The effect of additives on the crystallization and sintering of 2MgO-2Al(2)O(3)-5SiO(2) glass-ceramics

Crystallization and sintering behaviour of three cordierite (2MgO-2Al(2)O(3)-5SiO(2)) glasses containing different amount of additives were investigated and compared by using differential thermal analysis (DTA), X-ray diffraction (XRD), scanning electron microscopy (SEM), and the Archimedes method. The stoichiometric 2MgO-2Al(2)O(3)-5SiO(2) (MAS) glass and the 2MgO-2Al(2)O(3)-5SiO(2) glass containing 3 wt% of B2O3 and 3 wt% of P2O5 (MASBP) showed two exotherms (one for mu-cordierite formation from a glass and the other for alpha-cordierite formation from the mu-cordierite phase), whereas the 2MgO-2Al(2)O(3)-5SiO(2) glass containing 2 wt % of B2O3, 2 wt % of P2O5, and 2 wt % of TiO2 (MASBPT) showed only a single exotherm representing alpha-cordierite formation. By using Kissinger, Augis-Bennett, Ozawa, and modified Kissinger methods, the activation energy values for alpha-cordierite formation in the MASBP and MASBPT glasses were determined as 310 +/- 6 and 326 +/- 13 kJ mol(-1), respectively, whereas that in the MAS glass was determined as 868 +/- 5 kJ mol(-1). The MASBPT glass showed the lowest peak temperature value for alpha-cordierite formation (980 degrees C) amongst the three glasses. Both the MASBP and MASBPT glasses showed excellent sintering behaviour (> 99.7% of theoretical density).