Large E-field induced strain and polar evolution in lead-free Zr-doped 92.5%(Bi0.5Na0.5)TiO3–7.5%BaTiO3 ceramics

Structure, dielectric permittivity, strain, electric (E) polarization, and piezoelectric responses of (Bi1/2Na1/2)0.925Ba0.075(Ti1−xZrx)O3 (BNT7.5BT-100xZr; x = 0–0.04) ceramics were investigated as functions of poling E field and temperature. The BNT7.5BT ceramic reveals a phase transition from P4bm nanodomains to long-range-ordered P4mm domains. The Zr-doped BNT7.5BT ceramic reveals a reversible change of unit cell with dynamically fluctuating polar nanoregions, which are responsible for the large strain. The poled BNT7.5BT ceramic displays a depolarization temperature of Td = 90 °C, which correspond to a phase transition from ferroelectric to relaxor states. The Zr-doped BNT7.5BT ceramics have Burns temperatures (TB) in the region of 400–435 °C, below which polar nanoregions begin to develop. The Zr-doped BNT7.5BT ceramics display wide diffuse phase transitions, suggesting a transition from R + T to T phases. BNT7.5BT-2Zr ceramic shows a temperature dependent linear large strain of 0.482% at 150 °C and can be a potential candidate for lead-free actuator.