Effects of alkali oxides and ion-exchange on the structure of zinc-alumino-silicate glasses and glass-ceramics

Types and contents of alkali metal ions play important role on crystallization and ion-exchange properties in glasses. In this work, effects of Na2O/K2O ratio on crystallization and ion-exchange properties of zinc-alumino-silicate glasses were investigated. The crystalline phases precipitated in glasses changes from ZnO to β-Zn2SiO4 with the progressive replacement of K2O by Na2O in parent glasses. Ion-exchange depth of layer (DOL) decreases gradually with the increase in Na2O content in parent glasses. Precipitation of ZnO and β-Zn2SiO4 nanocrystals facilitated the ion-exchange and enlarged the DOL. Na+ and K+ ions were doped into ZnO and β-Zn2SiO4 nanocrystals during heat-treatment, and the extent of doping was facilitated by ion-exchange. Vickers hardness were improved significantly with the crystallization and ion-exchange. Results reported here are valuable for the controlled preparation and chemical strengthening of ZnO and β-Zn2SiO4 glass-ceramics.