2000 Volume 68 Issue 6 Pages 427-432
The effect of concentration, size, and distribution of Al2O3 upon scavenging siliceous phase at grain boundary, was studied in 8 mol% yttria-stabilized zirconia (8YSZ) containing 0.2-1 mol% Al2O3 prepared from ball milling and ultrasonic dispersion. The grain-boundary resistivity at 400°C decreased prominently with adding Al2O3 to 8YSZ, which reflects the scavenging of siliceous grain-boundary phase. The uniform distribution of fine Al2O3 particles (0.3μm) was more beneficial than that of coarse one (4-10 μm). However, the difference was not significant when the density is high, that is, when the connectivity between grain boundaries is good enough. As density decreases, the uniform distribution of fine Al2O3 particles becomes more important to decrease the grain-boundary resistivity. It explains that the scavenging reaction is assisted by rapid grain-boundary diffusion. From the 28Si− concentration map using imaging scanning secondary ion mass spectroscopy (SIMS), it was proved that the coarse Al2O3 scavenges the siliceous phase mainly by interfacial reaction.
