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Scintillators are used not only as single crystals in radiation detection systems but also as arrays, columns, and fibers. In this study, a novel optical-guiding crystal scintillator (OCS) was fabricated using an Eu:SrI 2 crystal as the core and borosilicate glass as the cladding. The OCS has an elongated shape and can be flexibly processed like an optical fiber. Furthermore, because inorganic scintillator crystals are used as the core, the OCS has high sensitivity to high-energy radiation, such as γ- and X-ray radiation, unlike plastic scintillators. In this study, by observing the cross section of the fabricated OCS, identifying the crystal structure, and investigating the radioluminescence spectrum under X-ray irradiation, OCS fabrication in accordance with the OCS design specifications was confirmed, and the SrI 2 crystal structure and Eu2+ 5d–4f luminescence were maintained. The γ-ray responses, such as light yield and decay time, were also investigated. [ABSTRACT FROM AUTHOR]

0.5, 1, 2, and 5% Er-doped La 3 Ga 5 SiO 14 (LGS) single crystals were synthesized by the Floating Zone method and the photoluminescence (PL) and scintillation properties were characterized. Emission peaks appeared at visible–near-infrared (NIR) regions. Their spectral features matched with those due to the 4f–4f transitions of Er3+. The PL quantum yields of 0.5, 1, 2, and 5% Er-doped samples were respectively 45.0, 73.3, 82.5, and 69.4%. The decay times due to the 2H 9/2 –4I 15/2 transitions of Er3+ were obtained when visible ranges were monitored under excitation of both visible lights and X-rays. All the prepared samples showed good linearity between the X-ray exposure dose rate and scintillation signals in NIR ranges. The best lower detection limit in prepared samples was 5 mGy/h recorded by the 2% Er-doped LGS. • Er-doped La 3 Ga 5 SiO 14 single crystals were synthesized by the Floating zone method. • Luminescence due to 4f–4f transitions of Er3+ was observed in both visible and near-infrared regions. • Quantum yields of 0.5, 1, 2, and 5% Er-doped samples were respectively 45.0, 73.7, 82.5, and 69.4%. • The best lower detection limit in prepared samples was 5 mGy/h obtained by 2% Er-doped sample. [ABSTRACT FROM AUTHOR]

• Raman spectral analysis confirmed the presence of Sn through the Ag(10) phonon mode. • Sn:β-Ga 2 O 3 crystal shows an enhancement in intensity of X-ray induced emission spectrum. • Sn:β-Ga 2 O 3 crystal shows enhancement in scintillation light yields. High-quality single crystals of both pure and Sn:β-Ga 2 O 3 single crystals were grown using the optical floating zone technique and a comprehensive study of its luminescence and scintillation properties was carried out. The pure and Sn:β-Ga 2 O 3 grown crystals were oriented along (1 0 0) by Laue diffraction pattern and its monoclinic structure was confirmed using a single crystal XRD. X-ray induced luminescence spectrum shows a maximum emission peak at 365 nm. The cut off wavelength was observed around 258 nm and the optical band gap was calculated to be 4.64 eV from UV–Vis-NIR transmission spectroscopy. The room temperature Raman spectra were recorded and the various vibration modes were investigated. Low temperature (10 to 300 K) and high temperature (325 to 675 K) TL measurements were carried out on X-ray irradiated crystals and its TL kinetic parameters such as activation energy (eV) and frequency factor (S) were calculated. Scintillation decay time profiles were measured for both pure and Sn-doped crystals under 137Cs γ-ray excitation. The calculated scintillation light output is 2300 Ph/5.5 Mev for Sn:β-Ga 2 O 3 crystal under α-particle excitation from 241Am radiation source. [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]

The high‐profile candidacy of low‐dimensional metal‐halide single crystals as promising light emitters originates from the intriguing emission properties (e.g., extremely broad luminescence spectra, large Stokes shift, high color rendition), which have enabled the recent great achievements on their application in lighting, artificial illumination, and scintillators. Among the family of low‐dimensional metal‐halide single crystals, zero‐dimensional (0D) materials have been featured in the lowest dimensionality, and as a consequence, strongest quantum confinement, softest lattice, and strongest electron–phonon coupling have been further translated into near‐unity photoluminescence (PL) efficiency with broadband emission. However, as far as it is known, 0D structures are significantly underexplored. Herein, an overview is provided on recent advances of 0D metal‐halide single crystals, with a focus on comprehensive understanding and insightful perspectives behind the photophysical mechanism. Additionally, the challenges and future opportunities currently faced by 0D bulk metal halides are discussed in order to provide a roadmap for the future development of novel materials with versatile optical properties suited for practical applications. [ABSTRACT FROM AUTHOR]

Large-size and -scale bismuth germanate (Bi 4 Ge 3 O 12 , BGO) crystals were grown in an oxidizing atmosphere using the modified Bridgman method. Although the growth condition has been optimized, we found a few reddish crystals, resulting in poor performance. In this work, the red-color-induced characteristic absorption bands corresponding to 506, 389, and 332 nm were studied by measuring the optical transmission and absorption spectra. A modified oxygen-annealing was applied to eliminate the reddish in BGO single crystal. Based on the comparison of the optical performance, the absorption band in the visible range of the reddish crystals disappeared after annealing. This phenomenon greatly improved the light output and energy resolution. The effects of annealing in reducing atmosphere were studied. The formation mechanism of crystal coloration was also discussed. [ABSTRACT FROM AUTHOR]

• CaNb 2 O 6 , as a new intrinsic scintillator was firstly reported. • The influences of the growth atmosphere on the optical and scintillation properties were investigated. • Crystals grown in an O 2 atmosphere displayed higher quantum efficiency, X-ray luminescence intensity, light yield, and lower afterglow. Single crystal CaNb 2 O 6 was grown by the optical floating-zone method and characterized for a new intrinsic scintillator. Under Ar and O 2 growth atmospheres, the as-grown crystal rods (Ф 4–5 mm) exhibit a greyish and a colorless appearance, respectively, which are related with the oxygen vacancy. They both show a broad emission band with the maximum at 480 nm under UV excitation, while the one grown in O 2 is brighter with a photoluminescence quantum efficiency of 44%. Consequently, a 25% higher scintillation light yield was obtained in the crystals grown in O 2 compared to those in Ar. The other scintillation properties including radioluminescence spectrum, pulsed X-ray decay and afterglow were also characterized and compared. [ABSTRACT FROM AUTHOR]

BaCl 2 :Eu transparent ceramics were synthesized by the spark plasma sintering method, and concentration dependence of Eu on optical and scintillation properties was investigated. BaCl 2 :Eu transparent ceramics showed photoluminescence (PL) and scintillation peaks at 400 nm due to 5d–4f transition of Eu2+. The PL and scintillation decay time constants of BaCl 2 :Eu transparent ceramics were ∼400 ns. The PL quantum yields (QY s) of 0.05, 0.1, 0.5, and 1% BaCl 2 :Eu transparent ceramics were 28.5, 25.6, 16.2, and 13.9%, respectively. The afterglow levels of BaCl 2 :Eu transparent ceramics were lower than CsI:Tl single crystal in practical use. The scintillation light yield of the 0.5% doped BaCl 2 :Eu transparent ceramic was 9800 photons/MeV when γ-rays by 137Cs were irradiated. • BaCl 2 :Eu transparent ceramics were synthesized using the SPS method. • We investigated the optical and scintillation properties. • The scintillation peak due to 5d–4f transition of Eu2+ was observed at 400 nm. • The 0.5% Eu-doped sample showed the highest LY (9800 ph/MeV) under 137Cs γ-ray irradiation. [ABSTRACT FROM AUTHOR]

The scintillation, luminescence and optical properties of the multicomponent Gd 3 Sc 2 Ga (2+x) Al (1-x) O 12 :Ce (x = 0, 0.25, 0.5, 0.75, 1), Gd 2.957 Sc 1.905 Ga (2.138+x) Al (1-x) O 12 :Ce (x = 0, 1) and the (200, 1000, 5000 ppm) Mg2+ co-doped Gd 3 Sc 2 Ga 2.75 Al 0.25 O 12 :Ce single crystals grown by the μ-PD method were characterized. Scintillation decay kinetics and light yield were correlated with the sum of the content of Ga and Sc in the host. While the Ga-admixed GSAG:Ce composition exhibited higher scintillation efficiency compared to pure GSAG:Ce, it also showed very high afterglow, due to an intense delayed electron-hole recombination at Ce3+ centres. This was supported by the calculated activation energy obtained from the temperature dependence of photoluminescence decay times. Codoping with Mg2+ significantly improved afterglow compared to pure GSAG:Ce, however, at the expense of light yield. • Ga-admixed GSAG:Ce single crystals were grown by μ-PD method. • Scintillation and luminescence properties were investigated. • Ga/Sc content strongly influences the band gap and scintillation efficiency. • High afterglow is explained by the delayed electron-hole recombination at Ce3+. • Co-doping by Mg2+ results in enhanced scintillation performance. [ABSTRACT FROM AUTHOR]

The studies of the influence of proton irradiation on the optical properties of the undoped Gd 3 Al x Ga 5-x O 12 (x = 0,1,2,3) single crystals were carried out. A set of induced absorption bands have been detected, which are most pronounced in Gd 3 Ga 5 O 12. The origin of the bands is discussed. It is shown that the intensity of the induced absorption bands gradually decreases and no additional bands appear as gallium is replaced by aluminum. The conclusion on the enhancement of the radiation hardness of Gd 3 Al x Ga 5-x O 12 with the substitution of Ga cations with Al is done. • The proton irradiation affects the absorption of Gd 3 Al x Ga 5-x O 12 crystals. • Induced absorption arises due to F centers and ions displacement defects. • Induced absorption is supressed as gallium is replaced by aluminum. • Substitution of Ga with Al ions improves radiation hardness of Gd 3 Al x Ga 5-x O 12. [ABSTRACT FROM AUTHOR]

Single crystals of Eu2+-activated SrI2, one of the most leading-edge scintillators for gamma-ray spectroscopy applications, have a low radioactive background, excellent energy resolution of 2.6%–3% at 662 keV, and high light yield of 80 000–120 000 photons/MeV. In this article, tetravalent ions codoping, namely, Hf4+ codoping, was used to enhance its scintillation performance. $\emptyset 12$ mm diameter SrI2:Eu2+ single crystals codoped with 0, 0.05, 0.1, and 0.2 at% Hf4+ were successfully grown by the multiampoule Bridgman method. All grown crystals are highly transparent, crack-free, and inclusion-free. The effects of Hf4+ codoping concentration on the optical and scintillation properties were studied. The gamma-ray energy resolutions of SrI2:Eu single crystals can be improved from 3.4% to 3.1% at 662 keV, and from 6.6% to 6.0% at 122 keV upon 0.05 at% Hf4+ codoping. [ABSTRACT FROM AUTHOR]

Effects of the tungsten (W) ions co-doping on the crystal growth, optical and scintillation properties for the Czochralski (Cz) grown Ce:Gd3Ga3Al2O12(GGAG) single crystals were investigated. The W 0%, 0.1%, 0.3%, 1%, and 5% co-doped Ce 1%:GGAG single crystals with a diameter of 1 in and length of 60–80 mm were grown by the Cz method. The effective segregation coefficient of the W ions was found as 0.002, 0.001, and 0.005 for W 0.1%, 0.3%, and 1%, Ce:GGAG, respectively. The segregation of W ions in GGAG host, light yield, and scintillation decay of the W co-doped Ce:GGAG were evaluated. The light yield decreased as the concentration of W co-dopant increased and toward the tail of the crystal. Furthermore, the defect role and related charge trapping in the W co-doped crystals were monitored by the thermo-stimulated luminescence. [ABSTRACT FROM AUTHOR]

• Eu concentration dependences of SrI 2 :Eu properties are analyzed. • Energy resolution better 4% sustains even at Eu concentration as low as 0.3 at%. • Scintillation properties of SrI2:Eu do not depend on growth method (Czochralski or Bridgman). SrI 2 :Eu crystals with the activator content of 0.1–5.5% were grown by the Bridgman-Stockbarger technique. The dependences of light yield, energy resolution, optical and luminescent properties on the Eu concentration have been studied. It has been shown that with a decrease in the amount of activator to 0.3% Eu, the energy resolution at 662 keV remains below 4%. The light yield gradually diminishes with decreasing Eu concentration. This makes it possible to revise the required amount of the expensive activator for growing high performance SrI 2 :Eu crystals. Scintillation parameters of crystals grown by the Czochralski and Bridgman-Stockbarger technique have been compared. [ABSTRACT FROM AUTHOR]

Nominally Nd 0.1, 0.5, 1 and 2% doped YAlO 3 (YAP) single crystals were synthesized by the floating zone method to evaluate their optical and scintillation properties. In photoluminescence (PL), all the samples showed sharp emission lines in the UV-VIS region, and the PL quantum yield in this spectral range was 5–15%. The PL decay time of the 4F 7/2 → 4I 9/2 transition was evaluated to be around 150 ms. In scintillation emission spectrum under X-ray irradiation, several emission lines due to the 4f-4f transitions of Nd3+ were observed in the UV-VIS range. These emissions was found to consist of two decay constants of a few μs and 100–150 ms. When irradiated with 662 keV γ-rays from 137Cs, the Nd 0.1% doped sample exhibited the highest scintillation light yield of 12500 ph/MeV determined by pulse height analysis. • Undoped and Nd differently doped YAP crystal scintillators were prepared. • Optical and scintillation properties of the undoped and Nd-doped YAP were evaluated. • Nd 0.1% doped YAP showed a clear photoabsorption peak in the pulse height spectrum. • The scintillation light yield of Nd 0.1% doped YAP was 12500 ph/MeV. [ABSTRACT FROM AUTHOR]

Sn-doped Ga 2 O 3 single crystals were synthesized by the Floating Zone (FZ) method. In photoluminescence (PL) under the excitation wavelength of 280 nm, we observed two types of luminescence: (1) defect luminescence due to recombination of the donor/acceptor pairs which appears at 430 nm and (2) the nsnp-ns 2 transitions of Sn 2+ which appear at 530 nm. The PL and scintillation decay time curves of the Sn-doped samples were approximated by a sum of exponential decay functions. The faster two components were ascribed to the defect luminescence, and the slowest component was owing to the nsnp-ns 2 transitions. In the pulse height spectrum measurements under 241 Am α-rays irradiation, all the Sn-doped Ga 2 O 3 samples were confirmed to show a full energy absorption peak but the undoped one. Among the present samples, the 1% Sn-doped sample exhibited the highest scintillation light yield (1,500 ± 150 ph/5.5 MeV-α). [ABSTRACT FROM AUTHOR]

Unidirectional (<200> plane) 1, 3, 5-triphenylbenzene (3PB) single crystal 150 mm long and 25 mm diameter was grown by SR technique. The grown crystal was subjected to UV–vis-NIR spectral analysis determine linear optical properties over the range of 200–1100 nm. The relevant optical parameters such as transmittance, absorption coefficient, extinction coefficient, band gap energy, reflectance, and refractive index were determined which reveal the suitability of crystal to couple with a photomultiplier tube or other light sensor. The wide band gap energy 3.65 eV of the 3PB crystal shows significant transmittance in the Vis and NIR region. The refractive index of the crystal is determined to be constant above 350 nm, and it confirms the required parameter to set high light yield. The temperature dependence refractive index was measured in the range of 30–70 °C, it illustrates the faster propagation light in the crystal. Third order nonlinear optical parameters of the grown crystal were estimated by Z-scan technique. It showed that the low absorption coefficient and negative refractive index. The second order hyperpolarizability (γ) of 3PB molecule was found to be 8.6411 × 10 −34 esu. The obtained all results in the present work which makes the 3PB crystal promising candidate for optical power limits, optical switching and other nonlinear optical applications. The Laser Damage Threshold (LDT) was determined to be 2.1612 GW/cm 2 and it confirms the suitability of crystal for device fabrication. [ABSTRACT FROM AUTHOR]

Metal halide perovskite nanocrystals (PNCs) have demonstrated intense luminescence and short emission lifetime, which perfectly match the requirements of X-ray fast scintillators. However, the poor stability of PNCs restricts their applications. Herein, CsPbBr 3 NCs in a wide band-gap Cs 4 PbBr 6 perovskite single crystal (PSC) matrix for efficient light extraction is reported. Benefitting from the protection of the PSC matrix and the perfect lattice matching, the PNCs embedded PSC show highly minimized nonradiative recombination and greatly improved stability. Moreover, by controlling the chemical equilibrium, the self-absorption of PNCs is reduced and the quantum yield increased to 78.5%. Furthermore, the PNCs embedded PSC demonstrates an appreciable light yield of 15,290 photons MeV−1, much higher than the commercial scintillator BGO (8200 photons MeV−1), and a decay time of 12.8 ns, significantly shorter than almost all the representative scintillators. This work demonstrates unambiguously the potential of PNCs embedded PSC for next-generation fast scintillators. • Highly luminescent nanocrystal embedded single crystal for scintillator was designed. • High stability of perovskite NCs was achieved without damaging the optical property. • The light yield was sharply increased by controlling the chemical equilibrium. • The scintillation decay time is superior than almost all the typical scintillators. [ABSTRACT FROM AUTHOR]

The optical properties of a highly dispersed bismuth orthogermanate powder Bi 4 Ge 3 O 12 : Pr3+ (HDP_BGO: Pr3+) were studied at Т = 300 K. The fluorescence of undoped HDP_BGO under ultraviolet (UV) excitation (λ exc = 266 nm) was shown to result from Frenkel excitons (GeO 4 4−, BiO 6 9−). The HDP_BGO fluorescence decay kinetics under UV excitation had a complex decay form similar to that of BGO single crystal and was a sum of four exponentials with lifetimes τ 1, 2, 3, 4 – 0.16/0.30/0.70/2.7 μs respectively. Two types of Pr3+ ions optical centers with lifetimes of ∼5.0 and 85 μs have been determined in a HDP_BGO: Pr3+. The resonance energy transfer of the electronic excitation from the HDP_BGO to Pr3+ions was identified. The effect of Pr3+ ions on the HDP_BGO fluorescence lifetime reduction from 160 to 35 ns was established. • A new highly dispersed Bi 4 Ge 3 O 12 powder, promising for LED phosphors and scintillators, has been proposed. • It is shown that the optical properties of a BGO powder are similar to those of a BGO crystal. • The effect of Pr3+ ions on the BGO fluorescence properties was demonstrated. [ABSTRACT FROM AUTHOR]

A new tantalum silicate, Rb 4 Ta 2 Si 8 O 23 , was synthesized as high-quality single crystals by the high temperature flux growth method. Rb 4 Ta 2 Si 8 O 23 was found to exhibit intense blue luminescence and scintillation as a self-activated luminescent silicate. Rb 4 Ta 2 Si 8 O 23 crystallizes in the triclinic space group P 1 ‾ with lattice parameters of a = 6.8916(2) Å, b = 7.7669(2) Å, c = 11.0018(3) Å, α = 76.3110(10)°, β = 89.2560(10)°, and γ = 71.8090(10)°. The structure consists of corner-sharing SiO 4 tetrahedra forming infinite ribbons connected by isolated TaO 6 octahedra. The synthesis, structure, and optical properties are reported, notably, bright blue scintillation when exposed to X-rays. The scintillation of Rb 4 Ta 2 Si 8 O 23 was quantitatively evaluated by radioluminescence (RL) measurements and was determined to be ∼47% of BGO powder. [Display omitted] • Rb 4 Ta 2 Si 8 O 23 was synthesized using flux crystal growth. • The crystal structure was solved using single crystal X-ray diffraction. • Rb 4 Ta 2 Si 8 O 23 exhibits photoluminescence and scintillation. • Scintillation intensity was quantitatively determined to be 47% of BGO powder from RL measurements. [ABSTRACT FROM AUTHOR]

The work is related to the growth of scintillators based on the single crystalline films (SCF) of Ce 3+ doped Lu 3− Gd x Al 5 O 12 mixed rare-earth garnets by Liquid Phase Epitaxy (LPE) method. We have shown, that full set of Lu 3− Gd x Al 5 O 12 SCFs with x values ranging from 0 to 3.0 can be successfully crystallized by the LPE method onto Y 3 Al 5 O 12 (YAG) substrates from the melt-solutions based on PbO-B 2 O 3 flux. The absorption, X-ray excited luminescence, photoluminescence, thermoluminescence and light yield measurements, the latter under excitation by α-particles of 239 Pu and 241 Am radioisotopes, were applied for their characterization. [ABSTRACT FROM AUTHOR]

The luminescence and scintillation properties of SrI 2 :0.5%Yb 2+ have been investigated. SrI 2 :Yb single crystals were grown by the vertical Bridgeman method from the melt. They showed a light yield of 38,400 ph/MeV and energy resolution of 12.5% for the 662 keV full absorption peak. Yb 2+ photoluminescence intensity and decay time were studied between 78 and 600 K. Two emission bands centered at 418 and 446 nm were observed and ascribed to spin-allowed and spin-forbidden Yb 2+ 5d-4f transitions, respectively. Their corresponding room-temperature decay time constants are 710 ns and 77 μs. Both, the emission intensities and the decay time constants vary with temperature. The obtained results were interpreted using a model of self-absorption of Yb 2+ emission and a model of non-radiative relaxation of the electron from the low spin to the high spin 4f 13 5d Yb 2+ excited states. The radiative lifetime of the low spin Yb 2+ excited state was determined as 400 ns. [ABSTRACT FROM AUTHOR]

• Growth of transparent and crack free single crystals of Ba doped CeBr3 of size 10 mm diameter and 15 mm length. • Ba2+ doping does not affects the structural and optical properties of CeBr 3. • Ba2+ doping decreases the hygroscopic nature of CeBr 3. • Scintillation performance of CeBr 3 improved with Ba2+ doping. In this work we have grown CeBr 3 :Ba single crystal of diameter 10 mm and length 15 mm and compared its crystal structure, luminescence and scintillation properties with pure CeBr 3 crystal. It is observed that Ba2+ doping don't change the structural properties of CeBr 3 and these crystals have same hexagonal UCl 3 type structure. Further, the transmission and radio luminescence spectra of Ba2+ doped and undoped CeBr 3 is almost similar. The hygroscopic nature of CeBr 3 is found to be remarkably reduced after Ba2+ doping. Ba2+ doping is also found to improve the scintillation performance of CeBr 3 crystal by decreasing the energy resolution though there is a slight increase in the decay time of CeBr 3. The energy resolution for 0.1 mol% Ba2+ doped CeBr 3 is 4.46% as compared to 4.7% for pure CeBr 3 crystal. [ABSTRACT FROM AUTHOR]

• The optical constants of Lu 2 O 3 single crystals covering the UV–VIS–NIR spectral region are firstly investigated • The bandgap energy 5.541 ± 0.004 eV of Lu 2 O 3 single crystal is derived experimentally • Large-size and damage-free Lu 2 O 3 single crystal is obtained by chemical mechanical polishing Lu 2 O 3 has attracted widespread attention in high-power lasers, scintillators, and semiconductors due to its high thermal conductivity, high stability, and large band gap. Due to the limitations of the growth process, high-precision characterization of polished quality and optical properties for large-size Lu 2 O 3 single crystal is extremely scarce, which hinders the design and optimization of optics based on Lu 2 O 3. In this study, we design a systematic machining scheme for large-size Lu 2 O 3 single crystal thick chip to obtain polished crystal with virtually no surface and subsurface damage. The surface/subsurface quality was evaluated utilizing optical profilometer, scanning electron microscope, and transmission electron microscope. Variable-angle spectroscopic ellipsometer was employed to measure the optical constants over wide spectral region (210–1690 nm), removing the lack of optical constants of Lu 2 O 3 single crystal in the ultraviolet region. The band gap is analyzed based on the optical constants results. The consistency of the measured data with the relevant literature verifies the reliability and accuracy of the measurement method along with the data. The surface/subsurface damage inspection method provides an effective approach for ultra-precision machining mechanism research and process optimization of Lu 2 O 3 and other hard and brittle materials. The band gap and the optical constants in wide spectral region provide critical fundamental data for the design and performance optimization of related optics. [ABSTRACT FROM AUTHOR]

Single crystal of organic scintillation material N-Phenylanthralinic acid (NPAA) with the dimension of 10×4x3 mm3 was grown by the temperature-lowering method. X-ray diffraction studies and FT-IR analysis of grown crystal revealed the crystal structure and functional groups present in the crystal. The optical quality of the crystal is ascertained from absorption spectrum and optical bandgap studies. The fluorescence spectra exhibit an intense emission band at 452 nm and fluorescence lifetime is obtained to be very short fluorescence of 1.14 ns for prompt and 18.98 ns for delayed component. TG/ DTA studies reveal the thermal stability and melting point of the crystal. The feasibility of the grown crystal in device application is substantiated from various mechanical parameters such as Vickers hardness, Meyer's index, yield strength and stiffness constant. The chemical etching and surface morphologies of the specimen were examined using an optical microscope. [ABSTRACT FROM AUTHOR]

Single crystal of organic scintillation material N-Phenylanthralinic acid (NPAA) with the dimension of 10×4x3 mm3 was grown by the temperature-lowering method. X-ray diffraction studies and FT-IR analysis of grown crystal revealed the crystal structure and functional groups present in the crystal. The optical quality of the crystal is ascertained from absorption spectrum and optical bandgap studies. The fluorescence spectra exhibit an intense emission band at 452 nm and fluorescence lifetime is obtained to be very short fluorescence of 1.14 ns for prompt and 18.98 ns for delayed component. TG/ DTA studies reveal the thermal stability and melting point of the crystal. The feasibility of the grown crystal in device application is substantiated from various mechanical parameters such as Vickers hardness, Meyer's index, yield strength and stiffness constant. The chemical etching and surface morphologies of the specimen were examined using an optical microscope. [ABSTRACT FROM AUTHOR]

Single crystal growth of novel dicesium molybdate (Cs 2 MoO 4) crystal by Czochralski technique was carried out. The single crystal phase was confirmed by powders X-ray diffraction analysis. The optical band gap of 4.22 eV was estimated from the absorbance spectra, measured at room temperature. The luminescence properties were measured under the excitation of 4.42 eV UV light from an LED source in the temperature range of 10–300 K. The photoluminescence light yield increases upon cooling down the grown crystal to 10 K. The luminescence decay time was analyzed with the sum of three exponential decay-time functions in the entire temperature range. The comparison of luminescence light yield with Li 2 MoO 4 (one of the promising scintillating bolometers for the neutrinoless double-beta decay search) at 10 K shows a similar light output. These preliminary investigations show that the grown crystal can be a good candidate crystal for the cryogenic dark matter and neutrinoless double-beta decay search. • The Cs 2 MoO 4 crystal has been grown by Czhochrlaski method for the 1st time. • Optical band gape of 4.22 eV was estimated from absorption spectrum. • A comparable luminescence yield with that of Li 2 MoO 4 crystal was obtained at 10 K. • The slow decay component was fitted with the three-level thermal quenching model. • This crystal has the potential to be used for the 0νββ decay search of 100Mo. [ABSTRACT FROM AUTHOR]

LiCaAlF 6 single crystals doped with different Eu concentrations varied from 1 at% to 5 at%, and LiCaAlF 6 :Eu single crystals co-doped with 3 at%Cu+, 2 at%Mg2+, 2 at%Ba2+ were grown by the Bridgman method in non-vacuum atmosphere. Their optical and scintillation performances were studied. The optimal scintillation efficiency was achieved in the LiCaAlF 6 :Eu single crystals with Eu concentrations between 2 and 2.5 at%. The influences of Cu+, Mg2+ and Ba2+ co-doping on optical properties, scintillation yield, scintillation decay and defect structures were studied. It was found that the Cu+ co-doping can improve the scintillation efficiency. The Mg2+ and Ba2+ co-doping have negligible effects on light yield. • Bridgman method in non-vacuum atmosphere were used to grow LiCaAlF 6 :Eu crystals. • The optimal scintillation efficiency obtained between 2 and 2.5 at%Eu concentration. • The Eu–Cu co-doping improve the scintillation efficiency than Eu doped LiCaAlF 6. • The Eu–Cu co-doping changed the defect structure than Eu doped LiCaAlF 6. [ABSTRACT FROM AUTHOR]

Ce:Li 6 Y(BO 3) 3 (LYBO) is a promising thermal neutron scintillator that can be grown into bulk single crystals by the Czochralski method although it melts incongruently. This study achieves 1-inch Ce:LYBO, and demonstrates the collateral flux-growth of LiY 6 O 5 (BO 3) 3 (LYOB) single crystals at the bottom of the crucible during the pulling of LYBO from a stoichiometric melt. Both LYBO and LYOB belong to monoclinic crystal system with the same space group. Thermal analysis shows that LYOB itself is more incongruent than LYBO, decomposing mainly into Y 16.86 B 8 O 38 phase when heated up to 1500 ​°C. In contrast to the typical bluish emission of Ce-doped scintillators, like the case of Ce:LYBO, Ce:LYOB crystals exhibit a broad emission peaking in the orange wavelength region, as a result from an extraordinarily large Stokes shift. The ultrafast photoluminescence (PL) decay of Ce:LYOB is due to dominant non-radiative processes that also cause obvious luminescence quenching. This study reports for the first time high-quality Ce:LYOB single crystals, which are characterized in terms of single crystal diffraction, thermal analysis, optical transmittance, excitation and PL at room temperature, PL decay and Raman spectroscopy. Simultaneous crystal growth of 1-inch Ce:Li 6 Y(BO 3) 3 and millimeter high-quality Ce:LiY 6 O 5 (BO 3) 3 , and investigations on their structure, thermal analysis and optical properties. [Display omitted] • 1-inch Ce:Li 6 Y(BO 3) 3 crystal that is transparent and cracks/inclusion-free. • Flux-growth of high-quality Ce:LiY 6 O 5 (BO 3) 3 single crystals. • Thermal and optical properties of Ce:LiY 6 O 5 (BO 3) 3 were reported for the first time. • Ce:LiY 6 O 5 (BO 3) 3 emits an orange-reddish light originating from large Stokes shift. [ABSTRACT FROM AUTHOR]

• LPS single crystals with Nd doping concentration of 0.1%, 0.5%, 1.0%, 2.0%, and 5.0% were synthesized by the FZ method. • Under X-ray irradiated, Sample exhibited scintillation emission at both UV and NIR ranged caused by Nd3+ 4–4f transitions. • X-ray induced scintillation decay time of Nd-doped LPS samples resulted in 3–4 μs. • Under 662 keV γ-ray, scintillation light yield of Nd-doped LPS reached up to 800 ph/MeV in the 2.0% Nd-doped sample. Lutetium pyrosilicate (Lu 2 Si 2 O 7 , LPS) single crystals were synthesized by the floating-zone method with different dopant concentration to investigate the Nd-concentration dependence on the photoluminescence (PL) and scintillation properties. The Nd-doped LPS presented PL peaking at 800–900 nm due to the 4–4f transitions with the PL quantum yield up to 34%. Under X-ray irradiation, the samples showed several sharp peaks in both UV–visible and NIR regions. The scintillation decay time constants were around 3–4 μs upon pulsed X-ray excitation, and the afterglow level at 20 ms after X-ray irradiation was 310–650 ppm. The scintillation light yields of the Nd-doped LPS under γ-rays from 137Cs were up to 800 ph/MeV. hMeV. [ABSTRACT FROM AUTHOR]

The luminescence, scintillation, and photoconversion properties of the single crystals of Ce3+ doped Tb 3−x Gd x Al 5-y Ga y O 12 (х = 0–1.5; у = 2–2.5) mixed garnets, grown by the micro-pulling-down (μ-PD) method, are investigated as a function of the Tb/Gd ratio with the aim of development of phosphor-convertors of white LED and scintillators. The partial Tb3+ substitution by Gd3+ cations leads to the suitable change of the crystal field splitting of the 5d energy levels of Ce3 ions due to different sizes of the Gd3+ and Tb3+ cations. For this reason, the cation engineering enables to improve the luminescence and scintillation characteristics of Tb 3−x Gd x Al 3-2.5 Ga 2-2.5 O 12 crystals due to increasing the efficiency of Gd3+→ Tb3+→ Ce3+ cascade energy transfer observed in these solid solutions. We have shown that from all the crystals under study, the Tb 3-x Gd x Al 2.5 Ga 2.5 O 12 :Ce (х = 1–1.5) crystal is the best promising candidate for the photoconversion and scintillation applications. • Single crystals of TbGdAGG:Ce grown by the micro-pulling-down method. • Tb3+/Gd3+ ratio control improving the color rendering and scintillation properties. • The best photoconversion properties are shown by Tb 2-1.5 Gd 1-1.5 Al 2.5 Ga 2.5 O 12 :Ce. [ABSTRACT FROM AUTHOR]

Lutetium pyrosilicate (Lu 2 Si 2 O 7) single crystals were synthesized by using the floating-zone method with 0.1, 0.5, 1.0, 2.0 and 5.0% of Tm-doping concentration. After the phase confirmation by powder XRD, photoluminescence (PL) and scintillation properties were systematically measured, including PL emission map, PL decay time, scintillation spectra, scintillation decay time and pulse height spectra. When we irradiated X-rays, we observed the scintillation emission at 360 and 460 nm caused by Tm3+ 4f-4f transitions. Under 662 keV γ-ray irradiation, we determined absolute scintillation light yield of 2340 ph/MeV for the 2.0% Tm doped sample. Taking into account whole optical and scintillation properties, 2.0% doping was the best for Tm-doped LPS crystals. • We successfully synthesized LPS single crystals with Tm doping concentration of 0.1 to 5.0 % by the FZ method. • When we irradiated X-rays, we observed the scintillation emission at 360 and 460 nm caused by Tm3+ 4f-4f transitions. • Under 662 keV γ-ray, scintillation light yield of Tm doped LPS reached up to 2340 ph/MeV with the 2.0 % Tm doped sample. • The optimal Tm doping concentration in the LPS single crystal for a scintillator was determined to be around 2.0 %. [ABSTRACT FROM AUTHOR]

The scintillators with Ce luminescent centers are widely used for radiation detection. In this study, we focused on the Ce 2 Si 2 O 7 pyrosilicate scintillator and evaluated its optical and scintillation properties. From the result of the temperature dependence of quantum yield of Ce 2 Si 2 O 7 under excitation into the Ce3+ 4f-5d 1 transition, it was revealed that at 300°C the Ce 2 Si 2 O 7 had a quantum yield of approximately 40% of that at the room. In addition, Ce 2 Si 2 O 7 had a light output of 9,400 ± 800 photons/MeV and fast decay time (~34 ns) at room temperature, and therefore, it has potential for application in radiation detection. • Ce 2 Si 2 O 7 single crystal was grown by the micro-pulling-down method. • Optical properties of Ce 2 Si 2 O 7 was investigated. • The decay time of Ce 2 Si 2 O 7 was accelerated compared with Ce-doepd (La,Gd) 2 Si 2 O 7. [ABSTRACT FROM AUTHOR]

• W co-doped Ce:Gd 3 Ga 3 Al 2 O 12 with 30–60 mm length grown by micro-pulling down method. • Light yield value was increased by small amount (200–1000 ppm) of W co-doping. • When the co-doping concentration of W was higher than 1000 ppm, the light yield decreased. Single crystal scintillators are extensively used in various radiation detection applications and their scintillation performances can be improved via co-doping. Therefore, in this study, tungsten-ion co-doped Ce:Gd 3 (Ga,Al) 5 O 12 (Ce:GGAG) crystals were grown using the micro-pulling-down (μ-PD) method to investigate the effects of co-doping on their scintillation properties. The relationships between the W concentration, optical and luminescence properties, and radiation response of the W-co-doped Ce:GGAG crystals were evaluated. The W-co-doped Ce 0.5%:Gd 3 Ga 3 Al 2 O 12 single crystals of diameter 3 mm and length 30–60 mm were grown by the μ-PD method. The light yield increased at W concentrations of 200 and 500 ppm and decreased at W concentrations above 1000 ppm. There was no significant change in the fast decay component of scintillation. [ABSTRACT FROM AUTHOR]

Pr doped Lutetium pyrosilicate Lu 2 Si 2 O 7 (LPS) single crystals were synthesized by the floating zone method with different Pr concentration from 0.1% to 2.0%. After the confirmation of the phase by powder XRD patterns, optical and scintillation properties were investigated. When we observed photoluminescence (PL) emission spectra, emission due to 5d-4f transition of Pr3+ appeared in all the samples at wavelength of 300–340 nm, and PL decay times were similar around 9–11 ns in all the samples. In scintillation properties, under the X-ray excitation, all the samples had the same scintillation emission spectral shape with different emission intensities, and scintillation decay times were around 18–21 ns. Under 137Cs γ-rays irradiation, the 1.0% Pr doped sample showed the highest scintillation light yield among the present samples, and the value was 9700 ph/MeV. Furthermore, linearity as a function of γ-ray energy was observed. • We successfully synthesized LPS single crystals with Pr doping concentration of 0.1, 0.3, 0.5, 1, and 2 % by the FZ method. • All of the samples have scintillation decay time around 18–21 ns. • When excited by 662 keV γ-ray, 1.0 % Pr doped LPS have scintillation light yield up to 9700 ph/MeV. • The optimal Pr doping concentration in the LPS single crystal for the scintillation purpose was determined to be around 1 %. [ABSTRACT FROM AUTHOR]

• Cs 2 HfCl 6 single crystal preparation by miniaturized and standard Bridgman methods. • Cs 2 HfCl 6 single-phase proved by XRD measurements. • Room temperature optical, luminescence, and scintillation properties of Cs 2 HfCl 6. • Room temperature photoluminescence and scintillation decay kinetics of Cs 2 HfCl 6. Time and cost effective methods are highly desirable in research and development of new scintillators. Modern techniques like micro-pulling down (μ-PD) are suitable for material screening but are unfit for the growth of some crystals. These crystals must be grown by different methods that are usually very time demanding. Modification of halide μ-PD apparatus by custom made elements allowed us to grow cesium hafnium chloride (Cs 2 HfCl 6) by vertical Bridgman method (VB) with significantly reduced growth time. Structural and optical properties of samples prepared from as-grown crystals were studied and compared to crystals grown by standard VB method. The X-ray diffraction confirmed the formation of cesium hafnium chloride single-phase and natural cleavage of the crystals along the (1 1 1) crystallographic plane. Photoluminescence emission, excitation, absorption, and radioluminescence spectroscopy revealed that the optical quality of the crystals grown by modified VB method was comparable to the quality of the crystals grown by standard VB method. Therefore we can use samples prepared by modified VB to estimate and optimize the performance of Cs 2 HfCl 6 based crystals in scintillation detectors. This setup allows the time and cost-effective material screening and it is a powerful tool for the development of new halide based single crystal scintillators. [ABSTRACT FROM AUTHOR]

• Growth of large (1 in.) diameter boules of single crystal Cs 2 HfCl 6 and Cs 2 HfCl 4 Br 2. • Intrinsic scintillator crystals with simple cubic crystal structures. • Energy resolutions below 3.8% at 662 keV and good proportional responses to photon energies. This paper reports on successful growth and performance evaluation of two large diameter Cs 2 HfCl 6 (CHC) and Cs 2 HfCl 4 Br 2 (CHCB), both recently developed scintillator crystals. The discovery of Cs 2 HfCl 6 (CHC) as a scintillator has lately generated much interest in this material and its family, which belongs to the K 2 PtCl 6 cubic crystal structure. CHC is an intrinsic scintillator that is non-hygroscopic (slightly deliquescent, i.e., slightly moisture sensitive but does not deteriorate much when left in air), has no self-radioactivity, provides excellent energy resolution, and has excellent non-proportionality. CHC has a moderate density of 3.9 g/cm3 and an effective atomic number of 58. Reported in this paper are transparent crack-free single crystal CHC and CHCB boules of one inch in diameter, both grown using the vertical Bridgman method. Samples retrieved from the boules, sized ∅23 mm × 30 mm and ∅23 mm × 26 mm, respectively, are characterized for their optical and scintillation properties. Energy resolutions of 3.5% and 3.7% (FWHM) at 662 keV, respectively, are reported. Light yields of 23,000 ph/MeV and 20,000 ph/MeV have been calculated for the large diameter CHC and CHCB crystals, respectively. Results comparable to previously reported results for smaller crystals have been obtained. Studies on decay time, non-proportionality, as well as detector characterization are also reported. [ABSTRACT FROM AUTHOR]

Europium doped strontium iodide (SrI 2 :Eu 2 +) is one of the cutting-edge halide scintillators for gamma-ray spectroscopy applications due to its low radioactive background, ultrahigh light yield (70,000–100,000 photons/MeV), and excellent gamma-ray energy resolution (2.6%–3% at 662 keV). In this work, we report an improvement in the scintillation characteristics of SrI 2 :Eu 2 + single crystals via tetravalent ion codoping, namely Zr 4 +. High quality SrI 2 :Eu 2 + single crystals codoped with 0, 0.05, 0.1, and 0.2 at.% Zr 4 + were grown by the Multi-ampoule Bridgman method. All of the as-grown crystals are transparent, crack-and inclusion-free. They have high optical quality with a transmittance of over 70%. The effects of Zr 4 + codoping on spectral properties and decay kinetics of SrI 2 :Eu 2 + under optical, and x- and gamma-ray excitation are studied. An enhancement of gamma-ray spectroscopic resolution from 2.8 to 2.5% at 662 keV and 5.4 to 5% at 122 keV is achieved upon Zr 4 + codoping with a slightly enhanced light yield of 95,000 photons/MeV. [ABSTRACT FROM AUTHOR]

This paper focuses on recent successful and improved growth runs of single phase Cs 2 HfCl 6 (CHC) as well as improvement to its radiometric and scintillation performance. Two single crystal CHC boules of 15 mm in diameter are grown using the vertical Bridgman method. Samples retrieved from each boule are characterized for their optical and scintillation properties. Energy resolution of 2.8% (FWHM) at 662 keV has been obtained. Gamma-ray non-proportionality of CHC is compared to those of NaI:Tl and BGO. Decay times are measured to be at least 246 ns (13%) and 3.3 μs (87%) for CHC, an improvement to previously reported values. In this paper we also present growth and scintillation performance of Cs 2 Hf(Cl 1-x Br x) 6 with Cl/Br = 2/1 relation (CHC/B), as well as its scintillation decay times. • Successful growth of a crack-free, transparent, and single crystal boule of intrinsic scintillator Cs 2 HfCl 6 (CHC). • Energy resolution of 2.8% (FWHM) at 662 keV and light yield of 27,000 ph/MeV have been achieved. • CHC has a linear response to photon above 100 keV. [ABSTRACT FROM AUTHOR]

In this paper, we present the photoluminescence and scintillation performance of Pr3+ doped (Lu 0.75 Y 0.25) 3 Al 5 O 12 single crystals as a function of Li+ concentration. Lithium concentration had no effect on the optical properties of LuYAG: Pr single crystal scintillators regardless of concentration. On the other hand, scintillation light yield increased by as much as 94% with the incorporation of lithium as a codopant, and the energy resolution at 662 keV was improved to 4.1%, which is an outstanding energy resolution for an oxide single crystal scintillator. Lithium codoping slightly lengthened the fast component of the scintillation decay time, and slightly decreased the contribution from the slow component. Additionally, the samples were annealed in air and scintillation properties were compared before and after this annealing treatment. The change in scintillation properties is explained through the analysis of thermoluminescence glow curves. • Li codoping of LuYAG: Pr can increase light yield, improve energy resolution. • Air annealing improves light yield of LuYAG: Pr, Li by reducing trap concentration. • Thermoluminescence suggests traps play important role in scintillation mechanism. [ABSTRACT FROM AUTHOR]

Single crystal growth of undope CaCl 2 , CaBr 2 and CaI 2 was performed by Bridgman–Stockbarger (BS) method. Investigations of their crystal phases, luminescence and scintillation properties such light yield, energy resolution decay time were performed. In addition, linearity of gamma-ray response in 32–1275 keV range were also evaluated. The light output of 106,000 photon/MeV, energy resolution of 3.2%@662 keV, and scintillation decay time of 834 ns (84%) 1460 ns (16%) were observed. Luminescence properties of CaBr 2 also firstly reported. [ABSTRACT FROM AUTHOR]