Interactions between silicon nitride particles and hydroxide precipitates were investigated using electrophoresis measurements. Conditions under which stable suspensions of silicon nitride particles and flocculation and heteroflocculation of silicon nitride/hydroxide mixtures occur were Identified. On the basis of the observations, a method for producing uniform mixtures of silicon nitride powders and additive precipitates was formulated and used to produce green compacts of improved compositional homogeneity. The effect of the mixing process on the sintering of green silicon nitride compacts was investigated and compared to the sintering behavior of conventionally prepared green compacts. The results show that the improved homogeneity obtained using the precipitation mixing process leads to enhanced sintering of the green compacts.