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Carbazole crystals were grown using self-seeding vertical Bridgman technique, and the scintillation properties for neutron detection were investigated. Results of powder X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) analyses indicated the single phase of the grown carbazole crystal with orthorhombic structure. Photo- and radio-luminescence measurements were carried out, and maxima of both emission peaks were at 420 nm. The light yield under 5.5-MeV alpha-ray irradiation was estimated to be 1.87 times higher than that of lithium glass GS-20. The scintillation decay time under neutron irradiation was estimated to be 11.4 ± 0.3 ns. It follows from the temperature dependence measurements that the light output under 662-keV gamma-ray excitation decreases with increasing temperature. [ABSTRACT FROM AUTHOR]

In this study, charge compensation was performed by co-doping Na + ions at the Ca2+ sites of Ce-doped LiCaAlF 6 single crystals to prevent the generation of cation vacancies owing to Ce3+-doping at the Ca2+ sites. Consequently, an improved radiation resistance and increased light yield under neutron irradiation was achieved. In contrast, the Al metal of the starting material used as a substitute for AlF 3 significantly increased the effective segregation coefficient k eff of the Eu2+ ions in Eu-doped LiCaAlF 6 and Eu-doped LiSrAlF 6 single crystals. The Al metal and EuF 3 in the starting materials produced EuF 2 via a chemical reaction, and the Eu2+ ions in EuF 2 could be substituted at the Ca2+ and Sr2+ sites. In addition, the Ca/Sr ratio control of the Li(Ca,Sr)AlF 6 :Eu solid-solution scintillator single crystals improved the light yield through band-gap control, and the Li(Ca,Sr)AlF 6 :Eu single crystal with a 25% Sr concentration exhibited the highest light yield. Charge compensation was conducted using Na co-doping to improve the radiation resistance of the LiCAF:Ce single crystals, thereby preventing the generation of cation defects by the Ce3+-doping at the Ca2+ site. It was determined that the improvement in the radiation resistance of the LiCAF:Ce single crystal via Na co-doping can contribute to the improvement in the durability of the production of LiCAF:Ce single crystals. [Display omitted] • Scintillation properties of LiCaAlF 6 and LiSrAlF 6 single crystals were improved by chemical composition control. • Charge compensation by Na co-doping for LiCAF:Ce single crystals prevents generations of cation vacancies by Ce3+-doping. • Al metal greatly increases the segregation coefficient of Eu ion in the LiCAF and LiSAF single crystals. • Effective segregation coefficient of Eu2%,AlM1%:LiSrAlF 6 crystal was improved to 0.986 using the Al metal. • Ca/Sr ratio control in the Eu:Li(Ca,Sr)AlF 6 single crystals improves the light yield under thermal neutron irradiation. [ABSTRACT FROM AUTHOR]

Eu-doped Li(Ca,Sr)AlF 6 [Eu:LiCSAF] single crystals with various Ca/Sr ratios were grown by the micro-pulling-down method, and their optical and scintillation properties were investigated to reveal the effects of Ca/Sr ratio on optical and scintillation properties of the Eu:LiCSAF single crystals. The Li(Ca 1− x − y Sr x Eu y )AlF 6 single crystals could be grown in 0 ≤  x  ≤ 0.1, 0.5 ≤  x  ≤ 1.0 and y  = 0.02 while the Eu:LiCSAF crystals with x  = 0.2, 0.25 and 0.4 included two colquiriite-type phases with different lattice parameters. The Li(Ca 1− x−y Sr x Eu y )AlF 6 single crystal with x  = 0.25 and y  = 0.02 showed the highest light yield under neutron irradiation. [ABSTRACT FROM AUTHOR]

Ba co-doped Ce:LiCaAlF{{6}} [Ce:Li(Ca,Ba)AlF{{6}}] and LiCaAlF{{6}} [Li(Ca,Ba)AlF{{6}}] crystals with various Ba concentrations were grown and their structures, optical and scintillation properties were investigated. As-grown Ce2%Ba1% and Ce2%Ba2%:Li(Ca,Ba)AlF{{6}} crystals were high transparency in all parts while an end part of as-grown Ce2%Ba5%:Li(Ca,Ba)AlF{{6}} crystal and all parts of as-grown Ba5%:Li(Ca,Ba)AlF{{6}} crystal included milky parts which decreased transmittance. Ce:Li(Ca,Ba)AlF{{6}} crystals indicated the emission peaks at 288 and 308 nm from which was attributable to the 5d-4f transition of Ce^3+ ion in the radioluminescence spectra under \alpha-ray irradiation. In the case of Ce1%Ba2%:Li(Ca,Ba)AlF{{6}} crystal, light yield under thermal neutron irradiation were improved. Decay times of Ce:Ce:Li(Ca,Ba)AlF{{6}} under thermal neutron irradiation systematically increased with an increase of Ba concentration. [ABSTRACT FROM PUBLISHER]

Abstract: Ce 1%, 2%, and 3%-doped LiCaAlF6 (LiCAF) single crystals were grown by the micro-pulling-down method. The crystals were transparent, 2.0mm in diameter and 30–60mm in length. Neither visible inclusions nor cracks were observed. Optical properties, including absorption coefficient, and photoluminescence emission spectra were measured. The strong absorption line was observed at 260nm, and absorption coefficients of this line were proportional to Ce3+ concentration. Emission due to Ce3+ 5d–4f transition peaking around 285nm and 310nm were observed by 260nm excitation. Simulating a neutron irradiation, 241Am 5.5MeV α-ray was used to excite the samples. After a correction of a quantum efficiency of photomultiplier tube and compared with Li–glass scintillator GS20, light yield of 6600ph/n, and 41ns decay were achieved 3% doped. [Copyright &y& Elsevier]