Effects of (K0.5Na0.5)(Nb0.96Sb0.04)O3 on microstructure and electrical properties of BNT-based piezoelectric ceramics

Abstract

In this work, (1-x)Bi0.5Na0.5TiO3-x(K0.5Na0.5)(Nb0.96Sb0.04)O3 [abbreviated as (1-x)BNT-xKNNS] lead-free piezoelectric ceramics were successfully prepared by the conventional solid-state reaction method, and effects of (K0.5Na0.5)(Nb0.96Sb0.04)O3 [abbreviated as KNNS] on microstructure structure and electrical properties of the ceramics were systematically discussed. Results of phase characterizations showed that KNNS led to phase transition from orthorhombic (O) phase to monoclinic (M)-O phase coexistence. However, KNNS had small effects on grain growth of the ceramics according to scanning electron microscope (SEM) analysis. The existence of KNNS resulted in unique dielectric relaxor behavior of such ceramics, i.e. vanished depolarization temperature (Td) and insensitive relative dielectric constants (εr) to frequencies when T < Ts. When T ≥ Ts, obvious frequency dispersion of εr resulted from thermally-activated B-site disorder. Furthermore, electrical properties and energy storage properties were studied and the ceramics with x = 0.02 possessed optimized dielectric properties of εr ~ 773 (@100 kHz) and dielectric loss (tanδ) ~ 0.02 over wide temperature range.