Search

Lutetium oxyorthosilicate Lu2SiO5 (LSO) and pyrosilicate Lu2Si2O7 (LPS) activated by Ce3+ or Pr3+ are known to be effective and fast scintillation materials for the detection of X-rays and γ-rays. Their performances can be further improved by co-doping with aliovalent ions. Herein, we investigate the Ce3+(Pr3+) → Ce4+(Pr4+) conversion and the formation of lattice defects stimulated by co-doping with Ca2+ and Al3+ in LSO and LPS powders prepared by the solid-state reaction process. The materials were studied by electron paramagnetic resonance (EPR), radioluminescence spectroscopy, and thermally stimulated luminescence (TSL), and scintillation decays were measured. EPR measurements of both LSO:Ce and LPS:Ce showed effective Ce3+ → Ce4+ conversions stimulated by Ca2+ co-doping, while the effect of Al3+ co-doping was less effective. In Pr-doped LSO and LPS, a similar Pr3+ → Pr4+ conversion was not detected by EPR, suggesting that the charge compensation of Al3+ and Ca2+ ions is realized via other impurities and/or lattice defects. X-ray irradiation of LPS creates hole centers attributed to a hole trapped in an oxygen ion in the neighborhood of Al3+ and Ca2+. These hole centers contribute to an intense TSL glow peak at 450–470 K. In contrast to LPS, only weak TSL peaks are detected in LSO and no hole centers are visible via EPR. The scintillation decay curves of both LSO and LPS show a bi-exponential decay with fast and slow component decay times of 10–13 ns and 30–36 ns, respectively. The decay time of the fast component shows a small (6–8%) decrease due to co-doping. [ABSTRACT FROM AUTHOR]

Erbium-doped Y3Al5O12 (YAG) single crystals grown using the micro-pulling-down technique were investigated. Three Er concentrations were chosen: 0.1, 0.3 and 1 at%. Er3+ electron paramagnetic resonance (EPR) spectra were measured in the ground and first excited states. The corresponding g tensors and 167Er hyperfine interaction were changing upon Er content indicating moderation of the Er-O bond length and/or Er local surrounding. Photoluminescence (PL) and radioluminescence (RL) spectra were complex, consisting of strongly overlapped typical Er3+ transitions. In addition, there were other broad PL band (3.1 eV) and RL band (3.95 eV) attributed to the F+ center and yttrium substituting for aluminum (YAl), respectively. The X-ray excited decay kinetics exhibited a decrease of the decay time of the YAl from hundreds of nanoseconds to nanoseconds upon Er doping level. This is discussed and explained considering EPR data. [ABSTRACT FROM AUTHOR]

PbWO4 single crystals with praseodymium doping in a wide concentration range (0.1–5 at % in the melt) were grown by Czochralski method. Absorption, luminescence, and scintillation characteristics were measured at room temperature. Similar to other trivalent dopants, heavy Pr3+ doping on one hand suppresses intrinsic host scintillation. On the other hand though, in the scintillation decay it introduces components with characteristic decay times within 500–2000 ns based on Pr3+ 4f-4f emission lines in the green-red part of the spectra. We discuss the suitability of such material for dual scintillation/Cherenkov light detector. [ABSTRACT FROM AUTHOR]

Abstract LaAlO 3 perovskite single crystals doped with Ce, Eu or Tb have been grown by micro-pulling-down method. X-ray diffraction analysis confirmed low-temperature rhombohedric phase. Energy-dispersive Laue mapping revealed sub-grains in the grown crystals. For the Ce-doped crystals, very low radioluminescence efficiency was found and the observed emission was ascribed to defects. Photoluminescence spectra were significantly different from the radioluminescence ones. They were significantly quenched at room temperature and the related luminescence showed also unusually high Stokes shift. High radioluminescence efficiency was found for the Tb-doped samples and especially for the Eu-doped ones, which would point to the fact that in LaAlO 3 the scintillation process is more favorable for the luminescence ions which tend to capture an electron first. Highlights • Morphology of the grown rare-earth-doped LaAlO3 crystals was studied. • Role of the growth atmosphere explained by its influence on Ce valence state. • Origin of radioluminescence explained by defect emission in Ce-doped crystals. • High radioluminescence efficiency found for Eu-doped crystals. [ABSTRACT FROM AUTHOR]

Nondoped Cs2HfCl6 (CHC) and alkaline earth metal-doped CHC (AE:CHC) crystals were grown by the vertical Bridgman–Stockbarger method. The spectra of the AE:CHC under X-ray excitation were similar to those for the AE-free crystal; thus, AE doping did not change emission wavelength of CHC. We determined the light outputs and energy resolutions of nondoped CHC and AE:CHC by measuring pulse-height spectra under 662-keV gamma-ray excitation of a 137Cs source. Both light output and energy resolution were deteriorated with AE doping. For example, nondoped CHC had a light output of ~44 000 photons/MeV and energy resolution of ~5.2%; on the other hand, Sr 0.5 at.%-doped CHC had a light output of only ~28 000 photons/MeV and energy resolution of ~10%. Scintillation decay also did not change. The nonproportional response values of light output versus gamma-ray energy did not improve in AE:CHC either. Therefore, doped AEs can be responsible for creation of defect trap levels which would hamper the carrier transport in CHC structure. [ABSTRACT FROM AUTHOR]

We have investigated Li 4 SiO 4 scintillation crystals for their possible application in neutron detection due to high Li content and low density of 2.35 g/cm 3 . The micro-pulling-down method employing the Ir crucible and afterheater was optimized for crystal growth of Li 4 SiO 4 taking into account the Li evaporation. To grow high-quality crack-free single crystals, the heating power was increased to establish milder temperature gradient, thicker meniscus, smaller crystal diameter and resulting smaller stress in the as-grown crystals. The undoped, Ti-, Cr-, and Al- doped crystals were prepared and studied. Radioluminescence measurements under X-ray excitation showed quite high overall scintillation efficiency of the Ti-doped sample reaching as high as 250% of that of Bi 4 Ge 3 O 12 reference scintillator. The emission spectrum was dominated by one broad band peaking at 350 nm related to Ti 4+ impurity. Reasonable light yield of 10000 photons/neutron was found. However, its long decay time of 54 μs might be a limitation especially for high counting rate applications. The overall scintillation efficiency of the Cr 3+ sample was much lower and the spectrum shows one broad peak at 463 nm which does not correspond to Cr 3+ luminescence. The radioluminescence spectrum of the Al-doped sample resembled to that of the Ti-doped one, just its magnitude is considerably lower, which was explained by Ti contamination. Peculiarities and optimization of crystal growth and a preliminary sketch of luminescence mechanisms and dopant incorporation are discussed. [ABSTRACT FROM AUTHOR]

The 3 inch size Mg co-doped Ce:Gd3 Al2Ga3 O12 single crystals were prepared by the Czochralski (Cz) 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. The timing resolution measurement for a pair of 3 \times 3 \times 3\;\mm^3 size GAGG:Ce.Mg scintillator crystals was performed using Si-PMs. [ABSTRACT FROM AUTHOR]

Ce and Pr doped YCOB single crystals were grown by the micro-pulling down (\mu - \textPD) method and characterized as for the structure and chemical composition. The expected 420 nm emission of \textCe^3 + 4f-5d has been observed in Ce:YCOB. Pr:YCOB shows broad emission spectrum peaking around 350 nm and this emission can be well ascribed to the 5d–4f emission of \textPr^3 + . Luminescence and scintillation characteristics of these crystals were also investigated. [ABSTRACT FROM AUTHOR]

This paper reports on the preparation and growth of Eu-doped strontium iodide (SrI2) single crystals by modified micro-pulling-down method. Influence of the Eu^2 + and Eu^3 + (introduced in form of EuI2 and EuCl3) 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 SrI2 crystals irradiated under \gamma -ray source were evaluated as well. [ABSTRACT FROM AUTHOR]

The role and effect of stable Ce^4+ centers in Ce-doped LuAG single crystal scintillator is further studied by means of measurements of several optical, luminescence and scintillation characteristics. Two LuAG:Ce single crystal samples are compared: in one of them the dominating Ce^4 + center is stabilized by high concentration Mg^2+ codoping while the other one shows only the presence of stable Ce^3 + center. Tailored (Eu, Mg)–doped LuAG single crystal is also prepared to test the presence and thermal stability of hole traps in the host which affect the timing characteristics of Ce^4+ scintillation cycle, namely its restoration back to 4+ charge state in last step of the cycle. EPR experiment was also employed at Mg- and (Eu, Mg) doped LuAG samples and the signature of the O^ - hole center stabilized by Mg^2 + ion was clearly obtained. [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 Nd-doped and Er-doped LuF 3 single crystals were grown by the micro-pulling-down method to study their scintillation properties in the vacuum-ultraviolet (VUV) region. The doubly Nd–Er codoped single crystal was grown to study possibility of scintillation performance improvement by energy transfer from Er 3+ to Nd 3+ ions. The LiF flux was to avoid phase transition below melting temperature. The 1%Nd-doped sample showed the highest overall scintillation efficiency under X-ray excitation which was 7 times as high as that of the LaF 3 :Nd 8% standard. The leading Nd 3+ 5d–4f emission was situated at 176 nm, while the Er 3+ 5d–4f emission for Er-doped samples was observed at 163 nm, which better matches the sensitivity of some VUV-sensitive photodetectors. The optimum Er concentration was determined to be around 1–3 mol%. No Er 3+ 5d–4f emission was observed for the doubly Er,Nd-codoped sample due to energy transfer from the Er 3+ to Nd 3+ ions. Slight improvement of the light yield was observed in the doubly-doped sample with respect to the Nd-only doped one. [ABSTRACT FROM AUTHOR]

Sc doped Y y Lu 3 − y Al 5 O 12 ( y = 0–1) single crystals were grown by the μ-PD method. EPMA techniques were employed to check their chemical composition. Luminescence characteristics were measured. Anti-site defect-related host emission was observed within 280–360 nm wavelength. The light yield was increasing with Y concentration and with an optimum for Sc2% concentration. The Sc 2% doped Y 3 Al 5 O 12 showed the highest light yield value around 30,000 photon/MeV and 670 ns scintillation decay time using a photomultiplier detector (R7600U). Substitution effects of the Lu site and their influence on luminescence and scintillation properties were studied. [ABSTRACT FROM AUTHOR]

Nd and Tm-doped Lu-admixed \BaY2 \F 8 crystals were grown by micro-pulling-down method. Lu was added to modify the host matrix to suppress the unwanted energy transfer from exciton levels to the \Tm^3+ 4f-levels. It was found that low Tm and Nd codoping does not bring much improvement of the scintillation performance and that 1%Nd-doped \BaY 0.8\Lu1.2 \F 8 single crystal reached nearly the same scintillation efficiency as the \LaF 3\:Nd8\% one, which is known as a suitable candidate for a VUV scintillator. It is clear there is a considerable room for an optimization of this material by changing the Lu/Y ratio and increasing the content of Nd. On the other hand, very high Tm concentrations (around 20%) suppress the excitonic emission (and also the 4f-4f emission) while increasing the 5d-4f one significantly. [ABSTRACT FROM PUBLISHER]

\ Pr\!\!\!\!:\!\!\!\!\! (\ Gd,\ Y)3({\ {Ga}},{\ {Al}})5 {\ {O}}12 single crystals were grown by the \mu-PD method with RF heating system. \ Pr^3+ 5d-4f emission within 300-350 nm, \ Pr^3+ 4f-4f emission within 480-650 nm and \ Gd^3+ 4f-4f emission at 310 nm are observed in \ Pr\!\!\!\!:\!\!\!\! (\ Gd,\ Y)3({\ {Ga}},{\ {Al}})5 {\ {O}}12 crystals. In order to determine light yield, the energy spectra were measured under 662 keV \gamma-ray excitation (^137\ Cs source), detected by a PMT H6521 (Hamamatsu). The light output of \ Pr1\%\!:\!\ Gd1 {\ {Y}}2{\ {Ga}}3{\ {Al}}2 {\ {O}}12 sample was of about one fifth of that of the Cz grown Pr:LuAG standard sample, i.e., around 4,000 photon/MeV. Two component scintillation decay shows the decay times (intensity) of 5.7 ns(5%), 38.7 ns (31%) and 187 ns (63%) using the PMT and digital oscilloscope TDS5032B detection. [ABSTRACT FROM PUBLISHER]

(Lu0.1Y0.9)AlO3\!\!:\!\!Nd0.1\% crystal was grown by the \mu -PD method and pure YAP single crystal was prepared as a reference sample. Then, two annealing procedures were performed for each sample at 1350^\circC and 1500^\circC for 20 hours in oxygen atmosphere to improve the crystallinity and scintillation properties. The XRD results for all the samples were consistent with JCPDS data (#33-0041) and possessed a space group of orthorhombic Pbnm while no impurity peaks were observed. The FWHM values of X-ray rocking curve measurements of the as-grown crystals and the crystals annealed at 1500^\circC were 70 and 200 arcsec, respectively. It can be due to the onset of decomposition. In the transmittance measurements, intense absorption peaks were observed approximately at 240 and 290 nm and they were consistent with the bands for color centers: the two-electron F center and one-electron F^+ center, respectively. These absorptions were enhanced by Lu substitution. The radio-luminescence spectra show several emission peaks due to Nd^3+ 4f-4f transitions and the most intense of which were assigned to ^2 F(2)5/2-^{4} F5/2, ^2 F(2)5/2-^{4}G7/2 and ^2 F(2)5/2 -^{4}G9/2 transitions at 395, 540 and 550 nm, respectively. The light yield after annealing annealing was as high as 5025 \pm 500~(Nphe/\rm MeV) when using Si-APD (S8664). The scintillation decay time constants were evaluated to be 3.44–3.80 \mus for each sample. Afterglow upon X-ray excitation of the as-grown and annealed samples coupled with PIN Si-photodiode was found to be approximately 1200 and 1000 ppm after 100 ms. [ABSTRACT FROM PUBLISHER]

Ce1%, 2% and 3% doped Gd3(Ga,Al)5 O12 (GAGG) single crystals were grown by the Cz method. Luminescence and scintillation properties were measured. Light yield change along the growth direction and effects of Ce concentration on scintillation properties in Ce:GAGG were studied. Ce^3+ 5d-4f emission within 520–530 nm was observed in the Ce:GAGG crystals. The Ce1%:GAGG sample with 3\times 3\times 1~mm size showed the highest light yield of 46000 photon/MeV. The energy resolution was 7.8%@662 keV. With increasing solidification fraction, the LY were decreased. It is proposed that the increase of Ga concentration along the growth direction is the main cause of the decrease of LY. The scintillation decay times were accelerated with increasing Ce concentration in the Ce:GAGG crystals. The scintillation decay times were 92.0 ns, 79.1 ns and 68.3 ns in the Ce1, 2 and 3% GAGG, respectively. [ABSTRACT FROM PUBLISHER]

Pr\!\!\!\!\!:\!\!\!\!(Lu,Y)3({\ {Ga}},{\ {Al}})5O12 single crystals were grown by the micro-pulling down (\mu-PD) method. Luminescence and scintillation properties were measured. The substitution phenomenon in the Lu^3+ sites with Y^3+ and \ Al^3+ sites with \ Ga^3+ in garnet structure has been studied. Pr^3+ 5d-4f emission within 300–400 nm accompanied by weak Pr^3+ 4f-4f emission in 480–650 nm were observed in Ga 0–60 at.% substituted samples. Only Pr^3+ 4f-4f emission was observed in Ga 80 at.% substituted sample. The light yield of Pr1\%\!\!:\!\!Lu2Y1{\ {Ga}}2{\ {Al}}2O12 sample was almost the same as that of Cz grown Pr:LuAG standard. Two-component scintillation decay of 17.9 ns (93%) and 68.0 ns (7%) were obtained using the PMT and digital oscilloscope TDS5032B. Slower decay components were reduced by Ga and Y substitution in LuAG structure. [ABSTRACT FROM PUBLISHER]

Ce:(Lu,Y)3(Ga,Al)5 O12 single crystals were grown by the \mu-PD method with RF heating system. In these crystals, Ce^3+ 4f-5d emission is observed within 500-530 nm wavelength. Emission peak shifts to shorter wavelength and the decay accelerates with increasing Ga concentration. In the case of Ce:Lu2 Y1(Ga,Al)5 O12 series,the Ce0.2% Lu2 Y1Ga3Al2 O12 crystal showed the highest emission intensity. In order to determine light yield, the energy spectra were measured under 662 keV ã-ray excitation (^137 Cs source) and detection by an APD S8664-55(Hamamatsu). The light yield was calibrated from Fe^55 direct irradiation peak to APD. The light yield of Ce0.2%: Lu2 Y1 Ga3 Al2 O12 sample was of about 30,000 photon/MeV. Dominant scintillation decay time was of about 50 ns. [ABSTRACT FROM PUBLISHER]

Doubly doped LaF3:Er, Nd scintillation crystals were grown by modified micropulling-down method. The Er codoping was chosen to enhance the energy transfer from the host lattice to the Nd3+ luminescence center via the 5d-levels of Er3+, which can be enabled by the overlap of Er3+ 5d-4f emission spectrum with the Nd3+ 4f-5d absorption. However, no relevant energy transfer was found by photo- and radioluminescence spectra measurements. The reasons of no significant positive effect of Er codoping are discussed. [ABSTRACT FROM AUTHOR]

A numerous set of Pr-doped YAP single crystals was prepared using Czochralski and micro-pulling down methods. Crystals codoped by bi-, tri- and tetravalent ions were prepared by the latter method as well. The scintillation performance of all the prepared materials was evaluated using radioluminescence, photoelectron yield and scintillation decay measurements at room temperature. The influence of shallow traps was studied by means of thermoluminescence in the 10-350 K temperature range. Though the intrinsic scintillation efficiency of Pr-doped YAP is higher than that of YAP:Ce, enhanced delayed radiative recombination processes are found to be responsible for lower-than-expected photoelectron yield of the former system. The possibilities of further optimization of Pr-doped YAP scintillator are discussed. [ABSTRACT FROM AUTHOR]

Tm3+ doped BaF2 single crystal scintillator has been investigated. Undoped, 0.1, 0.5, and 1% Tm -doped BaF2 are compared in terms of their decay time, light yield, non-proportionality and energy resolution. The fast component of Tm doped BaF2 is characterized by a 5 ~ 6 ns decay time and it can be related to the Tm3+ 5d - 4f VUV emission from 4fn-1 5d low-spin state (parity allowed and spin allowed transition). The light yield of Tm doped BaF2 is lower with respect to the undoped BaF2 and systematically decreases with increasing Tm concentration. However, 0.1%Tm:BaF2 showed a better non-proportionality and energy resolution than the undoped sample. [ABSTRACT FROM AUTHOR]

Abstract: The Pb-doped LiCaAlF6 single crystals were grown using the micro-pulling-down method. The temperature dependences of photoluminescence characteristics were studied to reveal the kinetic processes in the excited state of Pb2+ luminescence center. A simple three-level phenomenological model applied to the decay time temperature dependences shows that energy separation between the metastable 3P0 and the radiative 3P1 states of Pb2+ center is relatively high, about 180meV (∼1470cm−1). Induced absorption spectrum after UV illumination at 500K points to slight ionization of the Pb2+ excited state and creation of the color F-center with an absorption peak located around 260nm. [Copyright &y& Elsevier]

(CexCa1-x)F2+x single crystal with x = 0.0001 - 0.03 were grown by the μ-PD method. Ce3+ doping in CaF2 lattice gives rise to characteristic absorption and emission bands, which are governed by the characteristics of the isolated Ce3+ -Fi- C4v pair centers and small clusters composed from these pairs. With increasing Ce concentration there is a strong increase of the absorption bands related to the cluster centres, but the radioluminescence spectra are always governed by the emission of the isolated Ce3+ -F1- C4v pairs without noticeable changes in the emission band shape. Highest radioluminescence intensity is achieved for Ce0.1{%} concentration and above 1{%} of Ce the onset of concentration quenching is observed. Scintillation response is governed by the energy transfer from the CaF2 host lattice and even for the Ce3{%} sample the dominant scintillation decay time is about 50{%} longer with respect to the photoluminescence decay time of Ce3+ -Fi- C4v pair centres. Energy transfer processes and the role of different Ce3+-based centers are discussed. [ABSTRACT FROM AUTHOR]

Effect of Ga substitution in the (Lu,Pr)3Al5O12(Pr : LuAG) scintillator was examined at the crystals grown by the micropulling down (μ-PD) method. Host luminescence due to an exciton localized around the Lu-Al antisite defect was suppressed by Ga admixture. Concentration depenendence was investigated and suppression was observed even at the lowest Ga concentration of 5 mol %. Faster decay time as well as less intense slower components were obtained upon increasing the amount of Ga. In the thermostimulated luminescence measurement, the glow curve peaks are gradually shifted to lower temperatures with the gallium admixture, and noticeable intensity decrease was observed only for the (Lu, Pr)3 (Ga0.2Al0.8)5O12. The undesired quenching effect of Ga on the Pr3+ luminescence seems to be reasonably low up to (Lu,Pr)3(Ga0.2Al0.8)5O12 sample. It is estimated to introduce nonradiative losses of less than 10% with respect to Ga-free Pr:LuAG. Bulk crystals were also grown by the Czochralski (Cz) method and these effects were confirmed. [ABSTRACT FROM AUTHOR]

Ho3+ codoping of Lu 3 Al 5 O 12 activated with Pr3+ (LuAG:Pr) induces an acceleration of Pr3+ decay kinetics. This is caused by nonradiative energy transfer from Pr3+ to Ho3+ driven by a multipolar electromagnetic interaction. Luminescence and scintillation properties of LuAG:Pr codoped with Ho3+ ions were studied over a wide concentration range. A significant acceleration of response was achieved. The Förster-Dexter model was used to analyze the decay kinetics of the Pr3+ luminescence center and the interaction between Pr3+ and Ho3+ ions. Several concentration characteristics useful for tailoring the timing and light output properties are presented. • The effect of Ho3+ codoping of LuAG:Pr is studied over a wide range of Ho3+ concentrations. • The inherent decay time of Pr3+ in LuAG host is shortened by Ho3+ codoping. • The scintillation response of LuAG:Pr is accelerated by Ho3+ codoping. • Useful concentration dependences of timing and light output properties are obtained. [ABSTRACT FROM AUTHOR]

Abstract: Ce:Gd2Lu1(Ga,Al)5O12 single crystals were grown by the micro-pulling down (μ-PD) method. All grown crystals were yellow and transparent with 3.0mm in diameter, 15–30mm in length. Neither visible inclusions nor cracks were observed. Luminescence and scintillation properties were measured. The substitution at the Al3+ sites by Ga3+ and at the Lu3+ sites by Gd3+ in garnet structure has been studied. In these crystals, Ce3+ 4f–5d emission is observed with 500–530nm wavelength. The decay accelerates with increasing Ga and Ce concentration. Ce1%: Gd2Lu1Ga3Al2O12 shows the highest emission intensity. The light yield of Ce:Gd2Lu1Ga3Al2O12 sample with 3mmφ×1mm size was around 22,000photon/MeV using calibration from 55Fe direct irradiation peak to APD. Scintillation decay time was around 50ns. The theoretical density is 6.88g/cm3. [Copyright &y& Elsevier]

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]

Cr-doped (Gd x Y 1− x ) 3 Ga 5 O 12 crystals ( x =0.00, 0.25, 0.50, 0.75 and 1.00) were grown by the micro-pulling-down method and examined for their possible application as red and infrared scintillating detectors in medical field. Although Cr:(Gd 0.75 Y 0.25 ) 3 Ga 5 O 12 and Cr:Gd 3 Ga 5 O 12 had similar X-ray diffraction patterns, other samples showed some change in lattice constant. All the crystals had broad emission bands in the red and infrared region when excited by either 450 nm photons or X rays. These bands were associated with 4 T 2 →A 2 transitions. Moreover, redshift of the emission-peak wavelengths ( 4 T 2 → 4 A 2 ) and absorption peaks ( 4 A 2 → 4 T 1 and 4 T 2 ) was observed with increase of Gd content ( x ) in Cr-doped (Gd x Y 1 −x ) 3 Ga 5 O 12 due to the change of the crystal fields. The crystals had scintillation emissions in the wavelength region suitable for the real time dose monitoring in radiation therapy. [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]

1300 or 1400 °C pre–sintered Al/Ce/Mg:SrHfO 3 and Al/Ce:SrHfO 3 ceramics were prepared by the Spark Plasma Sintering (SPS) in order to search for a new scintillation material with a high–effective atomic number(Z eff ) and good light output. The SrHfO 3 has a high Z eff of 60, and high gamma–ray detection efficiency is expected. Meanwhile it has a high melting point of over 2500 °C, and single crystal is hard to be grown. On the other hand, high melting materials can be prepared as ceramics, and the SPS method is a simple process to fabricate the ceramics within a few hours. Thus, we prepared the samples using the SPS method, and their optical and scintillation properties were investigated. We found that Al/Ce/Mg:SrHfO 3 and Al/Ce:SrHfO 3 ceramics had an emission wavelength at around 400 nm originating from 5d–4f transition of Ce 3+ . Moreover, Al/Ce/Mg:SrHfO 3 pre-sintered at a temperature of 1400 °C had a light output of approximately 5,000 ph/MeV. In this paper, the light output of Mg-co-doped samples was improved compared with the Mg-free ones. The light output also depends on the pre-sintering temperature. [ABSTRACT FROM AUTHOR]

The Mg, Ca, Sr and Ba 200 ppm co-doped Ce:Lu 3 Al 5 O 12 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 the co-doping. The scintillation decays were accelerated by both Mg and Ca co-dopants. The Mg co-doped samples showed the fastest decay and the highest light yield among the co-doped samples. [ABSTRACT FROM AUTHOR]

The Mg and Ca co-doped Ce:Gd 3 Al 2 Ga 3 O 12 single crystals were prepared by micro pulling down method with a wide concentration range 0–1000 ppm of the codopants. 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 and Ca co-doping. The scintillation decays were accelerated by both Mg and Ca codopants. Comparing to Ca co-doping, the Mg co-doped samples showed much faster decay and comparatively smaller light output decrease with increasing Mg dopant concentration. [ABSTRACT FROM AUTHOR]

(Eu 0.01 , Gd 0.90 , La 0.09 ) 2 Si 2 O 7 (Eu:La–GPS) and (Tb 0.01 , Gd 0.9 0 , La 0.09 ) 2 Si 2 O 7 (Tb:La–GPS) crystals were grown by the floating zone method, and their optical and scintillation properties were investigated. Gd 3+ -to-Tb 3+ or –Eu 3+ energy transfer processes were found, and photo-luminescence and radio-luminescence emission spectra showed 5 D 0 – 7 F i ( i = 1–4) Eu 3+ transitions in Eu:La–GPS, and 5 D 3 – 7 F i ( i = 3–6) and 5 D 4 – 7 F i ( i = 3–6) transitions in Tb:La–GPS. Using these scintillators, alpha-ray imaging was possible with a CMOS camera. These materials can be used for X-ray detection as well. [ABSTRACT FROM AUTHOR]

Nd 1 mol% doped (Lu, Gd) 3 (Ga, Al) 5 O 12 (LGGAG) single crystals were grown by the micro-pulling down (μ-PD) method. Luminescence and scintillation properties such as absorption, excitation and emission spectra, light yield and decay time were evaluated. Nd1%:Lu 3 Al 5 O 12 showed the highest light output of around 8200 photons/MeV among the grown crystals. Scintillation decay time of Nd:Y 3 Al 5 O 12 was 1.32 μs (36%) 2.02 μs (64%). Nd:Lu 3 Ga 3 Al 2 O 12 was relatively high dense scintillator of 7.38 g/cm 3 with good light yield of 6800 photons/MeV and scintillation decay time of 0.20 μs (5%) 2.60 μs (95%). [ABSTRACT FROM AUTHOR]

Ce doped SrHfO 3 /SrAl 12 O 19 eutectics were grown by the micro pulling down (μ-PD) method and their directionally solidified eutectic system has been investigated. Investigations of obtained eutectic structure, luminescence and scintillation performances were also performed. Eutectics were grown at the speed of 0.60–0.90 mm/min. In the eutectics, Ce 3+ 4f–5d emission was observed at 410 nm. The eutectics showed light yield of around 300 photon/5.5 meV alpha-ray by 241 Am excitation. Scintillation decay time was 26.4 ns (45%) with slower decay component of 263 ns (55%). [ABSTRACT FROM AUTHOR]

Cr-doped (Gd X Y 1 − X ) 3 Al 5 O 12 ( X = 0, 0.25, 0.50) crystals prepared by the micro-pulling down method were investigated to develop a infra-red scintillator for implantable patient dosimeter in radiation therapy. In order to evaluate their optical and scintillation performance, the following properties were measured: (i) transmittance between ultra-violet and near-infra red region, (ii) photoluminescence spectra under Xe-lamp excitation, and (iii) X-ray excited radio-luminescence spectra. Cr:Y 3 Al 5 O 12 and Cr:(Gd 0.25 Y 0.75 ) 3 Al 5 O 12 crystals showed increased transmittance of 80%, while Cr:(Gd 0.50 Y 0.50 ) 3 Al 5 O 12 had a lower transmittance of 40% due to its polycrystalline structure. In addition, all the Cr:(Gd X Y 1− X ) 3 Al 5 O 12 crystals showed sharp scintillation luminescence peaks ascribed to Cr 3+ d–d transitions. Therefore, these results suggested that Cr:Y 3 Al 5 O 12 and Cr:(Gd 0.25 Y 0.75 ) 3 Al 5 O 12 crystals can be candidate materials for the dosimeter use. [ABSTRACT FROM AUTHOR]

Highlights: [•] Scintillation properties of GAGG:Ce & LuAG:Ce are compared. [•] LY dependence on sample height and shaping time are studied. [•] Intrinsic LY of 56,500ph/MeV and loss coefficient of 0.175cm−1 are obtained for GAGG:Ce. [•] Intrinsic LY of 29,000ph/MeV and loss coefficient of 0.380cm−1 are obtained for LuAG:Ce. [•] PL decays at room and low temperatures are studied for GAGG:Ce. [Copyright &y& Elsevier]

Abstract: Single crystals of pure cesium iodide (CsI) have been grown from the melt using micro-pulling-down (μ-PD) method. Two kinds of crucible (graphite one and quartz one) were used for the growth and the grown crystals were investigated by X-ray diffraction (XRD) and X-ray rocking curve (XRC) analysis. The XRD analysis did not confirm any impurity phases and a sub-grain structure was observed for each sample in the rocking curve measurement. Under X-ray irradiation, strong STE emission peaks around 300nm were observed together with some luminescence related to unintentionally present impurities. The STE emission peaks are characterized by fast decay times of several ns and about 20ns which are interpreted as the on-center-type STE (VK +e) and off-center type STE (H+F) recombinations, respectively. The light yield of the STE-related emissions has been estimated to be 3000ph/MeV. Other emission peaks were observed at 410nm and 515nm. The former one can be related to Br-contamination and it is characterized by a relatively slow decay time of 6μs. Concerning the latter one at 515nm, similar luminescence was observed for the water-doped CsI grown by Bridgman method. [Copyright &y& Elsevier]

Abstract: 0.1%, 0.5%, 1% and 3% Ce doped scintillation crystals based on NaF–CaF2–LuF3 solid solutions were grown from the melt using Micro-Pulling-Down (μ-PD) method. The grown crystals were transparent and their transmittance was approximately 80% for the wavelengths longer than 320nm. Concerning the scintillation properties, radio-luminescence peaks of the crystals were detected at approximately 330nm. The light yield of the crystals was also measured using γ-ray (137Cs and 22Na) as the excitation source. [Copyright &y& Elsevier]

Abstract: Micro-pulling down (μ-PD) method allows to prepare single crystals quickly and relatively inexpensively. Since it is a melt growth and taking into account segregation phenomena, the μ-PD method allows also to obtain single crystals characterized by dopant concentration gradients. Especially, taking the advantage of the grown crystal high aspect ratio, it allows to prepare crystalline samples with variable and wide range concentrations of dopants. These samples can help in understanding the correlation between dopant concentration and luminescence properties. [Copyright &y& Elsevier]

Abstract: Nd3+ 1%, 5% and 10% doped BaF2 single crystals were grown by the micro-pulling down method. Photoluminescence properties, including excitation and emission spectra and luminescence decay were measured under synchrotron radiation excitation at the Superlumi station in HASYLAB at DESY (Hamburg, Germany). The Nd3+ related 5d-4f emission lines peaking around 180 nm, 230 nm, and 260 nm, identified as the 5d–4Ij, 5d–4Fj, and 5d–2Gj transitions, were observed under 140–168 nm excitation. In photoluminescence decay under the 160 nm excitation, the dominant component decay time is about 12, 2.5 and 1.2 ns for Nd3+ 1%, 5% and 10% concentration, respectively. The decay time shortening is explained by the concentration quenching effect. Transmittance of Nd1% sample is about 80% for wavelengths above 185 nm. Finally, gamma-ray responses, non-proportionality and energy resolution of Nd1% sample were compared with the undoped BaF2 scintillator. The light yield of the Nd1%:BaF2 is about 93% of that of undoped BaF2. ©2009 Elsevier Ltd. All rights reserved. [Copyright &y& Elsevier]

Abstract: Pr-doped KY3F10 (Pr:KYF) single crystals were grown by the micro-pulling-down (μ-PD) method. The crystals were transparent with a slightly greenish color, 2.5–3.0mm in diameter and 35–45mm in length. Neither visible inclusions nor cracks were observed. Photoluminescence spectra and decay kinetics of Pr:KYF were measured. Emission due to Pr3+ 5d–4f transition, peaking around 260nm and of the decay time of 24ns was observed. The short decay time suggests such a Pr-doped material for a scintillator application. To our knowledge, this is the first report of the Pr3+ 5d–4f luminescence transition accomplished in a fluoride host. [Copyright &y& Elsevier]

Single crystal of the mixed-halogen compound Cs 2 HfCl 3 Br 3 was grown by the vertical Bridgman method, and we investigated its crystal structure and optical properties. Single-crystal X-ray diffraction and energy dispersive X-ray spectroscopy analyses indicated the chemical composition to be Cs 2 Hf(Cl 0.578(6) Br 0.422(6)) 6 (= Cs 2 HfCl 3.47(4) Br 2.53(4) , approximately Cs 2 Hf(Cl 0 58 Br 0.42) 6) where the number in the parentheses denotes the estimated standard deviation in the last digit. Cs 2 Hf(Cl 0.58 Br 0.42) 6 was found to have a cubic F m 3 ‾ m potassium hexachloroplatinate structure consisting of Cs+ cations and Hf(Cl 0. 58 Br 0.42) 6 2− anions. The emission peak of Cs 2 HfCl 3 Br 3 was red-shifted by Br substitution, and the photoluminescence decays of Cs 2 HfCl 3 Br 3 were accelerated when compared to those of Cs 2 HfCl 6. Cs 2 HfCl 3 Br 3 had an emission peak at 450 nm under X-ray irradiation, while under UV-excitation, two photoluminescence emission peaks at 420 and 525 nm were observed. The decay profile of the 420-nm emission band had a single-exponential component with a decay time of 1.95 ± 0.01 μs under the 280-nm-excitation. On the other hand, 525-nm-emisison had two decay components of 0.28 ± 0.03 μs (11%) and 6.54 ± 0.03 μs (89%) under 305-nm-photons excitation. • Crystal growth and luminescence properties of Cs2HfCl3Br3 were investigated. • The crystal structure was refined as a cubic F m 3 ‾ m potassium hexachloroplatinate structure via the single-crystal X-ray diffraction measurement. • Cs2HfCl3Br3 showed 450 nm emission under X-ray irradiation. • Cs2HfCl3Br3 had two photoluminescence bands at 420 and 525 nm. • Scintillation and photoluminescence decays were measured. [ABSTRACT FROM AUTHOR]