Effect of Bi2O3 addition on the sintering and microstructural development of gadolinia-doped ceria ceramics

The effect of small amounts (0.2–2.0 wt.%) of bismuth oxide on the sintering behavior and microstructural development of Ce0.9Gd0.1O1.95 (GDC) submicronized powders has been studied using XRD for the lattice parameter measurements, the constant heating rate (CHR) method in air to monitor the shrinkage kinetics of powder compacts, and scanning electron microscopy (SEM) to study the microstructure of the sintered samples. Sintering of GDC compacts was significantly improved by adding small amounts of Bi2O3 (≤2.0 wt.%), and samples of doped-GDC sintered at 1200–1400 °C for 2–4 h were dense bodies (98–99.5% of theoretical density). Measurements showed that the addition of Bi2O3 could reduce the sintering temperature by about 250–300 °C lower than that for undoped-GDC samples. A liquid phase-assisting mechanism was assumed as the main cause for the enhancement of the densification process. The average grain size of doped-GDC sintered samples grew with the increasing of Bi2O3 addition up to 1.0 wt.%, and then decreased indicating a poor wetting properties of the formed liquid phase.