Methodology for selection of charging agents for electrophoretic deposition of ceramic particles

The zeta potential of particles is a key factor in the electrophoretic deposition process. It plays a role in the stabilization of the suspension by determining the intensity of repulsive interactions as well as in determining the direction and velocity of particle migration. The zeta potential can be controlled by addition of charging agents such as acids, bases, and specifically adsorbed ions or polyelectrolytes, to the suspension. Thus there exist a variety of additives that affect the charge magnitude and its polarity. These additives act by different mechanisms. The main criteria for the selection of a charging agent are the preferred polarity and deposition rate of the particles. While the deposition rate is directly dependent on the zeta potential, which is determined by the charging additive, the influence of such an additive is exerted also by its effect on the ionic conductivity of the suspension. The latter determines the potential drop in the bulk of the suspension, which constitutes the driving force for the transfer of the particles to the electrodes. The present work will describe the methodology developed at Cerel for the selection of a charging agent based on its effect on the zeta potential/pH curve, on the isoelectric point and on the ionic conductivity of the suspension.