Crystallization Behavior of Cordierite-Based Glass with Excess SiO2 and Al2O3 at Initial Stage

Crystallization behavior of cordierite-based glass with excess SiO 2 and Al 2 O 3 (CM glass) was studied at the initial crystallization stage. Two kinds of glass-in-glass phase separation occurred during the heat treatment of glass powder. The secondary glass-in-glass phase separation, which consists of an SiO 2 -rich phase and an Al 2 O 3 -rich phase significantly affects the crystallization of the glass and the resultant microstructures of the crystallized glass. Mullite nucleated first in the Al 2 O 3 -rich amorphous phase which is no longer a stable glass-forming region. Metastable µ-cordierite crystallized in the SiO 2 -rich amorphous phase and grew rapidly. A fine-grained cordierite-mullite composite with mullite as the grain boundary phase was produced.