Electric field-induced strain in Sr(Hf0.5Zr0.5)O3-modified Bi0.5(Na0.8K0.2)0.5TiO3 piezoelectric ceramics

Abstract

Lead-free Sr(Hf0.5Zr0.5)O3-modified Bi0.5(Na0.8K0.2)0.5TiO3 (SHZ-BNKT) ceramics were synthesized using a conventional solid-state, mixed-oxide method. In complex solid solutions such as BNKT, the role of a ternary additive is important because it can break up the long-range dipole order, which destabilizes the ferroelectric phase leading to relaxor behavior. In this system, as verified by x-ray diffraction, SHZ was incorporated into the BNKT perovskite lattice throughout the studied compositional range. The coexistence of tetragonal and rhombohedral phase was observed for x = 0.00 and with the addition of SHZ, a transition to pseudocubic symmetry was observed, which is indicative of the onset of relaxor behavior. To characterize the relaxor properties of the material, the polarization–electric field hysteresis, dielectric, and electric-field-induced strain behaviors were studied as a function of composition. The temperature-dependent dielectric spectra showed frequency dependence for all the SHZ-modified BNKT ceramics, which is a typical characteristic of relaxor ferroelectrics. Furthermore, constriction in polarization loops and an absence of negative strain in the bipolar strain measurement for SHZ-modified BNKT compositions confirms that the addition of SHZ significantly disrupts the ferroelectric order. The addition of 2 mol. % SHZ in BNKT markedly enhanced the electric field-induced strain from 0.10% (for pure BNKT) to 0.33% (for 2% SHZ-BNKT). The corresponding normalized strain coefficient (d33∗=Smax/Emax) increased from 196 pm/V to 663 pm/V at a moderate electric field of 50 kV/cm. These results indicate that BNKT–SHZ ceramics can be designed for an improved strain response via a cation substitution-induced relaxor state for electromechanical actuator applications.

Re‐entrant ferroelectric relaxor phenomena in the (1 − x)[Bi1/2(Na1/2K1/2)1/2TiO3]‐xPbZrO3 system

“…This was expected due to the larger ionic radii of Pb 2+ (1.49 Å) and Zr 4+ (0.72 Å) as compared to the average radius of the A‐site cation of BNKT (1.23 Å) and Ti 4+ (0.60 Å). Similar XRD trends have been reported in earlier studies on the BNKT‐BZT, 9 BNKT‐BST, 18 and BNKT‐SHZ 19 systems.…”

Superior energy storage performance in (Bi0.5Na0.5)TiO3-based lead-free relaxor ferroelectrics for dielectric capacitor application via multiscale optimization design

“…Similar I-E behavior has been perceived in numerous BNTrelated systems. [51][52][53] To estimate the full potential of the BNT-BAT-xCT ceramics for energy storage, statistical E b via Weibull distribution tting was carried out, as shown in Fig. 3(b).…”

Improvements in piezoelectric and energy harvesting properties with a slight change in depolarization temperature in modified BNKT ceramics by a simple technique

“…This temperature indicates the start of the polarization process in relaxors. 62 To determine the T B , there are many techniques, such as the refractive index, 62,63 electrostrictive strain, 64 or deviation from the Curie–Weiss behavior. 62 In the present investigation, the T B was collected from the dielectric constant that starts to deviate from the Curie–Weiss law.…”

“…62 To determine the T B , there are many techniques, such as the refractive index, 62,63 electrostrictive strain, 64 or deviation from the Curie–Weiss behavior. 62 In the present investigation, the T B was collected from the dielectric constant that starts to deviate from the Curie–Weiss law. 65 The plot of the inverse dielectric permittivity (1/ ε r ) as a function of temperature at 1 kHz that was used to determine the T B values is shown in the supplementary information in Fig.…”

“…To further confirm the diffuseness of phase transition, the modified Curie–Weiss law is used, which is given in the following equation: 6,62,65,68,69 where γ is the degree of diffuseness, C ′ is Curie-like constant, T m is the temperature of the maximum dielectric constant, ε r is the dielectric constant, and ε m is the maximum dielectric constant at T m . The value of γ can be calculated from the slope of the fitting curves.…”