Review and analysis of characterization methods and ionic conductivities for low-temperature solid oxide fuel cells (LT-SOFC)

• Conductivities of doped ceria/carbonate composite electrolytes have been reviewed.
• Special attention has been paid on the measurement methods.
• Impedance, constant current and product analysis methods are presented and compared.
• The results from the methods cannot be directly compared with each other.
• Recommendations on conductivity measurements of composite electrolytes are given.

In recent years, doped ceria/carbonate composite is one of the most researched low-temperature SOFC electrolyte. Its ionic conductivity, which strongly influences the performance of the fuel cell, can be measured with several different methods including EIS, constant current and product analysis measurements. The conductivities of similar materials measured under similar conditions seem to vary quite much, which could be partly explained by the sample preparation affecting the properties of the electrolyte. However, we found that the used measurement approach may impose even a larger uncertainty. Therefore, results from different conductivity measurement techniques may not be comparable. In this article, conductivities of doped ceria/carbonate composites and measurement techniques employed in recent articles have been reviewed. Pros and cons of the different measurement methods are analyzed and discrepancies found in the measured conductivity values are explained. Finally, recommendations on conductivity measurements of LT-SOFC composite electrolytes are given.