IMF2017

Using Raman scattering spectroscopy, the sequence of phase transitions in antiferroelectric PbHfO₃ modified with Sn ions was investigated in the temperature range from 80-830K. The frequencies of the Raman lines were analyzed and discussed in terms of the sequence of structural phase transitions. The modifications of the Raman spectra were observed in details in the vicinity of structural phase transitions: AFE1-AFE2-IM-PE phase transition. The Raman measurements were supplemented by dielectric and DSC measurements. Light scattering and dielectric investigations were concentrated in PHS in order to explain the nature and sequence of the phase transition, as well as the large dielectric permittivity values measured at the phase transition, by searching for the soft-phonon-mode behavior. In the scenario developed recently for analogous antiferroelectric-PbZrO₃-there exists at once three relevant, strongly softening lattice modes however direct observation of the soft optic mode by Raman spectroscopy failed in pure PbZrO₃. In PbZr_0.72Sn_0.28O₃ enhanced polar fluctuations above Tc lead to the appearance of two soft optic modes that were experimentally observed in paraelectric phase. Here we tested the influence of Sn ions on the dynamics of phase transitions in PbHfO₃. It is demonstrated that the structural phase transformations in PbHf_1-xSn_xO₃ can also be considered as the result of softening of many modes, not only the ferroelectric one.