A diffuse phase transition study on Ba2+ substituted (Na0.5Bi0.5)TiO3 ferroelectric ceramic

Polycrystalline perovskite lead free material (Na0.5Bi0.5)0.91Ba0.090TiO3 was prepared by solid state reaction method. The crystal structure examined by X-ray powder diffraction indicates that the material was single phase with tetragonal structure. Dielectric studies exhibit a diffuse phase transition and characterized by a strong temperature and frequency dispersion of permittivity which relates cation disorder at A-site and exhibits relaxor behaviour. The dielectric relaxation has been modeled using the Vogel–Fulcher relationship, the calculated activation energy found to be Ea = 0.021 eV. Complex impedance analysis indicates the system undergoing a polydispersive non-Debye type relaxation. Also, used to characterize grain and grain-boundary resistivities of Ba substituted (Na0.5Bi0.5)TiO3 ceramic. The phenomenon was also interpreted by accounting for microstructural differences. The corresponding relaxation times were also used to confirm the interpretation of complex impedance spectra. Overlapping of grain boundary and electrode relaxation processes can be separated above about 4000 C. Electrical modulus spectroscopy studies have been performed. The conductivity parameters such as ion-hopping rate (ωp) and the charge carrier concentration (K1) have been calculated using Almond and West formalism.

► Substitution of Ba2+ into BNT produces single phase ferroelectric ceramic with tetragonal structure.
► Frequency dependent dielectric maximum with diffuse phase transition.
► A non-Debye type dielectric relaxation obeys Vogel–Fulcher law.
► Increasing temperature enhances the ion hopping rate and increases conductivity.
► Charge carrier concentration remains constant over a wide range of temperature.