Significantly enhanced dielectric breakdown strength of ferroelectric energy-storage ceramics via grain size uniformity control: Phase-field simulation and experimental realization

The utilization of ferroelectric ceramics in electrical energy storage has become a hot topic due to the urgent need for advanced pulsed power and high power energy storage applications. Much attention has been paid to achieving nanograined ferroelectric ceramics but little to the effect of grain size uniformity, which is critical for dielectric breakdown and reliability. We first investigated this effect via a model based on virtually constructed ceramic samples solved with the phase-field method. Ferroelectric ceramic samples with the same average grain size of typically 100 nm but different uniformity degrees by the variation of the standard deviation values of 83.7, 81.9, 80.1, and 78.7 were constructed via Voronoi tessellation based on a controlled seeding method. The effect of grain size uniformity on the dielectric breakdown was studied through a phase-field dielectric breakdown model. The results indicate that with the standard deviation decreasing, the dielectric breakdown strength is distinctly enhanced. Experimentally, BaTiO3-based ceramics with the same average grain size of 100 nm but different uniformity degrees were realized via conventional sintering and two-step sintering methods. The grain size uniformity of two-step sintered ceramics is greatly improved, which leads to the breakdown strength and discharge energy density of the two-step sintered ceramics about 50% and 100% larger than those of the conventionally sintered ones. This work demonstrates that significant enhancement in dielectric breakdown strength of ferroelectric energy-storage ceramics can be achieved via grain size uniformity control, shedding light on the meticulous design and fine tuning of the energy-storage properties of ferroelectric ceramics.