Field-induced large strain in lead-free 0.99[(1− x ) Bi 0.5 (Na 0.80 K 0.20 ) 0.5 TiO 3 – x BiFeO 3 ]–0.01(K 0.5 Na 0.5 )NbO 3 piezoelectric ceramics

Abstract Lead-free 0.99[(1− x ) Bi 0.5 (Na 0.80 K 0.20 ) 0.5 TiO 3 – x BiFeO 3 ]–0.01(K 0.5 Na 0.5 )NbO 3 (BNKT20–100 x BF–1KNN) piezoelectric ceramics were fabricated through conventional techniques. Results showed that changes in BF content of BNKT20–100 x BF–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 T F-R to room temperature. A large strain of 0.39% at the electric-field of 80 kV/cm (corresponding to a large signal d 33 * 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 10 6 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.