Impedance and energy storage properties of NBT-SrTiO3–KNbO3lead-free ceramics

Among the notable features of the lead-free material KNbO 3 (KNb) are its exceptional energy storage density (W rec ) and high breakdown electric field strength (E b ). However, the considerable energy loss associated with KNb limits its applicability in energy storage, adversely affecting both W rec and efficiency (η) under strong electric fields. This study explores an innovative approach to enhance the energy storage capacity of NBT-SrT- x KNb ceramics ( x = 0.1–0.4). The incorporation of KNb disrupts the long-range ordered structure and effectively reduces grain size, resulting in the formation of polar nanoregions (PNRs) that help mitigate energy density loss. As the concentration of KNb increases, significant improvements in both W rec and η are observed. NBT-SrT- x KNb ( x = 0.3) exhibits the best performance among all variations, achieving a high energy storage density (W rec = 3.13 J/cm 3 ), rapid conversion efficiency ( η = 85%), and excellent breakdown strength. Under a mild electric field 30 kV/cm, the substitution of KNb results in a significant strain response of approximately 0.24%. Additionally, a longitudinal strain value of 129 pC/N was recorded. These lead-free ceramics present compelling candidates for current energy storage applications as well as next-generation electro ceramics.