Insight into the dynamics of low temperature dielectric relaxation of ordinary perovskite ferroelectrics

Abstract

The temperature dependence of the dielectric response of ordinary ferroelectric materials exhibits a frequency-independent anomalous peak as a manifestation of the ferroelectric to paraelectric phase transition. A second anomaly in the permittivity has been reported in different ferroelectric perovskite-type systems at low temperatures, often at cryogenic temperatures. This anomaly manifests as a frequency-dependent local maximum, which exhibits similar characteristics to that observed in relaxor ferroelectrics around their phase transition. The origin of this unexpected behavior is still controversial. In order to clarify this phenomenon, a model-free route solution is developed in this work. Our findings reveal the same critical linear pattern/glass-like freezing behavior previously observed for glass-forming systems. Contrary to current thought, our results suggest that a critical-like dynamic parameterization could provide a more appropriate solution than the conventional Vogel-Fulcher-Tammann equation. The implemented methodology may open a new pathway for analyzing relaxation phenomena in other functional materials like relaxor ferroics.

The generalized Vogel-Fulcher-Tamman equation for describing the dynamics of relaxor ferroelectrics

“…This methodology is helpful in systems where their dynamic relaxation achieve a SA pattern described by:as is the case of SCL and RF systems. MFR has been recently extended for studying the low-temperature dielectric relaxations of normal ferroelectrics 31 , but this approach has never applied before to study the dynamic of RF.…”

Unfolding kinetic fragility in relaxor ferroelectrics

“…The parameters τ 0 and ∆E 0 define the relaxation time and activation energy at high temperatures, respectively, 𝑛𝑛 is a local order parameter and 𝑇𝑇 𝑁𝑁 is the divergence (freezing) temperature. 12,31,32 Noted that considering 𝑇𝑇 𝑟𝑟 = 𝑇𝑇 𝑔𝑔 and 𝑛𝑛 = 1 the classical equation of the VFT-fragility is reproduced. As shown in Eq.…”

Evidence for a dynamics crossover and its implication on the freezing temperature determination of relaxor ferroelectrics

“…This procedure was first successfully applied to a wide experimental data-set, ranging from low molecular weight liquids and polymers to liquid crystals and plastic crystals [26,27]. Furthermore, the procedure was recently applied to the study of the low-temperature di electric relaxations of ordinary ferroelectrics, and demonstrated the effectiveness of this approach for revealing changes in the dynamic behavior of these systems [28].…”