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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. © 2010 IEEE.

Time development of a Nphels/MeV photoelectron yield of various Ce and Pr-doped inorganic crystals (mainly garnets, perovskites and silicates) was studied in detail. Slow scintillation decay components influence time dependence, especially at those scintillators containing Lu as lattice ions where an increase of Nphels per 1 MeV in the time span 0.25–5 µs is more than 50%. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

A hybrid photomultiplier (HPMT) was used to study the scintillation response {Nphels(E) photoelectron and L.Y.(E) light yields and energy resolutions} of various known or newly developed scintillators—namely, Ce-doped crystals (perovskites or garnets), CsI(Tl) and the intrinsic BGO crystal—at different energies in the range 8 keV – 1.33 MeV . Detailed comparative studies of the scintillation properties of these crystals are presented. A newly developed fast and heavy LuAG:Ce scintillator is characterized by about a 50% higher L.Y. compared to that of well-known and popular BGO (roughly 12 500 ph / MeV against 8080 ph / MeV , respectively).

The cover picture of the current issue refers to the Rapid Research Letter by Martin Nikl et al. [1]. It depicts the structure of a Lu3Al5O12:Ce single crystal, a possible high performance scintillator material. Its scintillation performance is, however, degraded by the occurrence of antisite defects. Such defects arise in the material structure sketched in the figure due to the occurrence of Lu3+ ions at the Al3+ octahedral sites as seen in the middle left octahedron. This defect constitutes a shallow electron trap, which delays energy delivery to the Ce3+ emission centers, and thus slows down the scintillation response of the material. Thermoluminescence measurements appear as sensitive diagnostic tool to evidence these defects in the single crystals grown. Martin Nikl is senior scientist and head of the Laboratory of Luminescence and Scintillation Materials at the Institute of Physics of the Czech Academy of Sciences. His main research activities include the characterization of the luminescence and scintillation properties of wide band-gap materials and the influence of material defects on them.

This note provides a direct comparison between YAP:Ce{sup 3+} and LuAG:Ce{sup 3+} scintillators grown in the same laboratory as for radioluminescence light output, scintillation decay and thermoluminescence characteristics. A correlation between the occurence of thermo-luminescence (TSL) peaks round RT and of very slow components in the scintillation decay of LuAG:Ce{sup 3+} is revealed. Importance of understanding of the nature of such TSL active trapping states and their removal for further optimisation of LuAG:Ce{sup 3+} scintillator is concluded. (orig.)

We investigate and compare optical absorption, luminescence and scintillation properties of Pr-doped Y3Al5O12, Lu3Al5O12, Y2SiO5 and Lu2SiO5 single crystals. The processes determining the kinetics of the fast Pr3+ 5d–4f radiative transition are described. Among the studied host materials, only Lu3Al5O12 presents neither any 5d1–4f luminescence state nonradiative quenching nor Pr3+ ionization at room temperature. We evaluate the figure of merit of all materials for application as scintillators. The most promising system appears to be Lu3Al5O12 : Pr, since it combines an elevated density of 6.67 g cm−3, a fast scintillation response dominated by a 21 ns decay time and a spectrally corrected light yield about 160% with respect to that of Bi4Ge3O12 (BGO).

We use various techniques to study optical and scintillation properties of Ce-doped yttrium aluminum garnet, Y3Al5O12 (YAG:Ce), in the form of a high-quality industrial single crystal. This was compared to optical ceramics prepared from YAG:Ce nanopowders. We present experimental data in the areas of optical absorption, radioluminescence, scintillation decay, photoelectron yield, thermally stimulated luminescence and radiation-induced absorption. The results point to an interesting feature-the absence of antisite (Y-A1, i.e. Y at the Al site) defects in optical ceramics. The scintillation decay of the ceramics is faster than that of the single crystal, but its photoelectron yield (measured with I lts integration time) is about 30-40% lower. Apart from the photoelectron yield value the YAG:Ce optical ceramic is fully comparable to a high quality industrial YAG:Ce single crystal and can become a competitive scintillator material. (C) 2006 Elsevier B.V. All rights reserved.

The study of impurity related defect states in pure and Sc-doped lutetium aluminum garnet Lu3Al5O12 (LuAG) has been performed by the electron spin resonance (ESR) method. A presence of both Yb3+ and Mo5+ impurity ions, incorporated into the crystals from the Lu2O3 oxide and Mo crucible during the growth process, was revealed. It was found that Yb3+ ions substitute for Lu3+ at their regular sites and Mo3+ ions substitute for Al3+ at regular octahedral sites. Concentration of Mo3+ increases by a factor of 10 in the Sc-containing crystals. (c) 2006 Elsevier B.V. All rights reserved.

We investigated Czochralski-grown YAG:Pr single crystal as a potential novel scintillator. Optical characteristics including photoluminescence, radioluminescence, scintillation decay, radiation damage and thermoluminescence were measured. Their dependence on the dopant concentration was studied. The radiation damage results show that with increasing concentration of Pr the radiation damage reduces. Thermoluminescence above room temperature shows the dominant glow curve peak around 250 °C. Comparing to YAG:Ce scintillator an advantage of YAG:Pr is its much faster scintillation decay (16-17 ns at room temperature) and an absence of slow components in the decay. Therefore YAG:Pr appears as potentially interesting scintillator material. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Point defects acting as trap levels were investigated on undoped, Ce- and (Ce, Si)-doped Y 3 Al 5 O 12 (YAG) crystals by TSL measurements performed over a wide temperature range (10– 800 K ). Below room temperature, a composite glow curve was observed, whose intensity strongly increased after Ce doping. Moreover, Ce doping introduced new trap levels giving rise to glow peaks in the 100– 200 K range. On the other hand, Si co-doping did not influence the low T glow curve in a significant way. The spectral emission of the TSL was found to be governed by the Ce 3+ 5d–4f radiative transition, while defect related higher energy emission bands were detected only in the undoped crystal. Above RT, the glow curve was found to be much more influenced by Si co-doping since a strong increase of a glow peak at about 250°C was noticed. Scintillation time decays of Ce- and Ce,Si-doped samples are also reported and compared with TSL data. The significance of the results and the potential impact of defect states on the scintillation properties are discussed.

Scintillation properties like photoelectron yield and light yield of Ce3+-doped YAlO3 and mixed Lux(RE)1−xAlO3 (RE=Y3+ and Gd3+) perovskite crystals are presented. The photoelectron yields increase almost linearly with γ-ray energy but a small non-linearity is observed around 40 keV. Scintillation and spectroscopic properties like UV or X-ray excited emission, laser excited emission, excitation and absorption spectra and photo- and scintillation decay of the different crystals are compared. The influence of intrinsic absorption and reflecting tape on the yields are discussed. Selected YAlO3:Ce showed the highest light yield of 25,000 phels/MeV and an energy resolution of 4.5% for 662 keV γ-radiation. The γ-ray linear absorption coefficient increases with Lu content and that of LuAlO3:Ce is almost 10 times higher than that of YAlO3:Ce.

Various methods of crystal growth of Ce 3+ -doped Lu x (RE 3+ ) 1− x AlO 3 heavy and fast perovskite scintillators (Lu x (RE 3+ ) 1− x AP:Ce) are described and discussed (Czochralski, EFG and Bridgman–Stockbarger ones). Structural, spectroscopic and scintillation properties of these crystals are reviewed. Possible use and applications of these scintillators for hybrid photodetectors and γ-camera medical imaging are shortly discussed.

Photo- and thermo-luminescence techniques are applied to several kinds of single crystal complex oxide scintillators to reveal tunnelling-driven radiative recombination processes. The tunnelling mechanism provides the physical ground to interpret the observed luminescence and scintillation characteristics which could not be explained by classical radiative recombination schemes.