90-degree domain wall relaxation and frequency dependence of the coercive field in the ferroelectric switching process

TL;DR

This study investigates how 90-degree domain wall relaxation affects the frequency dependence of the coercive field in ferroelectric PZT ceramics, revealing defect influences and a frequency limit for switching behavior.

Contribution

It demonstrates the impact of defects and fatigue on domain switching dynamics and introduces a viscous medium model for domain reorientation in ferroelectric materials.

Findings

Strong relaxation of 90° domain walls at 100 Hz

Defect type and distribution influence switching dynamics

Identification of an upper frequency limit for coercive field changes

Abstract

The mechanisms involved in the polarization switching process in soft and hard Pb(Zr53, Ti47)O3 (PZT) bulk ceramics were investigated through the dependency of the hysteresis loop on the frequency. In order to determine the influence of the defects on the domain switching dynamics the samples were characterized in the virgin state and after a fatigue or a depinning process. The frequency dependence of the polarization revealed a strong relaxation of the 90 domain walls at 100 Hz. The results also revealed a strong influence of the kind of defect and their distribution into the ferroelectric matrix on the domain switching dynamics, which reflected in the frequency dependence of the coercive field and the percentage of the backswitching. Initially, it was observed that the frequency dependence of the coercive field for the soft and the hard PZT in the virgin state had just one rate of change per decade in all frequency range investigated, which is the standard behavior found in the literature. However, after the fatigue or the depinning process two rates of changes were noticed. Consequently, an evidence of an upper frequency limit for the coercive field changes was found. The percentage of the backswitching and its behavior for the soft PZT was almost independent of the fatigue state in all frequency range investigated. Nevertheless, for the hard PZT an opposite behavior was verified. The reorientation of the domains was modeled as occurring in a viscous medium where several forces such as viscous and restoring forces act on them.