Luminescence of undoped LuAG and YAG crystals

Emission and excitation spectra and decay kinetics are studied for the luminescence of undoped LuAG and YAG crystals. Two emission bands are located at 4.8 eV and 3.95 eV in YAG and 4.9 eV and 3.65 eV in LuAG, excited in the Eexc>6.5 eV energy region. They are both characterized by a relatively slow (µs) decay time, and ascribed to the transitions from two different configurations of an exciton localized near an antisite defect (Y3+Al or Lu3+Al). The corresponding excitation band, peaking at 6.9 eV in YAG and 7.2 eV in LuAG, is ascribed to the exciton perturbed by the antisite defect. Besides the two slow emissions, the weak fast (ns) emission of the self-trapped exciton, strongly overlapping with the high-energy emission band, is also observed. In Ce3+-doped garnets, the presence of the antisite defects results in a considerable decrease of energy transfer efficiency from the host lattice to Ce3+ ions. The possibilities of improvement of scintillation charactristics of this material are discussed. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)