Mechanism of Th4+, Zr4+ doping in PbWO4 crystals

To check the doping mechanism of trivalent ion doping in PbWO4 (PWO) and verify the formation of dipoles [2MPb3+–VPb], the researches on an investigation of tetravalent ion (Th4+, Zr4+) doped PWO was conducted by dielectric loss spectroscopy, thermoluminescence and optical absorption spectroscopy. The doping mechanism of tetravalent ion doping is similar to that of trivalent ion doping, while the dipole defects should be formed more easily due to the convenience for the two defects VPb and MPb4+ to get close to each other. However, in the case of Zr4+ doping, Zr was found to enter interstitial sites because of its small ionic radius, with the introduced charges compensated by VPb far away and hence does not exert an obvious influence on the performance of this material. Thus, no dielectric relaxation was found in the DS (dielectric spectra) experiment.