Combustion synthesis and characterization of Cu–Sm co-doped CeO2 electrolytes

Nano-sized CSO (Ce0.80Sm0.20O2−δ) and CSCO (Ce0.79Sm0.20Cu0.01O2−δ) were synthesized by the PVA assisted combustion method, and then characterized by the structure of PVA–cation complexes and nano-powders, as well as mechanical and electrical performance after sintering. The results indicate that the PVA–cation complexes (PVA–(Ce3+,Sm3+) and PVA–(Ce3+,Sm3+,Cu2+)) were formed by coordinating metal cations to hydroxyl groups, as well as the COO−1 group derived from the oxidation of PVA with NO3−1. Low temperatures (around 200 °C) caused intense combustion reactions, resulting in the direct crystallization of cubic fluorite nano-CSO (10–20 nm) and nano-CSCO (10–15 nm) crystals with homogeneous element distribution. This slight compositional modification of CSO by co-doping with 1 mol% CuO resulted in a significantly lowered densification temperature, as well as enhanced mechanical and electrical property. The strength improvement can be ascribed to the dense and fine-grained microstructure without normal grain coarsening, resulting in a transgranular-dominant fracture mode during strength testing.