Rheological properties of aqueous alumina–alumina-doped Y-PSZ suspensions

The effect of the substitution of alumina (Al2O3) by 0.3 wt% Al2O3-doped 3 mol% yttria-partially stabilized zirconia (Y-PSZ) on the rheological properties of concentrated aqueous slips was studied. Al2O3–Al2O3-doped Y-PSZ aqueous suspensions with different Al2O3-doped Y-PSZ contents: 0, 22 and 50 vol% were prepared using ammonium polyacrylate (NH4PA) as dispersant. The particle size distributions of Al2O3 and Al2O3-doped Y-PSZ powders were similar; however, the particle shape and the surface coating of alumina conferred a markedly higher specific surface area to the Al2O3-doped Y-PSZ powder. The substitution of Al2O3 by Al2O3-doped Y-PSZ in the mixtures decreased the negative surface charge of the powders at pH 9, thereby increasing the amount of NH4PA adsorbed and consequently the electrosteric repulsion between particles. However, the viscosity and yield stress values increased with increasing Al2O3-doped Y-PSZ content for all the solid loading studied. This could be explained by a larger interaction size of the Al2O3-doped Y-PSZ particles which resulted in a higher effective volume solid fraction and a lower amount of free-liquid available for flow.