Papers by Keyword: Scintillators

Abstract: Nowadays, single crystal scintillators play an key role in the scientific researches, high-energy physics and modern medical imaging. In this research, we studied the scintillation response of polished yttrium oxyorthosilicate with Ce-doped (Y₂SiO₅:Ce, YSO(Ce)) crystals grown by the Czochralski method. The nominal Ce³⁺ ion is about 0.5% for tested crystals. Energy resolution and photon yield of the scintillator are read out by the photomultiplier tube (XP5200B PMT) under excitation with gamma-rays. The polished YSO:Ce samples (5x5x1 mm³ and 5x5x3 mm³) was tested at room temperature. The 1 mm thick sample shows the better energy resolution than the 3 mm thick crystal. The light yield dependences on the height of crystal were evaluated under excitation with 662 keV gamma ray energy and the intrinsic light yield and loss parameter were also determined.

Abstract: The possibility of applying the spray drying method for the production of complex oxides powders with garnet structure is shown in paper. The processes occurring while heating of synthesized oxide-salt product, that lead to the formation of a material with a garnet structure were investigated by DTA, TGA, X-ray analysis. The possibility of producing single-phase structure of the garnet system (Y_xGd_(3-x))₃Al₅O₁₂ in wide range of compositions is demonstrated.

Abstract: Thermoluminescence (TL) is basically a super-sensitive phenomenon exhibit ted practically by all semiconductors/ insulators upon suitable excitation. The occurrence of TL peaks during the thermal scan of a previously excited material gives rise to a number of peaks whose trapping parameters and relative concentrations can be evaluated by well-known techniques. Thus, TL in principle is a unique tool to characterize scintillator crystals. The technique is capable to detect the relative abundance of carriers in traps as shallow as ≈0.1eV to as deep as 2.0eV; providing means to probe carriers having lifetime (τ) as low as ∼ps to as large as billions of years. Hence the technique can be used to design scintillator materials of desired properties specially the decay time, the rise-time and the afterglow by adjusting the presence/absence of relevant trapping levels.

Abstract: Li₆Y(BO₃)₃ and Li₆Gd (BO₃)₃ powders were synthesized using wet chemical method. Lithium-nitrate, yttrium-/gadolinium-nitrate and boric acid solutions were mixed in stoichiometric composition, and a colloidal precipitate was obtained by adjusting the pH of the mixture. Li₆Y(BO₃)₃/Li₆Gd (BO₃)₃ phase formation was achieved by annealing the precursors in the 650700 °C temperature range. The reaction steps were monitored by FTIR and Raman-spectroscopy, and the final products were characterized by X-ray powder diffraction and scanning electron microscope. XRD assessment shows that we obtained LYBO/LGBO as dominant phases after a 24 h treatment at 650 °C.

Abstract: Time-resolved luminescence characteristics have been studied for cerium doped YAG nanopowders (NP) and nanostructured ceramics (NC). The results obtained have been compared to the luminescence characteristics for the well studied YAG:Ce3+ single crystal (SC). It was detected that the luminescence decay kinetics of Ce3+ related emission in nanocrystals can be closely approximated by two exponents, whereas a single exponential decay was observed in the single crystal. It was also found that the luminescence decay time and light yield of Ce3+ emission are strongly dependent on the cerium concentration and an unusual concentration quenching of Ce3+ emission was observed in YAG nanocrystals. The origin of the differences of luminescence characteristics for cerium doped nanocrystals and SC are discussed. It is suggested that there are special Ce3+ sites which are closely related to the surface states and that they have a strong influence on the luminescence properties of cerium doped YAG nanocrystals.