ELECTROSTATIC ADSORPTION OF A COLLOIDAL SINTERING AGENT ON SILICON-NITRIDE PARTICLES

Pressureless sintering of silicon nitride requires addition of sintering agents. The main part of this study was done in order to homogenize the distribution of sintering agents, in this case Y2O3, in a silicon nitride matrix. Colloidal 10-nm Y2O3 particles were electrostatically adsorbed on Si3N4 particle surfaces. The adsorption was studied by X-ray fluorescence analysis and electrophoretic measurements. Addition of Y2O3 sol to a Si3N4 suspension decreased the viscosity of the suspension. The slip casting properties of Si3N4 suspensions with added Y2O3 sol were examined, and the homogeneity of Y2O3 in the green compacts was compared with conventionally prepared samples. An improved microstructural homogeneity was obtained when Y2O3 sol particles were adsorbed on the Si3N4 particle surfaces.