Lead‐vacancy‐related hole centers in lead tungstate crystals

Abstract

After UV irradiation of PbWO4 crystals at T > 140 K in the energy range around 4.05 eV, besides the thermally stimulated luminescence (TSL) peak at ≈193 K arising from electron {Pb+ − VO} centers, a TSL peak at about 225 K appears. We suggest that this ≈225 K TSL peak arises from the thermal destruction of non‐paramagnetic hole centers of the {VPb + 2h}‐type (two holes trapped at the oxygen ions in the vicinity of a single lead vacancy VPb). The recombination of thermally or optically released electrons with these hole centers at T > 140 K is accompanied with green G(II) emission peaking at about 2.5 eV. The processes of photo‐thermally stimulated creation of VPb‐related hole centers have been studied.

Electron and hole traps in X-ray irradiated Y2 SiO5 and Lu2 SiO5 crystals

“…One can notice that, like in the case of YSO, the hole‐related 347 K peak is characterized by a smaller E t value (0.8 eV) and relatively small frequency factor f 0 (≈6 × 10 9 s −1 ) as compared with the nearest electron‐related 354 K peak ( E t ≈ 0.96 eV, f 0 ≈ 9 × 10 11 s −1 ). Similar difference in the parameters of the electron and hole traps was observed, e.g., in lead tungstate , MgO:Be , etc.…”

Luminescence and photo‐thermally stimulated defect‐creation processes in Bi3+‐doped single crystals of lead tungstate

“…The positions of the TSL peaks at 188 and 225 K and their thermal stability parameters are similar to those obtained for the paramagnetic O − (I)‐type hole centers (a hole trapped at an oxygen ion located close to an Y 3+ or La 3+ ion associated with a lead vacancy V Pb ) and non‐paramagnetic {2O − – V Pb } centers (two holes trapped at two oxygen ions located close to a lead vacancy V Pb ), respectively. As it will be shown in Section 3.3.2, the peak at 188 K arises most probably from the {2O − –Bi 3+ }‐type paramagnetic hole center.…”

“…In the undoped PbWO 4 crystals and in the PbWO 4 crystals doped with Mo 6+ or/and trivalent rare‐earth ions, these processes have been studied in detail in our previous work (see, e.g., Refs. ) under irradiation in the band‐to‐band, exciton, and defect‐related absorption regions. A comparison of the results obtained in the present work with the data reported before allows us to explain the peculiarities of PbWO 4 :Bi crystals and to separate the Bi‐related defects from intrinsic defects in PbWO 4 .…”

Luminescence and photo-thermally stimulated defect creation processes in PbWO4 :Mo,La,Y (PWO III) crystals

“…No TSL glow curve peak ascribed in Ref. to the non‐paramagnetic single lead vacancy related hole centers of the type of {2O − – V Pb } is observed in this crystal.…”

“…The origin of these peaks is not clear. No evidence of the oxygen‐vacancy related electron centers of the type of {Pb + − V O }, responsible for the TSL peak at about 195 K with the value of E t ≈ 0.56 eV (see Table ), is observed.…”