In this lecture, two main goals have been shown: first, the state-of-art of the inorganic scintillator materials used for many important applications and, secondly, the illustration of the dynamics of this field by giving spectroscopic and scintillation properties of the most advanced oxide scintillator Ce3+, Mg2+-co-doped Gd3Al2Ga3O12 (GAGG) garnet host, grown by using both the micro-pulling-down (μ-PD) and the Czochralski methods at the Tohoku University, Sendai. The adopted strategy for optimization of garnet scintillator composition in both, the defect engineering and band gap engineering of this research program gives us the opportunity to discuss on the role of Ce4+ ion which has always been a challenge for Ce3+-doped luminescent crystals. By analogy with the approach used for commercial Ce3+, Mg2+-co-doped-doped orthosilicates as Lu2SiO5 (LSO) and (Lu1−xYx)2SiO5 (LYSO), we confirm the creation of stable Ce4+ oxidation state and we evaluate the Ce3+/Ce4+ ratio of concentrations in Ce3+, Mg2+-co-doped Gd3Al2Ga3O12 (GAGG) garnet by XANES spectroscopy analysed at the Ce LIII threshold of the European Synchrotron Radiation Facility (ESRF) in Grenoble.KeywordsFast scintillatorCe3+ and Ce4+ dopantsGarnet crystalsOptical spectroscopyXANES spectroscopy

In this paper we present the relationships between structural and spectroscopic investigations of neodymium ion dopant (Nd3+) in selected oxide host lattices with particular highlighting its role as a structural probe. The main goal is to get precious information about the symmetry and activator’s environment in the following different oxide host lattices like cubic Lu2O3 sesquioxide and molybdate compounds of tetragonal scheelite-type CdMoO4, monoclinic/cubic La2Mo2O9 (LAMOX) as well as cubic Y6MoO12, we met during research of new transparent ceramics. This choice gives us the opportunity to point out the usefulness of two techniques: the low-temperature high-resolution techniques applied to the 4I9/2 → 2P1/2 (around 432 nm) and 4I9/2 → 4F3/2 (around 875 nm) absorption transitions at 4.2 K and site-selective tuneable laser spectroscopy with OPO and Ti:Sapphire laser sources, applied to the 4F3/2 → 4I9/2 (around 900 nm) and 4F3/2 → 4I11/2 (around 1064 nm) emission transitions at 77 K. We hope that the results presented at the School will help the students to know how important is the role played by Nd3+ dopant not only as laser ion in near the infrared spectral region but also as structural probe for host lattices.KeywordsNd3+ ionOxide host latticesTransparent ceramicsStructural probeOptical materials