Colloidal processing of BaTiO3 using ammonium polyacrylate as dispersant

The variation of the ζ potential of BaTiO3 particles in aqueous suspension as a consequence of changing the pH and the concentration of ammonium polyacrylate (NH4PA) has been studied. An isoelectric point at pH ∼2.5 was found. The ζ potential decreases upon addition of NH4PA up to 0.1 g of dispersant/g of powder. Using sedimentation tests, it was found that the stabilization of suspensions is attained at pH greater than or equal to 8 and concentrations greater than or equal to 1.5×10−3 g of dispersant/g of powder. By rheological measurements, a pseudoplastic behavior and little thixotropy was observed in the suspensions. The maximum solid content attained during this work was 48 vol%. Infrared spectroscopy of the sedimented and dried powder was carried out. It was observed the presence of BaCO3 and the change of ionization of the NH4PA molecules when the pH changes. High green density values (up to ∼60% of the theoretical density) in BaTiO3 cakes were achieved at pH of 11.3, at 2.5×10−3 g of dispersant/g of powder and with a solid content between 40 and 48 vol%.