Heterogeneous crystal nucleation on bubbles in silicate melt

Abstract

Experiments reported herein document heterogeneous crystal nucleation on bubbles in supercooled lithium disilicate melt. Crystalline lithium disilicate (Li2Si2O5) nucleated and grew on small bubbles (∼1 μm) with a one-to-one correspondence between the number of bubbles and crystals (ranging from <102 to ∼105 bubbles/mm3). Crystals grew on large bubbles (>100 μm) only in samples fused in N2, suggesting a chemical control on nucleating efficiency. Bubbles ∼1 μm in diameter served as nucleation sites for polycrystalline lithium disilicate spherulites; bubbles smaller than ∼1 μm served as nucleation sites for the more common ellipsoidal crystalline form. This difference in behavior might be due to the additional surface area available for crystal nucleation on the 1 μm bubbles.