Observation of dipole complexes in PbWO4:La3+ single crystals

Abstract

The frequency dependence of dielectric loss factor (tan δ) in undoped and La-doped PbWO4 crystals has been investigated over a frequency range from 10 Hz to 10 MHz and a temperature range from 40 to 370 °C. A typical dielectric relaxation phenomenon in PbWO4:La3+ has been observed. Experimental results indicate that there exist intrinsic mobile defects in pure PbWO4 crystals and lead vacancies are the predominant mobile defects. In La-doped PbWO4 crystals, La3+ ions may be located at the Pb2+ sites and combine with lead vacancies to form the dipole complexes [2(LaPb3+)•−VPb″], which may be the origin of the dielectric relaxation phenomenon in PbWO4:La3+ crystals.