Giant electrostrain under low driving field in Bi1/2Na1/2TiO3-SrTiO3 ceramics for actuator applications

BiMg1/2Ti1/2O3 (BMT)/NaNbO3 (NN) was introduced into the Bi1/2Na1/2TiO3-SrTiO3 lead-free system to modify its phase structure and electrical properties. The ceramics were prepared by a traditional ceramic processing method. All samples exhibited pure perovskite structure, as well as dense microstructures. The modified compositions underwent a phase transition from a ferroelectric phase to an ergodic relaxor state with increasing BMT/NN content. This transition was identified from the decrease in the ferroelectric-relaxor transition temperature to room temperature. When the composition was located in the vicinity of the critical region, giant electrostrain was obtained owing to the field-induced reversible transition between the relaxor and ferroelectric phases. A schematic phase diagram was constructed based on the measured properties. Excellent actuating performance of s(max)/E-max > 850 pm/V with an ultra-low driving field of E <= 3 kV/mm was achieved in the modified compositions. This performance is comparable to that of the Pb(Zr,Ti)O-3-based counterparts and demonstrates the great potential of the current materials in piezoactuator applications. (C) 2016 Elsevier Ltd and Techna Group S.r.l. All rights reserved.