Optical, luminescence and scintillation characteristics of non - stoichiometric LuAG:Ce ceramics

Non-stoichiometric Lu 3+x Al 5 O 12 :Ce (Lu 3+x AG:Ce, x =1, 2, 3 and 4 %) ceramics were fabricated by solid state reaction method and further optimized by an air-annealing process. Absorption, luminescence spectra and scintillation characteristics such as light yield, scintillation decay times, energy resolution, proportionality and afterglow were measured and compared with those of the latest LuAG:Ce single crystal and stoichiometric LuAG:Ce,Mg ceramic samples. Thanks to the elimination of oxygen vacancies produced in the vacuum sintering process, air-annealing treatment led to a significant decrease of afterglow and a remarkable enhancement of radioluminescence intensity and light yield. The highest light yield was found in annealed 1% Lu 3+ rich Lu 3+1% AG:Ce ceramic, reaching 14,760 ph/MeV (1 μs shaping time) and 22,400 ph/MeV (10 μs shaping time). Scintillation decays of Lu 3+x AG:Ce ceramics consist of both fast (decay time 65–73 ns) and slow (decay time 740–1116 ns) decay components where the relative intensity of the latter is higher (~58%). A decreasing trend in scintillation efficiency was observed with increasing excess of Lu (with higher x values) in the samples. This can be explained by the existence of various electron traps due to Lu Al antisite defect and structure disorder at the gain boundaries and interfaces.