High discharge energy density in novel K1/2Bi1/2TiO3-BiFeO3 based relaxor ferroelectrics

An increasing number of new dielectrics are being reported for the development of next-generation ceramic capacitors for power electronics used in clean energy technologies. Here, high discharge energy density (W_dis) ~6.1 J cm⁻³ with efficiency (η)~72% under a pulsed field (E_max) of 410 kV cm⁻¹ is reported along with temperature stability up to 150 °C (E_max = 200 kV cm⁻¹) for 0.5 K_0.5Bi_0.5TiO₃-0.42BiFeO₃-0.08Sm(Mg_2/3Nb_1/3)O₃ (KBT-BF-SMN) bulk ceramics. The optimised composition is chemically heterogeneous but electrically homogenous, similar to several BiFeO₃-based dielectrics reported previously and adding to the growing body of evidence that electrical (measured at weak-field) not chemical homogeneity is the best guide to increased E_max and enhanced energy density. KBT-BF-SMN ceramics are therefore considered as promising candidates for pulsed power and power electronics applications.