Scintillation yield and temperature dependence of radioluminescence of (Lu,Gd)3Al5O12:Ce garnet crystals

Abstract

The scintillation characteristics of Lu3-xGdxAl5O12:Ce (x = 1, 1.25, 1.75, 2, and 2.25) garnet crystals were investigated. With increasing Gd content, the Ce3+ 5d1 → 4f luminescence band was red-shifted due to an increase in the crystal field splitting of the 5d levels. In addition, both the light yield value and contribution of fast scintillation component increased. We attribute this effect to the reduced electron trapping effects of shallow traps buried in the bottom of the conduction band, the lower-energy shift of which is due to the increasing Gd content. A decrease of scintillation yield at the lowest temperature region observed for all samples, showing large thermoluminescence peaks in the same temperature range, can be caused by the localization of electrons at shallow traps. Afterglow signals observed at 10 K for all samples after X-rays irradiation can be explained by quantum tunneling of electrons from nearby traps towards the holes captured at the Ce3+ recombination centers.