Crystallization of a Glass‐Ceramic by Epitaxial Growth
Abstract
The crystallization mechanism in a modified Li 2 O‐Al 2 O 3 ‐SiO 2 glass containing P 2 O 5 nucleating agent was investigated by transmission electron microscopy, X‐ray diffraction, and differential thermal analysis. During an initial 1000°C treatment P 2 0 5 and Li 2 O react to precipitate Li 3 PO 4 crystallites. At lower temperatures cristobalite, lithium metasilicate, and lithium disilicate crystallize by epitaxial growth on those Li 3 PO 4 crystallites. Crystallographic orientation relations for epitaxy were determined by electron diffraction, and lattice misfits were found to be in the range –5.3 to +3.8%. These results provide the first direct proof that glass‐ceramics can crystallize by epitaxial growth on heterogeneous nuclei formed from intentionally added nucleating agents.