Abstract
Lead‐free (1 − x)(Bi~0.5~(Na~0.85~K~0.15~)~0.5~TiO~3~)‐x__BiAlO~3~ (abbreviated as BNKT15‐BA, x = 0, 0.025, 0.050, 0.075, 0.100) piezoelectric ceramics were synthesized by a conventional solid‐state reaction method. The phase‐transition behavior in BNKT15‐BA ceramics with respect to changes in composition were investigated using X‐ray diffraction analysis, dielectric and ferroelectric characterizations, and electric‐field‐induced strain. The results of X‐ray diffraction revealed that a pure perovskite phase was formed for x ≤ 0.050. A phase transition from the coexistence of rhombohedral and tetragonal to a pseudocubic phase was observed at x = 0.050. The dielectric constant continuously decreased with increasing BA content, and the depolarization temperature (T~d~) was shifted towards lower temperature. The polarization and strain hysteresis loops indicate that the ferroelectric order of BNKT15 ceramics is disrupted significantly with the addition of BA. The destabilization of ferroelectric order is accompanied by an enhancement of bipolar and unipolar strains, and a large electric‐field‐induced strain (S = 0.21%) and a normalized strain ($d_{33}^{*} $= S__~max~/E~max~ = 276 pm/V) were obtained at x = 0.050. These results suggested that the BNKT15‐BA system can be employed in lead‐free electromechanical devices.