[Paper Review] Dynamic behavior of polar nanoregions in re-entrant relaxor 0.6Bi(Mg1/2Ti1/2)O3-0.4PbTiO3

Kaiyuan Chen, Zhang, Qi+10 more|arXiv (Cornell University)|Sep 11, 2020

Ferroelectric and Piezoelectric Materials4 citations

TL;DR

This study investigates the dynamic behavior of polar nanoregions (PNRs) in the re-entrant relaxor 0.6Bi(Mg1/2Ti1/2)O3-0.4PbTiO3 using dielectric spectroscopy and electrical modulus analysis. It identifies two distinct PNR states associated with low-temperature re-entrant relaxor transition and high-temperature diffuse phase transition, revealing three critical temperatures linked to PNR formation, freezing, and phase transition, with bismuth stoichiometry playing a key role in tuning PNR dynamics.

ABSTRACT

The existence of polar nanoregions is the most important characteristic of ferroelectric relaxors, however, the size determination and dynamic of PNRs remains uncertain. We reveal a re-entrant relaxor behavior and ferroelectric-paraelectric transition coexists in complex perovskite oxide 0.6Bi(Mg1/2Ti1/2)O3-0.4PbTiO3. Two dielectric anomalies (i) the low-temperature re-entrant relaxor transition and (ii) the high-temperature diffuse phase transition (DPT) were described by the phenomenological statistical model. The sizes of the two kinds of polar nanoregions (PNRs) corresponding to two ferroelectric states were obtained. The dynamic of PNRs were analyzed using isothermal electrical modulus, which shows three critical temperatures associated with the diffuse phase transition, the formation and freezing of PNRs, respectively. The temperature evolution of the PNRs evolution depends on the stoichiometry of bismuth. The results provide new insights into the dynamic behavior of PNRs and the modification way of re-entrant relaxor behavior.

Motivation & Objective

• To understand the dynamic behavior of polar nanoregions (PNRs) in complex perovskite relaxors, particularly in 0.6Bi(Mg1/2Ti1/2)O3-0.4PbTiO3.
• To resolve the uncertainty in PNR size determination and dynamic evolution in re-entrant relaxor systems.
• To investigate the coexistence of re-entrant relaxor behavior and ferroelectric-paraelectric transition in complex oxides.
• To identify the role of bismuth stoichiometry in modulating PNR formation and freezing dynamics.

Proposed method

• Dielectric spectroscopy was used to detect two distinct dielectric anomalies: a low-temperature re-entrant relaxor transition and a high-temperature diffuse phase transition (DPT).
• A phenomenological statistical model was applied to describe the two dielectric anomalies and extract the size of PNRs corresponding to each ferroelectric state.
• Isothermal electrical modulus spectroscopy was employed to analyze the dynamic processes of PNRs, identifying characteristic relaxation times and critical temperatures.
• Temperature-dependent evolution of PNRs was correlated with bismuth content to assess its influence on PNR formation and freezing.

Experimental results

Research questions

• RQ1 What are the dynamic characteristics of polar nanoregions (PNRs) in the re-entrant relaxor 0.6Bi(Mg1/2Ti1/2)O3-0.4PbTiO3?
• RQ2 How do the sizes and evolution of PNRs differ between the low-temperature re-entrant relaxor state and the high-temperature diffuse phase transition state?
• RQ3 What are the critical temperatures associated with PNR formation, freezing, and phase transition in this system?
• RQ4 How does bismuth stoichiometry influence the dynamic behavior of PNRs in this complex perovskite oxide?

Key findings

• Two distinct PNR states were identified, corresponding to the low-temperature re-entrant relaxor transition and the high-temperature diffuse phase transition (DPT).
• The sizes of the two PNRs were quantitatively determined using a phenomenological statistical model applied to dielectric data.
• Three critical temperatures were identified via isothermal electrical modulus analysis: one associated with the diffuse phase transition, one with PNR formation, and one with PNR freezing.
• The temperature evolution of PNRs is strongly dependent on the stoichiometry of bismuth in the material.
• The coexistence of re-entrant relaxor behavior and ferroelectric-paraelectric transition was confirmed in 0.6Bi(Mg1/2Ti1/2)O3-0.4PbTiO3.
• The results provide new insights into the tuning of PNR dynamics through compositional control, particularly via bismuth content.