Luminescence and scintillation properties of Gd₃Sc₂(Al_3-xGa_x)O₁₂:Ce (x = 1, 2, 3) garnet crystals

The luminescence and scintillation characteristics of Ce³⁺ - doped Gd₃Sc₂(Al_3-xGa_x)O₁₂ (x = 1, 2, 3) garnet crystals were investigated. The Ce³⁺ luminescence was blue-shifted with increasing Ga content due to the decrease of the crystal field strength. A decrease of Ce³⁺ luminescence intensity and luminescence decay time at high temperature was observed for all samples due to thermal ionization of the Ce³⁺ 5d₁ excited levels. With increasing Ga content the decrease of thermal activation energies, determined from temperature dependence of decay times, was obtained. Both Gd₃Sc₂Al₂GaO₁₂:Ce and Gd₃Sc₂AlGa₂O₁₂:Ce samples exhibited a comparable light yield (LY) value of 24,000 photons/MeV while the latter sample showed faster scintillation decay time of 12 ns (11%) + 56 ns (89%) with respect to those of 55 ns (28%) + 105 ns (72%) for the former sample. An acceleration of scintillation decay time with an expense of LY value was also obtained for the Mg²⁺-codoped sample. At low temperature a decrease of scintillation yield was observed in correlation with the intense thermoluminescence peaks, attributing to the localization of electrons at intrinsic shallow traps.