Some Y3+-doped PbWO4 crystals grown by using the modified Bridgman method exhibited an exceptional behaviour; an increase in light yield after low dose-rate irradiation and an improvement in the optical transmission at around 430nm. A study was made here of the influence of high-temperature annealing in an O-rich atmosphere upon the stability of scintillation properties and radiation hardness of Y3+-doped PbWO4. The results showed that annealing in O enhanced the absorption band at around 430nm and made optical transmission unstable at this wavelength after irradiation. After high-temperature annealing, the radiation-induced absorption coefficient was also negative at around 430nm. The 430nm absorption band introduced by high-temperature annealing in O had the same characteristics as the pre-existing bands in as-grown Y3+-doped PbWO4 crystals. So it decreased the stability of scintillation properties and radiation hardness of Y3+-doped PbWO4 crystals. The radiation instability was related to the formation of interstitial O ions (Oi”) during high-temperature annealing. The results revealed that the O-rich atmosphere during the crystal growth and annealing was the cause of the exceptional irradiation behaviour of Y3+-doped PbWO4 crystals.

The Origin of Radiation Instability in Yttrium-Ion Doped Lead Tungstate Crystals. X.Zhang, J.