Highly translucent nanostructured glass-ceramic

Transparent and translucent glass-ceramics (GCs) are found in an increasing number of domestic and high-technology applications. In this paper, we evaluated and optimized the effects of two-stage heat treatments on the resulting crystalline phases and microstructure of a glass of the SiO2-Li2O-P2O5-TiO2-CaO-ZnO-Al 2O3 system. The objective was to develop a transparent nanostructured glass-ceramic (GC). After numerous heat treatment trials, we found that a long nucleation period of 72 h at 455 degrees C followed by a crystal growth treatment at 660 degrees C for 2 h resulted in a highly translucent GC having homogenously distributed nanocrystals. The relatively high amount of P2O5 (2.5 mol%) induced the formation of lithium disilicate as the main crystal phase. We thus developed a GC having crystals under 50 nm, with a high crystallized fraction (52%vol. Li2Si2O5 and 26% vol Li2SiO3), transmittance of approximately 80% in the visible spectrum for 1.2 mm thick specimens, nano hardness of 8.7 +/- 0.1 GPa (load of 400 mN), a high elastic modulus of 138 +/- 3 GPa as measured by nanoindentation, and good flexural strength (350 +/- 40 MPa) as measured by ball-on-3 balls tests. Due to its high content of Li+, this GC has the potential to be chemically strengthened and can be further developed to be used in a number of applications, such as on displays of electronic devices.