Structure Property Relationship Studies and Low Temperature Sintering Strategies for Bismuth-based Relaxor Ferroelectric System

Relaxor ferroelectrics are well established as an intriguing class of dielectric materials with high scope for use in energy storage applications. Relaxors feature moderately high dielectric constant and reduced hysteresis in polarization- electric field characteristics, providing higher energy storage density and efficiency at relatively low electric fields. Bismuth-based compositions can be sintered at considerably lower sintering temperatures when compared to most extensively used dielectric ceramics, such as BaTiO3 (BT), due to the low melting point of Bi2O3. The weakly coupled relaxor ferroelectric BiScO3- BaTiO3 (BS-BT) has a simple pseudocubic perovskite structure with great possibilities for engineering of parameters by physical and chemical modifications to optimize the grain morphology, increase the breakdown strength, enhance the energy storage capacity, and ensure improved temperature and fatigue endurance. Therefore, this research focuses on understanding the effects of low temperature sintering and modification of the BS-BT binary system in enhancing the energy storage characteristics. Dielectrics have a critical field strength above which it can become conductive, leading to a dielectric breakdown. NaNbO3 (NN) doping can enhance the formation of smaller sized polar regions and increase the breakdown strength. Modification of the binary BSBT system with NN results in improved breakdown strength and temperature stability of its dielectric and ferroelectric characteristics. The optimized energy storage performance is observed for 5% NN doped 0.4BS-0.6BT, giving a recoverable energy density of 4.6 J/cm3 at 430 kV/cm with 90% efficiency. The dielectric and energy storage characteristics of NN doped BS-BT is maintained from 25⁰C to 200⁰C.