Luminescence and scintillation properties of Gd3(Al5-xScx)O12:Ce garnet crystals grown by floating zone method

The luminescence and scintillation properties of Ce3+-doped Gd3(Al5-xScx)O12 (x = 1, 1.5, 2, 2.5, 3) garnet crystals grown by the floating zone method were investigated. With increasing Sc content, the Ce3+ 5d1 → 4f luminescence was blue shifted due to a decrease in 5d1-5d2 crystal field splitting (Δ12) of the 5de doublet state. The Sc content showed a strong influence on purity of garnet phase in the Gd3(Al5-xScx)O12:Ce crystals. The presence of secondary phase (perovskite and/or α-Al2O3) results to a poor transparency and a lower light yield (LY) value. The Gd3Al3Sc2O12:Ce crystal exhibited pure garnet phase, highest quantum yield (∼76 %) and transmittance (∼80 %), and highest LY value (6,850 photons/MeV at 662 keV γ rays) among the studied samples. Above RT, a decrease of radioluminescence (RL) yield occurs for all samples due to the thermal ionization process. A decrease of the RL yield at low temperature observed in correlation with the intense thermoluminescence peaks can be explained by the localization of electrons at intrinsic shallow traps.