Abstract
Ce-doped tetracationic garnets (Gd, M)3Al2Ga3O12(M = Y, Lu) form a family of new multipurpose promising scintillation materials. The aim of this work was to evaluate the scintillation yield in the materials of quaternary garnets activated by cerium ions with partial isovalent substitution of the matrix-forming gadolinium ions by yttrium or lutetium ions.Materials were obtained in the form of polycrystalline ceramic samples, and the best results were shown by samples obtained from the raw materials produced by the coprecipitation method. It was found that ceramics obtained from coprecipitated raw materials ensure a uniform distribution of activator ions in the multi-cationic matrices, which enables the high light yield and fast scintillation kinetics of the scintillation. It was demonstrated that the superstoichiometric content of lutetium/gadolinium in the material is an effective method to suppress phosphorescence accompanied scintillation. For ceramics with the composition (Gd, Lu)3Al2Ga3O12 , a scintillation yield of more than 50.000 ph/MeV was achieved. The scintillation kinetics was measured to be close to the kinetics with a decay constant of 50 ns.In terms of the set of the parameters, the developed scintillation materials are close to the recently developed alkali halide materials LaBr3:Ce, GdBr3:Ce. Moreover, they have high mechanical hardness, are characterized by the absence of hygroscopicity, and are better adapted to the manufacture of pixel detectors used in modern devices for medical diagnostics.
Highlights
Exploiting the disordered crystalline compounds is found to be a promising approach for imparting new features to crystalline compounds
An incorporation of Lu ions into the lattice leads to an increase in the role of scintillation creation mechanisms due to interaction with self-trapped states in the lattice: auto-localized holes (ALH) and auto-localized excitons (ALE)
In contrast to the yttrium ion, lutetium has a high nucleus charge, higher than that of gadolinium; the formation of photoelectrons when interacting with gamma-quanta occurs mainly on electronic shells of lutetium ions
Summary
Exploiting the disordered crystalline compounds is found to be a promising approach for imparting new features to crystalline compounds. A relatively simple type of disorder is introduced into the crystal due to isomorphic or isovalent substitutions of cations in the matrix The advantage of this approach to improve the scintillation properties of crystalline materials based on oxides doped with Ce ions was demonstrated almost two decades ago [3,4,5,6,7]. The use of Lu in the garnet matrix creates some technological problems, the main of which are: creation of defect-centers due to the possible localization of small Lu3+ ions in oxygen octahedra [14,15,16] in the garnet matrices This creates cation vacancies in the dodecahedral positions of lutetium ion localization, and, gives a rise to the formation of traps of nonequilibrium carriers, which cause the phosphorescence of the material
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