Multisite structure of PbWO(4):Eu(3+) crystals investigated by site-selective laser-excitation spectroscopy

Defect structures of Eu(3+)-doped PbWO(4) crystals are investigated by site-selective laser-excitation spectroscopy. The excitation spectrum of the (7)F(0) --> (5)D(0) transition shows a strong dependence on Eu(3+)-concentration in PbWO(4) crystals. Only one substitution site for Eu(3+) is identified in the PbWO(4):Eu(3+) (0.01 at.%) crystal, while at least six inequivalent sites are observed in the PbWO(4):Eu(3+) (0.05 and 0.5 at.%) crystals. The charge compensation mechanisms for the observed sites are discussed in relation with annealing effects and temperature-dependent decay curves. The dominant site for Eu(3+) in the PbWO(4) lattice seems to be due to a formation of Eu(Pb)(3+)-V(Pb)'' dipole by charge compensation. The minor sites for Eu(3+) are attributable to the Eu(Pb)(3+)-O(i)'' dipole, a site perturbed by Eu(Pb)(3+*)-V(Pb)'' dipole, and a clustering of Eu(3+) in the PbWO(4) lattice. The energy transfer and site distribution of Eu(3+) are discussed in PbWO(4):Eu(3+) (0.01, 0.05, and 0.5 at.%).