Temperature-dependent broadband dielectric and ferroelectric properties of Ba_(1−x)Sr_xTiO₃ ceramics for energy storage capacitor applications

In the recent past, high energy storage and fast discharge capacitors have attracted considerable attention among the scientific community. In this context, a series of lead-free barium titanate-based ceramics with composition Ba_(1−x)Sr_xTiO₃ (x = 0.00–0.50) are synthesized using a solid-state reaction method to study their storage and discharge characteristics. The ceramics were sintered at different temperatures, and the ceramics sintered at 1300 °C/2 h showed the maximum relative density with tetragonal symmetry for x ≤ 0.3 and cubic symmetry for x ≥ 0.4. The uniformity in grain sizes for the ceramics improved with an increase in Sr content till x = 0.3. The pristine BaTiO₃ (BTO) displayed three humps at − 60, 20, and 125 °C corresponding to rhombohedral-tetragonal-cubic phase transitions, respectively, and T_c shifted to room temperature with an increase in Sr concentration. The recoverable energy density for x = 0.3 goes around 29 mJ/cm³ with an energy efficiency of 56.1%. For pure BTO, the recoverable energy density obtained is 31.2 mJ/cm³ with an energy efficiency of 38% at an electric field of 15 kV/cm. The samples' diffusive coefficient is obtained by fitting the modified Curie–Weiss law and found that all the samples exhibited ferroelectric behavior as the γ value is around one. This study focused on the structural, microstructural, broadband dielectric spectroscopy and the ferroelectric properties of Sr-modified BaTiO₃ ceramics. Such studies form an extensive evaluation of the properties of the synthesized ceramics for energy storage applications.