Low driving field and large strain in Bi0.5Na0.5TiO3-based relaxor/ferroelectric composite ceramics

Bi_0.5Na_0.5TiO₃-based ceramics are a promising lead-free alternative to lead-based counterparts due to large electro-strain. However, high driving electric fields required to trigger the giant strain hinder practical applications. Constructing 2–2 relaxor/ferroelectric composites is an effective and process-simplified method to decrease the driving field. Herein, flat and dense BNKT-0.01Ta/xBNKT 2–2 composite ceramics are fabricated by the solid state reaction, and the variations of driving field and electro-strain with the addition of BNKT layer are investigated systematically. The optimal performance (i.e., high electro-strain & low driving field) is obtained when x = 10 wt%. Under a low electric field of 40 kV/cm, a relatively high electro-strain (∼0.33 %) and a large d₃₃* (S_max/E_max=843 pm/V) are obtained. Moreover, the electro-strain of composites shows benign temperature stability within 25–105 ℃. Our work not only provides a simple and efficient method for fabricating 2–2 relaxor/ferroelectric composites but also gives formulations that enable large electro-strain under low driving fields.