Large electrostrictive coefficient with high electro‐strain dominated by modified ergodic state in BNT‐based solid solutions

Abstract

For ferroelectric electrostrictors, shifting their Curie temperature T C to the ambient temperature is an effective way to enhance their electrostrictive effect. However, the enhanced electrostrictive coefficient Q 33 in this way is often accompanied with an inferior electro-strain. In this work, by introducing CaZrO 3 /BaZrO 3 as the special kind of solid solution, with an effective regulation on the ergodic state, we simultaneously realize a larger room-temperature electrostrictive coefficient Q 33 (~0.04337 m 4 /C 2) with a superior electro-strain (~0.41%) in Bi 0.5 Na 0.5 TiO 3-based relaxor ferroelectric ceramics. The ions substitution with larger radius in either A-site or B-site of perovskite structure tends to facilitate the evolution from ferroelectric tetragonal phase P4mm to relaxor tetragonal phase P4bm along with the decrease in polarity in crystal, thereby shifting the transition temperature T F-R below room temperature. As a result of the effective regulation on the ergodic state, a large electro-strain with low hysteresis, just like electrostrictors, is successfully realized in BNT-based ferroelectric ceramics. Our investigation provides an effective way to simultaneously enhance the electrostrictive coefficient Q 33 and electro-strain for practical applications in precisely controlled displacement.

Temperature‐independent large strain with small hysteresis in Sb‐modified BNT‐based lead‐free ceramics

“…According to previous studies, γ = 1 and γ = 2 represent the normal ferroelectric state relaxor state, respectively. 41 Considering the errors during the linear fitting, the diffuseness exponent (γ) values in all the studied samples are greater than 1.8, further confirming the relaxor feature of BNKT-xSb ceramics system. In addition, from Figure 4A-D, it is obvious that the dielectric peak (T m ) is suppressed with the doping of Sb and is flattened for a higher Sb concentration.…”

“…According to previous studies, for ferroelectrics sharing the perovskite structure, the formation of a dielectric plateau in a wide temperature range should be attributed to the cooccupation of various ions at the A-site and B-site. 41 Furthermore, it is noticed that the T F-R decreases from 64°C to 40°C as the content of Sb increases from 0 to 0.0075. However, no T F-R was observed for x ≥ 0.02, indicating that T F-R lies below the room temperature.…”

Enhanced strains by flexible nanoscale domain structure in BNKT-SBT relaxor ferroelectrics

“…The asymmetric bipolar strain is frequently observed in BNT-based ceramics. 3,11,39 This asymmetry was attributed to the existence of an internal bias field due to the charged defects. During sintering, volatile cations lead to the formation of these defects.…”

Decoding the Atomic-Scale Structural Origin of Large Strain Performance in BNT-6BT Based Relaxor Ferroelectrics

“…The bipolar S−E curves show an asymmetry shape, and the asymmetry strain is frequently observed in BNT-based ceramics. 13,37,38 The asymmetry strain curve is attributed to the existence of internal bias field result from charge defect. 38 And this kind of defects seem to promote the reversibility of domain switching, resulting in a large recoverable strain.…”