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

Abstract

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.