Lattice dynamics and antiferroelectricity in PbZrO$_3$ tested by X-ray and Brillouin light scattering

TL;DR

This study investigates the lattice dynamics and antiferroelectric behavior of PbZrO$_3$ using X-ray and Brillouin scattering, revealing anisotropic phonon dispersion, softening of specific modes, and intrinsic ferroelectric instability.

Contribution

It provides a comprehensive analysis of phonon behavior and mode coupling in PbZrO$_3$, highlighting the role of intrinsic ferroelectric soft modes in its phase transition.

Findings

Anisotropic dispersion of TA phonons observed.

Pronounced softening of in-plane polarized TA phonons in [1 1 0] direction.

Structural transition driven by intrinsic ferroelectric soft mode.

Abstract

We report the results of comprehensive study of the critical dynamics of the prototype perovskite antiferroelectric PbZrO$_3$. The combination of inelastic X-ray and diffuse X-ray scattering techniques and Brillouin light scattering was used. It is found that the dispersion of the TA phonons is strongly anisotropic. The dispersion curve of the in-plane polarized TA phonons propagating in [1 1 0] direction demonstrates pronounced softening. Slowing down of the excitations at R-point is found, it is manifested in growing of the central peak. This slowing down is too weak to be considered as a primary origin of the corresponding order parameter. Obtained results are treated in terms of TA--TO flexoelectric mode coupling. It is demonstrated that the structural phase transformation in PbZrO$_3$ can be considered as the result of the only intrinsic instability associated with the ferroelectric soft mode.