Perovskite Na_0.5Bi_0.5TiO₃: a potential family of peculiar lead-free electrostrictors

Abstract

For perovskite ferroelectric oxides, the composition-induced transition from ferroelectrics to relaxors can enhance their electrostrictive coefficient Q33 remarkably, and has been attracting more and more attention in recent years.

Multifunctional barium titanate ceramics via chemical modification tuning phase structure

“…The highest Q 33 of ~0.02 m 4 /C 2 for lead‐based ceramics is much inferior to the lead‐free counterparts on the whole. Through chemical modification, lead‐free ST‐, BFO‐, KNN‐, BNT‐, and NN‐based ceramics can achieve the optimized Q 33 up to 0.02, 0.029, 0.034, 0.02‐0.047, and 0.04‐0.046 m 4 /C 2 , respectively 124‐131 . Pure BT exhibits strong electrostrictive effect with a high Q 33 of ~0.035 m 4 /C 2 , 124 and its Q 33 can be improved to ~0.04 to 0.055 m 4 /C 2 via chemical modification.…”

Domain‐scale imaging to dispel the clouds over the thermal depolarization of Bi0.5Na0.5TiO3‐based relaxor ferroelectrics

“…Temperature-dependent relative dielectric permittivity (ε r ) and loss tangent (tan δ) of (C, D) non-poled and (E, F) poled samples measured at 100, 1 k, 10 k, and 100 kHz, where D and F are the expanded part of C and E becomes predominant, leading to the sharp decline in tan δ when T > 100°C. 11,12 Compared with the variation trend in Figure 2D, we can say that the phase instability (decreasing R3c) should be responsible for the degenerated piezoresponses of the incipient domains. Figure 3A presents the temperature-dependent evolution of bulk domain after the local poling treatment, and the profile of domain exhibits an obvious change as the temperature crosses the T d region (see the broken domains at 100°C).…”

“…Variations of the dielectric loss factor tan δ can be tightly correlated with that of the phase instability, and the coexistence of tetragonal P 4 bm ( a 0 a 0 c + in‐phase tilting) and a − rhombohedral R 3 c ( a − a − anti‐phase tilting) at a certain ratio leads to the high level of tan δ observed in the range of 25°C ≤ T ≤ 100°C . With the further increase in operating temperature, P 4 bm gradually becomes predominant, leading to the sharp decline in tan δ when T > 100°C . Compared with the variation trend in Figure D, we can say that the phase instability (decreasing R 3 c ) should be responsible for the degenerated piezoresponses of the incipient domains.…”

“…For a better understanding about the relationship between the temperature‐dependent piezoresponses of the incipient topological domains and temperature‐induced evolutions of dielectric signal provided in Figure F, three characteristic parameters, including the piezoresponses under small (amplitude signal from the incipient domain derived from the peak marked in Figure C) and large (amplitude signal and coercive voltage derived from the switching spectroscopy provided in Figure B) driving voltage, are then extracted to depict the picture shown in Figure D. Variations of the dielectric loss factor tan δ can be tightly correlated with that of the phase instability, and the coexistence of tetragonal P 4 bm ( a 0 a 0 c + in‐phase tilting) and a − rhombohedral R 3 c ( a − a − anti‐phase tilting) at a certain ratio leads to the high level of tan δ observed in the range of 25°C ≤ T ≤ 100°C . With the further increase in operating temperature, P 4 bm gradually becomes predominant, leading to the sharp decline in tan δ when T > 100°C .…”

“…Variations of the dielectric loss factor tan δ can be tightly correlated with that of the phase instability, and the coexistence of tetragonal P4bm (a 0 a 0 c + inphase tilting) and a − rhombohedral R3c (a − a − anti-phase tilting) at a certain ratio leads to the high level of tan δ observed in the range of 25°C ≤ T ≤ 100°C. 11,12 With the further increase in operating temperature, P4bm gradually F I G U R E 1 General information of prepared BNKT samples. A, 3D 3 μm × 3 μm surface domain image (upside, the phase contrast is integrated into the amplitude information) and XRD pattern (downside) of unpoled BNKT sample.…”