Optimization of energy storage density in relaxor (K, Na, Bi)NbO3 ceramics

Energy storage properties have been widely investigated in lead-free relaxor ferroelectric ceramics due to high polarization saturation (Ps) and low remnant polarization (Pr). Among these lead-free relaxor ferroelectric ones, the investigation of energy storage in KNN-based ceramics showed some unique characteristics. In this work, (K0.48Na0.52)1−3xBixNbO3 relaxor ceramics were synthesized by the conventional solid-state method, and the phase structure of diffusion rhombohedral (R) phase can be found. In addition, the recoverable energy storage density (Wrec) increased with the increase of the electric fields, and a high Wrec of ~1.04 J/cm3 under a low dielectric breakdown strength (DBS) of ~189 kV/cm was achieved in the ceramics with x = 0.04. In particular, the influences of composition and sintering parameters on the Wrec values were also studied. As a result, an optimum Wrec value can be possessed in the relaxor KNN-based ceramics even if low DBS values were applied, which maybe benefits the development of energy storage materials and devices.