Homogeneous Distribution of Sintering Additives in Liquid‐Phase Sintered Silicon Carbide

Abstract

The addition of sintering additives to silicon carbide particles by electrostatic adsorption of colloidal A1 2 O 3 and Y 2 O 3 sols has been studied as a way to achieve an optimum homogeneity in the microstructure. The adsorption behavior of the sol particles was examined by electrophoretic measurements and X‐ray fluorescence analysis. Both A1 2 O 3 and Y 2 O 3 sols could simultaneously be adsorbed on the SiC particle surfaces. Viscosity measurements showed that the colloidal sol particles had a stabilizing effect on the slip, and hence slips with relatively high solid loadings could be prepared without adding extra dispersing agent. Liquid‐phase‐sintered silicon carbide materials (LPS‐SiC) with 2 wt% A1 2 O 3 and 1 wt% Y 2 O 3 were prepared by freeze granulation/ pressing and sintering at 1880 deg; C for 4 h. The homogeneity of the green compacts was quantified using a spot analysis technique in an electron probe microanalyzer. It was clearly shown that the addition of sols gave a more homogeneous microstructure than the reference sample with Y 2 O 3 and A1 2 O 3 added as powders. The addition of sintering additives as sols also enhanced the sintering behavior.