Challenges in spark plasma sintering of cerium (Iv) oxide

Cerium (IV) Oxide (CeO₂) is an electroceramic often used in electrolytes for solid oxide fuel cells, or a surrogate material for nuclear fuel. CeO₂ parts are typically manufactured via conventional sintering processes, which have inherent challenges such as long processing times and high power consumption. In this research, novel processing of CeO₂ via Spark Plasma Sintering (SPS) was performed and the effect of the electric current during sintering was investigated. The results indicate that SPS of pure ceria is challenging due to the self-reduction of ceria during SPS consolidation. The electric current passing through the ceramic plays a key role in the reduction kinetics. At temperatures above 1500°C and a holding time of 5 min, CeO₂ transforms into Ce₂O₃, which is associated with chemical expansion and deleterious effect on the integrity of the as-sintered material. The results of this work also suggest that changes to the SPS processing conditions, such as cutting off the electric current path, have a significant impact on the integrity of the as-sintered material.