Rheological behaviour of BaZrO3 suspensions in non-aqueous media

The colloidal behaviour of concentrated non-aqueous suspensions of barium zirconate is investigated. Optimum dispersing conditions are investigated for organic suspensions prepared with different solvent systems: methylethylketone (MEK)/ethanol, trichloroethylene (TCE)/ethanol, a methylisobutylketone (MIBK)/methylethylketone/cyclohexanone (CHN) and pure ethanol. Stabilisation of the suspensions is achieved by using two different dispersants: ester phosphate (EPH) and Hypermer KD-6. Rheological studies have been made in order to determine the optimum of each dispersant concentration as a function of the solvent systems. The best stabilisation of 30 vol.% suspensions is obtained by using EtOH with 3 wt.% KD-6 and TCE/EtOH with 1 wt.% EPH. Zeta potential studies show that the use of dispersants increases the positive surface potential on the particles. The zeta potential values increasing from +10 mV in the absence of EPH to +42 mV with 1.0 wt.% EPH and to +33 mV with KD-6. These results suggest that electrostatic repulsion plays an important role on the stability of these organic suspensions. Stabilised suspensions were slip cast in plaster molds and green densities higher than 55% of the theoretical density was obtained.