Epitaxial Crystallization of Seeded Albite Glass

Glasses that are extremely difficult to crystallize are generally avoided in making glass‐ceramics. It is now possible to crystallize such glasses epitaxially using isostructural seeds. The role of solid‐state epitaxy in the crystallization of such albite (NaAlSi₃O₈) glass to glass‐ceramic was investigated. The glass was seeded with extremely fine ZrO₂ (nonisostructural) and albite (isostructural) seed crystals. X‐ray diffraction results indicated that the albite‐seeded glass, heat‐treated at 1000°C for 100 h, epitaxially crystallized to albite, while the ZrO₂ and unseeded glasses did not crystallize in identical heat‐treatment conditions. In addition, the albite‐seeded glass, heat‐treated at 905°C for 10 d, crystallized mostly to albite, whereas the ZrO₂ and unseeded glasses at the same conditions contained only a small amount (<5 wt%) of nepheline (NaAlSiO₄). The microstructure of the epitaxially grown glass‐ceramics showed that extremely fine crystals (∼0.2 μm thickness) were formed around the seed.