Switching of morphotropic phase boundary and large electrostrictive effect in lead-free BNT-BKT-KNN ceramics

We report the phase diagram of the lead-free ternary (Bi0.5Na0.5)TiO3-(Bi0.5K0.5)TiO3-(K0.5Na0.5)NbO3 (BNT-BKT-KNN) system and study the switching characteristics of the morphotropic phase boundary (MPB). The addition of KNN intrinsically changes the structural nature of the system with shift of MPB type from (I) to (II), and also adjusts the depolarization temperature (Td) to room temperature. Accordingly, a high electrostrictive response with large electrostrictive coefficient Q33 (∝0.022-0.027 m4/C2) and a good thermostability comparable with that of traditional Pb-based electrostrictors was achieved in MPB (II) compositions. (copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)