Enhancement of recoverable energy density and efficiency of K0.5Na0.5NbO3 ceramic modified by Bi(Mg0.5Zr0.5)O3

As one of the most popular lead-free energy storage materials, K0.5Na0.5NbO3 (KNN)-based ceramics are expected to replace lead-based ceramics due to their high dielectric constant, high Curie temperature, and environmental friendliness. However, the high remnant polarization (Pr) and low breakdown strength (BDS) of KNN ceramic lead to its low energy storage properties, which limits its applications in energy storage field. In this work, the energy storage properties of KNN ceramic were improved by reducing average grain size and enhancing relaxor behavior. The 0.85K0.5Na0.5NbO3-0.15Bi(Mg0.5Zr0.5)O3 (0.85KNN-0.15BMZ) ceramic prepared by the solid state method not only has high recoverable energy storage density value (Wrec) of 3.47 J cm-3 but also has high energy storage efficiency value (η) of 89.14% at a high applied electric field of 320 kV/cm. In addition, the Wrec and η of 0.85KNN-0.15BMZ ceramic fluctuate slightly over the whole temperature range of 20–120 °C at 200 kV/cm, showing excellent temperature stability. At the same time, it can be concluded by first-order reversal curve distribution that 0.85KNN-0.15BMZ ceramic has excellent energy storage properties due to their enhanced relaxor behavior. In summary, the 0.85KNN-0.15BMZ ceramic can be used as the novel dielectric capacitor materials. [Display omitted] •The multiscale optimization strategy can serve as a paradigm.•A giant Wrec of 3.47 J cm-3 and a high η of 89.14% can be achieved.•The high temperature stability of 0.85KNN-0.15BMZ ceramic broadens its applications.