Field-induced large strain in lead-free (Bi0.5Na0.5)1−xBaxTi0.98 (Fe0.5Ta0.5)0.02O3 piezoelectric ceramics

High-strain lead-free (Bi0.5Na0.5)1−xBaxTi0.98(Fe0.5Ta0.5)0.02O3 (BNBT100x-2FT) piezoelectric ceramics were designed and fabricated through conventional techniques. Results showed that changes in Ba content of BNBT100x-2FT induced transition from the ferroelectric phase to the ergodic relaxor phase. These changes also significantly disrupted long-range ferroelectric order, thereby correspondingly adjusting the ferroelectric-relaxor transition point TF-R to room temperature. A giant strain of 0.40% (corresponding to a large signal d33∗ of 500 pm/V) was obtained at x = 0.06, approaching to that of lead-based materials. High-strain responses of the ceramic composition originated from the composition proximity to the ferroelectric-relaxor phase boundary. This phenomenon led to reversible transformation between the ergodic relaxor phase and the polar ferroelectric phase under cyclic field. Moreover, the high-strain material exhibited exceptional fatigue resistance (up to 106 cycles) as a result of the reversible field-induced phase transition. The proposed material exhibits potential for novel ultra-large stroke and nonlinear actuators that require enhanced cycling reliability.