α Cordierite is very important phase in MgO-Al2O3-SiO2 system because of their very outstanding thermal, chemical and electrical properties. In this presents study nonstoichiometry cordierite (MgO:Al2O3:SiO2 = 3:1.5:5) using 2 different initial raw materials ( (i)mixture of pure oxide, and ii) mainly mixture of minerals) were fabricated and compared in terms of phase transformation and physical properties. Cordierite was prepared by glass method at low melting temperature (1350°C). Low melting temperature has resulted in partly crystalline glass which has possesses higher hardness, required longer milling time and result in contamination from grinding media. However, α-cordierite has successfully crystallized and fully densified at 850°C/2h. Activation energy for densification was investigated from thermal expansion coefficient (TCE) results. Other properties that were discussed included thermal properties using DTA/TGA.
Indialite or α-cordierite was synthesized by glass crystallization method using mainly talc and kaolin and with small amount of MgO, Al2O3, SiO2 to compensate the chemical formulation of non-stoihiometric compositions of cordierite. (3MgO.1.5Al2O3.5SiO2). B2O3, P2O5 and CaO was also added to decrease the melting and sintering temperature of cordierite. The glasses were pelletized and sintered from 850 o C up to 1050 o C. Phase compositions of both heat treated glass was quantified by X-ray powder diffraction data by the Rietveld method using TOPAS Ver 3 software. Result shows that about 60wt% of α cordierite has successfully crystallized at 850 o C. Beside secondary phases (forsterite) which come from initial raw materials, phases from grinding media were also presents in the sample. The contamination was considered high since it has reacted with existence phases to form a new phase at higher temperature. Without any contamination from grinding it was expected to obtain more than 90wt% α cordierite using the same composition.