Ferroelectric relaxor behavior and dielectric spectroscopic study of 0.99(Bi0.5Na0.5TiO3)–0.01(SrNb2O6) solid solution

0.99(Bi0.5Na0.5TiO3)–0.01(SrNb2O6) was prepared by simple solid state reaction route. Material stabilized in rhombohedral perovskite phase with lattice constants a = 3.9060 Å, α = 89.86° and ah = 5.4852 Å, ch = 6.7335 Å for hexagonal unit cells. Density of material was found 5.52 gm/cm3 (92.9% of theoretical one) in the sample sintered at 950 °C. The temperature dependent dielectric constant exhibits a broad peak at 538 K (ɛm = 2270) at 1 kHz that shows frequency dependent shifts toward higher temperature – typical relaxor behavior. Modified Curie–Weiss law was used to fit the dielectric data that exhibits almost complete diffuse phase transition characteristics. The dielectric relaxation obeys the Vogel–Fulcher relationship with the freezing temperature 412.4 K. Significant dielectric dispersion is observed in low frequency regime in both components of dielectric response and a small dielectric relaxation peak is observed. Cole–Cole plots indicate polydispersive nature of the dielectric relaxation; the relaxation distribution increases with increase in temperature.

Research highlights
► Bismuth sodium titanate, Bi0.5Na0.5TiO3 (BNT), is one of the important ferroelectrics with perovskite structure.
► BNT based materials are considered to be good candidate for applications such as piezoelectric and pyroelectric devices, and high temperature relaxor.
► A conventional ceramic fabrication technique was adopted to prepare 0.99(Bi0.5Na0.5TiO3)–0.01(SrNb2O6) ceramic.
► Dielectric data analysis shows that the material undergoes complete diffuse phase transition characteristics.
► The dielectric relaxation obeys the Vogel–Fulcher relationship which is a clear identification of the presence of relaxor phase in the material.