Improved energy storage density in 0.475BNT–0.525BCTZ with MgO addition

0.475BNT–0.525BCTZ–x wt% MgO ceramics were prepared through a solid–solid state route and their phase structure, microstructure, dielectric and energy storage properties were investigated with the focus on optimizing properties for capacitor applications. The secondary phases of MgO and Mg2TiO4 were observed when the content of MgO is higher than a critical amount (5–7 wt%). Diffuse phase transition was observed due to the large differences of ion valences and sizes in B-site ions and the presence of secondary phases. The dielectric breakdown strength of these ceramics were significantly enhanced along with the addition of MgO, leading to a significant improvement of discharge energy density. The sample with x=5 shows a high dielectric breakdown strength of 15.67 kV/mm and the highest maximum discharge energy density of 1.04 J/cm3.