EFFECT OF (AlNb)4+ B-SITES SUBSTITUTION ON THE PHASE STRUCTURE, MICROSTRUCTURE AND ELECTRICAL PROPERTIES OF Bi0.47Na0.47Ba0.06TiO3 CERAMICS

Bi0.47Na0.47Ba0.06Ti1-x(Al0.5Nb0.5)xO3 (abbreviated as BNBT1-xANx) lead-free ceramics (x=0-0.05) were synthesized by the solid-state combustion technique. The effect of (AlNb)4+ content on the phase structure, microstructure and electrical properties was investigated. A pure perovskite structure was obtained from all specimens. Rietveld refinement revealed coexisting rhombohedral and tetragonal phases in all samples and the tetragonal phase increased with increased AlNb content (x). The morphology of the BNBT1-xANx ceramics displayed nearly round grains and anisotropic grain growth. Average grain size decreased from 1.8 to 0.7 µm when x increased from 0 to 0.05 and the grain size distribution became narrower. The density, maximum dielectric constant and remnant polarization rapidly decreased with increased x. The deterioration of the electrical properties induced by (AlNb)4+ substitution was due to shifting away from the morphotropic phase boundary (MPB), poor microstructure and low density.