and x-ray diffraction reveal the formation of Gd apatite-like silicate (Gd4.67O(SiO4)3) and of Gd pyrosilicate (Gd2Si2O7) nanophases whose morphology and crystallinity depend on the Gd concentration and thermal treatments. Optical absorption measurements demonstrate the role of the densification atmosphere in modifying the charge state of Ce ions. The incorporation of Ce3+ ions in the nanophases is put in evidence by photo- and radio-luminescence results.

This work deals with luminescence and scintillation characteristics of highly efficient cerium-doped scintillators, lutetium–yttrium orthosilicate (Lu2(1−x)Y2xSiO5:Ce3+, x = 0−1). The radioluminescence, photoluminescence excitation (PLE) and emission (PL) spectra of the CeLu1, CeLu2 centers in LSO, LYSO and YSO are measured and discussed between 80 and 400 K with respect to the CeLu1 and CeLu2 features assignment and separation. The influence of yttrium concentration in Lu2(1−x)Y2xSiO5:Ce3+ on CeLu1, CeLu2 luminescence characteristics is demonstrated. Temperature dependence shows that with increasing yttrium content the onset of the CeLu1 and CeLu2 decay time decrease and CeLu1, CeLu2 delayed recombination integrals increase shift to higher temperatures. The 5d1 thermally induced excited-state ionization of both CeLu1 and CeLu2 centers is confirmed and studied by purely optical methods.

We measured temperature dependences of emission spectra, prompt nanosecond decays and millisecond delayed recombination decays for the Ce3+ center in the SrHfO3 (SHO) host. We characterized two samples with 0.1% and 5Î prepared by the acetate and citrate combustion and solid state reaction, respectively. The decrease of nanosecond decay times above approximately 220 and 260 K, respectively, is due to thermal ionization of 5d1 excited state of the Ce3+ center. Energy barrier of 300 meV, governing this process, is calculated for both the 0.1% and 5Î:SHO samples. Thermoluminescence glow curve measurement after X and UV (310 nm) irradiation at RT provides another support for the 5d1 excited-state ionization of Ce3+ in the SHO host. © 2010 Elsevier B.V. All rights reserved.

Luminescence of the Bi3+ single and dimer centers in UV and visible ranges is studied in YAG:Bi (0.13 and 0.27 at% of Bi, respectively) single crystalline films (SCFs), grown by liquid phase epitaxy from a Bi2O3 flux. The cathodoluminescence spectra, photoluminescence decays, and time-resolved spectra are measured under the excitation by accelerated electrons and synchrotron radiation with energies of 3.7 and 12 eV, respectively. The energy level structure of the Bi3+ single and dimer centers was determined. The UV luminescence of YAG:Bi SCF in the bands that peaked at 4.045 and 3.995 eV at 300 K is caused by radiative transitions of Bi3+ single and dimer centers, respectively. The excitation spectra of UV luminescence of Bi3+ single and dimer centers consist of two dominant bands, peaked at 4.7/4.315 and 5.7/6.15 eV, related to the 1S0→3P1 (A band) and 1S0→ 1P1 (C-band) transitions of Bi3+ ions, respectively. The excitation bands that peaked at 7.0 and 7.09 eV are ascribed to excitons bound with the Bi3+ single and dimer centers, respectively. The visible luminescence of YAG:Bi SCF presents superposition of several wide emission bands peaking within the 3.125–2.57 eV range and is ascribed to different types of excitons localized around the Bi3+ single and dimer centers. Apart from the above mentioned A and C bands the excitation spectra of visible luminescence contain wide bands at 5.25, 5.93, and 6.85 eV ascribed to the O2−→Bi3+ and Bi3+→Bi4+ + e charge transfer transition (CTT) in Bi3+ single and dimer centers. The observed significant differences in the decay kinetics of visible luminescence under excitation in A and C bands of Bi3+ ions, CTT bands, and in the exciton and interband transitions confirm the radiative decay of different types of excitons localized around Bi3+ ions in the single and dimer centers.

The presented work gives an overview of recent advances in research and development of novel phosphors based on Eu2+-doped KxNa1-xLuS2 ternary sulfides which may be used as phosphors in white LED sources with tunable color correlated temperature. Tunability is achieved by using two different kinds of excitation diodes (nearUV and blue) in combination with the proper K/Na ratio in KxNa1-xLuS2:Eu2+ structure. Intense photoluminescence due to the Eu2+ 5d – 4f allowed transition covers a broad emission region in visible range under both nearUV (~390 nm) and blue (~450 nm) excitations. The possibility to change the intensity ratio of the excitation diodes yields the changes of the output color correlated temperature. These changes are clearly demonstrated by shifts in the CIE color space; light quality is also quantified and discussed using CRI (color rendering index) and CQS (color quality scale) metrics [1]. However, to fully understand the Eu2+ emission mechanisms in these sulfidic hosts and to be able to optimize phosphor preparation and its performance, additional experimental techniques are applied to characterize these KxNa1-xLuS2:Eu2+ phosphors. When a focused electron beam impinges on a cathodoluminescent (CL) material in a scanning electron microscope (SEM), secondary electrons, characteristic x-rays and visible photons are emitted. These signals can be used to construct a two-dimensional topographical, chemical and luminescence map, respectively [2]. Furthermore, thermal quenching and quantum efficiency measurements of KxNa1-xLuS2:Eu2+ phosphors will be discussed for the first time. V. Jarý, L. Havlák, J. Bárta, M. Rejman, A. Bystřický, Ch. Dujardin, G. Ledoux, M. Nikl. Circadian Light Source Based on KxNa1-xLuS2:Eu2+ Phosphor. ECS Journal of Solid State Science and Technology, 7 (1), R3182-R3188, (2018). doi: 10.1149/2.0231801jss. L.I.D.J. Martin, D. Poelman, P.F. Smet, J.J. Joos, Microscopic Study of Dopant Distribution in Europium Doped SrGa2S4: Impact on Thermal Quenching and Phosphor Performance. ECS Journal of Solid State Science and Technology, 7 (1) R3052-R3056 (2018). doi: 10.1149/2.0341709jss.

Single crystal of the Pr 3+ doped Lu 2 Si 2 O 7 was grown to test its luminescence and scintillation characteristics. Absorption, excitation and photoluminescence (PL) spectra manifest the 4f ↔ 5d transitions in the UV spectral region. Evaluation of temperature dependences of both the Pr 3+ PL decay times and intensities of the delayed radiative recombination enable to determine the ionization barrier of the 5d 1 relaxed excited state of Pr 3+ , being about 0.7–0.75 eV. Fast scintillation decay and efficient radioluminescence at room temperature indicate a good potential of this material system to become fast, high density scintillator though the mechanism of the host-Pr 3+ energy transfer are yet to be understood.

In this paper we report our follow-up research on the Bi 3+ luminescence in orthosilicate compounds, focusing on absorption, luminescent and scintillation properties of YSO:Bi and LSO:Bi SCFs with the Bi concentration ranging from 0.05 to 0.18 at%. For purpose of this research, single crystalline films (SCF) of Y 2 SiO 5 :Bi and Lu 2 SiO 5 :Bi have been grown by the LPE method onto YSO and LSO substrates from the melt-solution based on Bi 2 O 3 flux.

The optical properties of undoped RE2O3 (RE = Lu, Sc, Y) sesquioxides, which were prepared by different methods, are reported. Luminescent characteristics, including emission, excitation spectra as well as luminescence decay kinetics were studied in a wide spectral range. The main intrinsic emission bands are located in ultraviolet region and the origin of these luminescent bands is different owing to the different electronic structure. In present paper, the spectral characteristics of these samples are considered and compared with those studied before; the origin of the intrinsic bands is discussed.

Set of novel Eu2+-doped KxNa1-xLuS2 phosphors (where x = 0 – 1) was successfully synthesized in the form of transparent crystalline hexagonal platelets by chemical reaction under the flow of hydrogen sulfide. Their physical properties were investigated by means of X-ray diffraction, X-ray excited fluorescence, time-resolved luminescence spectroscopy and electron paramagnetic resonance. Special attention is given to photoluminescence emission spectra under the 395 nm and 455 nm excitation aiming to obtain white emission with tunable color temperature, which is desirable for circadian white LEDs construction. EPR method is employed to understand the Eu2+ incorporation and distribution in the KxNa1-xLuS2 hosts. CIE xy-coordinates are used to compare effects of different K/Na concentration in KxNa1-xLuS2 on resulting spectrum (Figure 1). The application potential of mentioned compounds in the field of white LED solid state lighting phosphors with tunable color temperature is thoroughly discussed. The realistic circadian light bulb is presented as well and its properties are addressed. Figure 1

The report is dedicated to development of scintillators based on the single crystalline films of Lu 2 SiO 5 (LSO), (Lu x Gd 1−x ) 2 SiO 5 (LGSO) and Y 2 SiO 5 (YSO) orthosilicates grown by Liquid Phase Epitaxy (LPE) methods. We also compare the luminescent and scintillation properties of Ce doped LSO and YSO SCFs with the properties of their single crystal counterparts, growth by Czochralski method.

Undoped, Ce3+, Pr3+ and Eu3+ doped lutetium oxyfluoride submicrometre powders have been prepared by a simple coprecipitation procedure in water. The synthesized samples are Vernier single phases with a stoichiometry assigned to Lu10O9F12, as demonstrated by X-ray powder diffraction. The structural disorder of the host matrix significantly affects the optical emission spectra of the lanthanide doped samples as well as their vibrational spectra. The observed bandwidths of the FTIR spectrum and Raman scattering of the undoped sample are consistent with a very disordered nature of the host. From an analysis of the emission spectra of the Eu3+ doped sample it was found that different sites accommodating the lanthanide ions are present in the crystal structure. The Pr3+ and Ce3+ doped oxyfluoride samples show radioluminescence emission both in the UV and visible regions. The UV emission is due to lanthanide 4d-5f transitions, differently from the behavior observed for Ce3+ and Pr3+ doped Lu2O3, showing no UV emission. Considering the high mass density (close to 9 g cm(-3)), and the suitable location of rare earth ion electronic levels in the material band gap, as demonstrated by the observation of radiative emissions for all activators, the materials under investigation can be considered interesting candidates for scintillator or phosphor materials in the UV and visible regions.

The heavily Ce-doped SrHfO 3 (SHO) and the undoped non-stoichiometric SHO sample sets were prepared by solid state reaction in powder form and their luminescence spectra and decay kinetics were measured. Concentration quenching effects and thermally induced ionization of the Ce 3+ excited states were followed and discussed in the former sample set. In the latter one new emission band at about 334 nm was found in Sr-deficient samples and temperature dependences of its emission intensity and decay times were studied in the detail. Room temperature decay time of about 180 ns and efficient and fast energy transfer from the host to the center of the 334 nm emission make this material promising candidate for X-ray phosphors.

We have recently started to investigate structural, scintillation, luminescence and paramagnetic (in case of Eu2+ doping) properties of the unexplored family of rare earth (RE)-doped ternary sulfides of general formula ALnS2 (A = Rb, K, Na; Ln = La, Gd, Lu, Y), which show prospective application potential in the field of X-ray and solid state white LED phosphors. The X-ray diffraction (XRD) detected only a single crystalline phase of rhombohedral lattice system, except NaLaS2 which has cubic structure. Time-resolved luminescence spectroscopy, XRD and electron paramagnetic resonance were employed to understand the nature of Eu2+ emission centre in these sulfidic hosts and find correlation between structural and optical properties of these materials. Eu2+ and Ce3+ emission features are investigated in a broad temperature and concentration ranges and phenomenological modeling and delayed recombination decay measurements are used to understand better the Eu2+ excited state dynamics. Optical properties of ALnS2 doped by another RE ions are presented as well. Motivating figure 1 shows clear energy shift of the Eu2+ emission spectra maxima with different chemical compositions, peaking from 498 nm (RbLuS2) to 779 nm (NaGdS2). Figure 1. RT Radioluminescence spectra of Eu2+-doped ALnS2.

We report a new discovery of Yb3+-doped ultrafast scintillators based on the Yb3+ charge transfer luminescence. Transparent ceramic Yb3+-doped Y2O3, Sc2O3, Lu2O3, and Yb2O3 were prepared by sintering. When irradiated by γ- and X-rays, they showed a well detectable photoabsorption peak in the pulse height spectra and ultrafast scintillation decay dominated by the decay time of about 1 ns. For the first time, the Yb3+-doped oxide materials show detectable scintillation in the pulse height measurement at room temperature with ultrafast scintillation decay.

In this paper, we investigate the temperature dependence of luminescence characteristics of highly efficient cerium-doped scintillator, lutetium-yttrium orthosilicate Lu2(1−x)Y2xSiO5:Ce3+. The photoluminescence excitation and emission spectra have been measured in a broad temperature range. The temperature dependence of the Ce1 and Ce2 decay times shows the onset of decay time decrease at about 300 K. This observation demonstrates that unlike so far reported, the Ce2 center is not substantially quenched until room temperature. The 5d1 excited-state ionization of both Ce1 and Ce2 centers is studied by purely optical methods.

The absorption, luminescence and scintillation characteristics of Y2SiO5:Ce (YSO:Ce) scintillator were investigated and compared to those of Lu1.95Y0.05SiO5:Ce,Ca (LYSO:Ce,Ca) scintillator. Due to the Ca2+ co-doping in LYSO:Ce quantified by GDMS analysis, the Ce4+ center is evidenced in the absorption spectra. For 662 keV γ-rays (137Cs source), YSO:Ce shows a light yield of 15,300 ph/MeV, which is much lower than that of 32,000 ph/MeV obtained for LYSO:Ce,Ca. The coincidence timing resolution for 511 keV annihilation quanta of 234 and 478 ps was obtained, respectively, for LYSO:Ce,Ca and YSO:Ce detectors in coincidence experiment using a BaF2-based detector. Time resolution was also discussed in terms of a number of photoelectrons and decay time of the scintillation pulse.