This work first explores high resolution transmission electron microscopy (TEM) to determine the interfacial regions and provide experimental evidences for interfaces between the SDC and carbonate constituent phases of the SD-carbonate two-phase composites to further investigate the superionic conduction mechanism in the ceria-carbonate composite systems and enhancement of conductivity. Schober first reported interfacial superionic conduction in ceria-based composites but without direct experimental proofs. Such superionic conduction mechanism remains unknown. Especially, in the nano-scale, this region is trifle to be detected.