A novel double-coating approach to prepare fine-grained BaTiO3@La2O3@SiO2 dielectric ceramics for energy storage application

摘要

We prepared submicron BaTiO3@La2O3@SiO2 particles with high uniformity and dispersity using a novel double-coating method. The monodispersed submicron BaTiO3 particles (diameter about 240 nm) formed a ferroelectric core that was coated with La2O3 and SiO2 as a modified layer and a layer with high electrical resistance, respectively, and the thickness of two shells was about 20 nm. We then obtained dense, fine-grained BaTiO3-based energy storage ceramics (grain size <= 300 nm) with the same particle structure by means of sintering in air at 1240 degrees C for 2 h. As the amount of SiO2 increased, the content of the tetragonal phase and the densification first increased and then decreased. When the amount of SiO2 exceeded 9.0 wt%, a secondary phase with Ba2TiSi2O8 appeared, and the core-shell structure disappeared. The BaTiO3@La2O3@SiO2 ceramics met the X8R requirements, with a maximum dielectric constant of 3362 at 6.0 wt% SiO2, and a low dielectric loss at room temperature (< 0.020, with a minimum of 0.011). The remnant polarization deceased from 13.80 to 1.21 mu C/cm(2), while the energy storage density first increased and then decreased as the amount of SiO2 coating increased from 0.0 to 12.0 wt%. The discharged energy storage density was highest (0.54 J/cm(3)) for samples containing 9.0 wt% SiO2 under a maximum polarization field of 13.6 kV/mm, and the energy storage efficiency of the ceramic was >85%. (C) 2016 Elsevier B.V. All rights reserved.