Luminescence and energy transfer processes in (Lu,Tb)3Al5O12 single crystalline films doped with Ce3+

The luminescence properties of terbium lutetium aluminium garnet single crystalline films, Lu3−xTbxAl5O12, doped with Ce3+ are investigated as a function of the Tb/Lu ratio with aim of an improved understanding of the energy transfer processes between Ce3+ and Tb3+ ions in the aluminium garnet hosts. Due to replacing the smaller Lu3+ ion with the larger Tb3+ ion, the crystal field splitting for the 5d energy levels of Ce3+ ions increases, causing the shift of the lowest 5d state of Ce3+ below the 5D4 energy level of Tb3+. This allows for the efficient energy transfer from Tb3+ to Ce3+ even at the low temperatures. The measurements of temperature dependence of the decay time of Tb3+ and Ce3+ luminescence confirm an efficient energy transfer from Tb3+ to Ce3+ and provide a qualitative understanding of this process. Furthermore, bi-directional energy transfer processes between Ce3+ and Tb3+ are revealed. Scintillation decays under α-particles excitation show presence of the fast and slow sub-microsecond components.