Influence of SiO₂ addition on the dielectric properties and microstructure of (Ba_0.96Ca_0.04)(Ti_0.85 Zr_0.15)O₃ ceramics

In this study, the effect of SiO₂ doping on the sintering behavior, microstructure, and dielectric properties of BaTiO₃ -based ceramics was investigated. Silica was added to (Ba_0.96 Ca_0.04)(Ti_0.85Zr_0.15)O₃ (BCTZ) powder prepared using the solid-state method. SiO₂ -doped BCTZ ceramics with a high density and a uniform grain size were obtained and sintered at 1220°C in a reducing atmosphere. A second phase (BaTiSiO₅) existed in samples when SiO₂ was added in excess of 1%. The amount of the second phases was observed to increase as the number of SiO₂ additives increased. It was found that BCTZ ceramics sintered with SiO₂ are helpful in reducing the sintering temperature for a typical thick film and MLCC applications. However, there were disadvantageous effects on the dielectric properties with mere addition of SiO₂ addition (3% and 5%) due to higher formation of BaTiSiO₅. Doping with a small amount of silica can improve the sintering and dielectric properties of BCTZ ceramics. In addition, to understand the effect of the BaTiSiO₅ phase on the dielectric properties of BCTZ ceramics, the BaTiSiO₅ composition was synthesized from individual BaCO₃, TiO₂, and SiO₂ powders using conventional solid-state methods. X-ray diffraction results show the presence of mainly the crystalline phase, BaTiSiO₅, in the sintered ceramics.