Luminescence characteristics of Pb2+ centres in undoped and Ce3+-doped Lu3Al5O12 single-crystalline films and Pb2+→Ce3+ energy transfer processes

At 4.2-350 K, the steady-state and time-resolved emission and excitation spectra and luminescence decay kinetics were studied under excitation in the 2.5-15 eV energy range for the undoped and Ce3+-doped Lu3Al5O12 (LuAG) single-crystalline films grown by liquid phase epitaxy method from the PbO-based flux. The spectral bands arising from the single Pb2+-based centres were identified. The processes of energy transfer from the host lattice to Pb2+ and Ce3+ ions and from Pb2+ to Ce3+ ions were investigated. Competition between Pb2+ and Ce3+ ions in the processes of energy transfer from the LuAG crystal lattice was evidenced especially in the exciton absorption region. Due to overlap of the 3.61 eV emission band of Pb2+ centres with the 3.6 eV absorption band of Ce3+ centres, an effective nonradiative energy transfer from Pb2+ ions to Ce3+ ions takes place, resulting in the appearance of slower component in the luminescence decay kinetics of Ce3+ centres and decrease of the Ce3+-related luminescence intensity.