Abstract During the sintering of porous liquid phase sintered silicon carbide (porous LPS-SiC) a strong interaction with the atmosphere takes place, influencing the composition and stability of porous LPS-SiC components. The present paper is focused on the interaction of Y 2O 3 with SiC, which is part of the common used sintering additives for LPS-SiC (Y 2O 3–Al 2O 3–SiC). The interaction of Al 2O 3 and SiC has been studied in a previous paper [J. Eur. Ceram. Soc. (in press)]. The reaction products of the interaction of Y 2O 3 with SiC and the resulting microstructures were analysed using model experiments. The effects of the influence of different sintering atmospheres, namely Argon and Ar/CO, as well as vacuum and different temperatures have been investigated. The phase formation was determined by X-ray diffraction (XRD) and can be explained on the basis of thermodynamic calculations. Depending on the sintering conditions, silicides or yttrium carbides can be formed in addition to stable oxides, which can result in the decomposition of the samples after sintering. Reactions between SiC and Y 2O 3 during sintering can be suppressed successfully if an Ar/CO atmosphere is used.