Air Atmosphere Annealing Effects on LSO:Ce Crystal

Cerium-doped lutetium oxyorthosilicate Lu₂SiO₅:Ce crystal is a well-known scintillator with an excellent figure-of-merit. In this paper, air annealing was used to further improve its scintillation properties. The samples cut from Czochralski grown Lu₂SiO₅:Ce crystals were annealed in air atmosphere at 1400°C for 10 h. Based on the analysis of the difference in the crystal´s spectra (such as absorption, emission, and thermoluminescence) obtained before and after annealing, we investigate the nature of the observed effects. To investigate the annealing effects on the valence state of cerium ion, synchrotron radiation was used in this work as an energy source to measure the X-ray absorption near edge spectroscopy of cerium ions. It is supposed that annealing in air atmosphere helps to reduce the content of deep traps, which possibly include oxygen vacancy, lower the intensity of afterglow, shorten the decay time of afterglow, and increase the luminescence intensity of Ce2 (6-oxygen-coordinated). However, this may also cause cerium ion to be oxidized to +4 charge state, which may introduce an additional nonradiative trap center, thereby weakening luminescence.