Large electric-field-induced strain in SrZrO3 modified Bi0.5(Na0.80K0.20)0.5TiO3 lead-free electromechanical ceramics with fatigue-resistant behavior

The effect of SrZrO3 (SZ) addition on the ferroelectric behavior and piezoelectric properties of Bi-0.5(Na0.80K0.20)(0.5)TiO3 (BNKT20) lead-free piezoceramics were investigated. Results showed that BNKT20-xSZ samples underwent a phase transition from ferroelectric rhombohedral and tetragonal phases to relaxor pseudocubic phase with increasing SZ content, and such transition are accompanied with the significant disruption of ferroelectric order and the shift of the ferroelectric-relaxor transition temperature TF-R down to room temperature. Accordingly, it induced an enhancement of the field-induced strain with a peak at a value of similar to 0.39% (at 80 kV/cm, corresponding to a large signal d*33 of similar to 488 pm/V) obtained in 1.5 mol% SZ-modified samples. Temperature dependent measurements of both polarization and strain suggest that the origin of the large strain is due to a reversible field-induced ergodic relaxor to ferroelectric phase transformation. Moreover, an attractive property for application as actuators was obtained in this system, as BNKT20 modified with 1.5 mol% SZ exhibits fatigue-free behavior up to 10(6) cycles. This exceptionally good fatigue resistance is identified due to the presence of an ergodic relaxor state. (C) 2015 Elsevier B.V. All rights reserved.