Dielectric and Electromechanical Properties of Zr-Doped BNT-ST Lead-Free Piezoelectric Ceramics

Piezoelectric ceramics 0.72(Bi_0.5Na_0.5)Ti_(1−x)Zr_xO₃-0.28SrTiO₃ (BNTZ-ST) with x = 0.00, 0.01, 0.02 and 0.03 were produced using a solid solution reaction procedure. Results from the X-ray diffraction (XRD) analysis showed the presence of a perovskite structure with cubic symmetry for all samples. Surface analysis was completed using field emission scanning electron microscopy (FE-SEM), and the grain size was found to decrease slightly with increasing Zr doping. The grain morphology was primarily rectangular, but morphed into a rounder shape with increases in Zr. In a dielectric constant study, the depolarization temperature was found to decrease with increasing Zr⁺⁴ content and increasing frequency. The strain was found to be 0.34% for the undoped samples with an equivalent dynamic strain (S_max/E_max) of 618 pm/V, without negative strain. However, the strain decreased slightly and hysteresis loops become slim and more symmetric, attaining a relaxor ferroelectric behavior with increasing Zr content.