Densification, grain growth, and microstructures in reactive sintering of mullite with and without 1 mass％ titania were studied in the temperature range of 1450℃-1650℃ in air. The addition of titania enhanced the mullitization of samples at all sintering temperatures and grain growth at early stage of sintering, but retarded densification at lower temperatures than 1550℃. Grain growth was expressed in an equation Dn ～ Kt with growth exponents of n＝4 and 2 for samples with and without titania, respectively. The activation energy of grain growth for samples with titania was larger than for those without additives. The precipitations and segregation of titania at the intersection of three grains and along grain boundaries were confirmed by TEM and EDX analysis. Experimental data were discussed in terms of the diffusion of ions in the liquid phase of SiO2-Al2O3-TiO2 system, which had lower eutectic point than that of SiO2-Al2O3 system.

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