Defects in UV‐irradiated PbWO 4 : Mo crystals monitored by TSL measurements

The origin of the centres responsible for the green emission, the processes of their excited-state disintegration, and the origin of defects created by UV radiation were studied for PbWO4 crystals with different Mo6+ concentrations, as well as for the Y3+ and Nb5+ co-doped PbWO4:Mo. After the selective UV irradiation, TSL appeared to be due to the recombination of defects formed after the exciton and defect-related state disintegration. The TSL intensity versus irradiation energy (3.4–4.3 eV) and irradiation temperature (80–180 K) were measured. For the exciton state disintegration, the activation energy was Ea ≅ 0.1 eV, while for the defect states disintegration Ea = 0.03–0.36 eV. At T < 130 K, temperature-independent defect creation processes were observed in some crystals. Defects of different origins exist in PbWO4:Mo crystals, and different defects can coexist in the same sample. Free electron release into the conduction band and also charge transfer processes can contribute to photo-thermally stimulated defects creation.