Nanoscale grain sizes in BNT-based ceramics with superb energy storage performances via coating boron nitride nanosheets

Electronic devices impose higher requirements on the energy storage performances of ceramic capacitors toward miniaturization and integration application in 5G industry. The micron ranges grain size of bulk ceramics severely constrains the improvement of the breakdown strength (BDS), which restricts the applicability of ceramic capacitors in terms of energy storage. However, it is still a long-standing challenge to achieve nanoscale ranges grain size of bulk ceramics. Herein, a novel strategy of all-inorganic nanocomposites ceramics by introducing BN nanosheets (BNNSs) is first time proposed to sharply reduce the grain sizes, leading to significantly enhance BDS. The BNNSs encircling BNST ceramic particles form the nano coating structure, which contributes to the record value of grain sizes ∼68.86 nm and ultrahigh BDS ∼640 kV/cm in Na0.325Bi0.395Sr0.245TiO3-0.005 BNNSs (BNST-0.005BN) ceramic. A combined phase-field simulation and experimental research is further performed to specifically investigate the effect of the ultrafine grain sizes on the BDS. Accordingly, the superior total energy density of 7.34 J/cm3 and recoverable energy density of 5.28 J/cm3 are attained at 640 kV/cm. More importantly, the present work provides an effective solution for the improvement of the energy storage performances of dielectric ceramics as well as the reduction of the co-fired temperature, which is anticipated to achieve extensive application in MLCCs field.