PNNL

Abstract

The microstructure and chemistry of a transparent gahnite glass-ceramic and its precursor glass were investigated at the nanoscale using atom probe tomography, transmission electron microscopy, and nuclear magnetic resonance. In the annealed precursor glass, statistically significant ZrO clustering was observed along with Si depletion within 2 nm of the ZrO clusters. It is expected that this clustering is the first step in the nucleation and crystallization of the nucleating agent, tetragonal ZrO2. In the glass-ceramic, the gahnite (ZnAl2O4) crystallites were found to exist in proximal locations to ZrO2 and not in a core-shell arrangement. Further, the residual glass composition was directly measured, showing higher than expected levels of Al2O3, ZnO, and ZrO¬2. At the interfaces between the crystallites and residual glass, no enrichment or depletion zones were found. The findings presented here provide answers to a number of questions surrounding nucleation and elemental partitioning, microstructure, and the residual glass composition of transparent gahnite glass-ceramics.