Research on Efficient Fast Scintillators: Evidence and X-Ray Absorption Near Edge Spectroscopy Characterization of Ce4+ in Ce3+, Mg2+-Co-Doped Gd3Al2Ga3O12 Garnet Crystal

Herein, the most advanced oxide scintillator Ce3+, Mg2+-co-doped Gd3Al2Ga3O12 (GAGG) garnet host, grown using the Czochralski method is reported. The charge transfer absorption band in UV, such as in other Ce3+, Mg2+-co-doped oxides, reveals the creation of stable Ce4+ oxidation state, in addition to the usual Ce3+ one, admitted as responsible of the scintillation mechanism improvement displayed by this garnet. Strangely, the confirmation of quantitative values of Ce4+ concentration has never been done, and the goal is mainly focused on the presence of Ce4+ and the evaluation of the Ce3+/Ce4+ ratio measured by X-ray absorption near edge spectroscopy (XANES) spectroscopy at the Ce L-III threshold of the European Synchrotron Radiation Facility (ESRF). This result is compared with those obtained for Ce3+, Mg2+-co-doped Lu3Al5O12 (LuAG) and, also, in garnets without any Mg2+ ions such as Ce3+-doped GAGG, Ce3+-doped LuAG, and Ce3+-doped YAG. The role of Li+ ion in place of Mg2+ one is also considered in Ce3+, Li+-co-doped LuAG single crystal.