Recent research in the field of phosphor and scintillator materials and related detectors is reviewed. After a historical introduction the fundamental issues are explained regarding the interaction of x-ray radiation with a solid state. Crucial parameters and characteristics important for the performance of these materials in applications, including the employed measurement methods, are described. Extended description of the materials currently in use or under intense study is given. Scintillation detector configurations are further briefly overviewed and selected applications are mentioned in more detail to provide an illustration.

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Scintillation detectors for x-rays

The synthesis of lanthanide-activated phosphors is pertinent to many emerging applications, ranging from high-resolution luminescence imaging to next-generation volumetric full-color display. In particular, the optical processes governed by the 4f-5d transitions of divalent and trivalent lanthanides have been the key to enabling precisely tuned color emission. The fundamental importance of lanthanide-activated phosphors for the physical and biomedical sciences has led to rapid development of novel synthetic methodologies and relevant tools that allow for probing the dynamics of energy transfer processes. Here, we review recent progress in developing methods for preparing lanthanide-activated phosphors, especially those featuring 4f-5d optical transitions. Particular attention will be devoted to two widely studied dopants, Ce3+ and Eu2+. The nature of the 4f-5d transition is examined by combining phenomenological theories with quantum mechanical calculations. An emphasis is placed on the correlation of hos...

Lanthanide-Activated Phosphors Based on 4f-5d Optical Transitions: Theoretical and Experimental Aspects.

The Ce-doped (LuyGd1–x)3(Gay,Al1–y)5O12 single crystals were grown by the micropulling down method. Their structure and chemical composition were checked by X-ray diffraction (XRD) and electron probe microanalysis (EPMA) techniques. Optical, luminescent, and scintillation characteristics were measured by the methods of time-resolved luminescence spectroscopy, including the light yield and scintillation decay. Balanced Gd and Ga admixture into the Lu3Al5O12 structure provided an excellent scintillator where the effect of shallow traps was suppressed, the spectrally corrected light yield value exceeded 40 000 photons/MeV, and scintillation decay was dominated by a 53 ns decay time value which is close to that of Ce3+ photoluminescence decay. This study provides an excellent example of a combinatorial approach where targeted single-crystal compositions are obtained by a flexible, time saving, and cost-effective crystal growth technique.

Composition Engineering in Cerium-Doped (Lu,Gd)3(Ga,Al)5O12 Single-Crystal Scintillators

Development of LuAG-based scintillator crystals – A review

Ce-doped (YyGd1−y)3(GaxAl1−x)5O12 (x = 0, 1, 2, 3, 4 and y = 1, 2, 3) single crystals are grown by the micro-pulling down method. X-ray diffraction and electron probe microanalysis techniques are employed to check their structure and chemical composition, respectively. Optical and photoluminescence characteristics are measured and radioluminescence spectra, light yield and scintillation decay measurements are further made to evaluate the scintillation performance. We show that balanced Gd and Ga admixture in the Y3Al5O12 structure can considerably increase the scintillation efficiency, and the spectrally corrected light yield value exceeds 44000photonMeV −1 . Scintillation decay times approach that of Ce 3+ photoluminescence decay and an additional less intense slower component is also observed. Physical aspects of energy transfer process and 5d1 excited state depopulation are discussed. The micro-pulling down technique is shown as an ideal tool for a directed combinatorial search for targeted single crystal compositions to reveal those with the highest figure-of-merit for a given application field. (Some figures may appear in colour only in the online journal)

https://iopscience.iop.org/article/10.1088/0022-3727/44/50/505104/pdf

Scintillator-oriented combinatorial search in Ce-doped (Y,Gd) 3 (Ga,Al) 5 O 12 multicomponent garnet compounds

Luminescence and scintillation dynamics can be extensively influenced by the energy transfer processes, which is demonstrated at three selected scintillator materials: PbWO 4 , Ce-doped aluminium garnets and PrF 3 :Ce single crystals. Charge carrier retrapping processes can delay radiative recombination at the luminescence centers in an extended time scale, which makes a substantial part of generated scintillation light technically unexploitable. Correlated measurements based on time-resolved emission spectroscopy and thermoluminescence are of great help to evaluate these phenomena and to understand their microscopic origin.

M. Nikl

Papers

Energy transfer phenomena in the luminescence of wide band‐gap scintillators