Sinterability of commercial 8 mol% yttria-stabilized zirconia powders and the effect of sintered density on the ionic conductivity

The sintering behaviour of a number of commercially produced 8 mol% yttria- stabilized zirconia powders has been studied. The effect of different sinte ring regimes on the density and microstructure of the sintered ceramic was determined using density measurements, scanning electron microscopy (SEM) a nd dilatometry. The chemical homogeneity, particle size and the morphology of the as-received powder were related to the sintering behaviour of the di fferent commercial powders. Powders prepared via a route which involved a s pray-drying step sintered more readily than those prepared without a spray- drying step. Plasma-derived powders did not sinter to as high an apparent d ensity as co-precipitated powders. The effect of sample density on the ioni c conductivity of sintered YSZ ceramics was studied using a.c. impedance sp ectroscopy. This technique allowed separation of the bulk and grain-boundar y components, enabling clear intepretation of the effects of sample porosit y of the conduction pathways. Ceramics prepared from the three different po wders achieved a bulk ionic conductivity of similar to 16 S cm(-1) at 1000 degrees C for sintered densities of 95% or greater. The results obtained ar e compared to values reported for a variety of other commercial powders. (C ) 1998 Kluwer Academic Publishers.