Phase transitions, ferroelectric and relaxor properties of nonstoichiometric NBT ceramics

abstractPhase formation, crystal structure, microstructure, dielectric, ferroelectric and relaxor properties of nonstoichiometric ceramics (Na0.5+xBi0.5)TiO3 and (Na0.5Bi0.5-x)TiO3 with ratio Na/Bi>1, (Na0.5-xBi0.5)TiO3 and (Na0.5Bi0.5+x)TiO3 with ratio Na/Bi < 1 and x = 0 – 0.1 have been studied. Anomalies near 400 K and peaks at ∼ 600 K corresponding to ferroelectric phase transitions were revealed on temperature dependences of dielectric permittivity. Phase transitions near 400 K demonstrate a pronounced relaxor behavior determined by the presence of polar regions in a nonpolar matrix. It is shown that increase in the Na/Bi ratio in ceramics I and II contributes to improvement of their dielectric and ferroelectric properties.