Morphotropic phase boundary and electrical properties in (1−x)Bi0.5Na0.5TiO3−xBi(Zn0.5Ti0.5)O3 lead-free piezoceramics

Abstract

͑1−x͒Bi 0.5 Na 0.5 TiO 3 − xBi͑Zn 0.5 Ti 0.5 ͒O 3 ͓͑1−x͒BNT− xBZT, x = 0, 0.025, 0.0375, 0.050, and 0.075͔ lead-free piezoceramics were prepared and their structures and electrical properties were investigated. It is found that BZT can increase the Curie temperature of BNT. A morphotropic phase boundary ͑MPB͒ separating rhombohedral and tetragonal phases exists near x = 0.0375. As the result, the MPB composition shows improved electrical properties; the saturated polarization, remnant polarization, and coercive field are 42.0 C / cm 2 , 36.5 C / cm 2 , and 3.5 kV/mm, respectively, while the piezoelectric coefficient, planar electromechanical coupling factor, and unipolar strain are 92 pC/N, 0.22, and 0.08%, respectively. The structures and electrical properties are discussed by comparing with that of other BNT-based piezoceramics. Our results do not only supplement for BNT-based lead-free piezoceramics, but also may provide a way to develop new lead-free piezoceramics with high Curie temperature.

A new Na0.5Bi0.5TiO3 based lead-free piezoelectric system with calculated end-member Bi(Zn0.5Zr0.5)O3

“…Thus, the value of BZZ content in (1-x)NBT-xBZZ at phase boundary composition is expected to be lower than 0.0375, the corresponding BZT addition in NBT-BZT lead-free system. 13 Also, the difference in calculated and experimental values of BZT is reasonable and our calculated values are consistent with other theoretical studies, 10,11 suggesting the accuracy of our calculation method. Anisotropic peak broadening model 21 was also used in for the full-profile fitting of rhombohedral phase where peaks are broader.…”

“…12,23 This is attributed to the low content of BZZ in our system. 13 Meanwhile, both the ε r value at Curie temperature and the depolarization temperature (T d as indicated by arrow in Fig. 4(b)) trend to decrease with increasing x, which suggests the phase boundary belongs to the MPB(II) between rhombohedral and pseudo-cubic phases rather than typical MPB(I) between rhombohedral and tetragonal phases 7 .…”

“…[8][9][10][11] Although pure BZT can only be synthesized under high pressure, many studies have demonstrated that BZTcontaining solid solutions can be stable in ambient pressure and show improved ferroelectric properties. [12][13][14] However, all these theoretical works are based on the fact that Bi(Zn 0.5 Ti 0.5 )O 3 has been experimentally proven to exist. 15 It is unclear that the theoretical prediction and phase boundary construction can still work without the existing experimental foundations.…”

“…Superstructure peaks marked with asterisk were observed for the x = 0 to 0.02 patterns, indicating the presence of R3c phase 13. A careful examination of the XRD patterns at 2θ = 48 o reveals a phase boundary at around x = 0.03 and thus, patterns at x = 0 was refined with rhombohedral symmetry belonging to R3c space group.…”

Semiconductor/relaxor 0–3 type composites without thermal depolarization in Bi0.5Na0.5TiO3-based lead-free piezoceramics

“…First, there are two sets of grains corresponding to BNT-6BT and ZnO, respectively. We suggest that there is limited cation diffusion between BNT-6BT and ZnO, since the solution limit is very low 24,25 . Some Zn ions have entered into the lattice as the sintering is enhanced and the grain size becomes larger with increasing ZnO content ( Supplementary Fig.…”