Effect of annealing on luminescence properties of the undoped and rare earth doped lead tungstate crystals

摘要

The paper reports results of comparable spectral investigation of thermal treatment effects on luminescent properties of the undoped and rare earth doped lead tungstate crystals. Annealing at 950 ℃ leads to pronounced changes in the emission and excitation spectra of the undoped PbWO_4 crystals whereas observed effect of annealing on the spectra of the RE-doped crystals is weak. Decrease of the relative contribution of blue luminescence emission band and changes at the sharp long wavelength edge of the excitation spectra are the most distinctive results of annealing on the spectra of the undoped crystals. Observed changes can be explained by manifestations of two exciton transitions in the corresponded spectra. Two types of exciton luminescence bands arise from the lattice regions with different defects of the crystal structure (e.g., with vacancies in the anion or cation sublattices). Adding of the RE ions decreases content of vacancies in the PWO crystal lattice and improves in such a way thermal stability of spectral properties of the blue luminescence of these crystals.