Effect of impurities on dispersion properties of alpha-alumina powder

Ceramic powders frequently have traces of different ions remaining from powder manufacturing. To understand how much the impurities will change the dispersion behaviour the powders were characterised very carefully. This study was focused on the surface composition and the dispersion behaviour of two α-Al2O3 powders from different manufacturing processes in aqueous suspensions at various pH. Several techniques have been used to determine the degree of dispersion (dispersion stability). More attention has been paid to moderate particle concentrations where the dissolved impurities play a decisive role. The variation in surface composition between the powders led to differences in initial dispersion pH and in the magnitude and sign of the initial mobility (zeta potential) of the dispersion. Both observations show the importance of examining ceramic powder dispersions near the concentrations that are used to process the material, e.g., slip casting or dip-coating.