Rapid densification by using Bi2O3 as an aid for sintering of gadolinia-doped ceria ceramics

Densification process and microstructure development in Bi2O3-doped gadolinia ceria (GDC) submicrometer powders have been studied by the constant heating rate (CHR) method in air and by SEM observations. Densification of GDC was strongly enhanced by adding small amounts of Bi2O3, and samples of GDC containing ≤1 wt% Bi2O3 sintered at 1200–1400 °C for 2 to 4 h were near theoretically dense bodies (98–99.8% of theoretical), i.e., about 250–300 °C lower than that for undoped-GDC ceramics. A transient liquid phase-assisting mechanism was assumed to be the main cause for such an improvement. The grain size of GDC ceramics was hardly affected by the Bi2O3 additions during sintering. A total electrical conductivity as high as 4 S m−1 at 700 °C for the doped-GDC samples sintered at 1400 °C, was measured.