Interfacial Effect of the Oxygen-Ion Distribution on the Conduction Mechanism in Strontium-Added Ce0.8Sm0.2O2-δ/Na2CO3 Nanocomposite

Nanocomposites composed of doped ceria as the primary phase and carbonate (Na2CO3) as the secondary phase are being investigated as electrolytes for low-temperature solid oxide fuel cell (SOFC) applications. Herein, we report the sintering temperature-dependent modification of the interfacial interaction between the Ce0.8Sm0.2O2-delta/Na2CO3 phases in the presence of strontium and its effect on ionic conductivity. Two composites of Ce0.8Sm0.2O2-delta/Na2CO3, one without and the other with 10 mol % strontium, were prepared by the coprecipitation method. The dried and consolidated pellets were subsequently sintered at 500, 600, and 700 degrees C. The structural modifications were investigated by XRD, TG/DTA, SEM, TEM, Raman, and FTIR techniques. Addition of strontium improved the ionic conductivity compared to those of the bare composites by converting the interfacial zone into a superionic path for oxygen-ion conduction. Lower sintering temperature (500 degrees C) and the presence of strontium were found to lead to higher conductivity (9.7 mS cm(-1) at 600 degrees C) as a result of the generation of larger compressive stress, which enhanced the oxygen-vacancy concentration in the interfacial zone. These nanocomposites with higher ionic conductivity at lower operating temperature are promising for potential developments in next-generation SOFCs.