Phase formation in porous liquid phase sintered silicon carbide: Part I: Interaction between Al2O3 and SiC

The structure and phase formation of porous liquid phase sintered silicon carbide (porous LPS-SiC), containing yttria and alumina additives have been studied. The present paper is focused on the system Al-Si-C-O, which is part of the system describing the interactions with sintering additives. The influence of different sintering atmospheres, namely argon and Ar/CO, and different temperatures on structure and composition was investigated by XRD and SEM. Additionally, reaction products were calculated from thermodynamic data and correlated with experimentally determined reaction products. Alumina and SiC reacted at 1950 °C in an argon atmosphere, forming a metal melt of aluminium and silicon. No reduction of Al2O3 was observed in a CO-containing argon sintering atmosphere. In the second and third parts of this paper the interactions between Y2O3-SiC and Y2O3 -Al2O3-SiC are analysed [J. Eur. Ceram. Soc. (in press), parts II and III].