Intrinsic and extrinsic contributions to energy storage performance in potassium sodium niobate-based ceramics

Both the intrinsic and extrinsic contributions to the high energy storage properties of (K0.5Na0.5)NbO3 were investigated herein by employing Bi(Mg2/3Ta1/3)O3 as a second component to synthesize novel environment-friendly energy storage ceramics. The role of the second component was confirmed to reduce the intrinsic activation of electrons, which effectively improves the band gap values and reduces the probability of intrinsic breakdown. Phase field simulation was employed to confirm that the smaller grain size of the modified ceramic microstructure enhances the extrinsic breakdown and dielectric breakdown strength. Moreover, ab initio molecular dynamics were used to investigate the critical role of the Mg ions in lowering the initial polarization and forming nanodomains, representing the intrinsic contribution to decreasing the initial polarization. An intrinsic structure with moderate polarization rapidly increases the polarization of ceramics under external electric fields, facilitating high energy storage density. The prepared ceramics achieve a recoverable energy density (Wrec) of 3.86 J/cm3 and energy efficiency (eta) of 81.2% at 385 kV/cm.