From core–shell particles to dense Ba0.8Sr0.2Zr0.1Ti0.9O3@Bi2O3–Fe2O3–SiO2 ceramics with low sintering temperature and improved dielectric, energy storage properties

Abstract

To achieve high energy storage in dielectric ceramics, a new designed material Ba0.8Sr0.2Zr0.1Ti0.9O3@Bi2O3–Fe2O3–SiO2 with core–shell structure was fabricated by the monodispersed submicron Ba0.8Sr0.2Zr0.1Ti0.9O3 particles (diameter ~ 180 nm) coated with the 25-nm-thick shell of Bi2O3–Fe2O3–SiO2. The influences of Bi2O3–Fe2O3–SiO2 amount, Bi/Fe ratio, and sintering temperature on the phase composition, microstructure, and ceramic electrical properties were investigated. X-ray diffraction analysis of the ceramics revealed the formation of perovskite Ba0.8Sr0.2Zr0.1Ti0.9O3 when the Bi2O3–Fe2O3–SiO2 amount was below 6.0 wt%. The secondary phases Bi2Fe4O9 and Bi4Ti3O12 formed in ceramics when the Bi2O3–Fe2O3–SiO2 amount exceeded 6.0 wt%, as the ceramic grain core–shell structure collapsed. Based on FESEM images, the densification of ceramics can be tenderly controlled at low sintering temperature, and the ceramic grains can maintain their core–shell structure. As the Bi2O3–Fe2O3–SiO2 amount, the ratio of Bi to Fe, and the sintering temperature increase, the ceramic room temperature dielectric constant increases up to a maximum value then decreases. The energy storage density exhibits a similar tendency to increase first and then decrease. Fine-grained Ba0.8Sr0.2Zr0.1Ti0.9O3@Bi2O3–Fe2O3–SiO2 ceramics with Bi/Fe ratio of 1.04 and 6.0 wt% Bi2O3–Fe2O3–SiO2 sintered at 1120 °C had a dielectric constant of 2599, the maximum energy storage density of 1.50 J/cm3 under 29.31 kV/mm. This work proposed a novel method to enhance electrical properties of functional materials, which could be potentially used in the fabrication of capacitors with high energy storage performance.