Large strain response in Bi4Ti3O12 modified BNT-BT piezoelectric ceramics

In this paper, a novel system of lead-free piezoelectric ceramics 0.94(Bi0.5Na0.5)TiO3−0.06BaTiO3-xBi4Ti3O12 (abbreviated as BNT-BT-xBiT) were prepared by the solid-state reaction method. The effects of Bi4Ti3O12 dopant on the strain behavior, dielectric, ferroelectric and piezoelectric performance of BNT-BT ceramics were systematically investigated. A optimal strain value of ~0.37% was achieved around the critical composition of x=6 wt% which corresponds to a normalized strain (Smax/Emax) of 465 pm/V. The large strain response in this sample is mainly originated from two aspects: one is that BiT addition induced ferroelectric-to-relaxor phase transition evidenced by “pinched” ferroelectric hysteresis loops and vanished negative strain of bipolar strain loops as well as downward shift of TF-R; the other is that the small-sized nanodomains (or polar nanoregions) facilitate the domain switching and domain wall motion with an applied electric field, which lead to large external contribution to strain response. These results indicate that BNT-BT-xBiT piezoelectric ceramics with large strain response may be a promising lead-free material for actuator application.