Characterizations of Co-Ionic Neodymium-Doped Ceria/Carbonate Composite Electrolytes

Abstract

Neodymium-doped ceria (Nd0.2Ce0.8O1.9, NDC)-based composite electrolytes with (Li/0.5Na)2CO3 have a higher conductivity than pure NDC in the intermediate temperature range (500-700°C). This may be attributed to protons that contributes to an improvement in the ionic conductivity across grain boundaries or phase interfaces, thereby providing conduction pathways between NDC and the carbonate material (interfacial super ionic conduction mechanism). In this research, the fundamental properties of the composite materials are characterized by a variety of experimental methods such as XRD, SEM, TEM, and TG-DSC. First, it is confirmed by XRD that the fluorite structure of ceria is maintained in the composite materials. Carbonates, which exist in form of an amorphous phase, as well as NDC particles, which have a cubic fluorite structure, are identified by SEM and TEM. A thermal analysis by TG-DSC is performed to determine the temperature at which the binary eutectic of (Li/Na)-carbonate is formed. Electrical conductivities of composite electrolytes are also analyzed by EIS at 250-650 °C in air atmosphere.