Study on the low-temperature annealing-induced color center in Y3+-doped PbWO4 single crystal

The optical transmittance spectrum of the as-grown Y-doped PbWO4 (PWO:Y) crystal exhibits annealing-induced absorption band peaking at 420 nm at low-temperature range (<400 °C). The annealing-induced 420 nm absorption coefficient gets to maximum at 400 °C and it can be effectively “bleached” by irradiating with UV light. On the other hand, high-temperature (here is 850 °C) treatment strengthens the 420 nm absorption band but exerts little influence on the induced absorption band. Due to the smaller ionic radii of Y3+, the substitution of Y3+ for Pb2+ results in large lattice relaxation, which is confirmed by FT-IR measurements. It is proposed that interstitial yttrium is an alternative doping way in PWO:Y and forms large defect aggregation of [(YPb3+)-2VPb″-Yi3+]. [(YPb3+)-2VPb″-Yi3+] is not stable and hence is considered as the origin of anomaly observed in PWO:Y crystal.