Dipolar defect complexes in single-crystal PbWO4

Abstract

We have previously demonstrated the presence of the defects complex ［2(La3 + Pb)·-V″Pb］in La-doped lead tungs tate (PWO). That earl ier experimental technique was supplemented with x-ray photoelectron, visible ab sorption and infrared absorption spectroscopies in the present investigation on PWO crystals doped with 3+, 4+ or 5+ cations, or co-doped with 3+ and 5+ impurit ies. Useful information has been deduced on dopant lattice sites, dipolar defect s complexes, their relation with materials properties, and their transformation during annealing. Some of the deductions have also been corroborated with comput er simulation. The present work argues against the conception that impedance spe ctroscopy cannot provide definite conclusions on defect structures in ionic soli ds.