Effect of oxidation annealing on optical properties of YAG:Ce single crystals

YAG:Ce single crystals were annealed in air atmosphere at different temperatures. Their optical properties, such as optical absorption, cathodoluminescence spectra, cathodoluminescence decay and thermoluminescence were studied. Growth of UV absorption with increasing annealing temperature is explained by ionization of Ce3+ ions during the oxidation annealing and consequent ligand-to-metal charge transfer to the Ce4+ ions. Near-UV luminescence emission caused by presence of the antisite defects is undesirable for fast scintillation applications. After oxidation annealing, the emission related to the antisite defects is partially quenched due to the spectral overlap of the charge transfer absorption and the antisite defects emission. Together with suppression of electron traps due to the oxidation annealing, the described mechanism effectively decreases luminescence afterglow and improves YAG:Ce scintillation characteristics.