Ceria-stabilized zirconia ceramics with irregular grain shapes

Toughened ceria-stabilized tetragonal zirconia ceramics with irregular grai n shapes and undulated grain boundaries were prepared by ceria doping. We i nvestigated the effect of doping times and annealing on the microstructures and fracture toughness. Irregularity of grain shapes increased with the am ount of ceria, but, in the case of a large amount of ceria, the grain bound aries migrated in the opposite direction of DIGM. Ceria-stabilized zirconia ceramics annealed at 1650 degrees C for 2 h, after twice dipping into ceri um nitrate solution of 0.2 M and sintering at 1500 degrees C for 2 h, showe d the longest grain boundary length, with a value of 23.6 mu m, compared to the samples with other heat-treatment conditions. The ceria concentration difference between convex and concave sides in irregular grains was greater than 1 mol%. No difference was observed in normal grains. Specimens with n ormal grain shapes showed intergranular fracture, whereas the specimens wit h irregular grain shapes showed transgranular fracture. (C) 2000 Elsevier S cience B.V. All rights reserved.