Relaxor effect on electric field induced large strain in (1−x)(Bi0.5Na0.5)TiO3–xBaTiO3 lead-free piezoceramics

Structures, strain, polarization, and dielectric permittivity of lead-free piezoceramics (1−x)(Bi0.5Na0.5)TiO3–xBaTiO3 for x=0.03, 0.07, and 0.11 (abbreviated as BNB3T, BNB7T, and BNB11T) have been investigated systematically as functions of electric (E) field and temperature. The results revealed that the piezoelectric behavior was significantly influenced by the domain configuration which depends on composition, E field, and lattice structure. The E-field induced strain in BNB7T composition can reach Smax/Emax=475 pm/V, which is comparable with the soft Pb(Zr,Ti)O3 (PZT) piezoceramics. The large field-induced strain is likely originated from the development of the nano-polar regions (or clusters) with sizes of ~5–10 nm, which could reduce the energy barriers of dipole reorientation (or switching) under E-field application.