Phase Structure, Microstructure, and Electrical Properties of Bi _0.47 Na _0.47 Ba _0.06 TiO ₃ Ceramics with (LiNb) ⁴⁺ Substituted into B-Sites

Abstract

Due to the substitution of complex ions into B-sites is very interesting in recent, lead-free Bi0.47Na0.47Ba0.06Ti1−x(LiNb)xO3 (BNBT1−xLNx) ceramics (with x = 0–0.04) were fabricated by the solid-state combustion method. The influence of (LiNb)4+ (x) on the phase structure, microstructure, and electrical properties was investigated. The X-ray diffraction (XRD) patterns exhibited a pure perovskite structure for all specimens. Coexisting rhombohedral and tetragonal phases were observed in all samples and the tetragonal phase increased with increased x, as analyzed by the Rietveld refinement method. The morphology of the BNBT1−xLNx ceramics, obtained by scanning electron microscopy (SEM), revealed almost-round grain shapes and anisotropic grain growth. The density and average grain sizes decreased from 5.84 to 5.54 g/cm3 and 1.7 to 0.9 µm, respectively, when x increased from 0 to 0.04. The grain size distribution decreased with increased (LiNb)4+ content. A reduction in the dielectric properties was observed, due to the phase ratio changing away from a morphotropic phase boundary (MPB), an inferior microstructure, and low density caused by (LiNb)4+ substitution. The (LiNb)4+ substitution induced the transition from non-ergodic relaxor to ergodic relaxor ferroelectric state.