ABSTRACT In this study, the role of TiO 2 , ZrO 2 , and CaF 2 nucleating agents in high‐Al 2 O 3 (26.5 mol%) spinel glass‐ceramics within the SiO 2 –Al 2 O 3 –ZnO–MgO–Li 2 O–Na 2 O system was investigated systematically. As‐prepared glass samples were studied using differential scanning calorimetry (DSC), Raman, Fourier transform infrared (FTIR), and ss nuclear magnetic resonance (NMR) spectroscopy. It was found that Si is predominantly present as Q 4 units, with a large amount of Al entering the silicon–oxygen glass network. Moreover, the nucleating agent type influences glass network polymerization degree. The depolymerizing ability of the three nucleating agents on the parent glass network follows the order of CaF 2 > TiO 2 > ZrO 2 . Molecular dynamics simulations further supported these findings and suggested that Ti and Zr have a tendency to induce glass phase separation, as evidenced by small‐angle X‐ray scattering (SAXS). Furthermore, the crystallization behavior of glass was meticulously assessed by a combination of X‐ray diffraction (XRD), Raman, FTIR, and transmission electron microscope (TEM), and the nucleation mechanisms were summarized. TiO 2 promotes the formation of zinc/magnesium aluminotitanate amorphous regions to facilitate the nucleation of ZnAl 2 O 4 /MgAl 2 O 4 . In contrast, ZrO 2 tends to accumulate into locally ordered ZrO 2 ‐rich heterogeneous regions, which are the precursors of ZrO 2 nanocrystals. Then ZnAl 2 O 4 /MgAl 2 O 4 grow around ZrO 2 epitaxially. CaF 2 , however, is ineffective for controlled spinel crystallization. Simultaneously, the relationships between glass network structure and crystallization behavior were also discussed, revealing the dual role of nucleating agents. Finally, scanning electron microscope (SEM) images showed that the glass‐ceramic doped with ZrO 2 as nucleating agent exhibited a fine crystalline microstructure, and performance tests indicated that it has excellent comprehensive properties, with a microhardness of 8.23 GPa and a high transmittance of 88.7% in the visible light range.
Liu et al. (Wed,) studied this question.