Well-sintered SDC-NC (Sm0.2Ce0.8O1.9-Na2CO3) nanocomposites have been prepared through a rare-earth/sodium complex carbonate precipitation, powder prefirings at the temperatures 400, 500 and 600 degrees C and sintering at 800 degrees C. Their sintering performances, phase components and microstructures have been characterized by,Archimedean method, XRD and FESEM techniques. In particular, the influence of the interfacial interactions between the phases of SDC and NC on the microstructures and electrical conductivities of SDC-NC nanocomposites have been investigated by AC impedance and Raman spectroscopies. It has been found that on the basis of the fitting analysis of AC impedance data, the oxide ionic and protonic conductivities of interfacial and non-interfacial phases in the SDC-NC nanocomposites are found to be strongly dependent upon their prefiring temperatures with the sample of SN-600 showing the highest values of 73.2/33.7 and 51.1/105.4 mu S/cm at 300 degrees C, respectively. The single cell based on the electrolyte of SN-600 presents an OCV of 0.992 V and peak power density of 421 mW/cm(2) at 550 degrees C. The interfacial interactions between the phases of SDC and NC inside SDC-NC nanocomposites are considered responsible for their differences in microstructure and electrical conductivity. (C) 2017 Published by Elsevier B.V.