Multiple stability of electrical properties for oxides-modified (K,Na)NbO3-based ceramics

Abstract

Lead-free potassium sodium niobate (KNN) ceramics have become crucial advanced functional materials with conspicuous performance. Although continuous improvements of electrical properties were achieved via various strategies these years, the poor stability leads to the bottleneck for application. Herein, the stability of electrical properties under different conditions (i. e. electric field, frequency and temperature) were emphasized on in KNN-based ceramics with addition of oxides based on the availability for optimizing properties. With addition of Fe2O3, high ferroelectric, piezoelectric and dielectric properties remain due to the maintained rhombohedral-orthorhombic-tetragonal (R-O-T) phase boundary at room temperature and little changed Curie temperature (TC), while deterioration happens with excess Fe2O3 attributing to the pinning effect from replacement of Fe3+ in crystal lattice. Furthermore, the elevated beginning electric field for stable ferroelectricity and negative strain under increasing electric field are gained with elevating Fe2O3 along with little changed piezoelectricity. Stable strain maintains with increasing frequencies when Fe2O3 content changes, as an enhancement are discovered for residual polarization (Pr) and coercive electric field (EC) at 0.5–1 Hz for x ≥ 1.0%. Moreover, improved temperature stability for piezoelectricity and strain as well as remained high ferroelectricity is presented with increasing Fe2O3, originating from the increasing diffusion behavior of R-O-T phase boundary and non-declined TC, respectively. Thus, this work provides an effectively strategy to optimize the stability of electrical properties for application of KNN-based materials.