Large electrostrain and structural evolution in (1-x)[0.94Bi0.5Na0.5TiO3-0.06BaTiO3]-xAgNbO3 ceramics

A lead-free system formulated as (1-x)[0.94Bi(0.5)Na(0.5)TiO(3)-0.06BaTiO(3)]-xAgNbO(3) exhibits an electrostrain of 0.50% at 80 kV/cm and a maximum d(33)(*) of 721 pm/V at 60 kV/cm for x = 0.3. The incorporation of AgNbO3 shifts the relaxor-ferroelectric phase transformation temperature (TF-R) to room temperature and lowers the energy barrier of the field-induced phase transformation. Furthermore, the in-situ electric field dependent high-energy synchrotron X-ray diffraction (SXRD) technique reveals that the sample x = 0.03 transforms from dominant P4bm phase to a phase mixture of R3c + P4mm at 55 kV/cm during the electric field loading, and returns to initial dominant P4bm phase at 15 kV/cm during the unloading cycle of the electric field. Furthermore, it can be demonstrated that the electric field induced-phase transition in NBTBT-3AN occurs in the whole sample, rather than in the single direction of electric field. Therefore, the electrocstrain in NBTBT-3AN is more uniform, which would be beneficial to its actuator applications.