Effect of molecular weight of an anionic dispersant on the properties of BaTi ₄O ₉ slurries

The colloidal stability of BaTi ₄O ₉ (BT ₄) aqueous suspensions with poly(acrylamide-co-4-carboxylamino-4-oxo-2-butenate) (PAC) of different molecular weights at pH 9 has been investigated by means of zeta potential, adsorption, sedimentation, and particle size measurements. The results indicate that PAC could improve the dispersion of the particles from agglomeration. The resulting suspensions became more stabilized, and contained powder with smaller particle size. Consequently, the compacts with PAC exhibited better properties in terms of density and dielectric constant than those without any polymer present. The performance of PAC increased with decreasing polymer molecular weight. Clearly, PAC1 (M _w = 1.8 × 10 ⁴) was most effective in dispersing the BT ₄ particles, and stabilizing the ceramic suspensions. This is attributed to the highest adsorption of this polymer onto BT ₄ powder, and causes strongest electrostatic repulsions among solid particles.