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The BaLu2F8 crystals doped with 1 mol% Tm, Nd and Er were prepared by micro-pulling-down method to study their scintillation and luminescence properties. The unwanted phase transition from orthorhombic structure to monoclinic one, which occurs some 50 °C below the melting point, was avoided using Li-flux. No Li-containing secondary phase was observed. Radioluminescence measurements of Nd-doped samples revealed 5d-4f Nd3+ luminescence situated around 180nm, the intensity of which was comparable with that of the LaF3:Nd 8% reference scintillator sample. Further slight enhancement of the Nd3+ 5d-4f emission was achieved by Tm3+ co-doping probably due to energy transfer from the Tm3+ 5d levels to the Nd3+ ones. (© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

Ce-doped Gd3Al3Ga2O12 (Ce:GAGG) crystal shows good scintillation performances, especially high light yield. However, its scintillation decay contains slower components. Such phenomenon is due to the delayed radiative recombination process which is caused by trapping effects in the transport stage of scintillation mechanism. Various defects including oxygen vacancy can give rise to shallow traps in the forbidden gap of the material which can cause such phenomena. To study the influence of such oxygen defects, 0.2-mol% Ce-doped GAGG single crystals were grown by Floating Zone method using growth atmosphere with different oxygen concentrations. The optical and scintillation properties of the crystals were examined. The light yield and emission wavelength of these samples did not depend on the oxygen content in the growth atmosphere. On the other hand, scintillation decays of the samples grown under the high oxygen concentrations (100 and 40% oxygen) were faster than that of the sample grown under the lower concentration (20%). Oxygen content in the growth atmosphere thus appears an important parameter in the optimization of the growth process of these materials (© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

Ce1%:(GdxY1-x)3Al5O12 (x=0, 0.2, 0.4, 0.6 and 0.8) crystals were grown by the μ-PD method. In the range of x=0∼0.4, the grown crystals showed single garnet phase, but x=0.6 and 0.8 crystals showed secondary perovskite phase. In these crystals, Ce3+ 4f-5d emission was observed within 500-530 nm wavelength. Emission peaks shifted to shorter wavelength and the decay times was delayed with increasing Gd concentration. The light yield of Ce:(Gd0.6Y0.4)3Al5O12sample was around 13,000 photon/MeV. Scintillation decay time was around 111 ns (© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

In recent work, Na co-doping have found to improve the light output of Eu doped LiCaAlF6 (Eu:LiCAF) for thermal neutron scintillator. We grew Eu 2% and alkali metal 1% co-doped LiSAF crystals by Micro-Pulling down method to understand the effect of alkali metal co-doping on scintillation properties and mechanism compared with LiCAF. In photo- and α-ray induced radio-luminescence spectra of the all grown crystals, the emissions from d-f transition of Eu2+ were observed. Without relation to excitation source, decay times of co-doped LiSAF were longer than Eu only doped one. The light yield of Na, K and Cs co-doped LiSAF under 252Cf neutron excitation were improved. Especially, K co-doped Eu:LiSAF reached 33200 ph/n, which outperformed Eu only doped one by approximately 20% (© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

Optical and scintillation properties of a 1.0-mol% Dy-doped yttrium aluminium garnet (YAG) grown under N2 atmosphere and undoped YAG crystals were investigated. Both crystals were grown by the Czochralski process. The one of the undoped YAG crystal was grown in an Ar + H2 (97:3) reducing atmosphere. Absorption peaks at 352 nm and 366 nm observed in 1.0-mol% Dy-doped YAG originated from 4f-4f transition of Dy3+. In addition, the crystal showed sharp emission lines at near 482 nm and 584 nm under 352 nm UV and alpha-ray excitation. The light output of Dy-doped YAG was estimated to be approximately 20,000 photons/(5.5-MeV alpha ray, 241Am). The scintillation decay time constants for Dy-doped YAG crystal was around 400 ns and 40 ns. Undoped YAG crystals grown under Ar + H2(97:3) atmosphere showed absorption and excitation peak at 370 nm. A 400-nm emission peak was observed under 370-nm excitation. The light output of the crystal was also estimated to be 50,000 photons/(5.5-MeV alpha ray). The scintillation decay time constants of the crystal were around 370 ns and 50 ns. (© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]