Investigation of grain boundaries influence on dielectric properties in fine-grained BaTiO3 ceramics without the core–shell structure

Grain boundaries of the Ca-doped and fine-grained BaTiO3 (BT) ceramics were investigated in order to understand the role of grain boundaries, using a high-resolution transmission electron microscope (TEM) analyses, X-ray diffraction (XRD) and chemical etching analyses. Electrical properties and complex impedance spectroscopy of multilayer ceramic capacitors (MLCs) using Ca-doped BT were also examined to investigate with reference to the roles of grain boundaries. Doped elements were peculiarly enriched at the grain boundaries and tetragonality of the BT ceramics recovered significantly after grain boundaries were etched. It is confirmed that the grain boundaries have a significant influence in stabilizing the temperature dependence of the dielectric properties, and that the residual stress is caused by grain boundaries with the grain growth inhibited during sintering. In addition, the high reliability of BT ceramics without the core–shell structure is considered to be due to the high resistivity of the grain boundaries.