Enhanced oxygen permeability and electronic conductivity of Ce0.8Gd0.2O2 − δ membrane via the addition of sintering aids

Fluorite oxide is an excellent material candidate for oxygen production from air with potentials in oxyfuel combustion for clean energy delivery and ceramic membrane reactor for chemical synthesis given its desirable CO2 resistance and high oxygen ionic conductivity. However, its limited electronic conductivity restricts its practical applications in these technologies. In this work, we probed the use of transition metal (Co, Fe, and Cu) oxides as the sintering aid and the electronic conductivity enhancement agent. The presence of these transition metal oxides can lower the sintering temperature of GDC up to 300 °C. Oxygen fluxes were also enhanced in their presence; reaching the highest value of 0.112 mL min− 1 cm− 2 at 900 °C through a 0.8 mm-thick GDC membrane containing 2 mol% Co. Among the three sintering aids, CoO provided the maximum enhancement effect for oxygen fluxes. Such enhancement was primarily sourced from the improved electronic conductivities and the modified element distribution across the grain boundaries. In overcoming the electronic conductivity limitation of a predominantly ionic conducting phase, the use of sintering aid offers an attractive non-precious metal-based alternative that enables competitive performance enhancement with respect to the external short-circuit decoration.