Fabrication of Ferroelectric Ceramics with Multi-Layered Structure by Solvothermal Solidification Method for Introduction of Internal Electric Field

To increase the Curie temperature (TC) of barium titanate (BaTiO3: BT) ceramics, we tried to fabricate BT complex ceramics with an internal electric field. We propose that the electric field originating from poled potassium niobate (KNbO3: KN) layers is applied on a BT layer by injecting the BT layer between the poled KN layers. Since such multi-layered ceramics is difficult to be fabricated without forming solid solution by a conventional sintering process, we fabricated the KN-BT multi-layered ceramics by a solvothermal solidification method at 230 °C. The TC of BT layer in the fabricated KN-BT multi-layered ceramics did not changed even after poling and it is attributed to insufficiently poling of the KN layers. Therefore, we intensively investigated the polarization of KN layers to optimize the microstructures and fabrication condition of the KN-BT multi-layered ceramics. We prepared the KN ceramics with various microstructures by the solvothermal solidification method, and the poling treatment was performed. The polarization of the KN ceramics can be improved by formation of strong necks and/or a densification of the ceramics.