Phase transition of chemically doped uniaxial relaxor ferroelectric

TL;DR

This neutron scattering study investigates the ferroelectric phase transition in Ce-doped SBN-61, revealing anisotropic diffuse scattering and domain wall behavior without evidence of a soft phonon, and compares it to pure SBN-61.

Contribution

The study provides new insights into the microscopic scattering mechanisms in Ce-doped SBN-61 during phase transition, highlighting similarities with pure SBN-61.

Findings

Diffuse scattering correlates with dielectric susceptibility.

Elastic scattering indicates ferroelectric domain walls.

No significant change in scattering properties due to Ce doping.

Abstract

We report a neutron scattering study of the ferroelectric phase transition in Sr$_{0.585}$Ce$_{0.025}$Ba$_{0.39}$Nb$_2$O$_6$ (SBN-61:Ce). We find no evidence for a soft transverse optic phonon. We do, however, observe anisotropic diffuse scattering. This scattering has inelastic and elastic contributions. In the paraelectric phase the susceptibility associated with the elastic diffuse scattering follows well the anomaly of the dielectric susceptibility of SBN-61:Ce. In the ferroelectric phase the lineshape of the elastic scattering is consistent with the form expected for the ferroelectric domain walls. In contrast to the macroscopic observations, the scattering properties of Ce-doped crystal do not exhibit important changes with respect to those of pure Sr$_{0.61}$Ba$_{0.39}$Nb$_2$O$_6$.