Luminescence spectra of Eu3+ ions and interstitial oxygen in PbWO4 crystal

The site-selective excitation and emission spectroscopy, and luminescence decay have been investigated under a pulsed, tunable, narrowband dye laser of the 5D0→7F0 region in the europium ions-doped lead tungstate PbWO4 (PWO) in single crystal. In as-grown sample, the experimental results show that there is only one 7F0→5D0 excitation transition indicating the only one Eu3+ site in PbWO4 lattices. The sequential annealing treatments were conducted to investigate the effects of oxygen components on the microstructure environments of Eu3+ in the lattices. The site distribution of Eu3+ was changed by the annealing in air atmosphere, which could create new sites in PWO lattices. Confirmation of interstitial oxygen and interpretations of charge compensation mechanism for the observed new sites were discussed in the context of site-selective excitation and emission spectra. The main Eu3+ site is related to the charge compensation by the [(EuPb3+)–V″Pb–(EuPb3+)] complex; the other minor new sites after annealing are originated from [(EuPb3+)–O″i–(EuPb3+)] defects. Emission spectra excited by 355-laser and RT-Raman spectra were also measured.