Deciphering the atomic-scale structural origin for large dynamic electromechanical response in lead-free Bi0.5Na0.5TiO3-based relaxor ferroelectrics

Abstract

Despite the extraordinary electromechanical properties of relaxor ferroelectrics, correlating their properties to underlying atomic-scale structures remains a decisive challenge for these “mess” systems. Here, taking the lead-free relaxor ferroelectric Bi0.5Na0.5TiO3-based system as an example, we decipher the atomic-scale structure and its relationship to the polar structure evolution and large dynamic electromechanical response, using the direct atomic-scale point-by-point correlation analysis. With judicious chemical modification, we demonstrate the increased defect concentration is the main driving force for deviating polarizations with high-angle walls, leading to the increased random field. Meanwhile, the main driving force for deviating polarizations with low-angle walls changes from the anti-phase oxygen octahedral tilting to the multidirectional A-O displacement, leading to the decreased anisotropy field. Benefiting from the competitive and synergetic equilibrium of anisotropic field versus random field, the facilitated polarization rotation and extension versus facilitated domain switching are identified to be responsible for the giant electromechanical response. These observations lay a foundation for understanding the “composition-structure-property” relationships in relaxor ferroelectric systems, guiding the design of functional materials for electromechanical applications.

Influence of temperature-induced A-site cation redistribution on the functional properties of A-site complex polar perovskite K1/2Bi1/2TiO3

“…, Bi-displacement along the 〈111〉 c is suppressed, and associated local structural heterogeneity is decreased. Yin et al 74 using first-principles calculation reported that there is a small energy gap, Δ E ≈ 16.7 meV, between [111] c and [001] c displacement directions of Bi 3+ cation. The more homogeneous distribution or more ordered A-site cation arrangement due to the quenching can be further rationalized from the fact that a significant increase in tetragonal distortion and domain wall density was observed.…”

“…In the case of thermal quenching of KBT from 900 °C, a more homogeneous distribution (less clustering) of Bi 3+ is established as quenching from high temperature did not provide the time necessary to form a signicant degree of the Bi 3+ -rich clusters, i.e., Bidisplacement along the h111i c is suppressed, and associated local structural heterogeneity is decreased. Yin et al 74 using rst-principles calculation reported that there is a small energy gap, DE z 16.7 meV, between [111] quenching can be further rationalized from the fact that a signicant increase in tetragonal distortion and domain wall density was observed. Previous works have reported the relation between increased tetragonal distortion and increased local Asite cation ordering in KBT by PDF analysis and DFT calculation.…”

Piezoelectric Materials and Sensors for Structural Health Monitoring: Fundamental Aspects, Current Status, and Future Perspectives

“…In addition, due to the toxicity of Pb, environmentally benign lead-free piezoelectrics have received intensive attention, such as BaTiO 3 [ 39 , 40 , 41 ], sodium bismuth titanate (BNT) [ 42 , 43 , 44 ], and potassium sodium niobate (KNN) [ 45 , 46 , 47 , 48 , 49 , 50 , 51 , 52 ]. In Figure 2 b, Jong et al demonstrated a BaTiO 3 hybrid film by adopting a simple and facile inkjet-printing process [ 53 ].…”

Enhanced Energy Storage Properties in Lead-Free (Na0.5Bi0.5)0.7Sr0.3TiO3-Based Relaxor Ferroelectric Ceramics through a Cooperative Optimization Strategy

“…Unlike the typical (Na 0.5 Bi 0.5 )­TiO 3 (NBT) matrix with strong FE properties, which is often used to form RFEs, − (Na 0.5 Bi 0.5 ) 0.7 Sr 0.3 TiO 3 (NBST) doped with 30 mol % Sr 2+ ions at the A-site of NBT has been widely studied for its equally large P m of 47.2 μC/cm 2 but lower P r of 8.2 μC/cm 2 . However, the W rec of NBST is too low to meet the application requirements owing to premature polarization saturation, and so much effort has been made to improve its W rec by introducing Bi­(Mg 2/3 Nb 1/3 )­O 3 , Bi­(Ni 0.5 Sn 0.5 )­O 3 , and Sr­(Ti 0.85 Zr 0.15 )­O 3 .…”