Nanoscale origins of small hysteresis and remnant strain in Bi0.5Na0.5TiO3-based lead-free ceramics

BiAlO3-doped Bi0.5Na0.5TiO3-Bi0..5K0.5TiO3 (BA-doped BNT-BICT) ceramics are greatly concerned due to their sufficient electric-field-induced strain with small hysteresis and remnant strain for high precision positioning devices and other actuators. In this paper, the structural analysis especially the high resolution transmission electron microscope (HRTEM) is used to reveal the origin of excellent properties obtained in 0.96(0.75BNT-0.25B1(T)-0.04BA, which exhibits a large strain of 0.21% at similar to 70 kV/cm, a small strain hysteresis of only 24% and a near-zero remnant strain. Using HRTEM, the antiferroelectric nano domains composited by three variants of in-phase a(0) a(0)c(+) octahedral tilting coexisted with the remnant ferroelectric nano-domains of anti-phase a center dot a center dot a center dot octahedral tilting are directly identified. Then a continuous tilting model is proposed to interpret the gradually transitional tilting involving nano-domains leading to the small hysteresis and near-zero remnant strain. The findings may pave a way for further optimizing the properties through creating stable antiferroelectric nano-domains in BNT-based ceramics and the analogues. (C) 2017 Elsevier Ltd. All rights reserved.