Electrostatic capacitors with high charge/discharge speed and long cycle lifetime play an essential role in advanced electronic and electrical power systems. However, their low energy density (usually less than 1 J cm-3) has limited their development. In this study, core-shell structured Ba0.4Sr0.6TiO3@SiO2 nanoparticles were synthesized by a wet-chemical method, and dense ceramics with enhanced energy storage density were fabricated by spark plasma sintering (SPS). In situ TEM and DSC techniques were used to investigate the interface reaction between Ba0.4Sr0.6TiO3 and SiO2. The results revealed that the secondary phase ((Ba,Sr)2TiSi2O8) was unavoidable, but it could be suppressed due to the low sintering temperature and short sintering period used in the SPS technique. With the increasing SiO2 coating amount, the polarization decreased monotonously, whereas the dielectric breakdown strength increased to a maximum of 400 kV cm-1 and then decreased slightly. The enhancement in the dielectric breakdown strength was ascribed to the formation of nanosized (Ba,Sr)2TiSi2O8 coating on Ba0.4Sr0.6TiO3 grains, whereas the subsequent degradation of performance might have been caused by the sub-micrometric secondary phase precipitated at the grain boundaries. The effect of microstructure on the breakdown strength was further confirmed by numerical simulation using COMSOL. As a result, the Ba0.4Sr0.6TiO3 ceramics with 8 mol% SiO2 showed a maximum energy storage density of 1.60 J cm-3 at 400 kV cm-1 with an ultrahigh energy efficiency of 90.9%. This study opens an effective way for the design of high-performance dielectric ceramics.
All Science Journal Classification (ASJC) codes
- Renewable Energy, Sustainability and the Environment
- Materials Science(all)