Luminescence and energy transfer processes in Ce3+ activated (Gd, Tb)3Al5O12 single crystalline films

The luminescence and scintillation properties of gadolinium terbium aluminium garnet single crystalline films, Gd3-xTbxAl5O12, doped with Ce3+ are investigated as a function of the Gd/Tb ratio with the aim of an improved understanding of the energy transfer processes between Ce3+ and Tb3+ ions in the aluminium garnet hosts. Upon replacing the Gd3+ by Tb3+, the crystal field splitting for the 5d energy level of Ce3+ does not change significantly, due to comparable sizes of the Gd3+ and Tb3+ cations. Temperature dependence of the decay time of Tb3+ and Ce3+ luminescence confirms an efficient energy transfer from the Tb3+ to Ce3+ and provides a qualitative understanding of this process. Furthermore, bidirectional energy transfer processes between the Ce3+ and Tb3+ are revealed. Scintillation decays under alpha-particles excitation show the presence of the fast and slow sub-microsecond components.