Comparative study of Ce0.85Sm0.075Nd0.075O2−δ electrolyte synthesized by different routes

In this work, four different methods, including polyvinyl alcohol (PVA)-assisted sol–gel process, polyethylene glycol (PEG)-assisted sol–gel process, citrate sol–gel process and oxalate coprecipitation process (OCP) are employed to synthesize the Sm and Nd co-doped ceria electrolyte with the composition of Ce0.85Sm0.075Nd0.075O2−δ (SNDC). The phase structure of the powders can be well indexed with the fluorite-type CeO2 structure. The morphology of sintered samples indicates that the ceramics can be highly densified. The relative density and the average grain size vary with the synthesis processes and the sintering temperatures. The bulk conductivities are quite close and the OCP–SNDC yields highest grain-boundary conductivities and total conductivities. The results indicate that the OCP process for the powder synthesis results in higher relative density and conductivities, lower grain-boundary resistance and activation energy. Grain-boundary space charge potentials for different specimens are calculated based on the Mott–Schottky model. The synthesis process and sintering temperature have significant effect on the space charge potential and the specific grain-boundary conductivity.

• How the four different processing routes of powder, including PVA-assisted sol–gel process, PEG-assisted sol–gel process, citrate sol–gel process and oxalate coprecipitation process (OCP), influence the microstructure and electrolytic property of the Ce0.85Sm0.075Nd0.075O2−δ electrolyte is investigated.
• The OCP process for the powder synthesis results in higher relative density and conductivities, lower grain boundary resistance and activation energy of total conductivity.
• The synthesis process and sintering temperature have significant effect on the space charge potential and the specific grain-boundary conductivities.