Effect of $Li^+$ ions co-doping on luminescence, scintillation properties and defects characteristics of LuAG:Ce ceramics

Monovalent $Li^+$ codoped $Lu_3Al_5O_{12}$:Ce (LuAG:Ce) optical ceramics were fabricated by solid state reaction method and further optimized by an air-annealing process. Optical absorption, radioluminescence spectra and scintillation properties such as light yield, scintillation decay times and afterglow were measured and compared with those of the $Li^+$ free LuAG:Ce ceramic and the commercial LuAG:Ce single crystal samples. Positive effect of $Li^+$ codopant consists mainly in the significant increase of scintillation light yield, acceleration of scintillation decay as well as the decrease of afterglow intensity. With 0.3% Li codoping, the obtained LuAG:Ce,Li ceramic displays a light yield of ∼29200 ph/MeV at 10 μs shaping time, higher than that of the LuAG:Ce single crystal and optical ceramic scintillators ever reported. The partial conversion of the stable $Ce^{3+}$ to $Ce^{4+}$ centers and the shallow and deep traps effect suppression by the $Li^+$ codoping are discussed.