Trap levels in Y-aluminum garnet scintillating crystals

Point defects acting as trap levels were investigated on undoped, Ce- and (Ce, Si)-doped Y3Al5O12 (YAG) crystals by TSL measurements performed over a wide temperature range (10-800 K). Below room temperature, a composite glow curve was observed, whose intensity strongly increased after Ce doping. Moreover, Ce doping introduced new trap levels giving rise to glow peaks in the 100-200 K range. On the other hand, Si co-doping did not influence the low T glow curve in a significant way. The spectral emission of the TSL was found to be governed by the Ce3+ 5d-4f radiative transition, while defect related higher energy emission bands were detected only in the undoped crystal. Above RT, the glow curve was found to be much more influenced by Si co-doping since a strong increase of a glow peak at about 250°C was noticed. Scintillation time decays of Ce- and Ce,Si-doped samples are also reported and compared with TSL data. The significance of the results and the potential impact of defect states on the scintillation properties are discussed.