The effect of slip casting parameters on the ultrafine microstructure and density of pore-free YAG ceramic obtained by vacuum sintering

In this study, the effect of slip casting parameters on the ultrafine microstructure and the density of pore-free YAG ceramic was evaluated. A stable, high concentrated aqueous YAG slurry using Dolapix-CE64 as a dispersant was prepared. The effect of dispersant concentration as well as the solid load on the stability and rheological behavior of the slurry was also studied. The optimal dispersant content for suspension was 1.5%wt which led to the slurry with minimum viscosity and near Newtonian behavior. The results show that increasing the solid load of the YAG slurry causes higher viscosity and alters the rheological behavior of slurry to slight shear thinning. By increasing the solid load of slurry up to a specific amount, 75%wt, relative green density of the slip cast sample was increased to about 65%, but further increase in solid loading reduced the green density. The density and the microstructure of the sintered body in the air and vacuum atmospheres bear a direct relationship to the green density of the slip cast body. Although, relatively the pore-free ultrafine YAG ceramic was obtained using vacuum sintering of the slip cast green body of 65% relative green density, the presence of nitrogen molecules in the air atmosphere inhibited full densification of YAG ceramic.