Iron oxide as an effective sintering aid and a grain boundary scavenger for ceria-based electrolytes

The effect of FeO1.5 addition on the densification behavior and electrical properties of Ce0.8Gd0.2O2−δ ceramics was examined. The small addition of FeO1.5 (e.g., 0.5 at.%) reduced sintering temperature (by ∼200 °C) and promoted densification rate. When sintered at 1300°C for 5 h, the 0.5 at.% FeO1.5-doped Ce0.8Gd0.2O2−δ has ∼95% relative density, as compared to ∼82% relative density for the undoped one. The measurement of lattice parameter indicated that the FeO1.5 addition also promoted the dissolution of Gd2O3 in CeO2 at lower sintering temperatures. On the other hand, the grain boundary (GB) conductivity could be significantly improved by small addition of FeO1.5. The optimum scavenging effect on SiO2 impurity was achieved by adding 0.5 at.% FeO1.5 to Ce0.8Gd0.2O2−δ ceramics and sintered at 1400–1500 °C.