Improving the electric energy storage performance of multilayer ceramic capacitors by refining grains through a two-step sintering process

Dielectric materials for multilayer ceramic capacitors (MLCCs) have been widely used in the field of pulse power supply due to their high-power density, high-temperature resistance and fatigue resistance. However, the low energy storage density is one of most critical issues hindering their miniaturization and integration development in cutting-edge technologies. In this manuscript, Na_0.5Bi_0.5TiO₃-based MLCCs with improved energy storage properties were fabricated via composition modification and sintering process improvement. The introduction of BiMg_0.5Hf_0.5O₃ weakens the ferroelectricity of 0.94Na_0.5Bi_0.5TiO₃-0.06BaTiO₃, while ensures high saturation polarization, delays polarization saturation, and low residual polarization, improving energy storage efficiency. Specifically, we adopted a two-step sintering process, by which the grain size of MLCCs sintered reduces by 60 %, the dielectric breakdown field strength increases by 33 %. The energy storage density reaches 7.8 J cm⁻³, 77 % higher than the MLCCs fabricated by traditional one-step sintering method. Moreover, the energy storage density changes by less than 10 % in a wide temperature range of 10 ∼ 180 °C. This study confirms that two-step sintering can also be applied to the preparation of Na_0.5Bi_0.5TiO₃-based MLCCs and provides a way to improve the energy storage performance of lead-free MLCCs, and benefits to the application of MLCCs as high voltage capacitors.