Field-induced large strain in lead-free 0.99[(1-x) Bi0.5(Na0.80K0.20)0.5TiO3--xSiFeO3]-0.01(K0.5Na0.5)NbO3 piezoelectric ceramics

Lead-free 0.99[(1-x) Bi-0.5(Na0.80K0.20)(0.5)TiO3-xBiFeO(3)]-0.01(K0.5Na0.5)NbO3 (BNKT20-100xBF-1KNN) piezoelectric ceramics were fabricated through conventional techniques. Results showed that changes in BF content of BNKT20-100xBF-1KNN 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 large strain of 0.39% at the electric-field of 80 kV/cm (corresponding to a large signal d33* of 488 pm/V) was obtained at x=0.06, which originated from the composition proximity to the ferroelectric-relaxor phase boundary. 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. (C) 2016 Published by Elsevier Ltd.