The Li2O-Al2O3-SiO2 glass-ceramic system (commonly referred as LAS) is one of the moreimportant glass ceramic systems from the commercial point of view for its mechanical and optical properties. The mechanical characteristics are due to the fact that the main crystalline phase is a lithium-silicate, lithium-aluminium-silicate solid solution, or a metastabile b-quartz solid solution or a solid solution of b-Spodumene or b-Eucryptite stable phases; the transparency properties are related to the cristallite size ( less than 40 nm). In this work, some results of a research made with the aim to obtain optically transparent, colourless and with good thermo-mechanical LAS glass-ceramics are presented. In particular, by varying thecomposition, the possibility to obtain the required properties by using a one-step thermal treatment no longer than 24 hours has been studied.

Glass-ceramics are polycrystalline materials formed by controlled crystallisation heat treatments of appropriate glasses. Their microstructure consists on a high concentration of generally small crystals uniformly distributed in the residual glass phase. The crystalline phases formed, the growth rate and the size depend on the parent glass, the imposed thermal treatment and the addition of nucleating agents.