Development of all solid ceramic batteries was investigated in our research. Sintering process was one of the facile ways to construct all ceramic batteries. But the drawback was that the heat treatment of an active material layer and a solid electrolyte layer in contact with each other induced the solid-state reaction between them, resulting in electrochemical deactivation of the interface. When phosphate solid electrolytes such as Li1.3Al0.3Ti1.7(PO4)3 (LATP), and phosphate active materials such as LiCoPO4 and Li3Fe2(PO4)3 were selected, both the solid electrolyte layer and the active material layers could be co-sintered without significant formation of new materials, and the resulted interfaces were found to be electrochemically active.