Dispersion of concentrated aqueous neodymia–yttria–alumina mixture with ammonium poly(acrylic acid) as dispersant

A stable aqueous slurry using ammonium polyacrylic acid polyelectrolyte as dispersant and a neodymia–yttria–alumina mixture was prepared as the starting powder. The effect of the polyelectrolyte concentration and the pH of the slurry on the stability of the suspension is studied, and the optimal pH value and the amount of dispersant needed to obtain a stable slurry were determined. Highly consistent slurries with optimal pH and dispersant concentration were prepared by ball milling. The rheological behavior of the slip with different solid loading (48–58 wt.%) has been studied by measuring the viscosity and shear stress as a function of shear rate. Slip with solid loadings of 53 wt.% shows near-Newtonian behavior but becomes non-Newtonian with typical shear-thinning behavior above this solid loading value. The density and microstructure of the cast product bears a direct relationship to the state of the slip induced by variation of the pH and the concentration of the dispersant as well as by solid loading. Transparent Nd:YAG ceramics were obtained by sintering of compacts prepared from optimized slurries at 1750 °C in vacuum.

Research highlights▶ We prepared stable aqueous slurry with ammonium polyacrylic acid as dispersant and neodymia-yttria-alumina mixture as the starting powder. ▶ A series of colloid chemistry properties of mixture was investigated. ▶ Transparent Nd:YAG ceramics were obtained from the optimized slurries.