Effects of trivalent rare-earth ions on spectral properties of PbWO4 crystals

The pure and trivalent rare-earth ions doped lead tungstate crystals have been grown using Czochralski method. Optical absorption measurements in the wavelength range of 200–800 nm have been carried out on the doped PbWO4 crystals. Trivalent rare-earth ions doping have a threshold effects on the optical absorption band gap of PbWO4 crystals. Compared to that of pure PbWO4, the optical absorption edge of La3+-doped samples at lower in low concentration (50 and 150 ppm), show the shift of to high energy region (short wavelength), while with increasing of La3+ doping, the optical absorption edge shift fast to low energy region (long wavelength). Raman spectra have been investigated in a series of lead tungstate crystals doped with La3+ ions. The data were compared with the results in undoped PbWO4 and a (Mo, F)-doped sample. The dependence of frequency shift on doping was employed to deduce and approve the doping mechanism of rare-earth ions in PbWO4 lattice. The effects of La3+ doping on the photoluminescence spectra were also investigated.