High piezoelectric strain response in lead-free (Bi,Na)TiO₃-based ceramics under the low electric field

Piezoelectric materials interconvert electrical signal and mechanical energy which are widely used in advanced electromechanical devices. Here, we applied a composition strategy to improve piezoelectric strain performance in the Sr and Zr co-doped (Bi, Na)TiO₃-xBaTiO₃ lead-free ceramics. The crystal structure, dielectric, and piezoelectric properties revealed that composition-driven phase transition occurred from the long-rage ferroelectric order to the short-range relaxor state. Hence, at the crossover phase boundary of normal and relaxor ferroelectrics a high piezoelectric strain response of 0.125 % with dynamic piezoelectric constant of 417 pm/V is achieved under a small driving field of 30 kV/cm. This excellent strain at a low electric field is mainly related to the flat free energy profile and reversible field-induced phase transition from the short-range order to the long-range order. More interestingly the 28 % variation over the temperature 25–120 °C and only 31 % strain hysteresis in the (Bi, Na)TiO₃-based ceramics are promising results for the piezoelectric actuators. This work provides the paradigm for the design and development of new lead-free ceramics for piezoelectric device applications.