Effect of heating rate on the shrinkage and microstructure of liquid phase sintered SiC ceramics

Abstract

This paper describes a study of shrinkage behavior in the liquid phase sintering of silicon carbide, SiC, using eutectic mixtures of Al2O3+Dy2O3 and Al2O3+Yb2O3 as liquid-forming additives. A volume fraction 10% of these mixtures was added to the SiC and homogenized in an attrition mill. Sintering was performed in a horizontal dilatometer at 1800 °C for 60 min, applying heating rates of 10, 20 and 30 °C/min. The results indicate that these heating rates affected neither shrinkage nor microstructure, from the standpoint of the complete sintering cycle. However, significant differences occurred during the non-isothermal sintering stage, leading to very different shrinkage results as a function of the heating rate. Higher heating rates produced lower shrinkage, and the work of final shrinkage occurred during the isothermal stage.