The origin of radiation instability in yttrium-ion-doped lead tungstate crystals

Abstract Some Y3+-doped PbWO4 (PWO:Y3+) crystals grown by the modified Bridgman method showed exceptional behaviours, namely the increase in the light yield after low-dose-rate irradiation and also the improvement in the optical transmission at around 430 nm. In this paper, we studied the influences of high-temperature annealing in an oxygen-rich atmosphere on the stability of scintillation properties and radiation hardness of PWO: Y3+. The results show that annealing in oxygen enhances the absorption band at around 430 nm and makes optical transmission unstable at this wavelength after irradiation. After high-temperature annealing, the radiation-induced absorption coefficient is also negative around 430 nm. The 430 nm absorption band introduced by high-temperature annealing in oxygen has the same characteristics as the pre-existing bands in as-grown PWO: Y3+ crystals. So it decreases the stability of scintillation properties and radiation hardness of PWO: Y3+ crystals. The radiation instability relates to the formation of interstitial oxygen ions (Oi”) during high-temperature annealing. The results reveal that the oxygen-rich atmosphere during the crystal growth and annealing procedure is the origin of the exceptional irradiation behaviours in PWO: Y3+ crystals.