Dielectric and piezoelectric properties of barium-modified Aurivillius-type Na0.5Bi4.5Ti4O15 Original Research Article

In this study, monophasic Bax(Na0.5Bi0.5)1−xBi4Ti4O15 (x=0.03, 0.06, 0.09 and 0.12) ceramics fabricated from the powders synthesized via the solid-state reaction route exhibited relaxor behavior. X-ray diffraction analysis revealed that the barium-modified Na0.5Bi4.5Ti4O15 ceramics have a pure four-layer Aurivillius phase structure. Dielectric properties and phase transitions were studied and are explained in terms of lattice response of these ceramics. A shift in ferroelectric–paraelectric phase transition (Tc) to lower temperatures and a corresponding increase in permittivity peak with increasing concentration of Ba2+ are also observed. The decrease of orthorhombicity in the lattice structure by the larger Ba2+ ion incorporation, indicating an approach of a and b parameters, results in lower Curie temperature. The piezoelectric activity of Na0.5Bi4.5Ti4O15 (NBT) ceramics was significantly improved by the modification of barium. The Curie temperature Tc and piezoelectric coefficient d33 for the composition with x=0.12 were found to be 635 °C and 21 pC/N, respectively. The relationship of polarization with lattice response is discussed.