Control of interfacial structure of potassium niobate-barium titanate ceramics and their dielectric properties

ANbO3-BaTiO3 (AK, Na, or K0.5Na0.5) system ceramics were prepared using a conventional sintering method, and their dielectric properties were investigated. It was found that the dielectric constant of KNbO3-BaTiO3 system ceramics did not strongly depend on temperature between 20 and 400 °C, making them useful for capacitor application. However, the dielectric constant of KNbO3-BaTiO3 system ceramics was low. The high dielectric constant is attributable to a large area of interfaces between KN and BT grains. Ceramics sintered by spark plasma sintering (SPS) are expected to suppress a grain growth, increasing area of the interfacial layer. In this study, SPS method was employed to achieve a large area of the interfaces and to see how the dielectric properties change with the interfacial structure. The structure was controlled by changing sintering temperatures and time of the spark plasma sintering. As a result, X-ray diffraction patterns showed that perovskite single phase and their relative densities were greater than 97%. By contrast, the dielectric constant was decreased.