Improved breakdown strength and energy storage density of a Ce doped strontium titanate core by silica shell coating

For single phase dielectric ceramics prepared using a traditional solid state method, the conflict between high dielectric permittivity and low breakdown strength has always limited the improvement of energy storage density. Here, we design a core–shell structure of Sr0.985Ce0.01TiO3 (SCT)@x wt% SiO2 combining a high dielectric permittivity core with an insulating shell material. The sample of x = 3 wt% sintered at 1300 °C has the largest energy storage density ∼2.23 J cm−3. The effects that different amounts of SiO2 have on phase, microstructure, dielectric and energy storage properties were investigated using X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy with energy dispersive X-ray spectrum (SEM-EDS) and dielectric measurements. As verified by finite element simulations, the energy storage properties are mainly governed by the electric field distribution owing to the introduction of a high dielectric permittivity core (SCT) in a low permittivity shell. The shell material provides an electrical shielding effect around the core, resulting in significant reduction in the field strength within the core material. A comparison of experimental and simulated results is also shown, which is in good agreement with the breakdown properties.