Large strain improvement of lead-free (1−x) Bi_0.5Na_0.42K_0.08Zr_0.02Ti_0.98O₃–xBa(Nb_0.5Fe_0.5)O₃ piezoelectric ceramics

In the past decade, great focus has been devoted to the possibility of employing electric fields to induce extremely large strains in Pb-free materials. In the present investigation, lead-free 1−x(Bi_0.5Na_0.42K_0.08)Zr_0.02Ti_0.98O₃–xBa(Nb_0.5Fe_0.5)O₃ or (1−x)BNKZTO–xBNFO ceramics where x = 0, 0.005, 0.010, or 0.015 were prepared via a solid-state reaction. An enhanced strain was achieved by doping a suitable amount of BNFO into BNKZTO, resulting in phase formation and microstructural changes that affect electrical properties, such as dielectric, ferroelectric, and electric field-induced strain (S‒E) behavior. X-ray diffraction analysis revealed both rhombohedral (R) and tetragonal (T) phases in all of the analyzed ceramic samples. The (1–x)BNKZTO-xBNFO binary system ceramics show remarkable strain coefficients at ambient temperature, exhibiting a maximum strain of 0.42% when given an electric field of 60 kV/cm and a normalized strain coefficient (d^*₃₃ = S_max/E_max = 700 pm/V).