Influence of KF substitution on the ferroelectric phase transition of lead titanate single crystals studied by Brillouin light scattering

摘要

The elastic properties of KF-substituted perovskite lead titanate (PbTiO_3) were investigated by dielectric measurements and Brillouin light scattering. The ferroelectric phase transition occurred at substantially lower temperature due to KF substitution, which was attributed to the modification of the covalency in Pb-O and Ti-O bonds. The longitudinal acoustic (LA) mode of KF-substituted PbTiO_3 showed a frequency softening in the paraelectric phase, which was accompanied by increasing acoustic damping. This indicated that polarization fluctuations responsible for the acoustic anomalies were enhanced by KF substitution.