In this paper, silicon nitride ceramics with Y2O3 and/or Al2O3 sinter additives, with and without TiN powder addition are compared. The Impulse Excitation Technique (IET), providing access to internal friction at elevated temperature, was used to study the intergranular amorphous phases. High Temperature X-ray Diffraction (HTXRD) was used to assess the thermal expansion of the beta -silicon nitride crystal lattice. It is shown that small amounts (< 5 wt%) of TiN additive contribute to the formation of a stable intergranular amorphous phase during liquid phase sintering. The thermal expansion of the crystal lattice parameters a and c of the beta -silicon nitride with TiN additive was smaller than that of the silicon nitride without TiN. The remarkable effects of the TiN addition on the microstructure of silicon nitride are proposed to be due to the solid solution of Ti-ions in the beta -silicon nitride crystal lattice, and the network forming ability of the Ti-ions in the intergranular amorphous phase.