Nature of polar state in 0.67BiFeO3–0.33BaTiO3

Yongxing Wei,Chenxing Bai,Changqing Jin,Weitong Zhu,Ye Tian,Zhonghua Dai,Gang Xu,Jiahao Shen

doi:10.1007/s10854-020-04462-9

Abstract

This study was conducted to understand the nature of the polar state in the morphotropic phase boundary composition 0.67BiFeO3–0.33BaTiO3 (0.67BF–0.33BT). Both the unpoled and poled specimens exhibit an average cubic structure. The poling induces a 0.14% increase in the lattice parameter. Macrodomains are absent both in the initial and polar state of 0.67BF–0.33BT. A typical relaxor-type dielectric anomaly was observed (Tf = ~ 627 K, TB = ~ 820 K). The remnant polarization (Pr), maximum value of electrostrain (Sm), and magnitude strain at Ec in the bipolar mode (Sneg) increase clearly during heating (Pr, ~ 40 µC/cm2; Sm, 0.191% under 40 kV/cm at 453 K). Unlike Bi0.5Na0.5TiO3-based nonergodic relaxors, the first-cycle bipolar electrostrain loops indicate that the minimum strain on the negative side of the bipolar strain curves is negative. Furthermore, the slopes of the relative permittivity versus log frequency plots in unpoled (− 21) and poled (− 23) specimens are similar. The transition between the relaxor state and ferroelectric-like state does not involve a clear dielectric anomaly even in the poled specimen.

Highlights

BiFeO3–BaTiO3 (BF–BT), first reported by Ismailzade et al in 1981 [1], aroused great interest because of its multiferroic properties in the initial stage [2,3,4]
Analyses based on the Rietveld refinement of X–ray diffraction (XRD) patterns, bright-field images and selected-area electron diffractions (SAED) demonstrate that the formation of the long-range ferroelectric domains is difficult under the poling field
The studies by Wei et al and Yang et al confirmed that the optimum piezoelectric properties were realized in compositions (BaTiO3 content, ~ 30 mol%) near the morphotropic phase boundary (MPB) [6,7,8]

Summary

Introduction

BiFeO3–BaTiO3 (BF–BT), first reported by Ismailzade et al in 1981 [1], aroused great interest because of its multiferroic properties in the initial stage [2,3,4]. The studies by Wei et al and Yang et al confirmed that the optimum piezoelectric properties were realized in compositions (BaTiO3 content, ~ 30 mol%) near the morphotropic phase boundary (MPB) [6,7,8]. If the transition from the nonergodic relaxor state to the ferroelectric state occurs, we could observe its effect on the first-cycle electrostrain loop, domain structure and dielectric properties like Bi0.5Na0.5TiO3-based ceramics [25,26,27,28]. Temperature dependence of dielectric behaviors, polarization responses and electrostrain responses, the initial electrostrain loops and poling effects on the structural and electrical properties of 0.67BF–0.33BT were analyzed to understand its polar state. MnO2 was introduced to reduce the conduction effects on the high-temperature electrical properties [3, 29]

Experimental

Results And Discussion

Conclusions