Dielectric, ferroelectric and field-induced strain response of lead-free (Fe, Sb)-modified (Bi0.5Na0.5)0.935Ba0.065TiO3 ceramics

Lead-free piezoelectric ceramics (Bi0.5Na0.5)0.935Ba0.065Ti1−x(Fe0.5Sb0.5)xO3 (BNBT6.5–xFS, x=0.005, 0.010, 0.015, 0.020) were prepared by a conventional solid sintering technique. The effects of B-site doping of (Fe, Sb) on the phase structure, microstructure, dielectric, ferroelectric, and piezoelectric properties of BNBT6.5 ceramics were systematically investigated. Results showed that (Fe, Sb) can completely diffuse in the BNBT6.5 lattice in the all studied components. The addition of (Fe, Sb) destroyed the ferroelectric long-range order, and thus promoted the electric field induced strain response. The maximum electric field-induced strain (Smax=0.37%) with normalized strain (d33*=Smax/Emax=454 pm/V) at an applied electric field of 80 kV/cm was obtained at x=0.015. Temperature dependent measurements of both polarization and strain from room temperature to 120 °C suggested that the origin of the large strain is due to a reversible field-induced ergodic relaxor to ferroelectric phase transformation.