Comparison of different zirconia powders for slip casting of alumina–zirconia ceramics

Two commercial 3 mol.-% yttria partially stabilised zirconia powders, 0·3 wt-%Al₂O₃ doped (Al doped Y-PSZ) and without Al₂O₃ (Y-PSZ), were used to produce alumina (Al₂O₃)–zirconia (ZrO₂) slip cast composites. The effect of the substitution of Al₂O₃ and/or Y-PSZ by Al doped Y-PSZ on the rheological properties of concentrated aqueous Al₂O₃–ZrO₂ slips was studied. In addition, the density of green cast samples was studied and related to the degree of slip dispersion. The viscosity and yield stress values of Al₂O₃ Al doped Y-PSZ suspensions were higher than those of Al₂O₃ Y-PSZ ones for all the compositions and solid loading studied. This behaviour could be explained by a larger effective size of the Al doped Y-PSZ particles, which resulted in a higher effective solid volume fraction and a lower amount of free liquid available for flow. The substitution of Y-PSZ by Al doped Y-PSZ in the Al₂O₃–ZrO₂ mixtures resulted in a less dense packing of cast samples.