Effects of co-doping on densification of Gd-doped CeO₂ ceramics and adhesion characteristics on a yttrium stabilized zirconia substrate

In this study, a small amount of CoO was added to commercial Gd-doped CeO2 (GDC) powder. The CoO addition greatly enhanced sinterability at low temperatures, i.e., more than 98% of relative density was achieved at 1,000°C. When GDC/8YSZ (8 mol% yttrium stabilized zirconia) bilayers were sintered, Co-doped GDC showed excellent adhesion to the YSZ electrolyte. Transmission electron microscope (TEM) analysis showed that there were no traces of liquid films at the grain boundaries of GDC, whereas liquid films were observed in the Co-doped GDC sample. Because liquid films facilitate particle rearrangement and migration during sintering, mechanical stresses at the interface of a bilayer, which are developed based on different densification rates between the layers, might be reduced. In spite of Co2+ doping in GDC, the electrical conductivity was not significantly changed, relative to GDC.