Enhancing energy storage performance of AgNbO₃-based ceramics by coating with insulating SiO₂ buffer layer

Dielectric ceramics are crucial materials in the preparation of high energy storage capacitors, where antiferroelectric ceramics have promising potential due to their large maximum polarization and low remnant polarization. However, their low energy storage density limits their wide application. In this work, core–shell structured ceramics were designed by coating AgNb_0.95Ta_0.05O₃ with SiO₂ and sintering in air for 2 h. The microstructure demonstrates that the SiO₂ layer is coated on the ANT nanoparticles, acting as a buffer layer to inhibit grain growth, which results in a significant decrease from 2.74 to 0.61 µm in the grain size of the ceramics during sintering. An increase in SiO₂ content builds up the depletion regions, restricts charge carrier transportation, and reduces the dielectric loss. The insulating SiO₂ buffer layer shares the electric field, thus preventing the premature breakdown of the ANT ceramics and increasing the breakdown field from 200 to 260 kV/cm. Consequently, compared to the 2.05 J/cm³ energy storage density and 33% efficiency of pure ANT ceramics, ANT@5wt.%SiO₂ ceramics achieve a W_rec of 3.52 J/cm³ and an η of 55%. Also, the ceramic shows significant charge–discharge properties with a fast discharge time of 102.5 ns and a high power density of 142.68 MW/cm³. This study indicates that core–shell structural design is one of the effective approaches to enhance the energy storage performance of ceramics.