Effects of Bi4Ti3O12 addition on the microstructure and dielectric properties of Mn-doped BaTiO3-based X8R ceramics

The effects of Bi4Ti3O12 on the microstructure and dielectric properties of Mn-doped BaTiO3 were studied using X-ray diffraction (XRD) and transmission electron microscope (TEM). From XRD analysis and scanning electron microscope (SEM) observations, second phase Bi2Ti2O7 was found when the Bi4Ti3O12 content was more than 4 mol%. The grain size was significantly enhanced with increased Bi4Ti3O12 content. The sintering temperature of Mn-doped BaTiO3-based ceramics could be reduced effectively to 1200 °C by doping them with more than 1 mol% Bi4Ti3O12. TEM results show an obvious core–shell structure with 2 mol% Bi4Ti3O12, which was destroyed when the Bi4Ti3O12 content increased from 2 to 4 mol%. It was found that the Curie temperature was shifted to a higher level and the variation of dielectric constant decreased when Bi4Ti3O12 content increased from 0 to 2 mol%. When the Bi4Ti3O12 content was more than 2 mol%, the Curie temperature decreased due to a change of the core–shell structure and secondary phase Bi2Ti2O7. The variation of dielectric constant as compared with that at room temperature was about −25% at −55 °C and less than ±10% at 150 °C. The stable temperature characteristics of the dielectric constant were caused by the presence of the core–shell grain structure. Due to the “clockwise effect”, ceramic materials have great potential as EIA X8R-type multilayer ceramic capacitors.