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

Abstract

Transparent ZnO–MgO–Al2O3–SiO2 (ZMAS) glass-ceramics comprising ZrO2 and SnO2 as nucleating agents were prepared via melting and two-step heat treatment. The effects of varying the SnO2 concentration (1–3 mol%) on the crystallization behavior, microstructures, and mechanical properties of the glass-ceramics were investigated. Increasing the SnO2 content promoted the precipitation of spinel and gahnite because SnO2 improved the formation of ZrO2 nanocrystals, which provided nucleation sites for subsequent crystallization. When the SnO2 content was varied between 2 and 3 mol%, the crystallization behavior of the ZMAS glass-ceramics showed little difference, and SnO2 crystals precipitated from the glass at a relatively low crystallization temperature. In addition, glass-ceramics containing 2 and 3 mol% SnO2 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 SnO2 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.