Effect of Bi(Zn0.5Ti0.5)O-3 substitution on structural and electromechanical properties of Bi-0.5(Na0.78K0.22)(0.5)TiO3 lead-free piezoelectric ceramics

Innovative (1 - x)(Bi-0.5(Na0.78K0.22)(0.5)TiO3)-xBi(Zn0.5Ti0.5)O-3 lead free piezoelectric ceramics ((1 - x) BNKT - xBZT, x = 0 - 0.100) were synthesized by the broadly used solid state reaction method. The outcome of BZT count into the BNKT ceramics was examined by X-ray diffraction (XRD), temperature, field dependent structure, microstructure, dielectric and ferroelectric characterization, and electric field-induced strain. The XRD data revealed that all the synthesized samples have perovskite phase, also a phase transition from tetragonal to pseudocubic phase is observed at x = 0.040. The temperature dependent dielectric study showed that as the BZT content increased, the transition point TF-R decreased and eventually disappeared at higher concentration of BZT(x = 0.040 - 0.100). The field emission scanning electronmicroscope (FESEM) images confirmed an increase in the average grain size of BNKT with increasing BZT content. The polarization and strain hysteresis loops showed that the ferroelectric order of the BNKT ceramics were remarkably disturbed by the addition of BZT, which results in degradation of the remnant polarization and coercive field. Though, the disruption of the ferroelectric order is escorted by a substantial improvement in the unipolar strain which peaks at x = 0.040 with a worth of similar to 0.36%, which resembles to a normalized strain, d(33)(=S-max/E-max) of 654 pm V-1. The results showed that the composition (x = 0.040) maintain high value of normalized strain (>= 500 pm V-1) at temperature around (110 degrees C), suggested that the material is a good candidate for actuator applications working in this temperature range.