HIGH DIELECTRIC MATERIALS FOR ENERGY STORAGE APPLICATIONS

Abstract

With the rapid advancement of power electronics towards miniaturization, dielectric materials with high dielectric constant, low loss, good thermal stability and high energy storage density are in high demand for energy storage applications. In the past few decades, lead-containing perovskite materials were dominating modern electronics. But the toxicity of lead is harming the environment. Therefore, lead-free ceramics with high energy storage densities are needed in comparison to their lead-based equivalents. Among the lead-free perovskite materials, sodium bismuth titanate (Bi0.5Na0.5TiO3, abbreviated as NBT) and barium titanate (BaTiO3, abbreviated as BT) are widely regarded to be materials of great importance. The BNT possess high Curie temperature along with strong ferroelectric property, a coercive field at room temperature and high remanent polarization. By choosing the suitable dopants, one can enhance the dielectric properties and hence the efficiency of BNT. Among the NBT based solid solutions, the (1-x)Bi0.5Na0.5TiO3-xBaTiO3 is high in demand due to its exceptional characteristics at the morphotropic phase boundary (MPB), which is, the boundary between the tetragonal phase of BT and the rhombohedral phase of NBT. BaTiO3 is chosen as it possess huge polarisation, high dielectric constant and remarkable thermal stability of the dielectric properties. According to recent research, saturation polarisation (Pmax) and the dielectric permittivity (ɛ) are improved by cationic vacancies. In this work, (1-x)BNT-xBT is used as the base material and Bi0.2Sr0.7TiO3 (BST) is introduced into it to lower the remanent polarisation (Pr) of the BNT-BT system and to enhance the energy storage capacity. Bi0.2Sr0.7⎕. TiO3 is reported as a novel lead-free relaxor ferroelectric material. In this material the production of strontium vacancies compensate the charge mismatch caused by the substitution of divalent Sr ions by trivalent Bi ions. In the present study, solid state reaction method was used to synthesize solid solutions of BNT-BT BST lead-free relaxor ferroelectric ceramics and their dielectric, structural, ferroelectric, and energy storage properties are explored.