Fabrication and electrical characterization of (Bi_0.49Na_0.49Ba_0.02)TiO₃-PVDF thin film composites

The barium doped bismuth sodium titanate (i.e., Bi_0.49Na_0.490.98Ba_0.02)TiO₃ (BNBT) powder was prepared by a conventional ceramic processing route. The thin film composites of BNBT- PVDF (polyvinylidene fluoride) were fabricated via a solution casting route. The scanning electron micrographs of the thin film samples show the homogenous distribution of grains with absence of cracks/pores. It is observed that with the increase of BNBT content in PVDF leads to enhancement in the dielectric permittivity and the reduction in the dissipation factor (tangent loss). The various electrical properties of the thin film samples were studied in the frequency range of 1 kHz to 1 MHz at different temperature between 25 and 100 °C. The prepared composite films have been used to study the (a) relationship between properties and crystal structure and (b) relaxation and conduction mechanism through the complex modulus and impedance spectroscopy. The contribution of grains was analyzed in the composite films by the fitting of equivalent circuit with the experimental data. An existence of the non-Debye type of dielectric relaxation was indicated by studying of the impedance and modulus parameters. The calculated activation energy from the temperature dependence of AC conductivity depicts hopping nature of charge carriers, which further explain the conduction process and mechanism in the prepared composites.