Dynamics of the ferroelectric transition and acentricity in PbHPO₄

Abstract

A Raman spectroscopy study has shown no evidence for a large structural acentricity in the paraelectric phase of PbHPO₄ (LHP) and that the crystal growth conditions are not a major factor in determining the phase transition properties of LHP. It is also found that the spectral response in the region of the central-mode frequency is well fitted by a single Debye relaxation function, indicating that a relaxational soft mode triggers the order-disorder type phase transition, which is probably due to polarization fluctuations of distorted PO₄ tetrahedra.