Search

In this study, we examine the impact of optical and scintillation properties on needle-shaped bis(butylammonium) lead bromide [(BA) 2 PbBr 4 ] crystals (average length of 12.7 mm and average width of 1.3 mm), considering different growth methods and dimensions. Needle-shaped crystals with a length-to-width aspect ratio greater than 10 are essential for cutting-edge radiation imaging technology. Through X-ray diffraction characterization, we observe lattice expansion in the needle-shaped crystals compared to previous single crystals. This expansion leads to a stronger overlap between absorption and photoluminescence (PL) spectra, resulting in a smaller Stokes shift of 26 meV. Time-resolved PL analysis reveals a fast decay component of 0.8 ns, which is 68 % faster than the previously reported best value of 2.0 ns, with an average decay time of 3.6 ns, 48 % faster than the best reported value of 7.0 ns. Although our measured sample exhibits a comparatively low light yield (LY) of 7.8 ph/keV due to strong self-absorption, the best energy resolution is observed with a value of 11.5 %, similar to the best reported value of 10.9 %. Despite this, the LY is notably superior to that of previously reported benzylammonium lead bromide [(BZA) 2 PbBr 4 ] crystals (3.7 ph/keV). Additionally, scintillation decay shows a fast component of 9.4 ns and an average decay time of 119 ns. These characteristics make two-dimensional-(BA) 2 PbBr 4 needle-shaped crystals promising candidates for cost-effective and scalable applications in radiation imaging technology. • Solution process 2D-(BA) 2 PbBr 4 needle-shaped crystals was successfully synthesized with an aspect ratio of length to width exceeding 10. • Time-resolved photoluminescence analysis reveals ultra-fast decay component of 0.8 ns, which is 68 % faster than the reported value of 2.0 ns. • Solution grown needle-shaped 2D perovskites are an interesting and versatile class of materials for cost-effective and scalable in cutting-edge radiation imaging technology. [ABSTRACT FROM AUTHOR]

Gd 2 O 2 S:Pr,Ce nanophosphors have been prepared by liquid-phase method using NH 2 SO 3 H as the sulfur source for the first time. The formula of the novel precursor was determined as Gd 2 (OH) x (NH 2 SO 3) 6-x ∙nH 2 O by EDS, TG-DSC and FT-IR spectroscopy, and the precursor exhibited an amorphous structure and lamellar morphology as deduced from XRD and SEM. The optimum pH was 8 and the optimum calcination temperature was 1000 °C for the preparation of Gd 2 O 2 S:Pr,Ce from the precursor. The PL quantum yield and the fluorescence lifetime of Gd 2 O 2 S:Pr,Ce powder was 53.62 % and 2.48 μs respectively, which will allow the preparation of ceramic scintillators with high optical output and energy resolution. Compared to the traditional sulfur sources such as sublimed sulfur, and H 2 SO 4 , NH 2 SO 3 H is harmless and avoids pollution gases during the preparation of Gd 2 O 2 S:Pr,Ce nanophosphors. It also eliminates the need to add additional reagents, simplifying the preparation steps and reducing production costs. • GOS powder was synthesized by using a new sulfur source NH 2 SO 3 H for the first time. • The novel precursor Gd 2 (OH) x (NH 2 SO 3) 6-x ∙nH 2 O was analyzed in detail. • GOS powder was with high PL quantum yield and short fluorescence lifetime. [ABSTRACT FROM AUTHOR]

Sm-doped CaCl 2 , SrCl 2 , and BaCl 2 bulk crystals were synthesized using the conventional vertical Bridgman method, and the photoluminescence, radioluminescence, and detector properties were evaluated. The Sm-doped CaCl 2 , SrCl 2 , and BaCl 2 samples show a broad emission band at 750, 690, and 650 nm, respectively, which is attributable to the 5d-4f transitions of Sm2+. The pulse height spectra under 137Cs γ-rays (662 keV) show that the Sm-doped CaCl 2 and SrCl 2 exhibit 9300 and 33000 photons/MeV, respectively. These samples can be used for γ-ray measurements in the red to NIR region. • Sm-doped CaCl 2 , SrCl 2 , and BaCl 2 crystals were synthesized using the conventional vertical Bridgman method. • The photoluminescence, radioluminescence, and detector properties were evaluated. • The samples show a broad emission band at 600–800 nm due to Sm2+. • Sm-doped CaCl 2 , SrCl 2 , and BaCl 2 exhibit light yield of 9300, 33000, and 16000 photons/MeV, respectively. [ABSTRACT FROM AUTHOR]

In order to estimate the stability of the light output of the scintillation detector, the Lu 2 SiO 5 :Ce scintillation crystals, additionally doped with Ca2+ ions at concentrations of 0 ÷ 0.4 at%, were studied. The spectra of optical absorption, gamma-luminescence, thermal luminescence, dose and temperature dependences of luminescence were measured. Gamma-luminescence in the dose range 10 - 5·107 Gy was recorded using 60Co gamma-source at the temperature range of 310–460 K. In contrast to the initial sample (non-doped with Ca), in the sample doped with 0.1 at% of Ca, an increase in the luminescence intensity was observed in the range of 390–425 nm, but further with an increase in the concentration of Ca (0.3–0.4 at%), the intensity of this band decreased to the initial level (undoped). At Ca concentrations of 0.3 and 0.4 at%, the intensity of the Ce1 center band remains practically unchanged up to a dose of 5·107 Gy. LSO crystals doped with Ce 0.1 at% and co-doped with Ca 0.1 at% can be recommended as a scintillation detector up to a gamma-dose of 105 Gy at room temperature. • Ca-codoped Lu 2 SiO 5 :Ce crystals are studied as a material for scintillation detector. • At Ca 0.1 at% an increase in the luminescence at 390–425 nm was observed. • At Ca 0.3 at% the Ce1 center emission doesn't change up to a γ-dose of 5·107 Gy. • Defect complexes completely discolor at room temperature in two days. [ABSTRACT FROM AUTHOR]

Single crystals of Gd 3 (Ga,Al) 5 O 12 :Ce,Mg with different concentration of Mg2+ ions varying from 0 to 0.029 at.% are investigated by the X-ray diffraction, steady-state and time-resolved photoluminescence, and thermally stimulated luminescence (TSL) methods in a wide temperature range (77–510 K). The origin and structure of the luminescence centers are considered. The influence of Mg2+ ions on the structure of the Ce3+-related excited state, the processes taking place in this state, and the TSL characteristics is clarified. At low temperatures, the photoluminescence optical quenching in close {Ce3+ - Mg2+} pairs is found to be responsible for the light yield reduction accompanied with the acceleration of the luminescence decay kinetics. At room temperature, the luminescence quenching can be additionally caused by the thermal ionization of the 5d 1 excited state of Ce3+ ion, whose probability increases with the increasing Ga content. The conclusion is made that in order to create the fast scintillator with the maximum light yield, the concentration of intrinsic crystal lattice defects in Gd 3 (Ga,Al) 5 O 12 :Ce,Mg should be minimized, the optimum composition of the host should be chosen, and the balance between the concentrations of the doped Mg2+ and Ce3+ ions should be optimised. • Photo- and thermoluminescence and XRD of Gd 3 (Ga,Al) 5 O 12 :Ce,Mg crystals are studied. • Influence of Mg2+ ions on the Ce3+-related luminescence and excited states is clarified. • Optical quenching in close {Ce3+ - Mg2+} pairs results in the light yield reduction and accompanied with acceleration of the Ce3+ luminescence decay kinetics. • Ga3+ ions and intrinsic defects strongly influence the luminescence thermal quenching. • Optimum host composition and preferable Ce3+/Mg2+ concentration ratio are considered. [ABSTRACT FROM AUTHOR]

Rare-earth aluminate garnet-type double oxides have practical applications as scintillators with high luminescence yields; however, several garnet compounds are metastable phases, and those scintillation properties are yet unclear. We prepared Ce3+-doped Gd 3 Al 5 O 12 (Ce3+:GAG) as a thick-film phosphor, using laser-assisted metal–organic chemical vapor deposition, and investigated its luminescence and scintillation properties. With a deposition rate of 48 μm h−1, the Ce3+:GAG thick film was epitaxially grown on a Y 3 Al 5 O 12 single crystal substrate with in-plane orientation relationship. Under UV light and α-ray irradiations, the Ce3+:GAG film exhibited a broad emission centered at 560 nm corresponding to the 5d–4f transition of Ce3+ ions. The scintillation light yield of the Ce3+:GAG film was 14250 photons per 5.5 MeV with a fast decay constant of 82.8 ns for the α-ray irradiation from the 241Am source. • Ce3+:GAG thick film phosphor was epitaxially grown using CVD method. • Ce3+: GAG exhibited photoluminescence at 560 nm due to Ce3+ 5d-4f transition. • Scintillation light yield was 14250 photons per 5.5 MeV, comparable to Ce3+:YAG. [ABSTRACT FROM AUTHOR]

Intrinsic luminescence in Ce-doped (Lu,Y) 2 SiO 5 (or LYSO:Ce) single crystals have been studied by means of excitation luminescence spectroscopy in the vacuum ultraviolet energy range under synchrotron radiation. A previously unreported luminescence band with emission at 250 nm has been discovered as well as its thermal behavior was described in the temperature range 10–120 K. The excitation spectra as well as time-resolved properties of this band suggest that this emission corresponds either to the singlet component of self-trapped exciton or to a self-trapped exciton in the lutetium sublattice of LYSO single crystals. • New previously unreported intrinsic emission band at 250 nm has been observed in LYSO single crystals. • Temperature dependencies of intrinsic luminescence have been measured and analyzed. • Two possible origins of new 250 nm emission are proposed and discussed. [ABSTRACT FROM AUTHOR]

Ce,Mg:Lu 2 YGa x Al 5-x O 12 (x = 1.5, 2, 2.5, 3) ceramic scintillators were fabricated by oxygen sintering combined with air annealing using nano-powders synthesized by the co-precipitation method. The Ce3+ 5d 1 → 4f (2F 5/2 , 2F 7/2) luminescence band was blue shifted with increasing Ga content due to the decrease in the crystal field splitting of the 5d levels. At room temperature (RT), the decrease of photoluminescence decay time and scintillation decay time was observed with increasing Ga content. At 662 keV γ-rays, the sample Ga2 exhibited high light yield (LY) of 28,700 photons/MeV, fast scintillation decay times of 17.7 ns (17 %) + 45.7 ns (83 %), and good time resolution of ∼220 ps. At RT, the decrease of LY value for the samples Ga2.5 and Ga3 could be attributed to the larger thermal ionization of the excited Ce3+ centers. • Scintillation properties of Ce,Mg:Lu 2 YGa x Al 5-x O 12 (x = 1.5, 2, 2.5, 3) ceramics are investigated. • All ceramic samples show fast effective scintillation decay time less than 47 ns. • Sample x = 2 shows high LY of ∼28,700 ph/MeV @662 keV γ rays. • Samples x = 2 and 2.5 show good coincidence time resolution of 220 ps. [ABSTRACT FROM AUTHOR]

Cerium-doped lutetium yttrium orthosilicate (LYSO:Ce) powders were synthesized using the co-precipitation method. The influence of sintering temperature on the crystallization and luminescence characteristics of LYSO:Ce powders was investigated via X-ray diffraction (XRD) and photoluminescence (PL). The XRD measurements indicate that the crystallization of LYSO:Ce powders was affected by sintering temperature. PL results show that with the increase of sintering temperature, LYSO:Ce samples have better luminescence properties. A dosimeter was also fabricated using LYSO:Ce powders with 0.3 mol% Ce doping concentration for an optimum result. Radioluminescence properties of the radiation dosimeter were studied using calibrated 60Co gamma sources in the dose range from 232.66 to 1022.26 mGy. The results show that the dosimeter response under γ-rays irradiation has a certain linear response and stability, indicating its potential applications in remote radiotherapy and real-time radiation monitoring. • LYSO:Ce crystal powder as scintillitor material was synthesized by co-precipitation method. • LYSO:Ce with different sintering temperature has been systematically investigated. • A dosimeter was made with the optimal LYSO:Ce crystal powder for low dose gamma radiation. [ABSTRACT FROM AUTHOR]

(C 4 H 9 NH 3) 2 PbI 4 and (C 6 H 5 C 4 H 8 NH 3) 2 PbI 4 single crystals were synthesized by the slow cooling method, and their optical and scintillation properties were evaluated. Both samples had sharp X-ray diffraction peaks with intervals of (0 0 2 l) (l = 5–7). Absorption edges of (C 4 H 9 NH 3) 2 PbI 4 and (C 6 H 5 C 4 H 8 NH 3) 2 PbI 4 were confirmed at 535 and 520 nm, respectively. They showed luminescence due to the recombination of excitons at 500–700 nm. Scintillation decay times at 0.5–0.7 ns were obtained by approximation of decay curves. The light yields of (C 4 H 9 NH 3) 2 PbI 4 and (C 6 H 5 C 4 H 8 NH 3) 2 PbI 4 were respectively evaluated to be 1200 and 1500 photons/5.5 MeV-α by measuring full absorption peaks of 241Am α-rays. • (C 4 H 9 NH 3) 2 PbI 4 and (C 6 H 5 C 4 H 8 NH 3) 2 PbI 4 single crystals were grown by the slow cooling method. • Luminescence due to the recombination of free excitons was observed. • Scintillation decay times of sub-nanoseconds were observed. • Light yield of (C 6 H 5 C 4 H 8 NH 3) 2 PbI 4 was 1500 photons/5.5 MeV-α. [ABSTRACT FROM AUTHOR]

0.05, 0.1, 0.5, and 1.0 % Dy-doped YVO 4 single crystals were prepared by the optical floating zone technique to obtain photoluminescence (PL) and scintillation properties. All the samples showed the emission owing to charge transfer from V5+ ions to O2− ions inside [VO 4 ]3- and the 4f–4f transitions of Dy3+ ions. Light yields exhibited 37,000 (0.05 % Dy), 42,000 (0.1 % Dy), 44,000 (0.5 % Dy), and 39,000 photons/MeV (1.0 % Dy), based on the pulse height spectra. In afterglow properties, afterglow levels were 37.7 (0.05 % Dy), 25.7 (0.1 % Dy), 23.2 (0.5 % Dy), and 20.6 (1.0 % Dy) ppm. • We have synthesized Dy-doped YVO 4 single crystals by floating zone method. • We have characterized the photoluminescence, and scintillation properties of the Dy-doped YVO 4 single crystal. • Pulse height spectra revealed that the light yield of 0.05, 0.1, 0.5, and 1.0 % Dy-doped YVO 4 single crystals was 37,000, 42,000, 44,000, and 39,000 photons/MeV, respectively. • In afterglow properties, afterglow levels were 37.7 (0.05 % Dy), 25.7 (0.1 % Dy), 23.2 (0.5 % Dy), and 20.6 (1.0 % Dy) ppm. [ABSTRACT FROM AUTHOR]

(C 6 H 5 C 2 H 4 NH 3) 2 Pb 1- x Ca x Br 4 (x = 0.05, 0.1, and 0.25) crystals were grown by the solvent diffusion method and evaluated for the photoluminescence and scintillation properties. When irradiated by X-rays, emission peaking at 440 nm due to exciton emission was observed. The pulse height spectra of (C 6 H 5 C 2 H 4 NH 3) 2 Pb 1- x Ca x Br 4 under 137Cs γ-ray irradiation demonstrate that the light yields were 20,000, 17,000, and 16,000 ph/MeV in x = 0.05, 0.1, and 0.25 samples, respectively. Ca-substitution significantly enhances the photoluminescence quantum yield and scintillation light yield. • (C 6 H 5 C 2 H 4 NH 3) 2 (Pb,Ca)Br 4 crystals were evaluated for the photoluminescence and scintillation properties. • (C 6 H 5 C 2 H 4 NH 3) 2 (Pb,Ca)Br 4 crystals exhibit a sharp emission peaking at 440 nm due to exciton luminescence. • Pulse height spectra under 137Cs γ-rays demonstrate the light yields was 20,000 ph/MeV. • Ca-substitution enhances both the photoluminescence and scintillation properties. [ABSTRACT FROM AUTHOR]

ZnO:Ga (GZO), as well as other band-edge luminous materials, exhibits fast time response properties, which makes it suitable for application as an ultraviolet scintillator for transient radiation detection. However, due to the serious self-absorption problem and low external quantum efficiency, the luminescence intensity cannot be intensified by increasing the volume of the crystals. To alleviate this problem, CsPbBr 3 quantum dot (QD) films were used to enhance the radioluminescence (RL) intensity of GZO. The effects of CsPbBr 3 QD films on the emission spectrum, intensity and angular distribution were experimentally analyzed under three different modes, namely, coating on the imaging surface, incident surface and both surfaces. The CsPbBr 3 QD film on the imaging surface could change the external quantum efficiency and luminescence angular distribution of GZO via its various surface morphologies. When CsPbBr 3 QD films were coated on both surfaces, the luminescence intensity reached 2.43 times that of GZO, while the proportion of emitted light from GZO was less than 6 %. Based on the experimental results, the principle of the enhancement and the difference among the three coating modes were discussed. The enhancement caused by CsPbBr 3 QD films on GZO was considerable and could be simply duplicated on many other materials, expanding their application in the field of detection and imaging. • Radioluminescence intensity of ZnO:Ga can be enhanced by coating perovskite films. • Scintillation performance of CsPbBr 3 QD film-coated ZnO:Ga was investigated. • Tuning the angular distribution by CsPbBr 3 QD film is beneficial for X-ray imaging. [ABSTRACT FROM AUTHOR]

Ce3+ activated high-density lanthanum lutetium germanate glass was fabricated by melt quenching method. Their densities, fluorescence decay curves, transmittance spectra, and luminescence excited by UV light and X-ray were measured and investigated. The densities of the glasses are between 5.90 g/cm3 and 5.97 g/cm3. The glasses present blue emission upon 379 nm light and X-ray. The blue emission lifetimes of the glasses are between 11.26 ns and 18.83 ns. The results shows that Ce3+ activated high-density lanthanum lutetium germanate glass would be a potential fast-event X-ray detection scintillating material. • Ce3+ doped germanate glasses with density around 6 g/cm3 were prepared. • The glass showed blue emissions upon UV light and X-ray. • The blue emission lifetimes were in the range of 11.26–18.83 ns. [ABSTRACT FROM AUTHOR]

Gd3+ and Ce3+ doped and co-doped NaCaYF 6 were synthesized noting the lack of luminescence studies in this material by using hydrothermal method. Synthesized NaCaYF 6 is also known by the mineral name Gagarinite. X-ray diffraction studies of prepared sample performed to confirm the identification of the phase pure fluoride compound. Energy dispersive spectra (EDS) and elemental mapping also recorded to confirm the compositions. Photoluminescence (PL) studies performed for recording PL Excitation (PLE) and PL Emission (PL) Spectra. Characteristic luminescence of Gd3+ ions and Ce3+ ions were observed in NaCaYF 6. The PLE of Ce3+ doped NaCaYF 6 phosphor shows broad excitation band centered at 294 nm with other weak shoulder peak at 272 nm. A typical double humped broad band emission obtained for the 294 nm excitation. Emission peak of 322 nm appears due to Ce3+ (5d–4f) transition with an additional shoulder peak at 315 nm. The PL spectra of the Gd3+-doped NaCaYF 6 excited at 272 nm consists of a dominant UVB emissions at 311 nm due to the transitions 6P 7/2 → 8S 7/2 of Gd3+ ions. No concentration quenching for Ce3+ was observed while luminescence of Gd3+activator got quenched at 1 mol %. The peculiarity of Gd3+ emission was the long lifetime of the order of 10 ms. Luminescence characteristics are explained using the known energy level diagrams for the lanthanide activators. The results revealed that Gd3+ and Ce3+ doped NaCaYF 6 compound could find a promising application for the UV-emitting phototherapy lamps. [Display omitted] • Novel results on observation of UV emission in NaCaYF 6 :Ln3+ (Ln3+ = Ce, Gd) materials are reported for the first time. • The samples of pristine and Ln3+ doped NaCaYF 6 have been prepared by the Hydrothermal method. • Characteristic line emission for Ce and Gd doped NaCaYF 6 are observed. • This can be useful in various UV applications. [ABSTRACT FROM AUTHOR]

Luminescence and scintillation properties of Lu 2 YAl 2.5 Ga 2.5 O 12 :Ce,Mg (0.02, 0.05 %) garnet crystals grown by the micro-pulling down method were investigated. The onset temperature for luminescence quenching at ∼365 K is determined from the temperature dependence of photoluminescence decay time. At room temperature, the Mg (0.05 %) sample exhibits high integral scintillation efficiency of ∼445 % of BGO crystal, light yield value of 23,500 photons/MeV, and fast scintillation decay times of 20 ns (15 %) + 54 ns (85 %). The higher radioluminescence intensity of the Mg (0.05 %) sample correlates with an appearance of its lower themally-stimulated luminescence intensity in 77–500 K range. • Luminescence and scintillation properties of Lu 2 YAl 2.5 Ga 2.5 O 12 :Ce,Mg (Mg = 0.02 %, 0.05 %) crystals are investigated. • Both crystals show onset of luminescence quenching at 365 K. • Lu 2 YAl 2.5 Ga 2.5 O 12 :Ce,0.05%Mg shows light yield of 23,500 photons/MeV. • Lu 2 YAl 2.5 Ga 2.5 O 12 :Ce,0.05%Mg shows scintillation decay time of 20 ns (14 %) + 54 ns (86 %). • Thermoluminescence characteristics are investigated. [ABSTRACT FROM AUTHOR]

Novel Sm3+ activated oxyfluoride glass was synthesized via the melt-quenching approach with subsequent heat treatment. The X-ray diffraction measurement discloses the amorphous nature of prepared glasses. And, FTIR illustrates the molar surplus of Bi 2 O 3 raises the network connectivity by creating bridging oxygen sites in the structure. The Judd-Ofelt (J-O) intensity parameters exhibit Ω 4 >Ω 2 >Ω 6 trend, witnessing the rigidity of the glass structure and ionic bonding between Sm3+ ions and surrounding ligands. The 4G 5/2 → 6H 7/2 transition of Sm3+ is the most applicable for reddish-orange lasers due to their higher values of radiative transition probability, branching ratio, and stimulated emission cross-section. The optimum emission intensity is obtained with 30 mol% Bi 2 O 3 and the corresponding decay time is 1.40 ms. Additionally, the F30 glass sample was lit in a reddish-orange region having a CCT value of 1689 K. The thermal luminescence quenching of the prepared glass was studied and the thermal stability parameters activation energy was estimated. Further, the contactless optical thermometry capability of the glass sample was explored within the range of 303 K–603 K using the luminescence intensity ratio (LIR) technique. Thus, the above studies on the glass sample suggest that it can be used as an active medium in lasers, contactless optical temperature sensing, and high-energy scintillator applications. [Display omitted] • Spectroscopic and structural characteristics of NaF– B 2 O 3 – Bi 2 O 3 –Sm 2 O 3 are explored. • These oxyfluoride glasses shows more rigidity with Ω 4 >Ω 2 >Ω 6 trend. • The reddish-orange emission is originated from 4G 5/2 → 6H 7/2 transition. • The optimum emission intensity has been observed with the 30 mol% doping of Bi 2 O 3. [ABSTRACT FROM AUTHOR]

To develop glass scintillators, Eu 2 O 3 -doped tellurite glasses (TeO 2 –Nb 2 O 5 –SrO–Eu 2 O 3) (TNbSrEu) were prepared, and their luminescence characteristics were investigated. Several photoluminescence peaks at about 578, 592, 613, 652, and 701 nm were observed when excited by 530 nm excitation light. They originated from 4f→4f transition of Eu3+. Their photoluminescence decay times under 530 nm excitation light were approximately 0.7 ms, which was a typical time of 4f→4f transition of Eu3+. Further, some scintillation peaks originating from 4f→4f transition of Eu3+ were detected at 577, 593, 613, and 652 nm, and scintillation decay times were in the time region of 0.21–0.35 ms. Furthermore, the afterglow levels were from 560 ppm to 317 ppm, showing a decreasing trend in levels with increasing Eu 2 O 3 concentration. • To develop glass scintillators, Eu 2 O 3 -doped tellurite glasses (TeO 2 –Nb 2 O 5 –SrO–Eu 2 O 3) were prepared. • Some scintillation peaks originating from 4f.→4f transition of Eu3+ were detected. • The tellurite glasses showed a decreasing trend in afterglow levels with increasing Eu 2 O 3 concentration. [ABSTRACT FROM AUTHOR]

Effects of Sc3+ admixture on luminescence and scintillation properties were studied in Ce3+ - doped Lu 2 Y(Al 5-x Sc x)O 12 (x = 1, 1.5, 2) garnet single-crystalline films grown by the isothermal liquid phase epitaxy technique. The Ce3+ photoluminescence (PL) was slightly blue shifted with increasing Sc content due to a decrease in crystal field splitting of the Ce3+ 5d levels. In addition, the thermal activation energy of PL quenching, estimated from the temperature dependence of PL decay times, decreased with increasing Sc content. Lu 2 YAl 4 ScO 12 :Ce exhibited the highest light yield (LY) value of 420 photons/MeV at 5.5 MeV α particles along with a fast scintillation decay time constant (τ e) of 17.4 ns. At room temperature, the decrease of LY value with increasing Sc content could be attributed to the thermal ionization process. • Lu 2 Y(Al 5-x Sc x)O 12 :Ce garnet single-crystalline films were grown by the liquid phase epitaxy technique. • Lu 2 Y(Al 4 Sc)O 12 :Ce exhibits good thermal stability with T q = 400 K. • Activation energy of photoluminescence decreased with increasing Sc content. • Lu 2 Y(Al 4 Sc)O 12 :Ce exhibits light yield (at α-excitation) of 362 photons/MeV and fast scintillation decay time of 17.4 ns. [ABSTRACT FROM AUTHOR]

The emerging laser-driven phosphor-converted white laser diodes (w-LDs) demand highly efficient and thermally stable color converters. To this end, the Ce3+ luminescence in the rekindled La–Si–O–N host, and the impacts of NH 4 Cl flux and post-processing are investigated systematically. On the basis of the XRD results, well crystalline Ce3+-doped La 5 Si 3 O 12 N and LaSiO 2 N are obtained at 1600 °C for 5 h and 1500 °C for 4 h, respectively. Impressively, the representative La 5 Si 3 O 12 N:0.04Ce3+ and LaSiO 2 N:0.03Ce3+ exhibit a broad excitation band from 240 nm to 400 nm, peaking at around 360 nm, which is well matched with emission from near-UV (n-UV) chip. Under excitation by a n-UV laser, the La 5 Si 3 O 12 N:0.04Ce3+ and LaSiO 2 N:0.03Ce3+ produce bright blue light in a wide emission band from 360 nm to 550 nm. The CIE chromaticity diagram reveals the tunability of the hue of these phosphors. The quenching temperature is determined to be 396 K and 429 K for La 5 Si 3 O 12 N:0.04Ce3+ and LaSiO 2 N:0.03Ce3+ respectively, indicating superior thermal stability. The addition of 3 wt% NH 4 Cl flux much enhances the emission intensity of both La 5 Si 3 O 12 N:0.04Ce3+ and LaSiO 2 N:0.03Ce3+. Furthermore, the post-treatments markedly improve the luminescence properties by increasing the crystallinity, reducing the surface defect, and changing the morphology. Therefore, it is believed that the present work has promising applications in LD lighting and promoting the development of laser display. • Ce3+-activated La–Si–O–N compounds generate bright blue light in a wide emission band of 360∼550 nm pumped by n-UV laser. • The quenching temperature (T 0.5) of Ce3+-doped La–Si–O–N phosphors is 396∼429 K, indicating favorable thermal stability. • As Increasing the NH 4 Cl dosage up to 3 wt%, PL intensity attains a maximum 148–263% of that of the samples without flux. • The post-treatments greatly improve the luminescence by enhancing crystallinity, reducing cluster, and smoothing surface. [ABSTRACT FROM AUTHOR]

We synthesized 0, 0.02, 0.2, 1.0, and 10% Ce3+ doped CaF 2 AlF 3 AlPO 4 glasses; and then, we evaluated their photoluminescence (PL), scintillation and thermally stimulated luminescence (TSL) properties. Depending on the concentration of Ce3+, PL quantum yield (QY) ranged from 15.8 to 62.8%. When the materials were irradiated by X-rays, scintillation was observed with an emission peak around 330 nm due to 5d→4f transitions of Ce3+. The scintillation decay times ranged 14–25 ns. The glasses showed intense TSL, and the glow peak was broad peaking around 100 °C. The 0.2% and 1.0% Ce3+ doped samples demonstrated high sensitivity with a good linearity over 5 orders of magnitude (0.1 mGy–10 Gy). • We evaluated Ce-doped CaF 2 AlF 3 AlPO 4 glasses PL, Scintillation and TL properties. • 0.2% Ce-doped samples had the highest QY. • By measuring scintillation properties, all Ce-doped samples emitted around 320 nm. • We measured dose response of each sample. [ABSTRACT FROM AUTHOR]

Scintillation and luminescence properties of a novel organic crystal scintillator, 1,4-bis(2-methylstyryl) benzene (bis-MSB), were measured and compared with those of the conventional trans-stilbene organic crystal scintillator. Although trans-stilbene has been used for beta or neutron detection, trans-stilbene cannot be applied at high temperature conditions due to a lower melting point (124 °C). Liquid scintillators or plastic scintillators also cannot be used at high temperature. Usually, bis-MSB has been used as dopant in liquid scintillators to obtain fast scintillation decay and high luminescence quantum yield, and its melting point is 181 °C higher than that of trans-stilbene. In this paper, we focused on bis-MSB in solid state. The bis-MSB and trans-stilbene crystals were grown by the self-seeding vertical Bridgman method using double quartz ampoules. The bis-MSB crystal had the fast decay time of ∼4.2 ns and the increased light yield of ∼12,000 ph/5.5 MeV(α), while trans-stilbene had the decay time of ∼8.5 ns and the light yield of ∼8500 ph/5.5 MeV(α). The photoluminescence quantum yield was almost constant up to 125 °C for bis-MSB and only up to 50 °C for trans-stilbene. We succeeded in obtaining the novel organic crystal scintillator which can operate even at higher temperature up to 125 °C. • The scintillation properties of the bis-MSB crystal were investigated. • Transparent crystals were grown by self-seeding vertical Bridgman method. • Bis-MSB had better scintillation properties compared to trans-stilbene. • The temperature dependence of luminescence quantum yield of bis-MSB was studied. [ABSTRACT FROM AUTHOR]

Time-resolved luminescence of YAG-Ce (150 ppm) fiber crystal with Mg co-doping was studied under pulsed X-ray excitation and γ-rays (Cs 662 keV). The initial part of decay kinetics under X-ray excitation is faster than for direct cerium excitation (63 ns). Decay kinetics is also characterized by the presence of slow components with at least two characteristic times longer than Ce3+ radiation time. The slowest one which dominates for t > 500 ns in YAG-Ce without Mg co-doping practically vanishes for samples with 50 ppm co-doping. Decay kinetics under γ-rays are characterized by slower rise time than that under X-rays. These properties can be explained by competition of energy transfer and energy losses in track regions. The distribution of excitations in tracks produced by X-rays differs from that in tracks produced by γ-rays, since the energy of primary electron after γ-quantum conversion is much higher than after X-ray absorption. The stopping power for energetic electrons decreases with increase of electron energy, and therefore the density distribution after X-ray conversion is shifted to higher densities, Therefore, the acceleration of recombination and quenching of excitations is more prominent under X-ray excitation. Specific role of Ce4+ induced by Mg co-doping is also discussed in the paper. • Samples YAG-Ce,Mg grown by micro-pulling-down were studied under X-ray and γ-rays. • Luminescence decay becomes faster with increase of Mg concentration. • Slow component vanishes for samples with 50 ppm Mg co-doping. • Decay kinetics under γ-rays show rise part and is slower than under X-rays. • The difference is explained using of the excitation densities distribution in track. [ABSTRACT FROM AUTHOR]

The scintillation characteristics of Gd 3 Al 2 Ga 3 O 12 :Ce, Li (GAGG:Ce,Li) and Gd 3 Al 2 Ga 3 O 12 :Ce, Mg (GAGG:Ce,Mg) single crystals were compared. Radioluminescence spectra and photoluminescence decay curves were measured at various temperatures between 77 and 500 K to investigate the thermal luminescence quenching. At 662 keV γ rays, the LY value of 35,400 photons/MeV and energy resolution of 6.9% obtained for GAGG:Ce, Li are superior to those of 24,200 photons/MeV and 9.5% for GAGG:Ce,Mg. Scintillation decays are approximated by a double exponentials with a fast principal decay component of 47 ns (83%) for GAGG:Ce, Mg and 90 ns (86%) for GAGG:Ce,Li. Coincidence time resolution of 282 ps obtained for GAGG:Ce, Mg is better than that of 389 ps for GAGG:Ce,Li. GAGG:Ce, Mg shows a much lower afterglow and thermally stimulated luminescence intensity with respect to GAGG:Ce,Li. • Scintillation properties of Li+ and Mg2+ -codoped Gd 3 Al 2 Ga 3 O 12 :Ce are compared. • Gd 3 Al 2 Ga 3 O 12 :Ce, Mg exhibits better timing performance. • Gd 3 Al 2 Ga 3 O 12 :Ce, Mg shows lower afterglow and TSL intensity. • Gd 3 Al 2 Ga 3 O 12 :Ce, Li exhibits high light yield and good energy resolution. [ABSTRACT FROM AUTHOR]

Abstract We report the synthesis and luminescence properties of new layered mixed-anion compounds, Sr 2 ScCuSeO 3 and Sr 3 Sc 2 Cu 2 Se 2 O 5. Sr 2 ScCuSeO 3 and Sr 3 Sc 2 Cu 2 Se 2 O 5 were synthesized by solid-state reaction and were investigated using x-ray diffraction, diffuse reflectance, and photoluminescence spectroscopies. Both compounds have very similar properties except for their optical band gaps and emission peak energies. At room temperature, Sr 2 ScCuSeO 3 and Sr 3 Sc 2 Cu 2 Se 2 O 5 exhibit optical band gaps energies of 2.9–3.0 eV. The excitonic luminescence with very fast emissions of ∼30 ps were observed in both compounds even at room temperature. This feature of the compounds makes them suitable for fast scintillator applications. Our results suggest that the luminescence properties such as emission peak energies and lifetimes of these layered mixed-anion compounds can be controlled by changing their structure and composition. Highlights • New layered mixed-anion compounds were successfully synthesized by solid-state reaction. • Sr 2 ScCuSeO 3 and Sr 3 Sc 2 Cu 2 Se 2 O 5 exhibit band gap energies of 2.9–3.0 eV, respectively. • Under UV excitation, Sr 2 ScCuSeO 3 and Sr 3 Sc 2 Cu 2 Se 2 O 5 exhibit a fast decay times around 30 ps even at room temperature. • Except for the emission decay, the observed optical properties are almost similar to other chalcogenide oxides. • The luminescence properties of these materials can be controlled by their composition and structure. [ABSTRACT FROM AUTHOR]

Photoluminescence and thermally stimulated luminescence of Gd 3 (Ga,Al) 5 O 12 :Ce single crystals and epitaxial films co-doped with different concentrations of Mg 2+ ions are investigated in the 77–500 K temperature range under excitation in the 4f - 5d 1 and 4f - 5d 2 absorption bands of Ce 3+ ions. Influence of Mg 2+ ions on the photoluminescence intensity, spectrum, decay kinetics, temperature dependence of the photoluminescence intensity, and the activation energy of luminescence thermal quenching is observed. Co-doping with Mg 2+ is shown to result in a drastic reduction of the afterglow and thermally stimulated luminescence and in a strong shortening of the afterglow decay kinetics. It influences also defects creation spectra and the activation energy of the photostimulated defects creation. The Mg 2+ - induced changes in the characteristics of the Gd 3 (Ga,Al) 5 O 12 :Ce, Mg single crystals and epitaxial films are found to be strongly different, and possible reasons of these differences are discussed. [ABSTRACT FROM AUTHOR]

TlSr 2 I 5 : Eu 2+ is a newly discovered scintillator that show promising scintillation properties for X- and γ-ray spectroscopy applications. Two zone vertical Bridgman technique is used for the growth of this scintillator. Luminescence properties of the grown crystals are measured under X-ray excitation at room temperature. Pure and Eu 2+ doped crystals contained broad emission bands between 445 and 670 nm peaking at 528 nm and 430–600 nm peaking at 463 nm, respectively. Energy resolution, light yield and decay time profiles are studied under 662 keV γ-ray excitation using 137 Cs radioactive source. Energy resolution of 4.2% (FWHM) is obtained for 3 mol% Eu 2+ doped crystal. For the same sample, light yield of 70,000 ph/MeV is also obtained. Three and two decay constants are observed for the pure and Eu 2+ doped samples, respectively at room temperature. Effective Z-number and density are found to be 61 and 5.30 g/cm 3 , respectively. [ABSTRACT FROM AUTHOR]

The crystal growth procedure and luminescence properties of pure and Eu 2+ -doped BaBrI and SrBrI crystals are reported. Emission and excitation spectra were recorded under ultraviolet and vacuum ultraviolet excitations. The energy of the first Eu 2+ 4f-5d transition and SrBrI band gap are obtained. The electronic structure calculations were performed within GW approximation as implemented in the Vienna Ab Initio Simulation Package. The energy between lowest Eu 2+ 5d state and the bottom of conduction band are found based on luminescence quenching parameters. The vacuum referred binding energy diagram of lanthanide levels was constructed using the chemical shift model. [ABSTRACT FROM AUTHOR]

The two-step approach to the Eu 2+ doped BaI 2 · n H 2 O powders synthesis in Ar atmosphere from precursors containing different concentration of Eu 3+ ions is reported. According to X-ray diffraction analysis the powders mainly consist of BaI 2 ·2H 2 O phase. Their morphological, structural and luminescent properties depend on the Eu-ions concentration. The luminescence spectra are composed of broad and strong emission band peaking at 420 nm, which was related to the Eu 2+ 5d–4f transition. Its intensity reaches maximum in the 2 at. % Eu 2+ doped sample. Detailed analysis of the measured electron paramagnetic resonance spectra in the samples with different doping level confirms them belong to the Eu 2+ ions substituting for the regular Ba 2+ site in the BaI 2 lattice. A sample exposed to the 330 nm UV irradiation exhibited an increase of the Eu 2+ spectral intensity occurred exclusively due to the Eu 3+ to Eu 2+ transformation. No other signals either prior to or after the irradiation which might be attributed to the ions resided in e.g., interstitial positions or in any secondary phases were observed. Possible mechanisms of the Eu 3+ stabilization in the host lattice with only divalent cation sites during the synthesis without additional treatment in reducing atmosphere are discussed as well. [ABSTRACT FROM AUTHOR]

Polycrystalline 0.2at%Pr:Lu 3 Al 5 O 12 (Pr:LuAG) transparent ceramics were fabricated by solid-state reaction using 0.01 wt% MgO as sintering aid. The as-sintered ceramics were annealed in air at different temperatures. Optical absorption, photoluminescence, X-ray excited luminescence and pulse height spectra obtained after different annealing were compared. Modifications of the oxygen vacancy concentrations are found to govern the changes of the optical and scintillation response for annealing temperatures lower than 1000 °C, while the oxidation of Pr 3+ to Pr 4+ plays a more important role for higher temperatures. Air annealing up to 700 °C is an effective tool to improve the 5d-4f emission efficiency of MgO co-doped Pr:LuAG transparent ceramics. The highest radioluminescence intensity is obtained for the 700 °C annealed sample. At variance, higher temperature annealing leads to the deterioration of 5d-4f photoluminescence and scintillation properties because of the self-absorption of Pr 4+ and energy transfer from Pr 3+ to Pr 4+ . In addition, we find that the 4f-4f slow emission of ceramics shows different response characteristics under different irradiation sources. [ABSTRACT FROM AUTHOR]

Eu doped LiSrI 3 /LiI eutectics were grown by the Bridgman method in a quartz ample with 4 mm inner diameter. and their directionally solidified eutectic system has been investigated. Growth rate was 0.3 mm/min. The eutectic showed well aligned eutectic structure and optically transparent. Grown Eu doped LiSrI3/LiI eutectic shows 400 nm emission ascribed to Eu 2+ 4f-5d transition under X-ray excitation. The light yield was around 26,000 photon/MeV for 662 keV gamma-ray and 35,000 photons for 5.5 MeV alpha-ray. [ABSTRACT FROM AUTHOR]

Single crystals of GdTaO 4 and GdTa 0.8 Nb 0.2 O 4 were grown by the Czochralski technique, and their luminescent and scintillation properties were studied. Both crystals demonstrate fast emission with decay time around 10 −8 s. Meanwhile, in GdTaO 4 the fast decay is accompanied by a huge build-up with the decay time around 1 μs, while in the mixed crystal the contribution of slow components is negligible. UV- and X-ray excited luminescence, curves of thermostimulated luminescence and absolute light yields of crystals are presented as well. GdTa 0.8 Nb 0.2 O 4 crystal is shown to be an ultradense (8.37 g/cm 3 ) and fast (shortest component decay time 17 ns) scintillator with a high stopping power. [ABSTRACT FROM AUTHOR]

Cr 3+ doped Lu 3 A1 5 O 12 transparent ceramics were developed as a new red scintillator ceramics. These ceramics were fabricated by a solid state reaction method under vacuum sintering at temperature range of 1550 °C–1890 °C for 10 h. The doping effect of different Cr 3+ concentration (0, 0.1, 0.3 and 0.5 at. %) and air annealing effect were investigated as well. The transparent ceramics (70% @1 mm in visible light range) with dense microstructure were obtained when sintered at 1890 °C for 10 h, the average grain size of 0.3 at.% Cr:LuAG was calculated to be 7 μm. Photo-luminescence spectra revealed that there are two typical excitation bands at around 450 nm and 600 nm which were ascribed to the d–d transitions of Cr 3+ . 0.3 at. % Cr:LuAG exhibited the optimum photoluminescence intensity and fast decay. Radio-luminescence under X-ray excitation indicated a characteristic Cr 3+ emission peaking at 687 nm and 706 nm respectively. The Lu 3+ Al antisite defects related emission at around 300 nm was observed to decrease with the doping of Cr 3+ . The steady luminescence efficiency (XEL spectrum integral) is around 20 times of the commercial BGO crystals, more important, the broad and continuous red emission between 600 nm and 800 nm demonstrated Cr:LuAG ceramics a prospective application as new red scintillators. [ABSTRACT FROM AUTHOR]

Photo- and radioluminescence and thermally stimulated luminescence characteristics of Ce 3+ - doped and Ce 3+ , Mg 2+ co-doped Gd 3 (Ga,Al) 5 O 12 (GAGG) single crystals of similar composition are investigated in the 9–500 K temperature range. The Ce 3+ - related luminescence spectra and the photoluminescence decay kinetics in these crystals are found to be similar. Under photoexcitation in the Ce 3+ - and Gd 3+ - related absorption bands, no prominent rise of the photoluminescence intensity in time is observed neither in GAGG:Ce,Mg nor in GAGG:Ce crystals. The afterglow is strongly reduced in GAGG:Ce,Mg as compared to GAGG:Ce, and the afterglow decay kinetics is much faster. Co-doping with Mg 2+ results in a drastic decrease of the thermally stimulated luminescence (TSL) intensity in the whole investigated temperature range and in the appearance of a new complex Mg 2+ - related TSL glow curve peak around 285 K. After irradiation in the Ce 3+ - related 3.6 eV absorption band, the TSL intensity in GAGG:Ce,Mg is found to be comparable with that in the GAGG:Ce epitaxial film of similar composition. The Mg 2+ - induced changes in the concentration, origin and structure of the crystal lattice defects and their influence on the scintillation characteristics of GAGG:Ce,Mg are discussed. [ABSTRACT FROM AUTHOR]

The short-wavelength sub-nanosecond luminescence in BaF 2 material, discovered in the early 80s, gave a new direction to research into fast scintillators and phosphors. In contrast to 'typical' luminescence occurring within the forbidden band gap, the new type of emission was due to transitions between the upper core and valence bands. Thus it was named core-valence luminescence (CVL); the terms cross-luminescence and Auger-free luminescence have also been used. Given its unusual nature, this new luminescence process has attracted considerable interest in the field of condensed matter physics. During the sequent decades (till the end of the previous century) CVL has been experimentally observed in several dozen compounds and the conditions for detecting CVL have been established. Interest in this kind of luminescence increased in recent years due to the emergence of new methods of crystal synthesis, the development of high-speed solid-state photodetectors, and the construction of unique modern set-ups using synchrotron radiation. This paper analyzes the numerous studies of CVL, obtained mainly over the past decade. Experimental and theoretical data on this topic are considered in detail. Special attention is given to new results on scintillation characteristics of BaF 2 in the form of single crystals, ceramics, nanoparticles, and composites. The features of CVL in binary and ternary compounds are discussed. Some Cs- and Ba-based ternary halides show relatively high light yields and represent promising fast scintillators. The prospects of using materials with CVL as fast scintillators for time-of-flight positron emission tomography and other applications are deliberated. • Overview of recent theoretical and experimental findings on Core Valence luminescence. • Most attractive CVL crystals for ultrafast scintillator applications analyzed. • Prospects for future studies and underexplored CVL materials listed. [ABSTRACT FROM AUTHOR]

Temperature dependences of the intensity and decay kinetics of the Ce 3+ - related photoluminescence and characteristics of thermally stimulated luminescence are investigated in the 77–500 K temperature range for the epitaxial films of the multicomponent garnets of the type of Lu 3−x Gd x Ga y Al 5−y O 12 :Ce with Ce content of 0.3–0.7 at. %, where x varies from 0.14 to 3 and y varies from 0 to 3.54. Different methods are used for the determination of energy distances between the excited 5d 1 and 5d 2 levels of Ce 3+ ions and the conduction band (CB) and their applicability is compared. The dependences of the 5d 1,2 – CB energy distances on the multicomponent garnet composition are clarified. The 5d 1 – CB energy distance is found to decrease by about an order of magnitude with the increasing Ga 3+ content. The most drastic decrease, observed at the Ga 3+ content around y ≈ 1.7, is suggested to arise from the change in the Ga 3+ position from the smaller tetrahedral to larger octahedral Al 3+ sites. This effect is explained by the lattice distortion due to the substitution of smaller Lu 3+ and Al 3+ ions by larger Gd 3+ and Ga 3+ ions. Application potential of these epitaxial films for fast 2D-imaging is discussed. [ABSTRACT FROM AUTHOR]

The paper demonstrates our last achievement in development of the novel scintillating screens based on single crystalline films (SCF) of Ce doped multicomponent garnets using the Liquid Phase Epitaxy (LPE) method. We report in this work the optimized content and excellent scintillation properties of SCF of Lu 3-x Gd x Al 5-y Ga y O 12 , Lu 3-x Tb x Al 5-y Ga y O 12 and Tb x Gd x Al 5-y Ga y O 12 garnet compounds grown by the LPE method from PbO B 2 O 3 based melt-solution onto Gd 3 Al 2.5 Ga 2.5 O 12 and YAG substrates. We also show that the Tb 1.5 Gd 1.5 Al 2.5 Ga 2.5 O 12 :Ce SCF possess the highest light yield (LY) in comparison with all ever grown garnet SCF scintillators. Namely, the LY of these SCF exceeds by 3.8 and 1.85 times the LY values of the best samples of YAG:Ce and LuAG:Ce SCF scintillators, respectively. The SCF samples of the mentioned compounds show low thermoluminescence in the above room temperature range and relatively fast scintillation decay time t 1/e in the 180–200 ns range. [ABSTRACT FROM AUTHOR]

Mg co-doping effects on scintillation properties of Ce:Lu 1 Gd 2 (Ga,Al) 5 O 12 (LGGAG) were investigated. Mg 200 ppm co-doped Ce:LGGAG single crystals were prepared by micro pulling down method. Absorption and luminescence spectra were measured together with several other scintillation characteristics, namely the scintillation decay and light yield to reveal the effect of Mg co-doping. Ce 4+ charge transfer absorption was observed below 300 nm in Mg,Ce:LGGAG which is in good agreement with previous reports. The scintillation decay times were accelerated by Mg co-doping. [ABSTRACT FROM AUTHOR]

Optical, luminescence and scintillation characteristics of Ce3+ - doped Gd 3 Sc 2 (Al 3-x Ga x)O 12 (x = 0, 1, 2) single crystalline films fabricated by the liquid phase epitaxy (LPE) technique are investigated. A blue shift of the photo- and radio-luminescence spectra is observed as Ga content increased due to a decrease in crystal field splitting of the Ce3+ 5d levels. Temperature-dependent characteristics of radioluminescence (RL) intensity and photoluminescence (PL) decay time are investigated. At room temperature, the decrease of PL- & RL- intensity and PL decay time with increasing Ga content can be explained by thermal ionization of the Ce3+ 5d 1 excited state. Gd 3 Sc 2 Al 2 GaO 12 :Ce exhibits the highest light yield (LY α) value of 1010 ph/MeV along with fast scintillation decay time of 12 ns (27%) + 52 ns (73%) under excitation with 5.5 MeV α – particles. Shortening of scintillation decay time with a decrease of the LY value is also obtained in Mg2+-codoped samples. • Gd 3 Sc 2 (Al 3-x Ga x)O 12 :Ce,Mg single crystalline films were grown by LPE technique. • Thermal activation energy decreased with increasing Ga content. • Luminescence quenching occurs at RT due to thermal ionization process. • Under α excitation, Gd 3 Sc 2 Al 2 GaO 12 :Ce shows a LY value of 1010 photons/MeV and effective decay time of 38 ns. • Luminescence quenching takes place at low temperature attributed to localization of carriers in traps. [ABSTRACT FROM AUTHOR]

Optical and scintillation characteristics of Mg2+-codoped Lu 2 Y(Al 5-x Ga x)O 12 :Ce (x = 2, 3) multicomponent garnet crystals grown by the micro-pulling down method were investigated. At RT, the shortening of scintillation decay time and a decrease of light yield (LY) value measured for a higher Ga containing samples can be explained by thermal ionization of the Ce3+ 5d 1 excited state. At 662 keV γ-rays, Lu 2 YAl 3 Ga 2 O 12 : Ce, 0.05%Mg exhibits high LY value of 29,000 ph/MeV along with scintillation decay times of 50 ns (86%) + 73 ns (14%). Co-doping with larger Mg2+ content leads to a decrease of LY value, scintillation decay time, and afterglow level. Radioluminescence quenching observed at low temperature region in correlation with large thermoluminescence peaks can be caused by trapping of electrons at intrinsic shallow traps. • Luminescence and scintillation properties of Lu 2 Y(Al 5-x Ga x)O 12 :Ce,Mg (x = 2, 3) crystals are investigated. • Temperature dependencies of photo-and radioluminescence are presented. • Lu 2 YAl 3 Ga 2 O 12 :Ce,0.05%Mg shows high light yield of 29,000 photons/MeV. • Lu 2 YAl 3 Ga 2 O 12 :Ce,0.05%Mg shows quenching temperature at 435 K due to thermal ionization. • Afterglow and thermoluminescence characteristics are investigated. [ABSTRACT FROM AUTHOR]

Optical, scintillation, and dosimetric properties of the undoped and Tb-doped CaYAlO 4 single crystals grown by the floating zone method were evaluated. Several photoluminescence (PL) emission peaks due to the 4f–4f transitions of Tb3+ ion were observed at 385–620 nm under excitation at 250 nm in Tb-doped CaYAlO 4 samples. Under X-ray irradiation, scintillation peaks of the Tb-doped CaYAlO 4 crystals were consistent with the PL emission peaks. In terms of a dosimetric property, the 0.1% Tb-doped crystal exhibited the highest thermally stimulated luminescence intensity and the widest linear responses in the range of 0.01–1000 mGy among the samples. • The undoped and Tb-doped CaYAlO 4 single crystals were synthesized by the floating zone method. • The Tb-doped samples exhibited luminescence due to the 4f-4f transitions of Tb3+. • The 0.1% Tb-doped crystal exhibited the widest linear responses in the range of 0.01–1000 mGy among the samples in TSL. [ABSTRACT FROM AUTHOR]

Gd3+ and Dy3+-doped borate glasses are considered attractive candidates for white light emission. In this work, the samples, developed by the melt-quenching route, contain a mixture of Gd3+ and Dy3+ with known molar compositions. The determined physical parameters indicate structural changes. Information regarding the Judd-Ofelt (JO) intensity parameters and spectral radiative features, calculated from absorption spectra and emission properties, respectively, are obtained. Excitation and photoluminescence characteristics of the developed samples are found. The energy transfer (ET) efficiency from Gd3+ → Dy3+ is determined by considering their emission intensities and lifetime. The quantum efficiency (QE) of glasses is evaluated. Inokuti –Hirayama (IH) model shows that the Dy3+ → luminescence center ET is dominated by dipole-dipole coulomb interaction. Due to the excitation of more secondary electrons, the X-ray luminescence shows an intense emission pattern. Furthermore, we find the integral scintillation efficiency to be 8.4% of the commercial BGO scintillator crystal for the 10 mol% Gd 2 O 3 -doped glass. Commission International deI'Eclairage (CIE) color coordinates and color correlated temperature (CCT) show the suitability of tested samples for white-light applications. • Synthesized 20Li 2 O 3 –30SrO-(49-x)B 2 O 3 -xGd 2 O 3 -1Dy 2 O 3 glasses with Gd3+ as sensitizer and Dy3+ as activator via melt quenching technique. • PL emission spectra showed reduced Gd3+ luminescence evidenced energy transfer. • CIE and CCT confirmed cool white emission. [ABSTRACT FROM AUTHOR]

A novel NIR emitting scintillator with 825 nm was developed by doping Sm2+ in Cs 4 Eu(Br,I) 6 crystal. The single crystals of Cs 4 Eu(Br,I) 6 :Sm were successfully grown by the Bridgman method. The crystal structure and valence state was approved by XRD and XPS methods. The luminescence properties and energy transfer were systematically investigated. The energy transfer mechanism is variable for different Sm2+ concentration. The PL decay profiles show that the Sm2+-related emission has fast decay of nanosecond. The proportion of fast decay can be tunable by adjusting Sm2+ doped concentration. The Sm2+ doped europium -host material will have a potential application for unclear detection as near-infrared (NIR) scintillators. • The novel NIR emitting Cs 4 Eu(Br,I) 6 :Sm scintillation crystals were successfully grown by the Bridgman method and the luminescence properties is tunable. • The proportion of nonradiative energy transfer from Eu2+ to Sm2+ was improved and the PLQY of Sm2+-related is up to 42.1%. • The fast decay time component of Sm2+ (50 ns) is up to 31.8% for Cs 4 Eu(Br,I) 6 : 3 mol%Sm crystal. • The proposed Sm2+ doped europium -host material principle is an effective method to develop near-infrared (NIR) scintillators for nuclear radiation detection. [ABSTRACT FROM AUTHOR]

The effect of Mg2+ co-doping on scintillation, luminescence, and optical properties of YAlO 3 :Ce perovskite was studied. Herein, a set of single-crystalline films with cerium content of 0.4% and various Mg concentrations ranging from 0 to 0.4% was grown by the liquid phase epitaxy. At increasing Mg content, the scintillation decays were gradually accelerated from 23 ns to less than 4 ns, however, at the expense of the light yield. At high Mg concentrations, the overlap of the 5d-4f(Ce3+) emission and charge-transfer absorption 2p(O2−)-4f(Ce4+) in the ultraviolet range became large and degraded scintillation properties. The low afterglow signal and independence of the light yield on the shaping time confirmed the low intensity of the delayed emission in the studied samples. • Optical and scintillation properties of Mg2+ co-doped YAlO 3 :Ce epitaxial perovskite film scintillator were studied. • High Mg2+ co-doping caused a considerable acceleration of the decay kinetics and simultaneously reduced light yield. • YAlO 3 :Ce,Mg films stand out by a low fraction of slow components in scintillation decays and very low afterglow. [ABSTRACT FROM AUTHOR]

(Ce x Yb 1−x ) 2 Si 2 O 7 (x = 0.00, 0.01) single crystals were grown by the micro-pulling-down method to test the possibility of its application as infra-red scintillator for medical imaging. Powder X-ray diffraction analysis indicated that the crystals were single-phase materials. The radioluminescence spectra of the crystals demonstrated presence of two near infra-red emission peaks (at 1010 and 1030 nm). The emission peaks at 420 and 580 nm ascribed to defects were also observed in the crystals. The human body has maximum transmission in wavelength range from 650 to 1200 nm. Therefore, Yb 2 Si 2 O 7 is expected to be used as efficient infra-red scintillator for medical applications. [ABSTRACT FROM AUTHOR]

Cerium doped Barium Fluoride (BaF 2 Ce) transparent ceramic was fabricated and its luminescence and scintillation properties were studied. The photoluminescence shows the emission peaks at 310 nm and 323 nm and is related to the 5d-4f transitions in Ce 3+ ion. Photo peak at 511 keV and 1274 keV were obtained with BaF 2 Ce transparent ceramic for Na-22 radioisotopes. Energy resolution of 13.5% at 662 keV is calculated for the BaF 2 Ce transparent ceramic. Light yield of 5100 photons/MeV was recorded for BaF 2 Ce(0.2%) ceramic and is comparable to its single crystal counterpart. Scintillation decay time measurements shows fast component of 58 ns and a relatively slow component of 434 ns under 662 keV gamma excitation. The slower component in BaF 2 Ce(0.2%) ceramic is about 200 ns faster than the STE emission in BaF 2 host and is associated with the dipole-dipole energy transfer from the host matrix to Ce 3+ luminescence center. [ABSTRACT FROM AUTHOR]

Ce-doped lutetium aluminum garnet Lu 3 Al 5 O 12 (LuAG) nanoceramics were fabricated at 1600 °C and 1700 °C by spark-plasma sintering (SPS) method from nano-powders prepared by radiation synthesis. Both undoped and Ce-doped LuAG ceramic samples were also prepared from the nano-powders at 1700 °C with significantly increased pre-heating rate. The backscattered electron images revealed large amount of pores in all the Ce-doped samples causing their significant opacity. On the other hand, very large grains and no pores were revealed in the undoped sample, which was the only transparent one. The radioluminescence measurements revealed superior overall scintillation efficiency of the samples sintered at the temperature 1700 °C, and their defect emission in the UV region was ascribed to oxygen-vacancy-related defects such as F + centers. The photoluminescence decay of the defect emission was characterized by an extremely fast decay time of a few nanoseconds. Influence of sintering procedure and subsequent annealing on the luminescence and scintillation properties is discussed. [ABSTRACT FROM AUTHOR]

The introduction of a small quantity of tungsten oxide (in the range 0.2–0.5 wt%) into the melt improves the growth of ZnMoO 4 crystals. No significant difference in the kinetics of scintillation decay, scintillation efficiency, emission spectra, optical transmittance was observed for three ZnMoO 4 crystal samples grown from the melt of stoichiometric composition, with excess of molybdenum and doped with tungsten. Using CaWO 4 as reference, the absolute light yield of ZnMoO 4 is found to be equal to 3550 ± 550 ph/MeV at 77 K. For two ZnMoO 4 samples 20 mm in diameter and 40 mm in length (grown from the melt of stoichiometric composition and doped with tungsten) it is confirmed that scintillation and bolometric response are similar at milli-Kelvin temperature. [ABSTRACT FROM AUTHOR]

Mg2+-codoped Y 0.6 Gd 2.4 Al 2 Ga 3 O 12 :Ce (YGAGG:Ce,Mg) single crystal was grown by the Czochralski method and its luminescence and scintillation properties were investigated. Temperature dependence of radioluminescence (RL) yield and photoluminescence (PL) decay time was measured, and activation energy of thermal ionization process was determined from temperature-dependent PL decay time measurement. YGAGG:Ce,Mg exhibited high X-ray excited RL yield almost 5 times higher than BGO reference scintillator. Its light yield of 41,500 ph/MeV and scintillation decay times of 12 ns (2%) + 52 ns (65%) + 207 ns (33%) were measured under excitation with 662 keV γ rays from 137Cs source. Afterglow and thermally stimulated luminescence characteristics are also investigated. • Luminescence and scintillation properties of Y 0.6 Gd 2.4 Al 2 Ga 3 O 12 :Ce,Mg crystal are investigated. • Temperature dependence of photo-and radioluminescence are presented. • Y 0.6 Gd 2.4 Al 2 Ga 3 O 12 :Ce,Mg shows high light yield of 41,500 photons/MeV. • Luminescence quenching above RT can be caused by thermal ionization. • Afterglow and thermoluminescence characteristics are investigated. [ABSTRACT FROM AUTHOR]

In scintillation crystals, at X-ray or gamma quanta registration, a noticeable time delay of the pulse is observed. This is due to the thermal delocalization of charge carriers from traps. The study of phosphorescence and relaxation of the conduction current can give information on these processes. However, their investigation requires knowing theoretical dependences of phosphorescence intensity attenuation and conduction current relaxation. A multicenter model of a crystal is proposed in which at least three types of traps (shallow, phosphorescent and deep) take part in the delocalization of charge carriers at the excitation temperature. For such a model, theoretical dependences for the phosphorescence intensity and the conduction current relaxation are obtained. These dependences take into account the processes of re-trapping of free charge carriers on more shallow traps. They show that the level of filling of different traps depends not only on the total radiation dose, but also on the intensity of excitation. An explanation of an experimental fact of intersection of phosphorescence and conduction current relaxation curves at the same irradiation dose, but at different excitation intensities, contradicting classical kinetic theory of luminescence, is obtained. All experimental dependences of phosphorescence intensity and conduction current relaxation for ZnSe crystals at different temperatures are well described by the obtained theoretical dependences. It is also established that the time of emptying of each type of traps is determined not only by the probability of thermal delocalization, but also by the ratio of the concentration of these traps to the total concentration of deeper traps. • The long-term phosphorescence and conduction current relaxation of specially undoped ZnSe crystals at different temperatures was studied. • Theoretical dependences for the phosphorescence intensity and the magnitude of the conduction current are obtained in analytical form. • An experimental fact that curves of phosphorescence and conduction current relaxation at the same irradiation dose intersect was explained. • It was confirmed that the traps' emptying time is determined also by the ratio of the trap concentration to the total concentration of deeper traps. [ABSTRACT FROM AUTHOR]