From core-shell particles to dense Ba_(0.8)Sr_(0.2)Zr_(0.1)Ti_(0.9)O_3@ Bi_2O_3-Fe_2O_3-SiO_2 ceramics with low sintering temperature and improved dielectric, energy storage properties

摘要

To achieve high energy storage in dielectric ceramics, a new designed material Ba_(0.8)Sr_(0.2)Zr_(0.1)Ti_(0.9)O_3@ Bi_2O_3-Fe_2O_3-SiO_2with core-shell structure was fabricated by the monodispersed submicron Ba_(0.8)Sr_(0.2)Zr_(0.1)Ti_(0.9)O_3 particles (diameter～180 nm) coated with the 25-nm-thick shell of Bi_2O_3-Fe_2O_3-SiO_2. The influences of Bi_2O_3-Fe_2O_3-SiO_2 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 Ba_(0.8)Sr_(0.2)Zr_(0.1)Ti_(0.9)O_3 when the Bi_2O_3-Fe_2O_3-SiO_2 amount was below 6.0 wt%. The secondary phases Bi_2Fe_4O_9 and Bi_4Ti_3O_(12) formed in ceramics when the Bi_2O_3-Fe_2O_3-SiO_2 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 Bi_2O_3-Fe_2O_3-SiO_2 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 Ba_(0.8)Sr_(0.2)Zr_(0.1)Ti_(0.9)O_3@Bi_2O_3-Fe_2O_3-SiO_2 ceramics with Bi/Fe ratio of 1.04 and 6.0 wt% Bi_2O_3-Fe_2O_3-SiO_2 sintered at 1120 ℃ had a dielectric constant of 2599, the maximum energy storage density of 1.50 J/cm~3 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.