Crystallization behavior and properties of ZnO–MgO–Al2O3–SiO2 transparent glass-ceramics with SnO2 and ZrO2 as nucleating agents.

Transparent ZnO–MgO–Al 2 O 3 –SiO 2 (ZMAS) glass-ceramics comprising ZrO 2 and SnO 2 as nucleating agents were prepared via melting and two-step heat treatment. The effects of varying the SnO 2 concentration (1–3 mol%) on the crystallization behavior, microstructures, and mechanical properties of the glass-ceramics were investigated. Increasing the SnO 2 content promoted the precipitation of spinel and gahnite because SnO 2 improved the formation of ZrO 2 nanocrystals, which provided nucleation sites for subsequent crystallization. When the SnO 2 content was varied between 2 and 3 mol%, the crystallization behavior of the ZMAS glass-ceramics showed little difference, and SnO 2 crystals precipitated from the glass at a relatively low crystallization temperature. In addition, glass-ceramics containing 2 and 3 mol% SnO 2 exhibited average grain sizes of ∼26 and ∼29 nm, respectively, but their transmittance decreased to ∼52% and ∼50%, respectively, owing to grain aggregation. The best overall performance was achieved when the SnO 2 content of the glass-ceramic was 3 mol% and heat treatment was conducted at 780 °C for 3 h and 960 °C for 2 h, with the resulting glass-ceramic exhibiting a bending strength of ∼187 MPa and a Vickers hardness of ∼845 kgf/mm2. [ABSTRACT FROM AUTHOR]