Microstructure and dielectric properties of SrTiO3 ceramics by controlled growth of silica shells on SrTiO3 nanoparticles

SrTiO3@SiO2 nanopowder was synthesized via a core-shell nano-scale technique that is known as the Stöber process. The effect of the SiO2 concentration on microstructure, dielectric response and energy storage properties of SrTiO3@SiO2 ceramics was investigated. Transmission electron microscopy (TEM) results confirmed the formation of core-shell nanostructures with controlled shell thicknesses between 2 nm and 13 nm. After increasing SiO2, a secondary phase with Sr2TiSi2O8 appeared due to inter-diffusion reactions between the SrTiO3 core and SiO2 shells during the sintering process. The results show that both breakdown strength and energy density improved apparently. The homogeneous coating of silica on ST cores is considered to dominate the contribution to improved breakdown strength. The composition for SrTiO3 coated with 2.5 wt% SiO2 shows the maximum energy storage density (1.2 J/cm3) and a breakdown strength of 310 kV/cm. The former is higher than for pure SrTiO3 (0.19 J/cm3). Measurements of the dielectric performance indicate that the SrTiO3@SiO2 ceramics possess good bias stabilities compared to pure ST ceramics.