Effects of impurities on the slip viscosity and sintered properties of low-soda easy-sintered α-alumina

The effects of the impurity on the rheological behavior of the aqueous slip and the resulting sintering properties of low-soda easy-sintered alumina were examined. The addition of Na+, Ca2+, Mg2+, Fe3+, and Si4+ resulted in a change in slip viscosity, where Na+ and Mg2+ increased the viscosity significantly. On the other hand, the changes in the zeta potential of the particles upon impurity addition were insignificant. The addition of Mg2+ and Fe3+ revealed a denser sintered microstructure along with more uniform grain sizes, whereas Na+, Ca2+, and Si4+ addition resulted in a lower sintered density and abnormal grain growth compared to those of the as-received powder. Overall, the impurity affected the slip viscosity and sintered microstructure of alumina significantly, while the color difference of sintered sample existed in two kinds of powders was difficult to explain only using the type and content of impurities.