CONTROLLED PHASE-TRANSFORMATIONS BY GLASS PARTICLE-SIZE IN SPODUMENE AND CORDIERITE GLASS-CERAMICS

The effects of the particle size of initial glass powders on the phase transformations in Li2O-Al2O3-SiO2 and MgO-Al2O3-SiO2 glass ceramics were investigated. Both materials undergo crystallization of glass to a metastable phase and a subsequent metastable-stable transformation. As particle size is decreased, the crystallization of glass to the met astable phase is accelerated, because of the increase in the total num ber of nucleating sites on the particle surfaces. The metastable-stabl e transformation is restricted as the particle size is decreased. This phenomenon is explained by the decrease in the crystal size of the me tastable phase as a result of decreasing the particle size. The metast able-stable transformation of the fine crystals is restricted by the c onstraint imposed by the surrounding matrix.