Enhanced electric field induced strain in SrTiO3 modified (K, Na) NbO3-based piezoceramics

Lead-free 0.96K(0.5)Na(0.5)NbO(3)-0.04LiTaO(3) ceramics modified with different amounts of SrTiO3 ( ST) from zero to 10 mol% were prepared by normal sintering. It was found that ST modification changed the crystal structure from orthorhombic to tetragonal and for ceramics with 10 mol% ST, pseudocubic structure was formed which was nonpolar. Investigation of bipolar strain revealed that with increasing ST content to 7.5 mol%, the negative strain decreased. This observation was attributed to the existence of nonpolar regions with local composition close to that of the ceramic containing 10 mol% ST. This phenomenon was accompanied with strain enhancement in unipolar strain curve because of the contribution of strain due to electric field-induced transition from nonpolar to ferroelectric phase, in addition to electric field induced strain. (C) 2014 Elsevier B.V. All rights reserved.